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Possible Hybrid Drive-Train Questions

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Hey everyone,

This is a lengthy explanation and I assure you I have looked for threads like this. Maybe I suck at searching. Either way, forgive me if this question as been posed before.

I have access to a Mustang II (It's either a Cobra or a Mach 1, I can't recall immediately, but it has the 302.) I have considered doing a complete EV conversion on it, but I think it would be better served by some kind of hybrid/assist system. Keep in mind my goal for this application would be assistance and light EV-only. The heart of the vehicle would still be the 302.

My plan would be to leave the 302 in the vehicle, with a fuel injection system installed to raise the efficiency and power of the really anemic carburetor and replace the four-speed manual with a T5 manual transmission. All that would make the drive line much more efficient just as-is.

At this point I would service the rear end. I'm debating what I would do here, exactly. If I went down to the 2.80 gear ratio then I could do 80mph at about 2150 RPM. Right now this makes the most sense for a gasoline engine. The goal is daily driver, not race machine.

NEXT I would chop the drive shaft and install an dual shaft electric motor to the differential, with all the attendant fabrication that would take. Yoke it on both ends and just let it be part of the drive train, the throttle for it and the gasoline engine would run off the same pedal.

Pros of this configuration that I see:

  • Immediate low end torque assistance from the electric motor, offsetting the lower final drive ratio.
  • Capability to shift to neutral, engage the clutch,or kill the ICE, and use only the electric motor if desired.
  • Increased fuel efficiency by reducing the time the ICE has to operate at lower gear ratios.
  • No need to relocate the transmission, crossmember, and shifter.
  • True hybrid charging of your battery pack via AC motor by the ICE.
  • Can run a lower voltage and/or smaller motor because it is not a true EV.
Cons of this configuration:

  • Difficult to service the motor if it must be removed or tested. You basically have to lift the whole vehicle.
  • Custom Fabrication of the driveshaft and motor mounts necessary.
  • The throttle for the ICU and the motor are on the same pedal.
  • The motor doesn't get the mechanical advantage of the transmission, only the final drive, reducing mechanical advantage if desiring to only run EV.
My biggest concern is in bold. Say you're giving the ICU a % of throttle that equates to 2100 RPM at the flywheel and is being reduced to 1428 RPM as it leaves the transmission. It seems to me that same throttle % is running the electric motor at a higher RPM, say 2000-3000 and up. That seems like a problem to me. I don't want the ICE being spun up by the motor, I always want the motor slaved to the ICE rpms.

Are the two-shaft motors capable of isolating what shaft is actually getting power? I wouldn't want the electric motor to spin the drive shaft side, only the differential side.

Anyway, that was a lot of explanation to ask that last question. I'm still looking for technical data on it, but I figured I would ask here.
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· Administrator
6,607 Posts
I would say don't worry too much about the throttles - both the IC and the electric "throttle" are essentially - Torque Control - NOT speed control

When you press the pedal 50% the engines intake butterflies open 50% and that lets 50% of the air and fuel into the engine developing 50% of the torque

When you press the pedal 50% the controller feeds 50% of the max current into the motor developing 50% of the torque

The rpm is set by the road speed and the gearbox ratio
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