Help with Mid Engine Design

[culver]

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]

"if"

[RacingManiac]

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]

^^^ 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]

SuspensionProductsPage

".....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]

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]

This I guess also avoid hacking up the chassis more....otherwise they need to add bracing to it.....

[TwiceBaked]

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]

^^^ Whaaa? to that last sentence. Please explain "OHV are tempermental". No gibberish. C&P from any engineering paper if you wish.

[Magnum9987]

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]

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]

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]

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! 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]

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]

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.