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

ok, say I was thinking to put an electric motor in the rear of a FWD wagon (and end up with a 4WD hybrid that could likely do most of my day-to-day driving in full electric mode).

The electric motor doesn't need gears necessarily (gearbox would add weight, but also would add a variable torque multiplier for the motor).

What is the best way? (Easy and Cheap are my biggest concerns... I think)

1. Get another FWD drive train from same or similar car?
2. Get a rear subframe and diff from an RWD car? (think miata)
3. Get a transaxle from a mid/rear engine car? (thinking MR2 or VW, but also fiero, etc)
4. Something really crazy like two smaller motors each attached to an independent motorcycle swingarm and chain drive?

p.s. I'm thinking about all of this in a challenge-priced Focus Wagon... am I nuts?

rcutclif wrote: (Easy and Cheap are my biggest concerns)

Well that aint happenin

Oooh... this should be fun!

No problem with the Challenged-priced Focus wagon, but it would be really tough to complete the build for Challenge prices.

I would go for option #1. While those other options would work, the simplicity of 2 identical drivetrains would make the project much more do-able.

A lot of mid-engine RWD setups are basically a FWD drivetrain moved to the center. A Yugo is essentially the same thing as an X-1/9, just has the drivetrain shifted to the middle. Same thing for the Citation/ Phoenix and the Fiero.

Whatever you work out in the front (with or without the transaxle), just repeat in the rear.

I feel like it would be all wonky with different amounts of torque and power being transmitted to the front and rear, and no way of maintaining a balance.

I say try it out anyway

i vote 2 if you don't want a transmission.

way back when i converted a 1990 grand prix to rear wheel drive i took the entire rear subframe from an mn12 thunderbird with IRS. it worked perfectly.

looks like these guys have a bolt-in option for a mustang 8.8 axle (NOT cheap though).

http://www.kugelkomponents.com/focus/focusv8.php

I do think a mustang axle is quite a bit of overkill for an electric motor, and has the downside of 'non-changeable' gears.

I am also leaning toward #1, especially with something like a focus, where getting two drivetrains should not break the bank.

Cool Hand Luke: I think we have to remember the ground connects all the wheels pretty well. Even on one axle the torque going to both wheels is rarely 'balanced'.... Am I right?

Easiest? Most likely a platform that already, in some cases, drives the rear wheels. Some Subarus, CR-V, etc. come in both fwd and awd variants, and some of those surely have the means to put an awd rear suspension on a fwd vehicle. Voila, a rear diff and suspension already engineered for you!

You can buy two cars, one electric, one gas. One fwd front engine, one rwd rear or mid engine. Cut both cars in half. Weld the two halves together. Find some place to stuff a fuel tank and batteries(You could stretch the body while you're welding the two halves together to make room for that crap, or put all that stuff on the roof). When finished it will be a)big b)heavy c)ugly d)expensive e)undrivable f)unsellable. You will be divorced. Thats worst case scenario. Best case scenario is you build it quick and cheap, it turns out awesome. It looks cool and gets 475 mpgs. Everybody wants one, the oil companies see the writing on the wall and have you killed to protect their bottom lines. Either way I want a well documented build thread.

NONACK wrote: Easiest? Most likely a platform that already, in some cases, drives the rear wheels. Some Subarus, CR-V, etc. come in both fwd and awd variants, and some of those surely have the means to put an awd rear suspension on a fwd vehicle. Voila, a rear diff and suspension already engineered for you!

Also check to see if any Euro/Japan variants had AWD. Sometimes they do and they just never came to NA.

NONACK wrote: Easiest? Most likely a platform that already, in some cases, drives the rear wheels. Some Subarus, CR-V, etc. come in both fwd and awd variants, and some of those surely have the means to put an awd rear suspension on a fwd vehicle. Voila, a rear diff and suspension already engineered for you!

hmmm, good idea. or just start with the AWD version and sell the motor/trans and buy a FWD version... you might even come out in the green a tad! Off to check the 'list!

gearheadmb wrote: You can buy two cars, one electric, one gas. One fwd front engine, one rwd rear or mid engine. Cut both cars in half. Weld the two halves together. Find some place to stuff a fuel tank and batteries(You could stretch the body while you're welding the two halves together to make room for that crap, or put all that stuff on the roof). When finished it will be a)big b)heavy c)ugly d)expensive e)undrivable f)unsellable. You will be divorced. Thats worst case scenario. Best case scenario is you build it quick and cheap, it turns out awesome. It looks cool and gets 475 mpgs. Everybody wants one, the oil companies see the writing on the wall and have you killed to protect their bottom lines. Either way I want a well documented build thread.

Challenge Accepted!

I thought of the "find an AWD version" idea as well, start with a Volvo 850 or v70 wagon and you're 3/4 of the way there! Okay, maybe only 1/4 or 1/100th the way but still. Having a drivable rear end that bolts right up is a huge step in the right direction. It would be super easy to take an AWD 850 and make it FWD only and then have an easy place to attach an electric motor to the rear end. I love this idea. Make the motor compact enough and you wouldn't even need to impact the floor pan of the wagon.

Also, to the "different power/torque amounts to different wheels" question, it doesn't seem to be an issue in practice. There have been a few dual-motor builds out there and they don't seem to be a problem. One was even manual front, auto rear transmission! (The doublesuck Toyota of Lemons fame)

http://solophotography.com/DuRocco/main.html

Maybe do it this way? Besides this car there is one other Scriocco with dual engines. That one is located in the Columbus, OH area and I saw it at a autox a couple of years ago.

Check Nashco's Fiero build for inspiration. Same idea, but backwards from what you are thinking.

http://grassrootsmotorsports.com/forum/grm/west-coast-2009-challenger-awd-fiero-hybrid/10519/page1/

Look up the V8 kit for the focus and use the rear suspension/diff, ect.

dculberson wrote: I thought of the "find an AWD version" idea as well, start with a Volvo 850 or v70 wagon and you're 3/4 of the way there! Okay, maybe only 1/4 or 1/100th the way but still. Having a drivable rear end that bolts right up is a huge step in the right direction. It would be super easy to take an AWD 850 and make it FWD only and then have an easy place to attach an electric motor to the rear end. I love this idea. Make the motor compact enough and you wouldn't even need to impact the floor pan of the wagon.

LOVE the volvo idea. I have even been wanting a volvo for quite a while...

bgkast wrote: Check Nashco's Fiero build for inspiration. Same idea, but backwards from what you are thinking. http://grassrootsmotorsports.com/forum/grm/west-coast-2009-challenger-awd-fiero-hybrid/10519/page1/

I remember seeing this in the Mag. sweet ride, yes, very similar idea. Maybe i'll ping Nashco for more info once I get started.

dculberson wrote: Also, to the "different power/torque amounts to different wheels" question, it doesn't seem to be an issue in practice. There have been a few dual-motor builds out there and they don't seem to be a problem. One was even manual front, auto rear transmission! (The doublesuck Toyota of Lemons fame)

Pretty sure I pitted next to those guys at one LeMons race... corolla FWD and MR2 chassis right?

Correct, front half of Corolla mated to back half of MR2..

https://grassrootsmotorsports.com/forum/off-topic-discussion/dual-engine-vw/30188/page1/

I change my vote.

The Volvo AWD approach would be even easier, if you are willing to give up in the Focus wagon.

If you want to do a Subie version, I've got a worthy Justy.

A little enabling:

Woot!

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).

Paging Vigo to the white courtesy phone...