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So, I am curious if one were to have a RWD mid(rear mount) ICE car and they say put in a tesla drive unit to power the front wheels without anything linking the two motors what possible pitfalls would you encounter? Just curious if a driveshaft/differential would be required for a setup like that or if it would be ok to run something like that without anything linking the two motors beyond the gas pedal.
 

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There is no reason to mechanically link (with a shaft) the front drive unit and the engine to control them, and it would be difficult to do that with a Tesla drive unit anyway. Control, including coordination of the front (electric) drive with the rear (presumably engine-only) drive is a job for a computer system; simply feeding the same accelerator pedal signal to the drive unit and to the engine's control computer is unlikely to be desirable.

Where is the energy coming from for the electric drive unit? If this is supposed to be a plug-in hybrid, you need to find a place for a substantial battery, and that's not easy... and even then, when it runs out you just have a big boat anchor in the front. A normal hybrid includes a generator connected to the engine-driven axle, so it can regeneratively brake and can provide power to be used at the front when that is needed for traction or performance. What's the plan?
 

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No need for any fancy control system!
Each end will simply work with the road surface ensuring that they are both at the same speed
 

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Discussion Starter · #4 ·
So, I am curious if one were to have a RWD mid(rear mount) ICE car and they say put in a tesla drive unit to power the front wheels without anything linking the two motors what possible pitfalls would you encounter? Just curious if a driveshaft/differential would be required for a setup like that or if it would be ok to run something like that without anything linking the two motors beyond the gas pedal.
With the frunk & trunk I think I should be able to fit 6-8 tesla power units or equivalent. I figure it'll likely end up being a around town/track tow as generators seem to be a little tough to obtain. I see bosch makes something but not sure if it'd fit a cayman. I thought maybe a belt driven generator but I couldn't really find much.
 

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No need for any fancy control system!
Each end will simply work with the road surface ensuring that they are both at the same speed
Yes, they'll turn at the same speed (or rather, the speeds corresponding to the radius of turn)... until one slips. And yes, you can just settle for a front-to-rear torque distribution depending on available power, as long as you don't mind it changing with engine speed and battery state of charge. If you want to do things in the worst possible hack way, this is it.
 

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"Until one slips"

Mother Nature doesn't make free sandwiches, so you'll have the opposite of a Subaru ad..."power from the wheels that grip to the wheels that slip"

Which is why the DUs need to be on separate inverters, not paralleled.
 

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Yes, they'll turn at the same speed (or rather, the speeds corresponding to the radius of turn)... until one slips. And yes, you can just settle for a front-to-rear torque distribution depending on available power, as long as you don't mind it changing with engine speed and battery state of charge. If you want to do things in the worst possible hack way, this is it.
the worst possible hack is at the same time better than 98% of all cars in the world which merely drive one pair of wheels
 

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Until you hit a patch of ice or snow.

Did that in the 69 Firebird my brother and I built...was happily motoring along on cruise control, one wheel hit black ice, positraction tried to do its job, cruise control said "nuh uh"...she was sideways faster than I could react, but I fortunately recovered vs flipping it.
 

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This is a great question and very timely. I'm just completing a hybrid sports car with mid engine ICE (a relocated front drivetrain from an Acura) and front drive AC-50 running through a Mazda Miata differential. There is no mechanical connection between the systems so the throttle settings will determine behavior. Throttle options so far considered are mechanically connecting an EV 5K potentiometer throttle to the ICE throttle cable, or adding a second throttle position sensor to the ICE for a 0.5 to 4.5 volt signal connection to the EV throttle. The AC-50 controller is programmable for throttle curve, dead band and regen settings. My original plan (with results TBD) would provide option for either max power or economy profiles and EV regeneration at low ICE throttle settings to allow charging while cruising under low loads. Remains to be seen whether this is a successful experiment. Has anybody done something similar to this? Would appreciate any advice or suggestions. Thx
 

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This is a great question and very timely. I'm just completing a hybrid sports car with mid engine ICE (a relocated front drivetrain from an Acura) and front drive AC-50 running through a Mazda Miata differential. There is no mechanical connection between the systems so the throttle settings will determine behavior. Throttle options so far considered are mechanically connecting an EV 5K potentiometer throttle to the ICE throttle cable, or adding a second throttle position sensor to the ICE for a 0.5 to 4.5 volt signal connection to the EV throttle. The AC-50 controller is programmable for throttle curve, dead band and regen settings. My original plan (with results TBD) would provide option for either max power or economy profiles and EV regeneration at low ICE throttle settings to allow charging while cruising under low loads. Remains to be seen whether this is a successful experiment. Has anybody done something similar to this? Would appreciate any advice or suggestions. Thx
Really great question. Can you provide more details about your project?
I have same idea, but did not started the project yet because of problem mentioned below.
Car is MR2 spyder powered by K20 ICE.
Car is just fro track days and idea is to make it AWD by swapping any electric motor in front for better performance. just use E motor while cornering out or power start (maximum acceleration time 15 sec)
Installing less than 50 KW motor is not giving such a big gain to add extra 100-150 Kg on front axle. By rough calculation 50KW by 15 sec is just 200-250 Wt-h, so In a theory 2 KWh battery is more than enough for short time acceleration but actually I can not find any battery having big continuous current discharge rate and small capacity.
 

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Really great question. Can you provide more details about your project?
I have same idea, but did not started the project yet because of problem mentioned below.
Car is MR2 spyder powered by K20 ICE.
Car is just fro track days and idea is to make it AWD by swapping any electric motor in front for better performance. just use E motor while cornering out or power start (maximum acceleration time 15 sec)
Installing less than 50 KW motor is not giving such a big gain to add extra 100-150 Kg on front axle. By rough calculation 50KW by 15 sec is just 200-250 Wt-h, so In a theory 2 KWh battery is more than enough for short time acceleration but actually I can not find any battery having big continuous current discharge rate and small capacity.
Hi,
I also built mainly for brief hard acceleration on the road / track but also for occasional boost when cruising for economy. I'm going to use [email protected], 65AH Odyssey deep cycle AGM batteries for a 6.5KW system. Lithium batteries may replace them later. The overall weight gain with batteries, motor, controller and diff is around 600 lbs. in a car estimated to total 2,750 - 3,000 lbs. Acceleration calculations suggest that the horsepower gain is a push, but the big gain is in torque for acceleration out of turns. The battery pack should provide an estimated 100 A for 25 minutes or 300 A for 5 minutes of high draw use. I chose the Odyssey for its high demand pulse and cold cranking current capacity. Check out their Extreme line at ODYSSEY® Battery - Official Manufacturer's Site for options. I'm guessing the weight increase (even with a smaller motor and battery pack) will be a challenge with a lighter car. Linking the electric motor directly to the ICE final drive and avoiding the second differential would help but I couldn't find any car / motor configuration that worked easily. Instead, I used the Miata diff, Acura front end (knuckle / hub) and custom CV shafts ($$) to connect them. Let me know if you plan to proceed. By then I will have had a chance to work out the mechanics and programming of the throttle system and can share any lessons learned.
 
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