theoretical build: best way to drive the rear wheels on a FWD car

rcutclif wrote:

SVreX wrote: A little enabling: Woot!

O. My. Gosh. Got the turbo motor and everything. Also seems to me in my limited research the FWD only ones are much more likely to be found with 3 pedals... So if I got something like this, sold the trans, and got jy parts from a manual... I'm going to ask the seller where the car actually is. The ad says both connecticut and california (not the same place).

In terms of Challenge dollars, it doesn't really matter. "Costs to pick up your hooptie from the seller are exempt".

Yeah, I understand it could still cost a few real dollars, but they are budget exempt, if that helps.

this is an excellent point, but uship is saying about 1200 real dollars. I was looking into cali vs. conn because I was considering picking up myself. sounds like the car is actually in conn, which is closer to me than cali, but still not close.

I'll certainly be watching the auction. Thanks for pointing it out!

Mitsubishi i-MiEV. Rear engine, rear drive electric. Terrible seller, terrible depreciation.

Right now, a 2012 with under 10k miles is a $10-$13k car.

Find one wrecked in the front, and sawzall it into your front driver.

I spent a lot of time thinking about this for my old van. Now i have another van and i just want to hook the rear wheels up to my gas engine like a boring n00b.

Anyway, to me the easiest way is to get a FWD version of something that had available AWD, and then use the factory rear diff/axles/hubs from the AWD and hook an electric motor to the diff.

You need to be aware of gearing. Electric motors are not TOO picky about rpm as far as their efficiency, but they ARE picky about being overspun, and unless you work a fancy clutch setup in between motor and diff (not happening) you need to match the gearing of the motor with the max speed you are ever going to drag those rear wheels down the road so the motor doesnt blow up. Unfortunately, having one gear ratio that allows a full normal range of speeds 0-100+ gives you very little torque multiplication. That's 'ok' when you have tons of motor torque but once you start looking into building a setup you will see that getting big torque is expensive in terms of motor/controller/battery etc even if you arent big on range. My 52hp motor only peaks at 110 lb ft and just goes down from there (at rated voltage ie not hot-rodded).

When i was planning this for my van i picked up a samurai transfer case which is a divorced case (i.e. it already has flanges for input/output instead of splined shafts) which basically worked out to one 'performance ratio' (4lo, 0-50) and one high speed ratio (0-115). I also had the very cool benefit with the Caravan awd rear diff of having an overrunning clutch built into the diff housing so that if i ever exceeded the speed the motor was turning it would decouple and freewheel.

Sounds really great, but i never did build this thing. I am a loser!

Mike wrote: Mitsubishi i-MiEV. Rear engine, rear drive electric. Terrible seller, terrible depreciation. Right now, a 2012 with under 10k miles is a $10-$13k car. Find one wrecked in the front, and sawzall it into your front driver.

Find a rear ended Mirage and you could come away with something looking almost factory.

In reply to Vigo:

Yes, gearing is a real issue, and makes an argument for a second FWD drivetrain in back. I have a motor in the garage waiting for a build (but it would definitely not fit challenge budget - would have to work on finding something else to go that route). The one I have goes to 6500 RPM. if I direct drive to a diff, its quite similar to 4th or 5th gear in most vehicles (whatever is 1:1). I could easily say "while racing do not shift higher than 4th" and then the gas motor would redline similar to the electric motor and all would be well.

Except: only a really B.A. electric motor will help much at all if it is 'stuck' in 1:1 at the diff.

I was almost thinking of trying to get a chain drive setup going and use a motorcycle trans, but then you get into more complications (Imagine trying to drive in anger while managing two separate drive trains and shifting for both, ugh). Maybe a snowmobile CVT?

The good thing about the electric motor is we are not talking about small block levels of power, so trans don't have to be beefy.

In reply to rcutclif:

Yeah, but a bike trans reduces weight SIGNIFICANTLY, and the sequential nature lends itself well to air shifters.

Shift points could be preset, and 2 separate systems could be engaged if the 2 drive trains are wanting to shift at different moments.

It would allow a trans that would shift automatically, to focus on driving while racing, which could be disengaged for paddle shifter fun when desired.

It's the best of both a manual AND auto trans, with a savings of 200 lbs per trans.

Sounds like a lot of win to me.

You want to read the C&D articles on "Super Synchronicity", a dual-engined CRX. Two automatic FWD drivetrains with no connection other than the transmission selector and the throttle cables.

In reply to Keith Tanner:

Not sure if I read the articles (maybe I have?) but I heard about the car.

Yes, I agree that the drivetrains can run very independently and don't have to coordinate much with each other. I guess, unless one is overpowering the other to the point of wheel-spin on one axle. Then it just depends on how much you trust the rev limiter.

It's one of those KISS things So what if you get wheelspin? It's no different (as far as the engine is concerned) than wheelspin on a 2WD car.

There were two issues that discussed the car, IIRC. One was the original with blueprints on the cover, the next had a couple of larger engines installed and some handling tweaks. Racing Beat did the fab work.

Come to think of it, I think it was just CRX^2 the first time. The SS moniker was added with the bigger engines.

Mosler had the Twinstar Eldorado. I think they advertised in GRM. http://www.caranddriver.com/reviews/mosler-twinstar-eldorado-specialty-file

http://forums.24hoursoflemons.com/viewtopic.php?id=8787