Mid or Twin engined Challenge cars

I remember everyone admiring the amazing work of Durrocco, and I know that there has been a Shogun replica at at least one Challenge. Somebody (I don't remember who and can't find it--not important) mentioned that mid-engined or twin cars don't necessarily make good autocrossers. Was this because of the mass between the two rear wheels affecting rotation? I asked because watching Top Gear yesterday there was a 6.0 liter V12 Golf with 640hp that was a rocket, but couldn't turn to save its life. Why was that, I ask the collective. This is the way I was planning to go with my Challenge car, but seeing this makes me wonder...and I wonder a lot

Yeah, that creates a massive polar moment. Probably more important than a 50/50 f/r weight ratio is concentrating as much of that weight as possible towards the center of the car. One engein in the front, and another in the back is going to make that car want to keep going whatever direction it already going.

I have heard the argument that you are better off concentrating the weight right on top of each axle. That way the car has a tendency to rotate smoothly around either axle instead of having a tendency to switch ends that are sliding mid slide. Probably marketing speak, who knows.

Another factor:

Most of the time a twin engine or a SHO style mid engined vehicle will likely have a home fabricated suspension setup.

It's hard to compete with the combined engineering prowess of all of the automakers in the world from your garage. I know it is theoretically possible to have a great custom built suspension, but it hasn't happened yet at the Challenge.

Even after market suspension components (which are too expensive for the Challenge budget) have a lot of engineering behind them.

I strongly suspect the biggest difference is in suspension engineering, not polar moment.

I've had the crazy thought of a twin engine Saturn SW2 - a wagon for easier access to the rear engine. The idea would be, borrowing from the tradition of the Fiero and AW11 MR2, to swap the front subframe and suspension as well as a drivetrain onto the back of the wagon. If some sort of cheap eBay coilover system could be modified to work, swap out the springs for whatever rates will work best for the added rear weight. If anything, the car would be closer to 50/50 in the end, since it's quite front heavy in FWD form.

Come to think of it, I've got a Challenge priced SW2 I could try this with. But I have nowhere near the engineering skill, nor space for the parts car that would donate so much of itself to the build.

I believe the lions/tigers/bears share of backyard twin engined handling maladies stem from the use of front wheel drive suspension components in the rear of the car. The added mass of a second drive train and supporting components is a fat-goblin of a problem too, even the lightest 4 cylinder setup will add close to 450lbs to the vehicle.

Were I to build another twin engined vehicle I would find a sub frame and suspension from a factory mid engined car, no use trying to sort a front suspension for the rear if a cheap used option is available.

http://sportcompactcar.automotive.com/71692/0202-sccp-1998-hyundai-tiburon-uscc/index.html

Here's a well done example

ccrelan wrote: http://sportcompactcar.automotive.com/71692/0202-sccp-1998-hyundai-tiburon-uscc/index.html Here's a well done example

I remember the issue when they did that challenge. Car didn't place too well but with one engine in gear going forward and one in reverse, it would make EPIC burnouts.

This is a seriously good question. I've always wondered why people didn't just grab the whole front subframe off of two decently powered cars and go to town. Has anyone tried that at the challenge with the factory front suspensions?

tuna55 wrote: I've always wondered why people didn't just grab the whole front subframe off of two decently powered cars and go to town.

That's what I did with my car; stuck an A2 golf front sub frame, control arms and struts in the rear. I pulled the large geared rod out of the golf rack and pinion assembly, welded on a pair of mounting tabs and bolted it to the sub frame in the same position as the stock rack. My car has some nasty behavior in turns, the rear end seems to steer itself slightly with any change in direction. So far I've messed around with toe settings in a haphazard fashion but have not made any geometry changes.

Shot of the rear drive train out for a transmission change.

I can't see any way of doing a twin engine using different powerplants. The would most likely have different engine outputs, different gear ratios, and different shift linkages. Would you fumble around with 2 shifters? I'd guess an upsided clutch master would be able to control both clutches, but if the length of pedal travel was different for each clutch it could be impossible to get a smooth shift.

The Hyundai was an automatic. The drivetrains were pretty much the same, but there's still going to be some difference. As I gather, he just let the slop in the automatics compensate.

That thing was beatly. Neat when he put it in reverse and forward at the same time, and did a slow rotating burnout.

there is pics of a yugo running around with HUGE flairs, a v8 out back (longitudily mounted ala caddy trans or something) and a 2.2/5 turbo mopar up front... wish i could find pics when I want haha

anyway... this guy welded in the front portion of a buick into the back of the le mans a back in '02 or so for the challenge...

wasn't super fast at mid 14's in the 1/4 with the stock 3800 as I recall and had massive front brake bias killing auto-x times... i SO wish i could have bought it when it was FS :(... for $1000 it's by far one of the kewlest cars around doh

http://s46.photobucket.com/albums/f123/mr2donalson/lemans/

ansonivan wrote:

tuna55 wrote: I've always wondered why people didn't just grab the whole front subframe off of two decently powered cars and go to town.

That's what I did with my car; stuck an A2 golf front sub frame, control arms and struts in the rear. I pulled the large geared rod out of the golf rack and pinion assembly, welded on a pair of mounting tabs and bolted it to the sub frame in the same position as the stock rack. My car has some nasty behavior in turns, the rear end seems to steer itself slightly with any change in direction. So far I've messed around with toe settings in a haphazard fashion but have not made any geometry changes. Shot of the rear drive train out for a transmission change.

ansonivan, etc look at the rear suspension of an X-1/9 for ideas on how to correct the geometry in your rear suspension.

http://merope.as.arizona.edu/~agaspar/x19/index.php?m=05&y=08&d=19&entry=entry080519-185503

Looks like removing the steering rack all together and mounting a outer tie-rod where the inner tie-rod went and mounting it to the rear control arm mount should get you closer to reducing the bump-steer in the system.

MR2's used a similar solution (not surprisingly since they were Japanese knock-off's of Bertone's design)

http://www.mr2turbo.info/pics/rearsuspension.html

Oh and I thought this was interesting:

http://www.toyotanation.com/forum/showthread.php?t=283731

I need to learn suspension speak so I can describe things more cleanly, here goes with the mess:

The major geometric differences I see between the mr2 or X-1/9 and my A2 setup: the inner control arm pivot points on the mr2 and x-1/9 control arms appear to form a line pointing away from the center front of the car whereas my A2 pivot points form a line pointing towards the front center of the car. The tie rod/stabilizer rod on both the factory mid cars and mine appear to have similar angles: semi parallel to the control arm and angling down towards the inboard side of the car.

Another mr2 shot

My A2 setup

Yes I know the tire is mounted backwards

Bump steer cure for early Fiero suspension, gives me ideas for things to try:

http://www.kitcarmag.com/howto/pontiac_fiero_rear_bumpsteer_kit/index.html

If you want an easy way to stick a second powertrain in the back of a car, why not start with a cradle/powertrain that was in the back of a car to start with? The '88 Fiero stuff is easy to work with and cheap. Four big ass bolts for the subframe/cradle and two mounting points for the tops of the struts gives you a rear mounted powertrain; just six attachment points makes the mechanical part fairly easy. Use an automatic and don't worry about gearing differences. The stock Fiero auto is kind of a POS, but of course GM being GM, you can easily stick in a newer, better GM engine/trans. The '88 is the one to get because you don't have the horrible bump steer to deal with (true multi-link suspension) and you get vented rotors to boot.

Full disclosure: I'm horribly biased, as I've got two '88 Fieros and have created a twin powertrained challenge car.

Bryce

ansonivan wrote: Bump steer cure for early Fiero suspension, gives me ideas for things to try: http://www.kitcarmag.com/howto/pontiac_fiero_rear_bumpsteer_kit/index.html

BTW this is fargin awesome.

Nashco wrote: why not start with a cradle/powertrain that was in the back of a car to start with?

I completely agree with you and fully intend to do so next time, I just need to make my existing mid/twin handle well enough to sell with a clear conscience.

Nashco wrote: Use an automatic and don't worry about gearing differences.

Better still, use a pair of dsg transmissions with paddle shifters, all the control of stick shift with none of the linkage headaches.

One of the big dollar VW tuners needs to do this and if they do they heard about it here first

mk5 golf/jetta/scirocco twin 2.0t dsg

• both transmissions controlled by the paddle shifters
• launch control
• manual variable front/rear bias control thanks to drive by wire throttles
• stability control reprogrammed to reduce understeer in turns or even induce oversteer aka "drift mode"

i have a very sneaky plan for 2011

ansonivan wrote:

Nashco wrote: Use an automatic and don't worry about gearing differences.

Better still, use a pair of dsg transmissions with paddle shifters, all the control of stick shift with none of the linkage headaches. One of the big dollar VW tuners needs to do this and if they do they heard about it here first mk5 golf/jetta/scirocco twin 2.0t dsg * both transmissions controlled by the paddle shifters * launch control * manual variable front/rear bias control thanks to drive by wire throttles * stability control reprogrammed to reduce understeer in turns or even induce oversteer aka "drift mode"

wow, that would be awesome! Especially if you slap a big turbo on both, maybe putting out 300hp each, you would have a 600hp, awd monster!

Sorry to bring this thread back, but I wanted to throw out a suggestion... How about a twin engine Subaru or DSM (I think the DSM has been done a few times http://video.google.com/videoplay?docid=-7810839976065329866#)? I have read these rear suspensions can swap awd/fwd components.

Find a fwd model (they should be cheaper), swap the rear knuckles/hubs for awd rears, relocate gas tank, cut floor, fab engine/trans mounting, make custom axles if necessary and finally plumb/wire. Am I missing anything?

I'm sure I will be flamed on how an awd single engine would be better all around, but if you really want a twin engine, I would think this idea would leave suspension design to a minimum.

get a fwd 4age powered corolla and a drivetrain from mk1 MR2. That would help solve a bunch of little problems.

donalson wrote: there is pics of a yugo running around with HUGE flairs, a v8 out back (longitudily mounted ala caddy trans or something) and a 2.2/5 turbo mopar up front... wish i could find pics when I want haha anyway... this guy welded in the front portion of a buick into the back of the le mans a back in '02 or so for the challenge... wasn't super fast at mid 14's in the 1/4 with the stock 3800 as I recall and had massive front brake bias killing auto-x times... i SO wish i could have bought it when it was FS :(... for $1000 it's by far one of the kewlest cars around doh http://s46.photobucket.com/albums/f123/mr2donalson/lemans/

I remember that also, but I thought it was yours at one point. Wonder where it's at now?

Who could forget Mosler's (yes that Mosler) twin engined Eldorado?

http://www.caranddriver.com/reviews/car/00q3/mosler_twinstar_eldorado-specialty_file