Help with Mid Engine Design

[V8turbo4me]

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]

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]

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]

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]

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]

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.

[Egg Nog]

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]

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]

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]

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.

[SIMPLETON]

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.

[Mr-Supercar]

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]

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]

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]

heres where it has been for the last 5+ years



the hole


another view from when we pulled the planned motor out


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.