ClownP

The title says it all why don't more supercars use transverse mid-engine layouts? It seems to me liek teh cars would benifit from a lower moment of inertia and better steering response. I was wondering if the only reason not use transverse layouts is because the v10s and v12s used in most supercars don't fit in a transverse configuration or maybe it''s because of not being able to overcome torque steer.

Off the top of my head i can only hink of two cars with this layout and thats the NSX and the Miura.

ogermax

Sounds like you kinda answered your own question. If those are the only 2 you can think of,must be a reason.

ClownP

Yeah i think i have the answer i just want to know if there is a more technical reason other than packaging and torque steer. The miura did it with a 2.9l v12 back in 1966 i think, so i imagine it would nto be that hard for engineers today to design a similar car.

Old SStroker

Packaging is the big problem. With a traverse engine, the trans/final drive has to be behind it. To get any reasonable half-shaft length you'd need to have the final drive centered and aft of the trans. Now getting the power from the crank to the trans requires either a chain or gears on one end of the engine, both of which are heavy if you are talking supercar power.

Lower polar moment isn't necessarily the driving force (pun intended) for supercar handling. Wheelbase, track and front/rear weight distribution may be more critical. With a longitudinal engine you can place the trans behind the diff and put the engine mass pretty much where you need it. Not so with the transverse design.

The length of any V engine with more than 6 cylinders makes a fairly wide package. Who really wants a 6 cylinder "supercar"? Additionally, exhaust packaging from the front cylinders is tricky. Lots of header heat next to your back.

As far as torque steer, with a central diff and equal length half-shafts, the drive doesn't know whether the engine is longitudinal or transverse so that should be no worse than a conventional supercar rear drive.

Ever wonder why most all mid engine race cars have a longitudinal engine, even when they have a choice?

ClownP

Thanks for answering my post; i assumed packaging was the main reason.
I assumed one of the biggest reasons for longitudinal midengine layouts in racecars has to do with aerodynamics (which goes back to packaging).

racenutz

I think the Cizeta-Moroder V16T was the last production car to use this layout http://en.wikipedia.org/wiki/Cizeta-Moroder_V16T

Steve Bryant

iTrader: (1)

You guys are all on the right track in my book. The biggies are torque steer and packaging not only of the drive train components, but everything else. Any powered vehicle has a longitudinal shape and it works best for most everything else to be oriented fore-aft to complement that longitudinal shape. This would include exhaust system, sub-frame support of the drive train and tying that into the chassis, fuel tank, cooling system, seats . . . almost everything has to have this orientation. However, torque steer alone would be enough for me. I owned a couple of FWD cars in the early 80's and if you've never experienced torque steer, you don't know what a pain it can be. The Wikipedia article cites the fact that the power output of the twin straight eights of the Cizeta-Moroder V16T was in the center of the transversely-mounted engines. If this is true, they must have had a 90 degree drive (which adds friction and complexity and raises the CG).

On another note, the only advantage in my book for FWD (especially transversely-mounted) is cost savings during assembly. You can make a point for enhanced traction in adverse weather conditions . . . but only a small point in my book. Every where else you loose.

Steve

spy2520

iTrader: (3)

if the motor is transverse and in the rear, does it really experience torque steer like in a FWD? i'm not seeing it, but i'm here to learn.

Old SStroker

No more so than any IRS if the half shafts are of equal length. Perhaps some folks get confused because the only transverse engine cars they have driven are FWD where the tires do both steering and driving and the forces/functions interact. It's not the engine orientation. In fact, longitudinal engines load/unload left and right tires due to torque reaction of the chassis. Transverse engine torque reaction is fore/aft.

FWD torque steer is a good reason to separate the drive wheels from the steering wheels, or at least make all the wheels drivers.

In the end, all driven wheels "steer" to some extent depending on suspension geometry, dynamic loading, traction, among othe rthings.

Steve Bryant

iTrader: (1)

Old S Stroker,
I agree with what you said above. I was thinking about unequal length half shafts on the front wheels and transferring that thought process to a rear wheel drive vehicle. Thanks for "straightening" this out.

Steve

Wide Open

The Fiero comes to mind, though it would never be confused with a supercar The Fiero didn't drive well because it had too much weight hanging behind the rear axle centerline.

Steve Bryant

iTrader: (1)

Here an interesting website on the development and concepts of the Fiero http://www.fierofocus.com/articles/a...o-history.html.

Steve

Old SStroker

Hmmm. How about 911 and on Porsches? They really hang the flat 6 engine out there behind the axle centerline, and they are fair-to-middlin' drivers.

FWIW, the last Fiero wasn't all that bad with decent rubber on it. The front and rear suspension (from production econocars) was about as far from supercar as you could get.

STRIPSTAR

iTrader: (4)

crash test data and packaging are the main factors

qwikz28

iTrader: (12)

i remember a road test on the porsches saying they are great street cars, but when pushed to the limit, you see the effects of its retarded engine placement. if you think about it hypothetically, i can imagine not having enough weight on the front tires and too much on the rear would cause alot of understeer.

Wide Open

The 88 model actually did handle significantly better, probably something to do with using something other than a Chevette suspension, but they still lacked the rubber to make them great handling cars. Mid/rear engined cars have huge advantages in forward traction and braking.

thelostartof

and that is why the 911's have always done so bad when it comes to thier track cars right?

STRIPSTAR

iTrader: (4)

Yeah, um porsches have always been one of the best handling cars. rear engine layout combined with the boxer engine design that has a very low center of gravity is their game.

Steve Bryant

iTrader: (1)

I used to have a 1970 911. It was a great but temperamental car in many ways. I did learn to balance multiple carburetors though. Older air cooled engined vehicles with air conditioning also had their issues, but then I had a 1972 240Z with similar problems until I re-cored the radiator.

The 911 (and the 356) Porsche was actually infamous for over steer. The mass at the rear causes the rear end to pull toward the outside of the turn. I'm sure that they did some things to change suspension geometry and weight distribution over the years and improve things. The 914 was a mid engine car, although anemic. The 924 and 928 were front engine with longitudinal layout.

Steve

Old SStroker

They are the ones to beat in production classes they run, and have been for a long time.

The mid-engine Daytona Prototypes with Porsche race engines have been getting beaten regluarly by 5.0L GM LS6-based engines, which does my ol' GM heart good. I like it that they limit the LS to 5.0L(down from 5.4 initially), 7100 rpm, a valve lift and duration rule, stock LS6 valve sizes, stock LS intake manifold and 75mm TB, and it still kicks butt. Not to say that tons of time and money hasn't been expended to make that DP engine work. It has!

BTW, the truck LS intake works better (in that application) than the LS6 or LS1 intake. Who'd a thunk it?