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V8turbo4me
05-16-2004, 05:00 PM
Hello Everyone,

I have always dreamed of designing and building my very own car since I was a little boy. I have decided to sell my VR-4 to begin to pursue that dream. Only I am going to need a little help in one of the design areas. That area is Mid Engine setup. I have never owned or worked on a mid engine car and frankly I have no idea how they work or need to be set up. My list of questions is humongous as you might have guessed. Most importantly though, I need to see some kind of diagram of a successful mid engined car so I can see and understand what all is comprised in the system. Secondly are a special transmission and rear end need because I was planning to use a 700R or 1200R transmission and a 9 inch rear end but if that won't work I am going to need to seriously need to rethink the whole drivetrain of this project, which I am willing to do! So if you can help me out in this department, please lend me your knowledge and enlightend me.

Matra et Alpine
05-16-2004, 05:10 PM
I need to see some kind of diagram of a successful mid engined car so I can see and understand what all is comprised in the system.
A goo dplace to start woul dbe to review the various kit cars usign mid-engine.

Most of these transplant a transverese front engine front wheel drive into the rear. Newer ones use newer longtitudonal engines from front wheel drive cars. ( Suka ? Can you scan and post the build diagrams for the Libra ? )

Look for Mini-based cars from the 70-80s. They were very common.
Lotus have published a few articles on the Elise design. It's a custom design from ground up but will likely answer a lot of the detail questions. Thought I had a ref but I don't :(

Lots of experience here of stock, kit and modified mid-engined cars. Maybe if you give a bit more detail on what you expect to do? Complete car design, purpose, road or track, size and we can help more.

V8turbo4me
05-16-2004, 07:56 PM
More details huh? well I plan to build a roughly 14 foot long mid engined small block V8 turbo charged car. The emphasis of the project will be on keeping the auto as light as possible to allow for maximum cornering power and great acceleration and braking response. The car would be used for road racing and driving very similar to this. My biggest problem is that I want to develope a lot of horsepower on this car and at this point I don't even understand how the transmission and rear end fit into the car! As you can image I am a little concerned about all of this and am in desperate need of some answers, any help will be greatly appreciated.

Matra et Alpine
05-16-2004, 08:28 PM
More details huh? well I plan to build a roughly 14 foot long mid engined small block V8 turbo charged car.
OK, first MAJOR problem is you're talking about putting a lot of power down.
14 feet long doesn't leav a ot of space for a driver and engine :)
These bring issues in building a safe chassis that a scrutineer will pass for competition.
You'll have problems if the pedals are forward of the wheels as the tub would have to be shown to be strong enough to prevent suspension in gress in the event of an incident.
What are you planning for suspension ? Are you going to take it all from a donor or build-your-own like the Locost ??

The emphasis of the project will be on keeping the auto as light as possible to allow for maximum cornering power and great acceleration and braking response.
To race it competitively you will ahve to make it strong enough to handle the speeds and stresses of the power you're proposing.
You're heading along an expensive route, but we'll see if we can assist :)

at this point I don't even understand how the transmission and rear end fit into the car!
Do you plan to lift engine and transmission from a donor or can you do engineering to mate engines and transaxles ?
How much money do you plan to spend ?

As you can image I am a little concerned about all of this and am in desperate need of some answers, any help will be greatly appreciated.
OK, if I'm going to take 'standard' layouts you would want to put the engine mid-ship front to back and mate it with a transaxle - gearbox and diff combined. Your choices are a full race-spec unit from companies like ZF - expensive - or to seek simialr layouts and 'borrow' transaxles. Sounds like you're US so I cna't help. One of the cheapest/strongest in Europe is the Renault as used in my A610.
An alternative layout would be to take the transmission from a fwd car using the engine you plan to use. Then plant the whole thing in the middle. The disadvantage of this solution is usually the height. BUT depends on the donor. Again you need to source US parts.
Suspension.. do you have a car in mind to take working suspension from ? If so then as with the engine, you've all the measuremnets to design the chassis to. If you plan to do something 'special' then you're not going to get it to work. Chassis and suspension design is not easy. There are too many variables to get anywhere near right, sadly. So I'd recommend sourcing a decent donor. In Eureop the Ford parts bin is used for many kits :)
Now once you've chosen a reasonable set of possible donor or new parts you then need to sit down with a calculator and work out the weight of all the parts and calculate the corner weights to determine the suspension needs for springs/dampers and the front/rear bias. If you don't get enough weight forward then you'll have a car that will go off backwards every time you lift off the throttle :) Get too much and you'll have a car that will do the same eery time you turn in :) Once you have designed the chassis to meet a reasonable weight split ( between 40:60 and 50:50 ) THEN you need to look at the polar centre of momentum. This is the point that a car rotates around. To be competitive as a race car you want that to be as close to the centre driver position as possible. If you don't the car will be hard to 'feel' during cornering.
Now to do all those calculations you are best to have an engineering degree to know how to do it for scratch designs. Alternatively you can ask here and it will take us a couple of years to teach you the calculations :)
SO far we've not even covered the complex suspension settings, camber, castor, wishbone lengths etc etc. Get these wrong and you will get bump steer effects at front, back or both :(
Sorry but designing a race car from scratch stopped being a back-street-garage task about 50 years ago.

You are thinking about undertaking a very complex task.
You might want to research kits that meet the goals you've set.
There will be one out there !!

Someone else has done all the calculations and even better have then modified their deisngs based on EXPERIENCE of driving it. You will find that you will ahve to redesign parts as the foibles of the car surface on the track. That is time consumming an dpotentially expensive.

Sorry if this sounds too negative, but if you plan to be serious about racing than you're biting off more than you can chew based on the question you've asked here. Realising that now will be healthier for your bank account and mental health :)

V8turbo4me
05-17-2004, 05:45 AM
Well I don't think you realize how qualified I am to undertake in this endevour. I am an Engineering student and fully understand all the wonderful workings of the suspension. Also I am not really talking about building this car for club races because that is by no means what I wish to do with it. Yes I will drive it hard and fast on the backroads and hills but I won't be doing any endurance races anytime soon. So with the thought of competition out of the way my options are a little more open as you can see. Yes, I do plan on building the whole suspension and frame myself with the help of another engineer and a master mechanic with 27 years of racing experience.

I have a hard time believing that any front wheel drive set up or any renault short of full race is going to be able to handle much more than 300 horsepower, and that would be assuming that I could actually fit the unit to the engine.

Matra et Alpine
05-17-2004, 06:19 AM
Well I don't think you realize how qualified I am to undertake in this endevour. I am an Engineering student and fully understand all the wonderful workings of the suspension.
Sorry V8, it was your initial quesiton and comments about not knowing mid-engine layout made it sound like you didn't know what you were bgetting in to.
There are lots of public descriptiosn of lots of alternative mid-engine layouts. If you were more experienced I would have expected you to have questioned alternatives rather than open-ended.
My apologies.

Also I am not really talking about building this car for club races because that is by no means what I wish to do with it. Yes I will drive it hard and fast on the backroads and hills but I won't be doing any endurance races anytime soon.
OK. What kind of roads. Do you plan to take it on unmade or off-road ?
Again a totally different proposition :)

So with the thought of competition out of the way my options are a little more open as you can see. Yes, I do plan on building the whole suspension and frame myself with the help of another engineer and a master mechanic with 27 years of racing experience.
So what are you planning for the rear ?
Double wishbone will make it tight for space in the rear if you want reasonable suspension travel.
Trailing arm would be the easiest but most difficult to fabricate.
WIshbone and Macpherson would likely be easiest but then you need to decide which donor as that's not the kind of layout you can fabricate from scratch cheaply.
You will need to go round the design options a few times to decide what is easiest, cheapest and meets your needs.

I have a hard time believing that any front wheel drive set up or any renault short of full race is going to be able to handle much more than 300 horsepower, and that would be assuming that I could actually fit the unit to the engine.
The Renaullt transaxle I was talking of has been used in many sports cars and outright race cars. It's capable of taking 500-600bhp.
Lots of modern transverse boxes are capable of taking 300bhp.
You just aren't intriduced to them as Euroepan cars are generally frowned on beyond the 'luxury' names :(
The TRANSVERSE boxes I discussed I pointed out needed to be thought of in conjunction with the engine. So maybe you're engine is smaller :)
The weight balance is important and equally so trying to get good traction.
It's easy to put an engine/box IN, getting one in that works effectively won't be so easy. So maybe a smaller lighter engine is a better all round choice for performance. Could you afford a K-series engine/box and Rover suspension ? A good starting point.

If you are planning rough or off-road work, you need to look at narrow gearbox, long driveshafts.
Tarmac will involve less suspension travel and can handle a wide box/diff and short driveshafts.
You say you plan to build suspension.
What about driveshafts ? Are you also able weld and heat-strengthen components ? Again, if not - or cost-driven - then sourcing a complete engine/drivetrain AND suspension should be looked at.
This was VERY common in kit and mainstream manufacturers in the 70s. Studying their choices will help guide you.

Coventrysucks
05-17-2004, 06:39 AM
Have you looked at the chassis of the Ultima?

It is a 14ft mid engined sports car, designed to take engines over 500hp :)

Matra et Alpine
05-17-2004, 07:54 AM
here's some details of how small ( and fast ) it can be.
Versions of the ABS Frestyle do extremely well in the UK Autotest circuit.
http://www.funbuggies.co.uk/gallery.htm

V8turbo4me
05-17-2004, 07:12 PM
well I am planning on taking the car on tarmac roads and DEFINATELY not offroad! lol. Yes I have looked at the Ultima and it was key in my inspiration to undertake this project. I was planning on (this of course was when I was thinking of using a ford 9 inch rear end) using a satchell four link rear suspension to provide adaquate support to the axle and allow myself to achieve the highest amount of anti-squat possible without getting brake hop. I am planning on using an Independent suspension on the front obviously and I was thinking that I would probably use a double A arm setup that would allow the car to pick up some negative camber as the suspension went through its travel. My thought was that this type of front suspension would significatly help to negate the effects of any body roll.

Matra, I have actually heard of a lot of those european auto companies unfortunately their components are not easily obtainable over here in the states so I tend to rule them out for practical reasons. My reasoning for the open ended questions is that nothing that I have designed is set in stone yet and this project is still very much so in its infancy, I havent even sold my other sports car yet, so I was looking for opinions. And you have been very helpful! I am not really going to consider a smaller engine because the whole idea for this car was that it would be a turbo V8, something I have always wanted to do.

This brings me to my next question. I am planning on developing in upwards of 800HP on this car, now do you think that a twin set of TO4 turbos or one GT-45 or T-88 or comprable turbo would produce better response? Obviously with proper sizing neither set up should have much in the way of lag time, even the T-88 will get going pretty fast considering the large amount of exhaust gas it will be barraged with from a V8 engine. Again this is just a theoretical question, so if anyone has some turbo knowledge and would care to lend your expertise, please give me some input.

Matra et Alpine
05-17-2004, 10:35 PM
well I am planning on taking the car on tarmac roads and DEFINATELY not offroad! lol. Yes I have looked at the Ultima and it was key in my inspiration to undertake this project. I was planning on (this of course was when I was thinking of using a ford 9 inch rear end) using a satchell four link rear suspension to provide adaquate support to the axle and allow myself to achieve the highest amount of anti-squat possible without getting brake hop.
If I understand US terminaology, you are planning to use a rear diff ?
You won't have the space to fit a V8, then gearbox, then sperate diff.
Unless you are willing to push the driver well forward of the midship and legs between front suspension.
Normal mid layout is either
- transverse to shorten engine length - but often ends up taller.
- engine with transaxle - diff with gearbox behind cf a ZF race tran
- rear-engine is an alternative but makes the handling MUCH more difficult :)
Never seen a designer get the space to put seperate gearbox/diff with short prop. Is this what you are thinking ? ( Sorry but terminology makes me think it is )

My thought was that this type of front suspension would significatly help to negate the effects of any body roll.
With mid-engine you will have to spend much more effort on the rear geometry to prevent body roll as the main momentum force will be applied to the rears.

Matra, I have actually heard of a lot of those european auto companies unfortunately their components are not easily obtainable over here in the states so I tend to rule them out for practical reasons.
sounds a sensible idea :)

I am not really going to consider a smaller engine because the whole idea for this car was that it would be a turbo V8, something I have always wanted to do.
Good to know the aims and preferences. Understood.

This brings me to my next question. I am planning on developing in upwards of 800HP on this car, now do you think that a twin set of TO4 turbos or one GT-45 or T-88 or comprable turbo would produce better response?
The biggest challenge you are going to face with that amount of power is the heat dissipation. You may have to consider forced colling.
A single turbo will require you to route the exhaust gasses to one area and THIS will generate heat issues and the long pipes from header to turbo will make lag inevitable.
For a self-design ( rather than taking a 'stock' solution I'd recommend the twin JUST to get those hot spots low and to the outer edge of the engine where you can easily scavenge cool air flow.

We're needing to find a forum to share drawings :)
Maybe you can do a few sketches of the componenets you WANT to incorporate and we can then discuss the issues. I'm not aware of "satchell" suspension, but as he IS a respected US race designer from NASCAR days ( we do get SOME US coverage over here ) it made me think of live rear axle which is't on either. So before going further maybe a sketch or a link to description of the components of choice can help us move forward

Matra et Alpine
05-17-2004, 11:13 PM
got 15 mins to kill and did a seach.

Taking comments at http://www.427cobras.com/rear_suspension.html then I presume you are considering a live rear xle. Aint going to work for mid-engine.

Also that site is VERY dubious on it's suspension comments.
That a live axle is as good as IRS is just "BS" :)
On a theoretically smooth road and on cornering with NO body roll then it is possible to be equal. But in the real world. independant rear allows the designer ( and setup ) to dial-in the same live-axle characterstics AND to have thenm available over bumps and extreme cornering.
You can't make a live axle have compliant suspension AND corner well.
If it's stiff enough to keep the wheels planted then it will lift an inner wheel on cornering. If it's soft enough to keep the wheels down then it has horrendous body roll and the handling nightmare THAT introduces when driving real road twisties.

V8turbo4me
05-18-2004, 01:04 PM
Matra, I know your right about the live rear axle not working, that was just my original thought when I was thinking about this project. Also I know that an IRS would be the ideal solution if road adhesion is the goal but it is literally impossible to develope more than 30% anti-squat with an IRS where numbers over 100% are available with the live rear axle. Yeah, there are many challenges and compromises that need to be made and overcome in designing a suspension and there are a lot of factors that influence each decision. I am not sure what I am going to do exactly at this point in time, but hey thats why I am here talking about it with you. Sometimes you need to bounce ideas off of someone and you have been pretty good to me in that department.

V8turbo4me
05-18-2004, 01:52 PM
Well I guess my question now is does anyone know of any Transaxles that can handle around 800HP that can be made to fit a small block chevy V8? This where I am right now and I cant go forward at all until I have some answer to this question, lol it is kind of critical.

Matra et Alpine
05-18-2004, 04:00 PM
...it is literally impossible to develope more than 30% anti-squat with an IRS where numbers over 100% are available with the live rear axle.
I'd like to explore this to see if I can help.
What do you mean by "30%" ? and can we check what YOU mean by squat..

An IRS only tries to squat (one definition) when the diff is located ABOVE the wheel centre line. The squat is as the power forces the driveshafts to straighten. Once they're straight the challenge becomes them being allowed to move up or down again for as long as power is pushed.
If you can afford the loss in ground clearange to get the diff as close to centre line as poss then it will not be significant.
CV ( of whatever type ) can get to be expensive and or bulky for the torque you're going to apply, so that may be the limiting factor.

If you mean whole car squat that's a function of mid-engine I'm afraid.
You need weight to the front of the car if you want to utilise the weight most effectively to keep the rear up/nose down. Of course you could go for Citroen pneumatic suspension and with race settings you can make the WHOLE car squat as one on acceleration :) But that's old technology.

How much money are you willing to put to theis project ?
You could clearly get a second hand race transaxle like a ZF fairly easily.
But they are V expensive to repleace/repair gears :(

FOr home builds with LOTS of power, it pays to go look oat light truck/large vans. They are built to take lots of torque due to the high weights carried so there might be a local solution. ( Can't think of a UK equivalent, but you may have more luck )

Suggest a wander down to local stock car meeting and wander in the pits and have a chat with the guys for some inspiration. They ususally know 'strong' solutions :)

Matra et Alpine
05-18-2004, 04:07 PM
Well I guess my question now is does anyone know of any Transaxles that can handle around 800HP that can be made to fit a small block chevy V8? This where I am right now and I cant go forward at all until I have some answer to this question, lol it is kind of critical.
OK, thinking kits, I contacted a mate and he recommends talking to these guys about suitability of your proposals.
This is a GT40 kits using ZF transaxle - with prices :)
They sell kit with 400bhp, but should be able to advise what the trannie can take and options if it's too wek.
Good luck
http://www.erareplicas.com/gt/gt.htm

PS: Having a look at the site, I tihnk you can get MANY answers confirmed. The kit is described in detail including suspension, mounting etc.

Egg Nog
05-18-2004, 05:26 PM
Well I guess my question now is does anyone know of any Transaxles that can handle around 800HP that can be made to fit a small block chevy V8? This where I am right now and I cant go forward at all until I have some answer to this question, lol it is kind of critical.

Renegade hybrids does an excellent 914/Chevy small block conversion, and use different tranny set-ups for different power outputs. the Porsche 930 Transaxle can be used for street applications of up to around 700hp. They have adapter plates for a variety of choices.

Check it out here, at the bottom of the page:

http://www.renegadehybrids.com/914.htm

V8turbo4me
05-18-2004, 08:00 PM
wow, thanks a lot guys, you are super helpful. I know that it sounds kinda rediculous but I don't think that 700HP capacity is going to work, but maybe it will, I guess I could tone it down a bit, but thats not very much fun! I will check out both of those web sites.

I am willing to spend what it takes to do the project well. Emphasis on well and not to the best possible standards. That is not my aim with this project, perhaps once I have completed this car and see how I like it I will move on to greater things but for now I am just having fun here. As I said before though I would really like to have a transaxle that could handle 800 to 850 horses without problems or having to worry about snapping a gear or driveshaft.

I have decided that I will use a twin turbo setup for the sake of keeping a cleaner engine bay and to also keep the cooling situation at hand. I really like the idea of not having to fabricate eight into one headers, lol.

Egg Nog
05-19-2004, 12:25 PM
If you can afford it, I found an ideal engine for you... Banks Power's turnkey TT 6.0. 800hp, or if you want more, you can go all the way to 1600hp ;)

http://www.bankspower.com/twin-turbo-engine.cfm


By the way, I'm pretty sure that Renegade Hybrids would be able to set you up with a beefed-up 930 transaxle. They tend to do a lot of custom work, especially when it comes to handling more power.

V8turbo4me
05-19-2004, 01:37 PM
wow, Eggnog, you are also an extremely helpful person! I just can't get over how much positive feedback I have gotten. Do you think that Renegade would simply have the components to beef up a 930 transaxle to carry those kinds of loads? Also I am a little curious as to their pricing, it seems like they wouldn't be really high but I've been unfortunately surprised in many instances.

I know it is on a totally different note but do you think that a four wheel drive differential would be easier/cheaper to come across? or is a mid engine AWD/4WD vehicle just not really a feasable endeavour? You have to rember I am going to miss the AWD that my VR-4 runs when that car goes. though the extra driveshafts would add weight it seems like the overall performance of the car would improve.

Matra et Alpine
05-19-2004, 02:13 PM
I know it is on a totally different note but do you think that a four wheel drive differential would be easier/cheaper to come across? or is a mid engine AWD/4WD vehicle just not really a feasable endeavour? You have to rember I am going to miss the AWD that my VR-4 runs when that car goes. though the extra driveshafts would add weight it seems like the overall performance of the car would improve.
Definately not cheaper or easier to source and install an AWD drivetrain.
Also if you are mainly tarmac then you won't want to lose the power into the AWD drivetrain when a well-balanced mid-engine RWD will give better traction on all but the very tightest of corners.
To handle 800bhp, the centre diff will take a LOT of loading and will be very expensive to make it slip when required. With that amount of power, you're certainly looking at needing adjustable diffs and now you're into GroupB technology. Want to spend 50 grand on a drivetrain ?
There are plenty of sites and books on the GroupB cars, see what the 6R4, RS200 and 206T16 were doing. Have you thought about buying one of those and saving the hassle :)

V8turbo4me
05-20-2004, 06:43 PM
You are perhaps very correct there Matra. Maybe I should consider turning the power down a bit and get back to what was my original goal of awesome handling and great acceleration and braking. Here is the deal though, I still want to produce about 700-750 hp at around 12psi of boost from dual turbo chargers, though I am considering boost levels from 8-15 psi. I was wondering about what size block and what compression ratio you guys think I should run. I would like to use 93 octane gas in the car which would have dual intercoolers to occumpany the turbos. If you have any suggestions please let me know, I would love to hear them, always looking for input.

mechanixfetch
05-20-2004, 07:18 PM
Matra, I have actually heard of a lot of those european auto companies unfortunately their components are not easily obtainable over here in the states so I tend to rule them out for practical reasons
well you seem to be planning on spending a whack load of money so wouldn't the cost of shipping the parts really end up as being inconsequential anyway? Why sacrifice tried and tested performance and use when you want to build the ultimate car?

V8turbo4me
05-21-2004, 01:11 PM
Well I'm not really planning on spending a "whack load of money" and I don't intend to settle for a transaxle that will not have the capabilities I need it to have. A transaxle from a renault is obviously not going to have ideal gear ratios for a V8 engine so I don't think I want to go that route either. I also looked into the porsche 930 transaxle and it really isn't that great of a deal, It would be about $8000. That is a lot in my opinion for a transaxle that will be overstressed and out of date reguardless of how much it is updated. So again, I am looking for suggestions on a transaxle.

Matra et Alpine
05-21-2004, 06:14 PM
Well I'm not really planning on spending a "whack load of money" and I don't intend to settle for a transaxle that will not have the capabilities I need it to have. A transaxle from a renault is obviously not going to have ideal gear ratios for a V8 engine so I don't think I want to go that route either. I also looked into the porsche 930 transaxle and it really isn't that great of a deal, It would be about $8000. That is a lot in my opinion for a transaxle that will be overstressed and out of date reguardless of how much it is updated. So again, I am looking for suggestions on a transaxle.
First, the Renault transaxle is used by serious racers and is often used in GT40 kits with BIG V8s.
It IS good for lots of power and my A610 manages 0-60 in 5.5 and 165mph in factory condition. So I'd not dismiss it so out of hand perhaps :)
"out of date" ? for a transaxle. With the exception of computer controlled LSDs then I'm afraid not much has changed in gearboxes in 50 years. So not sure what you are looking for :) I presume you are still lookign for manual as auto's are the only area of major improvement over the years.
The ZF transaxle range is one of the most widely accepted competition setups and is used in may different formula's/ Not much is diffferent from the ZF' of 20 years ago.
We're trying to help, but I'm not sure of the decision-making and it makes it hard to suggest alternatives.

V8turbo4me
05-23-2004, 08:32 AM
I didn't mean out of date as far as technology is concerned I am talking out of date as in out of time, all things wear over time as more and more stress is applied to them. I am planning on putting a lot of strain through whatever transaxle I end up with and I need to be confident in its ability to take that strain without giving due to fatigue in the components. And yes I am looking for a manual, either a five or six speed and preferably with overdrive but not necessary. The renault transaxle is something I will seriously consider if you can prove to me that it can handle the stress, I need to say that I am by no means dissmissing any transaxle at this point. I was even thinking that maybe I could have some work done to a pontiac fiero transaxle, but there again the gear ratios will be horrible for an engine that developes 700+ HP. I am looking for a transmission that has shift points at around 45, 85, and 125 mph at 6000 rpms. Actually I would prefer that first go faster than that because by the time the turbos kick in I will already be going 25, so 0-55 in first would be ideal, but maybe not attainable with anything short of a ferrari gearbox.

sandwich
05-23-2004, 09:53 AM
daaaaaaaaaaaaaaaaaaaaaaaamn did i come to this thread late. I could've saved you a lot of time.

I recently tried to build a kit car with dreams similar to yours, albeit significantly smaller in scale. 700-800hp is wacky, and you will likely find yourself playing the "bigger turbo, bigger tranny, bigger turbo, bigger engine" downward spiral until your wallet kills you or you end up bankrupt.

Why don't you aim for a more reasonable 650 hp, or a n/a 550hp ish design? I can promise you this- if you can't afford an 8g 930 tranny, you can't afford anything with 800hp.

the options are:
porsche g50/52, five or six speeds, ~500hp capacity, needs to be inverted with a few mods. You can get them through various places, including ultima, for about 5gs or more, depending on your desires. Chevy's are the engine of choice.

930, from a porsche, 4 speeds, 750hp capacity, good gear ratios. Problem is, you WON'T find one for under $3000 in any good condition, and then you have to give it to renegade to have it converted so you can actually use it in a mid-engine design. Renegade WILL charge you an arm and a leg for anything they do. They can charge you whatever they want because nobody else will do what they do. Good finished project, but expect to spend money, and lots of it.

Audi 5000, 450 bhp, buy an adaptor plate from kennedy engineering, and drop it in. It's not 800hp, but you can drive it, and buy about 30 of them for the same cost of one 930 transaxle with no mods.

The fiero can hold about 450 hp, the ZF is way up there. The problem with the ZF is that you're stuck with a ford and you're looking at 5-8g's. I'm not sure of hp, but i wouldn't put it past 750.

You can probably get something to hold 800, but it'll be custom and it will cost you your firstborn son.

As for the renault transaxles that matra is pimping, the only renault trannies in the us can hold like 150hp, and have no place in a performance car. If you want to pay the 1g or more to get a french tranny shipped, then more power to you.

If I were you...I would try to put the engine of your 3000gt in front of the rear wheels. You can use a suzuki samurai transfer case, with no rear driveshaft, locked, to drive a 3-piece driveshaft with carrier bearings back to the front wheels, flip your rear differential and mount it in front, and you now have a 300hp twin turbo, v6 awd mid-engined car. You will of course have to weld in a firewall, a roll cage, and significant rear end stiffeners, not to mention some custom driveshafts. The actual cost of such a project, lots of time and research, ~1000 in driveshafts, 850 for the samurai Tcase (http://www.high-impact.net/transmission_and_gear/),and maybe 1000 in other parts (eg cable shifter, air intakes, wiring, etc). I thought about doing it to an eclipse, and I almost did it to my old kit car, which I sold for similar reasons, btw. I just don't have the garage space or the experience that you might.

For referance I'll include some other pictures of a few midengined frames. One of them used to be mine. Lots more available http://community.webshots.com/user/dileu16 .

Hope this helps, i have lots more info if you'd like, this is just the summary.

V8turbo4me
05-23-2004, 02:49 PM
Thanks alot Sandwich, that was nice of you to come in and contribute albeit late. Do you think there is anyway to strengthen a fiero or audi 5000 transaxle to about 650 hp capacity? I guess I am really big on the fiero because it is so easily accessable for me here in the midwest, so I thought maybe shot peening the components or maybe someone out there does upgrades for the fiero or audi transaxle. Its not that I don't have the money to buy the other transaxles it is just I would rather not waste money that I don't need to waste. I do have lots of garage space and time though, I have a three car garage that is my "big boy play house" I am by no means going to start chopping my poor VR-4 man, lol, that car is going to be a collectors item someday and is a great car now, it doesn't need to go under the knife.

sandwich
05-23-2004, 08:44 PM
www.v8archie.com

If there is any question of a fiero transmission's reliability, he can answer it. I honestly do not think the fiero can hold much more than that, but you never know.

I don't think the audi can be beefed up too much. I have heard someone flew all the way to england to do it (someone over there had the ability to machine gears for it) but they wanted like a year to have it done, etc. etc., and it wasn't a very good option.

I still think your best option is to go for a zf or g50, converted. It's a good step, cost is not too high, comparitively. If you get a fiero tranny, the trans itself will cost next to nothing, but expect to put several thousand into building it up. Even then, it's still transverse mounted.

Do a search for ultima gtr, and poke around a little. The g50 can hold 550 easily, and i do believe I heard of one that had 650 or 700 and ran in the texas high-speed cross state race. I got a ride in one, and I can safely say it is an excellent way to go.

I was at the carlisle kit car show this weekend....audi transaxles are the hot sh.t right now, they were even in some very high end gt40s. The top of the line racing ones had ZFs, however. It all comes down to how deep your wallet is...the more you spend, the more you get.

sandwich
05-23-2004, 08:54 PM
also, check out some forums and kit car sites.

Ones to note:
www.lambolounge.com
Incredibly helpful, lots of trans info.

There are also a lot of kit car clubs in yahoo groups. I would encourage you to become a member of some, like mantacars, kelmark gt, etc.

You are building a kit car, so keep that in mind. Magazines like kit car will help. You may also want to talk to some gt40 manufacturers, like

era cars,
roaring forties,
lone star motors.

kitcar.com, kitcars.com have some good info.

transaxleengineering.com, kennedyeng.com, have good info.

There are three companies making porsche adaptors, kennedy, renegade, and another, starts with rod, maybe rod simpson hybrids? All are similar in price.
http://www.porchev.com/ (Rod simpson- i was right).

V8turbo4me
05-27-2004, 02:57 PM
Just need to say thanks again for all the info and if you find anything interesting please let me know.

veloce
10-15-2008, 10:05 AM
Just need to say thanks again for all the info and if you find anything interesting please let me know.

It has been awhile from this post....just wondering if you have been able to start on your dream project?

SIMPLETON
10-16-2008, 12:23 PM
If your not dead set on using a V8 then you could use a subaru flat 4 or flat 6 with its tranny and block out the rear drive. These engines are really short front to back but might be a little wide depending on your design constraints.

cmcpokey
10-16-2008, 12:53 PM
It has been awhile from this post....just wondering if you have been able to start on your dream project?

Last Activity: 06-13-2004 02:15 PM

hasnt been on for a little bit. dont think he's checking this anymore

Mr-Supercar
12-02-2008, 10:00 AM
im thinking the same as you. im designing my car now its a cross between a pagani zonda, noble m15, ferrari 360, and a super touring car it touchs the zonda and super touring car the most i was thinking of using the 572 chevy big block but it would have had to much power so im dropping it to 600hp im just having trouble finding the engine. im no mechanic but im looking into it suspensions etc you know the drill. if anyone could help me in explaining the parts needed i have the money to dip in but im just not sure how this works btw 800 thats gonna be a beast. good luck who knows we might end up producing our cars in the future

Rockefella
12-02-2008, 12:40 PM
im thinking the same as you. im designing my car now its a cross between a pagani zonda, noble m15, ferrari 360, and a super touring car it touchs the zonda and super touring car the most i was thinking of using the 572 chevy big block but it would have had to much power so im dropping it to 600hp im just having trouble finding the engine. im no mechanic but im looking into it suspensions etc you know the drill. if anyone could help me in explaining the parts needed i have the money to dip in but im just not sure how this works btw 800 thats gonna be a beast. good luck who knows we might end up producing our cars in the future

A 572 probably isn't the best choice for something in the realm of a 'Pagani Zonda'. You'd be better off going with an LS7 if you have money to dip into.

Mr-Supercar
12-04-2008, 07:10 AM
yea but i was looking in the region on 600+ hp naturally aspirated engine but maybe the LS7 isn't so bad do you know the price range ?

Simon_Tuman
06-17-2011, 11:06 PM
Lets bump this thread back up, but lets try to bring it back down to earth. I'm in the process of building a car Ive dreamt about for years. Its an A1 chassis Volkswagen. It also has a big hole cut in the rear. Ive always wanted to build a mid engine/ rear wheel drive Jetta Coupe. I saved this car from someone else who gave up on the project. He got as far as cutting the hole in the back. The jetta coupes are fairly rare, but they are basically a rabbit (or golf) with a trunk...

Ive done a bunch of research so Im not asking how to do everything, but more about how I can achieve that elusive 50/50 balance.

Heres the basic plan. Take the entire motor and drivetrain and move it into the back. simple right?

Some rough numbers to get us started. Factory curb weight is right around 2000lbs and roughly a 60/40 fr/rr bias. so lets say thats 1200lbs in front and 800 in the back. Im estimating the motor/ trans combo to be around 400 lbs so by moving that to the back we can flip the 1200fr/800rr to 800fr/1200rr and shifting the bias to 40fr/60rr. obviously this isnt a real world number, but it should give us a place to start... so now we need to move 200lbs back over the front wheels to get it to 50/50. i know it will be difficult getting it to 50/50, but thats my target, the short wheelbase will already make it tail happy. i really want this car to handle and it will probably be a track only car because it might be hard to make a car like this street legal.

ive already decided on a few things. radiator will be mounted up front in the stock location.the fuel tank will be right in between the strut towers in front and the battery will also be in the front. i dont think thats enough weight in front though...

motor and trans will be mounted to an A2 subframe and I will be fabricating frame rails in the back so the whole subframe can be dropped effectively getting the entire motor and transmission out without too much difficulty.

i can go on, but ill end this first post now and post some pics of the project car

Simon_Tuman
06-17-2011, 11:15 PM
heres where it has been for the last 5+ years

http://img.photobucket.com/albums/v290/2manvr6/the%20other%20coupe/timetomove.jpg

the hole
http://img.photobucket.com/albums/v290/2manvr6/the%20other%20coupe/empty.jpg

another view from when we pulled the planned motor out
http://img.photobucket.com/albums/v290/2manvr6/the%20other%20coupe/motorout.jpg

thats a VR6, but Im planning on starting with a 2 liter 8valve motor with a 16G turbo from the mitsu EVO8. i already have a ton of parts ive been gathering.

as far as suspension goes, in the front i will raise the strut towers and just run a stock A1 setup up front and I will be fabricating new struts towers in the back using essentially an A2 front suspension in the rear. koni adjustables and ground controls, front and rear anti-sway bars. full cage, gutted interior, with a dash and one seat... i think that covers the idea behind the car

ok so ill stop here and wait for some responses, but here are the overall goals of the car. as close as possible to 2000lbs wet, 50/50 power should be around 300bhp, though I think I can get to 300whp without getting too wild on this first setup.

culver
06-17-2011, 11:29 PM
Why do you want 50:50?

Simon_Tuman
06-17-2011, 11:35 PM
why not? the few people who have converted FWD VWs into RWD VWs all complain about how tail happy they are so Im trying my best to build it properly. most are hack jobs or have everything in the back and nothing in the front. do it right or do it twice right?

culver
06-17-2011, 11:59 PM
Again, why 50:50? What makes you think that is the number to shoot for? What makes you think the problem with the other cars was a rearward weight bias vs poor suspension?

Simon_Tuman
06-18-2011, 09:36 AM
Culver, thanks for challenging my thinking. I decided I better do more research and found a great archive

http://www.ngnl.net/hall.pdf

Though I didnt understand everything stated 100%, I will be reading it over and over until I do. I also have some books I have been reading about suspension design and race car dynamics. The article above dispelled my determination for 50:50 bias. Thinking about it more, I am willing to bet most of the people who gave up on the rwd VWs werent used to having a cars ass swing around nor were they designing a car to be a competitive track car, but more for the purpose of rear wheel burnouts lol. ... i must admit years ago that was most of my motivation too, but as the years have progressed and Ive gotten older (im turning 30 in a few weeks) I really want to build a car that satisfies my love for racing and my love of vws and having a dedicated FWD race car just doesnt seem to fit the bill, so now this is the car that will.

culver
06-18-2011, 12:02 PM
I'm glad you caught on to what I was saying. Many people read the marketing stuff and assume 50:50 is ideal. At one point I believe most of the marketing stuff as well (Hp/L, 50:50, etc). Once you start asking WHY you find that often it isn't what we think. I think my favorite is the Corvette guy who replaces the leaf spring with coil overs because he knows he want's "independent" suspension. Then he asks the forum if he should remove the roll bar while he's at it!

Here's a post I did a while back.

I put this post together to look into the whole matter of 50:50 weight distribution. I’ve seen this come up many times and I suspect that many people don’t know why it is good or when it may not be good. I have a friend with a BMW who swore the car handled well because of the 50:50 distribution. He seemed to have overlooked so many other reasons and stuck with the one delivered by BMW marketing. Of course please keep in mind that I am going into general terms and the handling devil is often in the details.

As for 50:50, it’s not really the best but there are reasons would want it. For straight line pure performance cars you would want a rearward weight bias. It helps in both acceleration and braking. It’s in cornering that we have to look at the details.

Start with changing direction. When changing direction the front tires act like a lever turning the car about the center of gravity. When dealing with a lever a longer lever always makes it easier to move something. So how do we get a longer lever, we either make the wheelbase longer or we move the CG back. A rearward weight distribution will move the CG back and effectively act as that longer lever. This is why mid/rear engine cars typically have very quick steering response.

Now that we have started to turn we need the tires to hold that turn. The next thing we need to know is that tires grip more with more weight (go figure) BUT the increase in grip is proportionally less than the increase in weigh. So if increase the load on a tire from 500lb to 1000lb you will not get twice as much grip. Also, grip is proportional to area. This is a surprise to no one. We all know wirer tires grip more than skinny ones.

So you want to pull some Gs while turning. Well if you are going into a turn without accelerating or decelerating the lateral load on the tires will be split between the front and rear wheels based roughly on weight distribution. So if you have 50:50 weight distribution half the cornering load will be on the front axle. That works out nicely for most cars as they normally have equal sized tires front and rear. However, if we have more weight in front we would want larger tires in front to balance out the grip (GM does this on the V8 Grand Prix). If we have more weight in back we want larger tires in the back. The larger tires, in combination with the heavier load effectively make it so that the front and rear tires have the same load/ square inch of contact pact. That will make the front and rear tires slide at the same time (neutral handling) when cornering. It may seam odd, but GM put larger tires in the front of the Grand Prix because that makes the car more neutral rather than understeering.

So what about braking while turning or accelerating while turning. Each of those will transfer weight fore or aft while cornering. Shifts in tire size or weight distribution can make the car under or oversteer more or less based on the same principle I mentioned above. Increasing the front tires in size or adding load relative to the rear will make the car more likely to over steer at the limit (not talking about initial understeer). Going the other way makes the car more likely to understeer.

So do we still want 50:50 weight distribution? Well that depends. If the car is FWD, 50:50 doesn’t help acceleration. That rearward weight shift moves too much weight off the front wheels and we get wheel spin. For that reason I might want my FWD car to be nose heavy. Of course I can deal with some of that nose heavy understeer with some larger sized tires in the front and suspension tuning. Then again, most people would prefer equal sized tires just for convenience. For the other reasons (braking, cornering) we would want a rearward weight bias even in a FWD car.

In a RWD car we don’t need weight over the front axles for acceleration so we want something like 50:50 or even rearward biased. If we are going to have equal sized front and rear tires we want around 50:50. That will help keep the car approximately neutral in most handling situations.

If we aren’t stuck with equal tires front and rear then a rearward weight balance can work quite nicely.

While many car companies love to brag about the 50:50 weight distribution, it’s really only good under certain circumstances. Depending on other design decisions it may be undesirable (FWD, RWD with a rearward weight bias and wider tires in back).

PS: The above is certainly not the end all be all on this subject. There are lots of detailed reasons why designers may want to do something different than what I have listed above. All that typing is largely meant to illustrate why something that many people think is a pillar of handling isn’t a pillar in all conditions.

Matra et Alpine
06-18-2011, 12:57 PM
Another very important point when looking at cornering in particular is the "polar moment" which is sinmply where the weight is in relation to the centre of the vehicle.

So if in trygin to get 50:50 with a rear wngine you then try to put lots of stuff as far forward as possible - because that will get 50:50 then you ahve something VERY bad.
As much as possible you want all weigh in the centre of the car. So if the car is 1m behind the centre in "theory" you want to put the same weight 1m ahead. WHcih is half the weigth, 2m ahead. Not do that and that weight 2m out acts differently during cornering and is bad. So often you DONT go 50:50 so that you can keep the polar moment of the mass closer to centre !

But as this all depends on steering and suspension and at the end of the day are you wanting a car that "drives" or one that can win autosolos ? :) Because getting the weight and handling is the bigger challenge than just gettin gthe engine/drivetrain in which is going to be a hard enough task :)

Best of luck with it and look forward to reading further musings !!!

pimento
06-18-2011, 07:00 PM
I often see 47:53 being referred to as perfect, I think the idea being that you have more weight over the rear for acceleration then when you brake the shift forwards tends to even things out. I think that was in regards to FR cars though.

culver
06-18-2011, 10:10 PM
I'm not sure there is a "perfect". It depends greatly on the tires. The Panoz front engined sports racer of about a decade back was front engined in part because they figured the rules allowed more front tire than most rear engined race cars (mid engine in street car parlance) needed yet less rear tire than they wanted. In order to offer a weight balance that was more appropriate for the tires weight was moved forward. Conversely, the old 1970s F1 cars as well as the proposed Delta racer are very rear heavy. If you are expected to use equal tires all around I would say you would likely want something closer to 50:50 vs a car with staggered tire sizes.

If you have a FWD you don't want 50:50, you want forward weight and possibly larger front tires.

RacingManiac
06-19-2011, 06:27 AM
If you have a FWD you don't want 50:50, you want forward weight and possibly larger front tires.

Essentially you'll want the tires balanced to your weight distribution....regardless of the drive wheel, since that will dictate the amount of the available grip at that given axle. With some margin to the amount of abuse the axle might see.

Most RWD sporty cars(front engine) features staggered tire width with width biased to the rear despite them being possibly closer to 50/50 distribution. But you rarely see that FWD car does the opposite. I think that is mostly due to the nature of many of those cars. FWD car are more typically seen in cost conscious platform and that for an OEM, a staggered design means more cost on wheels and tires. Where as on the sportier car their higher price will mean better margin for them to "do it right"....Interesting to see though I think now the new RS3 from Audi(front engine, AWD, based on a FWD type design), will actually feature wider front tire....a concept that'll be more suited to its weight distribution...

Matra et Alpine
06-19-2011, 06:38 AM
IN racing saloon cars with same wheel sizes all round you'll see the tyre pressures radically different front to back to get the same control over grip you seek with weight balance or tyre footprint :)

RacingManiac
06-19-2011, 06:41 AM
I often see 47:53 being referred to as perfect, I think the idea being that you have more weight over the rear for acceleration then when you brake the shift forwards tends to even things out. I think that was in regards to FR cars though.


I think that can apply to all rear drive cars....and its possible to see the rational to it also. Most cars are capable of much better braking performance than they are accelerating forward. Given rearward bias will allow for the drive wheel to have more advantageous setup. I'd also imagine that in the past when you might be more limited to braking power, a 50/50 car is fine for not over stressing the front brake/tire as your weight transfer might be limited dynamically. But as modern tire and braking system are capable of more, more severe weight transfer to the front will mean that if you can get the rear to do more work under braking, will help you in those situation. 911s typically are pretty good in braking situation since in those cars the they have more work done by the rear wheel due to their wacky layout....So if you can get a more rearward bias car you can help out the cause...

Interesting to note that nowadays in even modern racing we are seeing a shift to more forward weight distribution. Most LMPs now are probably closer to 45/55 if not 50/50....and with them also using the front tire that are much closer to size to the rear. The same shift was happening to F1 also as Bridgestone(before the last season where they changed the balance of their front to rear) and the current Pirelli both produce much more front "biased" tire to give them that more "positive" front end. My guess is that since you will be quite severely traction limited in those formula due to the tire regulation that a shift in design focus toward a car that is more balance in cornering and braking(more so, not to say LMP/F1 car were not before) means more gain overall...

culver
06-19-2011, 09:56 AM
Essentially you'll want the tires balanced to your weight distribution....regardless of the drive wheel, since that will dictate the amount of the available grip at that given axle. With some margin to the amount of abuse the axle might see.

Most RWD sporty cars(front engine) features staggered tire width with width biased to the rear despite them being possibly closer to 50/50 distribution. But you rarely see that FWD car does the opposite. I think that is mostly due to the nature of many of those cars. FWD car are more typically seen in cost conscious platform and that for an OEM, a staggered design means more cost on wheels and tires. Where as on the sportier car their higher price will mean better margin for them to "do it right"....Interesting to see though I think now the new RS3 from Audi(front engine, AWD, based on a FWD type design), will actually feature wider front tire....a concept that'll be more suited to its weight distribution...

GM did larger fronts with the last gen V8 Grand Prix. One of the auto rags noted that it did help the handling.

Ferrer
06-19-2011, 10:29 AM
This was also the case on the front wheel drive V8-engined Impala SS, wasn't it?

Simon_Tuman
06-19-2011, 10:54 AM
Great info everyone, I really appreciate it.

So my next question would be in regards to the cooling system and the stuff placed up front. Im still keeping the fuel tank, and the battery up front, but should I still keep the radiator up front. I think from an airflow standpoint the stock location is best, but it creates other issues like having all that coolant flow from the front of the car all the way to the back. I think its fairly straightforward, but it creates possible problems with air in the system and I imagine I would need a 2nd pump up front to push all the coolant to the back. For packaging reasons it would be nice in the back, but I just dont see enough airflow on the sides of the car without substantial body modifications (like the renaults) to draw air into the radiator. One guy mounted the radiator in front of the motor (behind the driver) and wanted to draw air up from underneath the car, which I think is a bad idea.

What ideas do you guys have for this piece of the puzzle?

culver
06-19-2011, 12:18 PM
This was also the case on the front wheel drive V8-engined Impala SS, wasn't it?

I believe the Impala didn't use the staggered sized tires. I might be confusing which used them but I recall the article specifically mentioning the larger fronts made the cornering more neutral.

culver
06-19-2011, 12:20 PM
Great info everyone, I really appreciate it.

So my next question would be in regards to the cooling system and the stuff placed up front. Im still keeping the fuel tank, and the battery up front, but should I still keep the radiator up front. I think from an airflow standpoint the stock location is best, but it creates other issues like having all that coolant flow from the front of the car all the way to the back. I think its fairly straightforward, but it creates possible problems with air in the system and I imagine I would need a 2nd pump up front to push all the coolant to the back. For packaging reasons it would be nice in the back, but I just dont see enough airflow on the sides of the car without substantial body modifications (like the renaults) to draw air into the radiator. One guy mounted the radiator in front of the motor (behind the driver) and wanted to draw air up from underneath the car, which I think is a bad idea.

What ideas do you guys have for this piece of the puzzle?

No great idea there but many old race cars used from mounted radiators. Perhaps you could post the question on Apexspeed where someone might know about old front cooled Formula Fords.

Matra et Alpine
06-19-2011, 03:25 PM
Matra used the front rad, rear engine in road cars fine :)
Alpine did it in all the competition race/rally cars.
So did imps and most cars with high power/engine-size.
Just use nice big bore pipes. One pump is sufficient.
If you were trying to get >200hp/litre then you MIGHT benefit from an additional pump to assis, but electric is simple to add.

Magnum9987
06-19-2011, 05:12 PM
All that tire size/weight distribution stuff is some good stuff. It makes for some great reading. :D I can't help with that but I will provide some input with the radiator placement.

No, an additional pump shouldn't be required. Air in the system shouldn't be a problem as long as you do a proper coolant system bleed. Once you got the coolant in, run the engine until the water pump turns on, and let all the air out, and add coolant until bubbling stops.

Matra et Alpine
06-20-2011, 02:55 AM
^^^ self-run piping - esp larger bore - can be a pain to avoid any pockets where air can remain trapped.

Even if so, dont panic, an adjunct to Magnum's plan is to use what became standard for the Matras..

First have a fill point manifold at the engine side and as high as you can get it. THEN make up a "header tank" that screws on the fill cap and is basically 1m of 2" copper pipe and a small tank on top. Fit and fill and then follow magnum's procedure and now run the engine till very hot and rev it so the mechanical pump is working hard. The "header tank" of fluid means there is always a positive pressure to fill any voids, reduced aeriation and saves you having to keep an eye on it.

Based on experience, the Matra you could bleed "normal" and STILL find it gurgling in the paddock after a hard session :( Never had it after I'd made one of these - copied from other Matra owners :)

However for just street use a small air isn't going to be a problem :)

Badsight
06-22-2011, 02:57 AM
I'm glad you caught on to what I was saying. Many people read the marketing stuff and assume 50:50 is ideal. At one point I believe most of the marketing stuff as well (Hp/L, 50:50, etc). Once you start asking WHY you find that often it isn't what we think.the Ultima GTR is an excellent example . it was a race winner in the 80's/90's before they started banning it

its got a 65-35 distro - far from the supposed ideal but with excellent handeling

btw - isnt the coil-over swap for Corvettes the way to go to improve their handeling ?

Matra et Alpine
06-22-2011, 03:28 AM
It was the Mk2 a differnet chassis that was the winner and Ultima love to cite "we were banned because we were too fast" when in reality they were "banned" ( along with lots of other prototypes ) because they didn't confirm to the emerging production, safety and weight standards set to make the sport safer.
Look at some of the spaceframe crashes of the 80s and you'll see why :(

Badsight
06-22-2011, 03:45 AM
yeah its one thing to hang steel pipe together for suspension forces, quite a step up again to have a properly deforming crash structure

the GTR kit they sell now is a beast all the same.

culver
06-22-2011, 06:39 AM
btw - isnt the coil-over swap for Corvettes the way to go to improve their handeling ?

Yes and no. There is no issue with the leaf and handling. However, the leaf spring rates were chosen as a compromise between ride and handling. If you want sharper handling you may need a stiffer spring. There are only a few options for replacement leaves. If none have the spring rate you want then you have to go coil over. The leaf would be replaced for the same reason the coils on a Miata would be replaced to improve handling.

The other part of the equation which is really the big part is replacing OEM dampers with far more expensive aftermarket units. OEM dampers are almost always a compromise (the mag dampers are perhaps an exception) between cost, supplier certification, etc. Also with the OEM dampers again you get what the manufacture considered the best trade off not necessarily what YOU think is the best ride handling cost trade off.

So yes, you may end up with better handling with coil overs but you likely would get that same better handling if you could get the aftermarket damper and an equivalent rate leaf spring.

Matra et Alpine
06-22-2011, 06:57 AM
"if" :)

RacingManiac
06-22-2011, 07:38 AM
I think you can also run coil-overs that adds to the factory leaf. I think the current Callaway Vette is config as such. Being springs in parallel the rate will be additive to the stock rate.

Matra et Alpine
06-22-2011, 11:23 AM
^^^ oooo, that's generally not clever :(
The RS200 was hyper critical on settings on the double spring/damper on each corner on tarmac !!
They can set up their own harmonics. Differencies in spring rates cause transitions in forces at the suspention connection point.
You got details on the car and where it's used ?

RacingManiac
06-22-2011, 12:06 PM
SuspensionProductsPage (http://www.callawaycars.com/callaway/main/contentpages/products/SuspensionProductsPage.htm)

".....companion helper and tender springs supplementing the OEM composite leaf springs..."

I'd imagine the rate on those spring to be relatively low since I'd guess being a rather sporty car the stock rate is pretty high already....

edit: the blurb underneath has a decent explanation...

Matra et Alpine
06-22-2011, 12:10 PM
CHeers RM, can see the appeal ....

We do not put the full spring loads of the suspension through the shock towers. First they were not designed to carry those loads
So they must have been limited in control if the towers flexed :(

RacingManiac
06-22-2011, 12:12 PM
This I guess also avoid hacking up the chassis more....otherwise they need to add bracing to it.....

TwiceBaked
08-06-2011, 10:13 AM
Good read. Thanks. Building a 1973 Lamborghini Urraco to 2011 mid engine design. I know its weird but I have a reason.. See I rebuilt this car 30 years ago.. Now no more transverse mounted lil V8 going to go mid engine V8. Audi 4.2l mounted to triptronic transaxle. Want to figure a way to bring the quatro drive back into play.. Yup I know weird

csl177
09-15-2011, 02:20 PM
^^^ Whaaa? to that last sentence. Please explain "OHV are tempermental". No gibberish. C&P from any engineering paper if you wish.

Magnum9987
09-15-2011, 02:43 PM
If you have any doubts about the OHV engine you need to talk to the Corvette Racing Team with their "outdated" OHV engines revving to 8 grand for 24 hours strait and winning in their class 8 years in a row, with 72 victories. And lets not forget Cadillac Racing entering the scene, or the stellar season the Camaro GTRs had in ALMS.

Yes, the OHV engine cannot rev as high, for as long, but a slew of aftermarket parts (for beer money, I might add) will remedy that. And OHV engines generally have great low end torque because they are so huge, but a good choice of cams/heads will allow you to build an engine with power anywhere you want in the rev range.
And I will tell you right now that no OHC American V8 is a cheap as an OHV one. Nor will any OHC (American) V8 perform as well or as reliably as an OHV one.

Magnum9987
09-15-2011, 03:30 PM
I can understand your qualms about the unreliability. It used to be that the pushrods would have solid lifters in conjunction with early flat tappet cams, you would have to adjust the whole setup every 500-1500 miles depending on make/model/mechanic. But the combination of roller cam and hydraulic lifters have completely eliminated that practice. Adjustments only need to be done during tune ups. GM includes valve adjustment in the 60k (miles) service.

While I can't know for sure, the combination of fewer cams and valves, it would mean the same if not fewer moving parts. The real issue is that those parts can get very heavy. But again, the after market has a massive variety of lightweight aluminum and even titanium parts available. NASCAR, the NHRA, and the various GM racing teams all use titanium valve train parts and bespoke carbon fiber pushrods. In conclusion, the OHV engines limitations are up to the builder and the parts they want to invest in. And in the end you will get alot of power on a good budget.

culver
09-15-2011, 04:27 PM
There is NO reason to avoid OHV vs OHC engines. Of course there are very few modern OHV engines commonly available. The GM LSx and Chrysler HEMI models are the only recent, large volume pushrod motors. The GM motors are great for kit car projects if you are looking for a motor of that size and power.

Anyone who suggests a modern pushrod motor is temperamental is simply wrong. Really, for both OHV and OHC engines, how many of the problems are related to the valve train class?

Magnum9987
09-15-2011, 05:01 PM
I am legitimately curious about what you are saying. I too clicked on this thread because I was also deciding on a mid-engine powerplant, albeit in the past, and wanted to offer advice upon the basis of my conclusions that I myself had come across.

Could you recommend me an engine for a good price. Preferably a link as well.

Their are dozens of engines to choose from. I'm a GM fan, so I'll always say any Third or Fourth Generation LSx motor is a solid choice. But any Gen 2 with hydraulic lifters is a solid choice as well, if not as powerful, efficient, or reliable as an LSx, but much cheaper, and easier to work on. All of these can be bought brand new at GM Performance Parts (just google them). But any junkyard will have Gen 2 small blocks, and theirs a high chance LSx motors, but most likely truck motors (or Vortec) motors. Those can handle HUGE horsepower, for cheap too, but high in the rev range. Hot Rod magazine took a 4.8l Gen 3 Vortec to 1200+hp with Ebay turbos and a virtually stock engine with only a new cam, valves, and a new intake manifold. And it did it over 60 dyno pulls, without a hitch. With minor mods, it will reliabely (sp?) put out 600-800 hp. Any LS engine is like that.

While I am not a Ford fan in anyway, I must admit the Windsor 5.0 motor is a solid choice. And thats about it from ford. Their previous Y block cannot handle any power at all, they only have 10 bolt heads, so they can only have relatively low compression, and can't handle as much boost. The water pumps have 14 bolts though, so by god the water pump will never fall off! :p Ford has their own performance division, but I do not know the actual name, but I assure you a quick google search will find it.


I will never recommend a Chrysler motor. Yes, the HEMI is a legendary motor, steeped in tradition. But they simply are not reliable. The new ones, are much more reliable, but they are much more expensive than any GM motor, and again, not as reliable. And parts are much more expensive as well, harder to work on, and higher maintenance. They can handle minor mods, but not much more. If you are interested, look up Mopar Performance Parts.

culver
09-15-2011, 06:07 PM
I think this backs up my statement of it being temperamental. Although, this isn't for all motors as of today;

http://en.wikipedia.org/wiki/GM_LS_engine#Problems


Trouble spots can be found for many many engines. The Mazda 1.8L used in the '99-'00 Miatas had an issue with crank failures. Does that mean all Mazda 1.8 B series engines should be avoided or that even all '99-'00 Miatas will have that problem? Also, note that neither failure mode was related to the pushrod valvetrain.

The LSx and related truck motors are some of the most common engines used in the US. MILLIONS are on the road. They are good motors.

Magnum9987
09-15-2011, 07:04 PM
The LSx and related truck motors are some of the most common engines used in the US. MILLIONS are on the road. They are good motors.

GM recently posted that in its nearly 6 decades in production, GM has built 100 MILLION small blocks. Their will never be a short supply of parts for Small Block Chevies.

Matra et Alpine
09-16-2011, 07:56 AM
Biggest advantage is the ease of valve timing adjustment with seperate verniers on inlet and outlet.
OHV needs to have dual cams in block to achieve that.

Matra et Alpine
09-16-2011, 08:19 AM
no we gave up rebuilding the A40 Farina Monte replica ... too much missing metal and not having the car ready we both did different things.

Been competing in the Scottish Sprint and Hillclimb Championship.
Check our youtube/facebook.
Sitting 2nd in class.
Finished 2nd in class in the Scottish Highland Speed Championship.

All was going well in the RX-8 till I had a big "off" last weekend :)
All OK to run again this weekend !!

culver
09-16-2011, 08:46 AM
Well I completely agree with you both, but when you build a vehicle, at least in my mind, cost, dependability and ease of maintenance are key factors.

The problems with the OHV engine seem pretty serious, random at times and require monetary as well as back aching attention...obviously this depends on the precise model.

But standing on my original decision of buying an OHC engine from a well known crate engine supplier directly from the United States can be worth it in costs and time in the long run. You would be spending more time on the road and less time in the garage searching and ordering parts from a minuscule amount of suppliers.

The problems were hardly unique to OHV engines and they are not related to the engines being OHV. Furthermore, they only applied to a few versions of the engine. The early LS1s with piston slap would date back to ~1997 and 1998. The head issue was with a truck specific version and we have no information on how common it was. You are certainly concluding a mole hill is a mountain. Using this limited evidence to claim there is something wrong with OHV engines is very flaky.

Do also keep in mind that GM's got a very good crate engine program and the support and knowledge base for their engines (both OHV and OHC is extensive). Also keep in mind they aren't the only good option and depending on the application other choices may be better. The Audi 1.8T out of a B5 platform car for instance has a transaxle that nicely plops into a mid-engine configuration. Conversely, the LSx motors were almost always FR setups so you can't keep the whole powertrain in the family with that motor. A common setup seems to be the LSx + Porsche transaxle.

Matra et Alpine
09-16-2011, 09:50 AM
Good job on the second place. Hill climbing always intrigued me because of the constant mix of high and low ratio gearing mixed with power and high rpm per section.
Scottish hills are particularly tight and twisty and short relative to European climbs. So gearing and power delivery are key to getting a winning machine. Winner in my class has a Rover 25 with a JUDD ex-BTCC engine and short diff :(

What type of differential and transmission pairing do you use?
I race in "standard production class" so it's as it came from the factory.
Sadly the RX-8 didnt' have many options so little scope to swap in different final ratios :(

and LOL on the "off"...any pics?
Worse ... video .... http://www.ultimatecarpage.com/forum/showpost.php?p=974615&postcount=56 might get some pics once it's out of the garage after resetting the suspension tonight

Matra et Alpine
09-16-2011, 10:12 AM
Drink the night before may have been contributory .... sharing malts is a tradition for weekend events :) Went out an hour later and posted my fastest time. It's only a car and it's racing, shit is ALWAYS gonna happen -- or your not trying hard enough !


Yeah well the dates are there once in the thread and if it's stuff that's off-topic of the original thread then we do tend to direct. But apart from this little digression, it's been pretty much on the same stuff as then and we kinda rely on folks reading the dates themselves.

culver
09-16-2011, 10:20 AM
In my defense, it is not really limited evidence when it is commonly known and published.

As for how common; http://www.pistonslap.com/tsb.htm. As for the problems, they require serious attention and a pocket book (replacing pistons, cranks, and heads).

I am not claiming something is wrong for all the OHV engines. Several times I mentioned "precise models". Not all. Since I do not know the bloke who started the thread, by initial advice was to avoid them just so he can avoid any hassle because if someone has an OHV engine and needs to sell it AFTER it is rebuilt, they are possibly going to mislead someone in thinking it is a Corvette engine because of the misnomers surrounding all other OHV engines because of the mistake they initially made.

I think you will find that most engines that have been produced in the same volumes as the LSx family (including the truck and other variants which aren't labeled as LSx) will have some documented problems. The fact is these are VERY good motors and to avoid them if they are otherwise task appropriate is silly. More so to recommend someone else avoids them based on the limited information and knowledge you have presented is also quite silly. If you want to come up with a list of motors to avoid I think there are others that would be higher on the list than the GM small blocks.

Perhaps these guys could answer any of your specific concerns.
Chevy | Camaro | Firebird Reviews, Performance Parts, Modifications - LS1Tech.com (http://ls1tech.com/forums/)

culver
09-16-2011, 04:11 PM
I am simply challenging the notion that for reliability reasons people should avoid OHV motors. That idea is not well supported and the information contained in the Wiki hardly provides any sort of conclusive proof that even the GM small blocks should be avoided nor does it show that alternative motors will be less problematic. All I'm looking for is a show of the logic behind the post thus others can make better use of the information you have presented. It's not a mater of being for or against as requesting facts to back the statements.

culver
09-16-2011, 06:00 PM
Here;

http://auto.howstuffworks.com/camshaft1.htm

They even provide colourful pictures and animations.

I don't think the question is "what is a camshaft". I think the discussion was, did you present sufficient evidence to back your statement that OHV motors should be avoided. So far, at best, we know we should avoid some versions of the Gen 3/4 SMC. You haven't shown we should avoid any other OHV motor.

csl177
09-16-2011, 11:06 PM
Well in all fairness, I am entitled to my own opinion as are you...

Being that I posted my opinion in this seven 7 year old thread I think that that was a mistake...even though it was bumped recently by someone and they should have just made a new thread with a link to this thread.

I made a simple statement that needed a complex answer that people want to debate. I have backed up what I stated with links and so forth that they themselves can read and derive information and knowledge from...but I still cannot figure out your loyalty to OHV. I am not sure if it is directed at brand loyalty or what exactly.
Oy... it has nothing to do with loyalty, and the most recent posts to this thread are from June 2011.
"Simple" is an accurate description of your statement. Complex answers had been previously provided.

But again, to each their own. I stated why to avoid them, if someone chooses otherwise its up to them. I cannot be bothered to debate this anymore.
You haven't "debated" at all. I asked for an explanation which you haven't provided. You can't, because your declaration was false.

It did provoke some hilarious two-steppin' though:

For fun I am going to post this link again but without the link to the limitations section so individuals can read for themselves and come to their own conclusion.

http://en.wikipedia.org/wiki/Overhead_valve

http://static.howstuffworks.com/flash/camshaft-pushrod.swf

I will also post the link to which I am suggesting so I am not just bashing a particular type. This I apologize for. I should have posted a link to which I support.

http://en.wikipedia.org/wiki/Overhead_cam

http://static.howstuffworks.com/flash/camshaft-dohc.swf

And I think we can let other individuals come to their own conclusion instead of us beating a dead horse. I think we can both agree on this.

No, you posted a blanket supposition. For fun, How Stuff Works and Wiki are not engineering sources and relate in no way to the
question of what engine type is best for a mid engine layout. I've been a member of SAE for over 30 years. If in the course of conversation a fellow professional made a declaration as overreaching as yours regarding a TYPE of mechanical system (and not a specific EXAMPLE) without supporting data, he/she would never hear the end of it. A more reasonable "opinion" would be that OHV engines have inherent limitations of volumetric efficiency related to rev limits and displacement; given similar parameters OHC engines CAN be somewhat more efficient.

The drivetrain layout has no bearing on the choice, only budget and application does.

You began this little escapade with:

Well I have to say DO NOT go with OHV. I have not read everything everyone wrote because I will be here forever and I think it is more suited for you to make the appropriate final decision based off of what we say.

Remember OHC not OHV or else it will be the most expensive mistake you'll ever make.
I suggest that next time you read the entire thread. Opinion is useless without information, and blanket statements are rarely accurate.

culver
09-17-2011, 06:56 AM
M,
The simple facts are you posted an absolutism that OHV motors should be avoided because they will require expensive maintenance. The evidence you presented was poor and even if it applied 100% to all GM gen3 and 4 small block V8s it STILL would be poor as those aren't the only OHV engines available. Please don't get mad at me for questioning your statements when they the statements themselves are wide open for questioning.

csl177
09-23-2011, 09:59 PM
No point rationalizing with M acting a twit, culver. He just showed his ass and took the inevitable course expected when called out. ;)

clutch-monkey
09-23-2011, 10:54 PM
Good point...but those are racing teams working with top of the line materials that are being changed every race (I am pretty sure).


awesome evidence captain persuasive