# Hybrid parallel system with awd vehicule



## imsomagic (May 11, 2016)

Hello!

I would like to know if the my concept is achievable. I have a Subaru Impreza 2.5i 2007 and I would like to had a AC motor in parallel. I can't add the motor where is the transmission, I was wondering if I can connect the electric motor to the timing belt (I will connect another belt to the timing belt and relocate the air intake to place the electric motor). The motor would give power to the wheel for 0 to around 60 km/h. Once the speed is high the electric motor will only charge the battery and the petrol engine will only work. At slow speed, the petrol engine will coast. 

The battery pack will be small to give around 30 km autonomy on electric motor only. The petrol engine is about 172 hp. I was thinking for a AC motor around 20-40 hp and peak to 100 hp. 

Maybe the problem will be about the acceleration pedal to prioritize the electric motor at slow speed. 

What do you think ?


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## Yabert (Feb 7, 2010)

Hi

A friend of mine is doing similar project with his BRZ.
He is doing this by the hard way since he build his motor who will replace a part of the drive shaft (RWD car). 
He plan to use a chevy Volt battery.

Your idea of using the timing belt seem strange to me, but I don't know subaru engine very well.
You can maybe have gas engine powering front wheel and an electric motor on the rear wheel.
Think at Lexus 450h or hybride Toyota Highlander. Their rear motors are really nice 50 Kw unit.



> At slow speed, the petrol engine will coast.


At city speed you can probably only use the electric power and turn off the gas engine.


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## imsomagic (May 11, 2016)

I got the this idea because the car is already awd and I can't add an electric motor near the transmission because the transmission is so big and I don't want to touch the interior of the car.


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## madderscience (Jun 28, 2008)

DIY hybrids are problematic for several reasons:

1) adding the weight and volume of the EV drive system without offsetting any of that gain by removing ICE stuff
2) complexity of managing two drive systems in a manner to actually achieve a net benefit.
3) locating the EV drive motor, when the ICE stuff is still in place. an AWD solution does make that part easier. In fact, some OEM AWD hybrids already work that way, the rear axle is solely electric powered. 

It should be telling that there are basically zero known DIY hybrid conversions that have been completed. At one point I think I heard of somebody who had done it with a full size pickup by putting the drive motor in series with the rear axle similar to what you are thinking, but it was a large vehicle with room to carry the extra stuff. And for his effort and cost I think I recall he could increase his gas mileage by 3-4mpg for an hour or so.


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## imsomagic (May 11, 2016)

I spoke with an electrical engineer who gave me some details. It is possible to connect the electric motor on the timing belt, even if it's not a Standard method. By cons, it is very difficult to operate the two motor assemblies because of the difference in torque. Best to run either one or the other. For the electric motor, the electric circuit must be protected to prevent the engine generates power at the wrong time and burn the batteries.

I know that it adds weight to the vehicle, I think that by limiting the batteries to a range of about 20-30 km it would be a fair environment to not add too much weight or having to recharge the batteries for 5 minutes.


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## hostage (Aug 2, 2007)

I worked on a kit that went behind the transmission (DC) and replaced a section of the driveshaft. At 48 Volts you could expect ~15-25% improvement in fuel economy. At 72% the electric assist would work to a higher speed and also provided greater acceleration and could improve economy about 33%+. We also investigated the method you described (serpentine belt driven). It worked but the improvement of driving "thru the engine" limited the economy gains to around 6%. You may be able to get more info at http://www.hrivnak.com if it's still available there... BTW: This was circa 2004, newer high power controllers that speak to the CANbus, wireless OBD-II connectors, the Torque app, etc. would make life easier for you today (IMHO).


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## imsomagic (May 11, 2016)

OK thank you for this useful information. It's interesting to hear from those who have tried it! Your website seems interesting, I'll go and read your experience!


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