Adding these electric motors to the back wheels of my FWD gas car?

[ciano22]

Originally Posted by vskid3

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.

I totally understand that I can get a much faster car for not too much money, but I am trying to see if it is possible that I can make this car into something really special. This car has a V8 in it, which could be upgraded to get some good power, but then it just cannot put power down until about 40 mph. This car consistently chirps the tires if I floor it at under 40 mph, and it has nothing to do with the sheer power of the engine, and more to do with the fact that its FWD.

I am wanting to see if adding RWD power to it will remedy this situation. Once the car is going, it is definitely respectably fast, but its a joke off the line. If these electric motors can get the car off the line faster, then I think it can compete very well with cars that are naturally much faster, once the gas engine is also upgraded. I want to do this electric stuff for under 10k, because it will be around 7k to get the gas engine upgraded to putting out close to 500hp by itself, which is possible, but incredibly stupid in a car that is FWD.

The main thing that I'm asking is the price and the expected outcome. Will have 2 electric motors, putting out roughly 300lbft of torque(150 to each rear wheel), coupled with my gas engine, putting out(realistically) around 280 lbft of torque, make my car get to 60 mph all that much faster, or are there seriously limiting factors that make the performance gain not worth it?

[ciano22]

Originally Posted by SwamiSalami

you must really, REALLY love this car!

Definitely! I am also a modder at heart though, so, once I get a different car, this car will most likely be a project. That is what this whole thread is about. I will hopefully own myself either a Tesla Model S, or a Chevy SS within the next few years.

[ciano22]

Originally Posted by puddleglum

Are you wanting to pull 400lbft torque from your electric motors in addition to your gas engine?

At first, just to get things going, I would like to use the small, cheap motors to see if I can get them to work, as well as see if there is a noticeable performance gain. After that, assuming I am satisfied with the results, the real money spending starts, including buying more powerful electric motors and getting performance modifications for the gas engine as well.

Originally Posted by puddleglum

Did Chevy make your car with a 4WD option? Are you thinking of having the motors direct drive to the wheels?

No, and Yes.
My car is based off of the GM W Body platform, which has had no AWD or RWD vehicles. However, I have read about people doing RWD conversions on W body vehicles using rear axles from certain GM suvs, such as the Pontiac Aztec, which I may be able to find a rear axle of for very cheap.

Originally Posted by puddleglum

Do you have room to mount both motors end to end and still run cv driveshafts to the wheels?

If you mean perpendicular to the wheels, then maybe.... If you mean to mount them longways along the center of the undercarriage, then I seriously doubt it.

I managed to look at the underside of my car once while it was being serviced, and took some pictures as well. Do you think I can fit 2 small electric motors in this space? What are these things, and can they be removed? Do you think it will be difficult to connect the motors to the frame of the car? I am definitely not opposed to a new exhaust system to make it work. Also not opposed to losing my spare tire space if that will make the room that is necessary.

Originally Posted by puddleglum

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?

Now all of that is good info for me. Definitely haven't heard about most of those issues. Basically, here is how bad I want this:

If I have to completely mangle the undercarriage of my vehicle in order to try and fit electric motors along the center, to then go into a diff off of a random SUV, then it may not be worth it to me, just because that is only half of the work, and will be very expensive.
However, if there is any chance of getting this to work by mounting the motors directly to the wheels along the space that a rear axle would be, then yes, I definitely do want to do this. Remember that I can use the front drivetrain to do anything other than go fast in a straight line. The economy stuff is just something that I would like to do if possible. If it would make this whole project THAT much more difficult, then I would totally just leave the motor off until I got to the strip.

That being said, I don't actually know what is under that undercarriage cover. If I find out that there is room for 2 electric motors to be coupled to each other and run through a differential, and that moving the gas tank isn't as hard as I think, then I would totally do it.

The other option is using one single powerful electric motor that is double-sided to drive both wheels. This basically means I will have a locked differential, which may not be ideal, but then again, this car is going to be just for straight lines. I have already had a close enough call involving a slight curve on a long, high limit road, where torque proved to be a scary thing. I do not ever want this car to be over 3k rpm on an even remotely curved road. Basically, if I have to simply not use the electric part of the car if it is wet, or if I am on a gravelly road, then I wont.

Here's a video that made me consider using that particular motor.

That motor has about a 12 inch diameter, which means im pretty certain it can fit in that cavity. However, the reason I think 2 separate motors would be better, is because they will actually put out more power, while also having a smaller diameter. If the gas tank is in the way for the 12" motor, then perhaps it won't be in the way for two 9" motors. Then the question would be whether to couple the 2 motors into one, like in this video, or have them each drive a wheel by themselves.

They have a 13" motor that puts out much more power, but is also much more expensive.

Thanks a lot for your comments. I hope you can make more sense of what I want to do now, and, hopefully, tell me about how totally possible it is.

[vskid3]

Originally Posted by ciano22

What are these things, and can they be removed?

What things are you referring to?

In my opinion, doing the axle swap from an Aztek or similar would be the easiest way to connect the motor to the wheels (I use the word "easiest" loosely here). You're already going to have to redo your suspension and swap in hubs that can be powered. You'll probably need the gearing in the differential as well to keep the motor happy. It would probably be best to go all out on the motor, controller, and battery the first time. Cheap parts won't be a whole lot cheaper and there's not much that you could transfer from a low power setup to a high power one.

Don't forget to consider the horsepower the motors put out, the one you linked to in the first post is 38hp at 72v (not sure if/how much you can overvolt it). Torque isn't everything, a 100lbs person can produce 300lb-ft of torque just hanging on a 3ft breaker bar, but that won't rocket a car down the drag strip.


Have you done anything to try to keep the front tires from lighting up? A limited slip differential and sticky tires would help you get the power to the road as it sits and would be beneficial to have even if you do add the rear motor.

[ciano22]

Originally Posted by vskid3

What things are you referring to?

Pretty much everything in that picture that is not suspension, exhaust, or the gas tank. I have no idea what that stuff is for.

As for the horsepower comment, I have a V8 gas engine for horsepower. These electric motors put out over double the torque than horsepower. The BMW m3 from that video puts 850 lbft of torque to the actual wheels on a dyno, but only 342 hp. That is exactly what I want. Raw torque to launch my car because the front engine sucks at making it happen. Once the car is going, maybe around 70 or 80 mph, the front engine will continue producing torque and horsepower, while the electric motor will just be fading off.

The reason it is so hard to keep the front tires of lighting is because the car is not completely built for that, like, say, the new Honda civic type R. When my car launches, weight transfers off of the front tires and on to the back tires, leaving the front tires with less grip. Sticky tires would probably help a little, but even then, it wont be anything special.

[freebeard]

I have a 2006 Impala SS. It is FWD ... I'm sure you guys all know about that.

Impalas are FWD?

Single speed electrics need about twice the torque for starting up compared to one with a [two speed] transmission, per EVTV. For instance my Lexus MGR would rev to 10,000rpm with 6.something reduction (after another $12,000 investment. ).

Frankly, since your going to be saving up for a while, by years-end they will have reverse engineered the CAN Bus controls for the Telsa drivetrain. 400hp. You could ditch the V-8 and have a faster car.



Sit through a few back episodes of EVTV and see what you think. It's on Youtube and at EVTV Motor Verks - Custom Electric Car Conversion Instructional Videos

Pretty much everything in that picture that is not suspension, exhaust, or the gas tank. I have no idea what that stuff is for.

Crossmember and brake lines?

[hootis]

Realistically this mod is too complicated. Its far simpler to just get a car with better mileage, or a car that you can do other mods on.

[pete c]

This, as described absolutely will not work for a few reasons.

1. These motors are heavy. Using them in an unsprung application would result in horrible handling and probably destroyed tires/rims from hitting potholes.

2. As has been stated already, these are low speed high torque. Good for a forklift. Bad for a car, unless you are going to use it as a yard tow vehicle.

I think there is a definite application for hub mounted rear wheel drive as an add on to something like a civic or a metro, primarily to give it hybrid capabilities, secondarily to give it 4x4 capabilities. Such a motor would be a high voltage AC motor with pretty modest power output.

If you want to make a large american V-8 sedan accelerate, it is simple physics. You gotta spin the wheels where the weight is, via that big lump that is already producing lots of power. Kinda like the way they did it the prior half century in impalas.

[user removed]

Get an electric motorcycle.

regards
mech

[Xist]

Get a bicycle!