# Add EV motor to drive rear wheels???



## andyberude (Feb 3, 2016)

Hi All,

Thanks for reading my Idea/Question.

Effectively I'd like to create a capable AWD performance hybrid car. I currently drive a 2011 Honda CRZ. I've been toying with a lot of ideas to make this car more capable as well as more fun but need great gas mileage. 
The car's hybrid system is a little wonky. IMA is basically gas motor-electric motor-transmission. Integrated Motor Assist. 
What I'd like to do:

Find an electric drive motor to hook up to the rear wheels in place of the existing hybrid components. A 200HP EV motor driving the rear wheels would give me a nice jump. I'd be looking at about 111HP driving the front wheels and 200HP driving the rears. That just sounds insanely fun and should be good for at least an equivalent 50MPG.

Stock figures on my car are; Gas motor= 111HP/106 ft.lbs Electric Assist Motor= 14HP/58 ft.lbs

At 311HP a 36/64 rear biased AWD car would be so much fun. I'm hoping someone might have experience on some level with this type of conversion. I may be delusional and I know anything is possible with enough money. Just looking for realistic, constructive information on the possibility and maybe some source for parts/kits/info.

Thanks for over indulging me by reading my lunatic idea. Why Honda didn't just stick the 123HP/189ft.lbs motor from the Fit EV in the hatch to drive the rears I'll never know. Or why they didn't give it the drive train from the S2000. Both vehicles are related(Fit) or close to the same length/width (S2000) so why not? Oh well.

Thanks again.


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## okashira (Mar 1, 2015)

It's a fun idea and something we plan to do. But you may be underestimating the control of the car. You can't just press the gas and have the motor and engine work together automatically. :-D
The s2000 motor has poor efficncy not good for a hybrid or crx.
The Fit EV is a compliance/R&D car and the motor would be far too expensive to just slap it in the rear.

Just be ready for a crazy setup where you control the engine and motor seperatley.

Is the CRZ available with AWD anywhere? You'll want some of those parts to make driving the rear wheels much easier. Otherwise, you have alot of custom parts to make and fab work to do.


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## andyberude (Feb 3, 2016)

They didn't/don't offer an AWD CRZ anywhere no. My thought (most likely wrong) was if I could somehow connect the throttle for the EV motor to the drive by wire electric throttle of my existing car, then the same electronic information could be split to both sources. 
Similar to having a guitar go to two separate amplifiers using an A/B/Y box. 

Guitar (electric throttle) ---}A/B/Y Box (controller?) ---}Amplifier 1 (Gas Motor) and Amplifier 2 (Rear EV Motor) simultaneously. 

I guess in my brain since I don't know much if anything about any of this, it should work in a similar fashion. Electronic signals are electronic signals. I'd just need to find out how to guide them to their end source. 

Probably all impossible but would be interested to see if anyone has source websites for a 100+ horse power EV motor and controller with drive axles so I could estimate if it's worth my time.


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## Gator417 (May 3, 2018)

I totally get what you're saying and I've thought about doing exactly the same thing. I'm positive one could use the signal coming from the engine's TPS &/or speed sensor to control the motor output. I've thought about this with just a direct drive setup, for frequent starts in traffic, since that's where an engine is least efficient. I hope you get somewhere with this idea.
Gator


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## brian_ (Feb 7, 2017)

This section (_DIY Wiki Discussion_) is supposed to be for "Planning and discussion for what goes on the wiki" (_EV Information_). This is a discussion of a specific project proposal, which certainly doesn't belong here.


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## arber333 (Dec 13, 2010)

andyberude said:


> They didn't/don't offer an AWD CRZ anywhere no. My thought (most likely wrong) was if I could somehow connect the throttle for the EV motor to the drive by wire electric throttle of my existing car, then the same electronic information could be split to both sources.
> Similar to having a guitar go to two separate amplifiers using an A/B/Y box.
> 
> Guitar (electric throttle) ---}A/B/Y Box (controller?) ---}Amplifier 1 (Gas Motor) and Amplifier 2 (Rear EV Motor) simultaneously.
> ...


Hm... 

I have seen Volvo V60 hybrid motor. It is 60kW motor with integrated reduction gear and halfhshafts inline. You could just install it to the rear axle and use Lebowski brain to drive it. 
https://upload.wikimedia.org/wikipedia/commons/6/63/Volvo_V60_Hybrid_motor.jpg

And you dont need different throttle pedal. You couple your throttle pedal signal to the rear drive and see if it needs a little delay. To take care of that you could put an arduino to read the throttle sensor and you can tune a delay.

A


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## brian_ (Feb 7, 2017)

arber333 said:


> I have seen Volvo V60 hybrid motor. It is 60kW motor with integrated reduction gear and halfhshafts inline.


This is a good idea: use the hardware built by various manufacturers for exactly this purpose (driving one axle electrically, as a supplementary drive system). Examples include rear units from any AWD transverse-engined Toyota (including Lexus), such as the RAV4, Highlander, and RX hybrids. More examples would be the similar Honda/Acura models (Pilot and MDX hybrids). Some are front units from vehicles with the engine driving the rear wheels (BMW i8, Acura NSX).

These units will include - not just a motor and reduction gear - but also either a differential, or two separate motor and gear sets. The Toyota/Lexus units (and most others) have a differential; some (such as those in the i8 and Honda/Acuras) have two motors and even additional gearing.

The target car's suspension and hub components still need to accommodate driven hubs, which means replacing at least some components with those from a related AWD model (such as a Honda CRV or Element).



arber333 said:


> And you dont need different throttle pedal. You couple your throttle pedal signal to the rear drive and see if it needs a little delay. To take care of that you could put an arduino to read the throttle sensor and you can tune a delay.


"Just couple" likely means accept an input from the pedal assembly and put out something completely different. It seems exceptionally unlikely that any rear drive unit is controlled by a variable resistance or analog voltage as would come from an accelerator pedal; it would logically be network-controlled.

I don't know why anyone would want a delay in this control, especially when reducing power.


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## arber333 (Dec 13, 2010)

brian_ said:


> "Just couple" likely means accept an input from the pedal assembly and put out something completely different. It seems exceptionally unlikely that any rear drive unit is controlled by a variable resistance or analog voltage as would come from an accelerator pedal; it would logically be network-controlled.
> 
> I don't know why anyone would want a delay in this control, especially when reducing power.


Well i am thinking of fwd drive car and driving it from the rear should create some imbalance in steering geometry. To fight that you should use a little delay from when fwd gives power to when rwd components push. So as not to just turnaround when applying throttle out on a bend.

Yes coupling means just taking analog signal from 5V acc pedal and using it to create whatever signal you need in your second drive. This signal gets tuned up later in the IC of the second inverter unit. At least i would have done it that way.

A


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## Duncan (Dec 8, 2008)

Hi arber
You are overcomplicating things - there is no need to have a delay


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## brian_ (Feb 7, 2017)

arber333 said:


> Well i am thinking of fwd drive car and driving it from the rear should create some imbalance in steering geometry. To fight that you should use a little delay from when fwd gives power to when rwd components push. So as not to just turnaround when applying throttle out on a bend.


A delay would not help, and would only cause problems.

Until electronic management took over AWD cars, they had a centre differential to split power between front and rear (and some still do). This system has no way to introduce a delay, and in fact keeping the torque (not power) balance between front and rear constant is valuable.


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## arber333 (Dec 13, 2010)

Well i will just have to try it then. If i took 2x Leaf motors i imagine i would have to control torque since they are of the same power. But i think i would be safe using Volvo V60 rear motor since it is weaker.


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## julian77 (Jan 30, 2021)

Gator417 said:


> I totally get what you're saying and I've thought about doing exactly the same thing. I'm positive one could use the signal coming from the engine's TPS &/or speed sensor to control the motor output. I've thought about this with just a direct drive setup, for frequent starts in traffic, since that's where an engine is least efficient. I hope you get somewhere with this idea.
> Gator


I was thinking of putting a rear drive electric my Maxima and keeping the stock powertrain and controls. I have a modified tandem bike that has 2 independent electric motors, one in front and one in back. Everybody asked me how to sync the drives, I don't. There is no issue. I can run either or together. It works fabulously. When I run them both it just allows either to run up to the speed the other is holding before load carrying sets in. One is a twist throttle the other is a thumb throttle. Although you can run 2 electric, front and back on one throttle I suspect there would be complications to sort out running gas and electric on the same control exceeding current controls sophistication or design. I believe if there are peculiarities the human brain would easily sort it out and get use to it. It would be a lot of fun. That would be a true hybrid.


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## brian_ (Feb 7, 2017)

julian77 said:


> I have a modified tandem bike that has 2 independent electric motors, one in front and one in back. Everybody asked me how to sync the drives, I don't. There is no issue. I can run either or together. It works fabulously.


It works fine because the power level is so low (compared to the vehicle mass) that it doesn't matter much which wheel is driving.


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## julian77 (Jan 30, 2021)

I've done some more thinking on this. For simplicity you can run a jumper cable from your throttle cable. Set up a lever to the electric drive throttle with several options as far as ratio of activation. Start low and work up to your comfort level. Or just have a separate throttle peddle to the left of your brake. use both feet to run the motors separately. I do this with my handle throttles. You will adapt very quickly and this will give you an opportunity to play with many variations. Make sure regeneration is either off or only activated manually. Some bikes systems have this set up on a reostat that deactivates as some as pressure is removed. Of course if you want to use the brakes your left foot leaves the rear drive throttle so it goes to coast, no interference. There is almost no challenge in operation. Think of the boost you'll get when you suddenly unleash all those horsepower in the electric rear powertrain.


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## M. Lewisham (May 14, 2021)

Ha, ha. Don't you guys on the left of the Atlantic have any road worthiness/ safely inspections on vehicles ?


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## arber333 (Dec 13, 2010)

Duncan said:


> Hi arber
> You are overcomplicating things - there is no need to have a delay


Sorry I did not mean a time delay. 
Rather i meant a different calibration of throttle pedal for each of the lebowski brain. That way your front drive would pull first and after traction is established you get the rear drive to push. 
Also regen needs to be ramped down at really low RPM.
It could be done with a single Prius pedal and two inverters.


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## dr futon (4 mo ago)

Fantastic discussion. My idea was adding a cheap electric motor in hub wheel to the rear of an existing gascar. Orbis does that commercially, but expensive.


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## remy_martian (Feb 4, 2019)

Hub motors are not cheap. They also suck for torque and are the quickest way to a bent rim if you use low profile tires.


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