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Old 08-01-2015, 10:09 PM   #1 (permalink)
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Adding these electric motors to the back wheels of my FWD gas car?

I have a 2006 Impala SS. It is FWD and I want to add electric drive to the rear wheels. Since it is a big V8 in a FWD car, when you gas it hard, weight goes to the back tires, leaving the front tires without good traction. I'm sure you guys all know about that. Either way, it is a very fast car... once it gets going.


TL;DR
So I would like to put 2 of THESE motors in the back of the car- one on each wheel. This means that one would have to be set up to spin the opposite way, which the site says is possible upon request. They also have single-ended versions. So I'm just posting this here to see just how possible/viable it is to do.


My main concern is whether or not those motors can work together with each other, the gas engine in the front, and the car's transmission. Also, how reversing would work. I'm assuming the electric motor controller would tell them not to work, or to spin backwards, in reverse, but I am not sure.


If you are interested in all the reasons and the end goal, read on. However, most people can probably tell me if this is possible just from the TL;DR/



Here my full on goals and reasons:
Speed!
My engine has more torque(327lbft) than is practical in a FWD car, but I feel like I can solve that problem, and make my car incredibly fast, by adding these high torque motors to the back wheels. The primary goal is speed, particularly speed during the launch of the car. Once the car is in 2nd gear, I would like the electric motors to just stop, because they probably won't be helping after the car is over 50 mph, which is when the gas engine can really shine like it should.

So, if at all possible, I would like a controller for the rear motors that I can hook up to the car's ECU that I can set up to do that whole "turn off after 2nd gear", or 50mph, thing. I would use this in conjunction with a flash tuner for the actual car engine that would be set up for an open exhaust(courtesy of an electric cut-out, allowing me to go back and forth between stock exhaust and pretty much straight pipe) and all out speed. I would get this tune custom made by some pros at a dyno after the electric motors were installed.

Economy!
For this idea, I would like to use the flash tuner to force the car to stay in 4-cylinder mode(it has active fuel management already) and rev limit the 4 cylinder engine to 2200 rpm, which is how it is already limited. Trying to go above 2200 rpm in 4-cylinder mode will just re-enable 8 cylinder mode. Then I would use the electric motor controller to only enable the electric motors after the throttle is pushed beyond a certain threshold, like maybe 40%. The idea is that the electric motors will only help the 4-cylinder engine in acceleration BEYOND what 2200 rpm would allow. So I would find out the throttle % for 2200 rpm in 4 cylinder mode(lets say its 34%) and then I would tell the electric motor controller not to engage until the throttle is at 40%, giving me a little leeway before the electric motor kicks in when im cruising. I understand that I would probably have to then have the electric motors start at whatever ampage is necessary to accelerate the car organically at whatever speed I am going, which may be difficult unless the controller can have a different setting for each individual gear that the transmission is in.

Loose ends
I would like to have a decently sized battery, with maybe 20-30 miles or so of hybrid range, that I can charge up with power from the grid, allowing me to do all of this without having to load the engine, thus avoiding the whole "mechanical into electric back into mechanical" loop that would just make my economy even worse.

If the battery, which I assume will be in the trunk, ends up getting too hot, I will probably go with water cooling routed to a radiator in a wheel well(or both wheel wells, for double the cooling), assuming I find out that there is sufficient air speed in the wheel wells.. If not, then I'll suck it up and make a legit radiator in the front of the car for it.

I would also like to load the wheels on command, if possible, using a switch in the cabin or something. This way, if I had used all of my battery, but I wanna off my car's totally awesome launch ability, I could just drive around with the wheels loaded and charge the battery enough for a launch. Or, if I knew I was about to coast to a complete stop down a hill, which actually happens a lot for me, I could just flip the switch and get a little juice back. I am just assuming that automating this would be a little more difficult than is worth it, but I would like to have the feature.

Finally, the car needs to be able to go back to basically operating like stock at any time.

Summary
Speed mode: Open exhaust, super fast tune, electric motors on full blast from launch(or as much power as I can without them peeling tires), and then electric motors shut off at a certain MPH or gear.

Eco Mode: 4 cylinders, 2200 rpm limit, electric motors only for acceleration.

Stock mode: Obvious

Extras: A switch to operate the loading mechanism to recharge the battery. It would look nice next to the switch that would open/close my exhaust cut out.

SO, am I naive and foolish, or is this a viable project that I should spend my time/money on? Basically, if it is not too hard, I want to do it. As long as it doesn't cost more than ~$5k, money won't be the issue. Right now, I just need to know if it can work the way it does in my dreams.

Thanks!


Last edited by ciano22; 08-01-2015 at 10:17 PM..
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Old 08-02-2015, 12:23 PM   #2 (permalink)
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For $5k, not gonna happen unless you get a screaming deal on all the parts. $5k will get you two motors and maybe a controller from the site you linked to (you'll probably need two controllers if you use two motors). Then you also need the battery (which could easily be $5k on its own) and however you're going to get the power from the motors to the wheels. Best way to do that would be using the rear drivetrain from a RWD or AWD car either based on the same platform or at least similar dimensions. Then you could hook up the motor to the differential (in which case you could just use one if its enough power).

Probably best left as just a dream unless you have a pile of money to burn.
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Old 08-02-2015, 02:36 PM   #3 (permalink)
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A pile of money and a lot of time to spend figuring out how to integrate this auxiliary driveline with the stock electronics of your ride.
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Old 08-04-2015, 06:24 PM   #4 (permalink)
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Ok, so how much would it cost, realistically? Under 10k at least? Can you guys recommend some batteries that I should look at?

Someone else recommended the motor-per-wheel approach over the idea of getting a RWD axle put in, but of course, a lot of people also recommended the RWD axle. The guy who recommended the 2 separate motors made his case by saying that the fact that I was keeping the entire stock drivetrain in tact meant that I could get away with not having the rear wheels hooked up to a differential and transmission, for reverse and what not. I could even get motors with no option to reverse, but they would need to be allowed to be "driven" by the main engine.

Also, do you guys maybe know if the performance gain would be worth it? If this electric car thing works out well, I would then proceed to get the front engine upgraded, as well as even trying to replace the 2 small electric motors with 2 bigger ones. If I had 2 motors in the back, providing roughly 400lbft of torque, along with a front engine with a turbo making around 400hp and a little more torque than that, would that really make the car brutally fast in a straight line?
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Old 08-05-2015, 12:18 AM   #5 (permalink)
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Quote:
Originally Posted by ciano22 View Post
Someone else recommended the motor-per-wheel approach over the idea of getting a RWD axle put in, but of course, a lot of people also recommended the RWD axle.
I'm favorable to the flexibility of a hub-motors setup, but wouldn't object for a single motor driving through a rear differential since it doesn't increase the unsprung mass as individual hub-motors do. Also, you would avoid the need to compensate electronically the lack of a differential in curves.


Quote:
Also, do you guys maybe know if the performance gain would be worth it? If this electric car thing works out well, I would then proceed to get the front engine upgraded, as well as even trying to replace the 2 small electric motors with 2 bigger ones. If I had 2 motors in the back, providing roughly 400lbft of torque, along with a front engine with a turbo making around 400hp and a little more torque than that, would that really make the car brutally fast in a straight line?
Seems like you mean a thru-the-road hybrid setup, it's perfectly doable and even offered as a factory option in some European hybrids.
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Old 08-05-2015, 02:58 AM   #6 (permalink)
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How about some stiffer springs? I'm imagining a stereotypical bouncy castle on wheels!
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Old 08-05-2015, 05:12 PM   #7 (permalink)
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Quote:
Originally Posted by markweatherill View Post
How about some stiffer springs? I'm imagining a stereotypical bouncy castle on wheels!
While the Impala SS is by no means a "sports car", it definitely has a decent suspension set up. Mine is about ready for new springs anyway, but the car rides much firmer than most stock sedans that I've been in. I've had people complain that my car is a bumpier ride than their Camry, Sonata, Malibu, etc., and therefore the suspension is not as good. Ha. It is also lower than a typical Impala and the spoiler actually seems to have a purpose at high speeds, even though I thought it was pointless on my car. Along with the bumpy ride, people use the fact that I occasionally bottom out on crappy driveway entrances as evidence that my car is not as nice as their cheaper, slower, smaller sedans.

Also, I wont be spending any time on a track. I'll mostly be at the drag strip. As long as it doesn't feel like a boat on the highway, I think it will be fine. I'll have to wait until all the added weight is there to really know though.
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Old 08-06-2015, 12:05 AM   #8 (permalink)
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Interesting idea but honestly I think you are being totally unrealistic about what you can accomplish for under $10k, if I am understanding all that you want. Are you wanting to pull 400lbft torque from your electric motors in addition to your gas engine?
I will throw out some thoughts to consider, but please understand I have no first hand experience.
Did Chevy make your car with a 4WD option? If so, maybe you could find a parts car to adapt parts from. Are you thinking of having the motors direct drive to the wheels?
Do you have room to mount both motors end to end and still run cv driveshafts to the wheels? They can't be hub motors. I really don't think they would be the best motor choice anyway with all you want from them. One would be okay through a diff. but series motors don't regen. well which is on your wish list. Yes they have high torque on start up but if you run them direct, they will be running slow all the time and probably will overheat. I think controlling them to get even torque will be a nightmare as well. Series motors don't self limit their max rpm so if you ever spun a wheel on a slippery spot it could overspeed the motor and do damage. A single motor through a diff. would be easier and cheaper. The brushes will be wearing even when the motor isn't being used and if you do use a diff, you need to be sure you gear it so you don't over speed your motor at top speed. AC motors are much easier to control and will do regen, but will cost even more and finding low speed/high torque motors could still be an issue. If you lower your performance goals, you might be able to fit hub motors to the rear wheels but they likely won't have the torque you want.
When you are talking battery pack you need to pick batteries that can deliver the high currents you want as well as the range. Once again more power means more money. High quality lithium will be a must.
I think anything can be done with enough time and money, the question is how bad do you want this?
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Old 08-06-2015, 02:06 PM   #9 (permalink)
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you must really, REALLY love this car!
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Old 08-06-2015, 05:50 PM   #10 (permalink)
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If you want a unique car that'll probably be faster than any other FWD Impala SS, then go ahead and do it. Your first step should be figuring out how you're going to physically get power from the motor(s) to the rear wheels. Using the rear axle from another car and connecting the motor(s) to the differential is probably your best bet.

If you want the fastest V8 car for the money, you might be better off getting a RWD car. For $10k you can easily get a car that is faster than your car currently is, maybe even faster than it would be with the electric motors.

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