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Subaru Gas/electric hybrid


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4 replies to this topic

#1 Ionlyhave3suubs

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Posted 23 April 2011 - 08:19 AM

I am considering the build of a Subaru based Electric vehicle that will operate on both battery power and a gasoline engine. At various stages of the build (if I am able to do it) I am sure I will be coming to the message board for advice and tech questions. I am going to outline the basic theory of how I intend for the car to work then go from there.

The car will retain a factory type gasoline engine up front and the gas engine will drive the front wheels. During operation the gasoline engine will be running at all times. The gasoline engine will drive power accessories (power steering, A/C, engine vacuum for power brakes, and alternator). When the vehicle is operating in electric mode, the gasoline engine idles, turning the accessories and contributing at least a small amount of charge to the batteries.

The electric drive will connect to the rear differential and propel the car at lower speeds and/or until the battery bank runs out of charge. The electric motor will most likely not be used at highway speeds, just for around town and lower speeds (target upper limit 50 mph).

At higher speeds (50mph and higher) the gasoline engine becomes the primary drivetrain in FWD mode. During highway driving the gas engine drives the car and at its higher RPM will contribute more to battery bank charging. In gas only operation, the electric motor will "freewheel" and not be used.

To assist in additional charging. I may install additional alternators to the engine.

If you have helplful suggestions or words of encouragement please add your comments.

My first question relates to ej series rear differentials.

Without major modification, will the rear diff/axles hold up to the low speed application described? keep in mind that an electric motor for this app develops maximum torque almost as soon as it starts turning, unlike a gas motor that has to wind up a bit.

I am considering using a 97 outback as my project vehicle.

If you need more information about the car or build, post it. The car I have to work with is a 2.5d powered automatic Outback. Nearly 230k miles, failed headgasket. Currently has undiagnosed cause torque bind.

I already know a lighter car with manual trans would be better to start with, but I am in the exploratory stage of trying to use what I have. If anyone has an impreza with m/t for cheap in not too bad of condition to start with, let me know (needs to be close to VA.)

#2 Ionlyhave3suubs

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Posted 23 April 2011 - 12:53 PM

My second question for this build relates to the automatic transmission. If I were to remove the driveshaft that goes back to the rear differential, will the transmission still function normally? If so will I be losing power/energy out the rear of the transmission? Will any fluids leak out with the driveshaft missing? I guess that's more than 1 question.

#3 ferox

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Posted 23 April 2011 - 02:17 PM

If you have helplful suggestions or words of encouragement please add your comments.

I am considering using a 97 outback as my project vehicle.

I already know a lighter car with manual trans would be better to start with, but I am in the exploratory stage of trying to use what I have.


If you are a 40 year old (like me) with as much time as will be required to do this build (unlike me), then I strongly suggest you fix the head gaskets and torque bind in the '97 (or not) and buy a Justy ('88-'94) for your gas electric hybrid. The '97 is simply too heavy and the wheels and tires too large.

The transmission in any subaru will not function without the rear driveshaft; the transmission will drain all it's fluid.

#4 grossgary

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Posted 23 April 2011 - 04:36 PM

highly recommend doing a bunch of reading and research. the project you describe is theoretically amazing but practically impossible.

for the auto trans, that would be really simple. the driveshaft is two pieces so you can remove the rear portion and just leave the front portion in place to plug the trans. once this thing is running then you can entertain fabricating a plug if you want.

car will run fine as FWD.

electric conversions typically increase weight of the vehicle even with the engine removed - taking on all the extra heavier load of the electrical driven mechanisms while retained the engine and fat transmission. weight will derail power consumption, efficiency, and it'll kill your range, etc. but again - research it and verify the weight to range ratios, etc. you'll be doing tons of work, costs, for little gain.

#5 Ionlyhave3suubs

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Posted 23 April 2011 - 10:52 PM

highly recommend doing a bunch of reading and research. the project you describe is theoretically amazing but practically impossible.

for the auto trans, that would be really simple. the driveshaft is two pieces so you can remove the rear portion and just leave the front portion in place to plug the trans. once this thing is running then you can entertain fabricating a plug if you want.


car will run fine as FWD.

electric conversions typically increase weight of the vehicle even with the engine removed - taking on all the extra heavier load of the electrical driven mechanisms while retained the engine and fat transmission. weight will derail power consumption, efficiency, and it'll kill your range, etc. but again - research it and verify the weight to range ratios, etc. you'll be doing tons of work, costs, for little gain.


I am unfamiliar with driveshaft removal in these vehicles, never done a Subaru driveshaft. is there something that will hold that front section in place with the rear section removed, and how hard is it to separate the pieces?


I have been doing quite a bit of reading on electric vehicle conversion and what concerns me about the process is the potential for getting stranded without a place to re-charge. My plan for the car is to use as my to and from work daily commuter vehicle. I have about a 26 mile commute to work. About 11 miles of the commute is highway with a traffic flow of 65 mph.

My return trip home is around 15 miles. The difference being I drop my kids off at school on my way to work. That leaves a 41 mile total trip to and from. That does not take into consideration if I have to run over to another work site which I sometimes do. The 41 miles is close to the limit on the range of many electric cars without a re-charge. Unfortunately re-charging the car at work is not an option, thus the reason I am looking to extend my range with a gasoline engine at highway speeds where the gas engine is at its best fuel efficiency.

Just for further consideration, the car is loaded with around 470# of people on the way in and only 170# of me on the way home. Total of 4 people including me going in. Plus maybe 100# of bookbags, musical instruments, lunchboxes, etc.

Edited by Ionlyhave3suubs, 23 April 2011 - 10:55 PM.
correct error





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