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Discussion Starter #1
I have a 1996 HB that I've converted to EV. I used to autocross the car, so it still has the transmission that I built for that, which is a S40 (1996 EX) with a Quaife LSD. The gearing was great for the gas engine, but with the much lower rpm range of the electric motor, I'd like to see what might be possible regarding gearing changes. I'd like to keep the Quaife... it's probably the single best immprovement I've ever made to the car, and it still holds up well after over a year of use behind an electric motor.

A few questions:
  • What is the highest possible ring gear ratio I can get, while (of course) keeping the large bearings for the Quaife LSD?
  • What are the highest ratios possible for 2, 3, 4 and 5?
  • Is there a company or another good source for these parts?
I've done some searching, but all I can really find are options for lower ratios, which makes sense as most people are going that direction with higher reving gas engines. My needs are the opposite... I have all my torque down low, max at 0 rpm and falling off from 3k and gone at 4.5k. As it is, 1st gear is useless, maybe only good for burning up tires. 2nd still needs to be feathered to get a good launch, and 3rd is a normal start off gear for daily driving. By 5th, I am petering out at around 95mph, so a bit more gear up high would be great. A higher final drive would b e better overall, but not sure if there are options for a higher 5th gear ratio.

Thanks in advance for all your help. You guys are the experts.

More info about the car and the build in general here and here.
 

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Brokedick Millionaire
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If it has the stock 5th gear, nothing to really change.

92-95 3.250 is lowest OEM that will work, esp with EV having massive low end torque. Sounds like the motor is "done" by 4000 rpm, so lets limit things to 3500 to compare.

5th gear, what is now 80 mph, would be 105 mph

With VX/CX FD you would only need 2-4-5 gears. You could find a 96-00 HX/CX gearset and use the VX FD...

What is now 3rd gear speed, would be 2nd, what is now 5th would be 4th, then have another gear.

Honda Transmission Calculator by ZealAutowerks
 

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Wouldnt most of the gears be unnecessary? Seems like with most of the EV conversions Ive seen that still utilize an OEM transmission they end up leaving the car in a particular gear or maybe moving between 2 gears.
 

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Discussion Starter #4
Isn't the 92-95 CX/VX P20/A000 35mm? As I have a 40mm LSD, what's the lowest OEM 40mm final drive?
 

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Discussion Starter #5
Wouldnt most of the gears be unnecessary? Seems like with most of the EV conversions Ive seen that still utilize an OEM transmission they end up leaving the car in a particular gear or maybe moving between 2 gears.
It really depends on the motor... I am using a DC motor to get the kind of power I want, but DC has a much lower RPM limit than an AC motor would. As I mentioned I only use 2-5, but I would like to use 1-5 if possible...

If money was no object, and I could get an AC motor with 150kW+, then I could get away with less gears. Some actually remove the unused gears to save weight.
 

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B-series Destroyer
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Final drives are interchangable
 

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Brokedick Millionaire
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Isn't the 92-95 CX/VX P20/A000 35mm? As I have a 40mm LSD, what's the lowest OEM 40mm final drive?
just the ring and pinion would need swapped, I don't think I have any on hand. Last few I've sent to Germany for Mini swaps and tiny tires.
 

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Discussion Starter #8
just the ring and pinion would need swapped, I don't think I have any on hand. Last few I've sent to Germany for Mini swaps and tiny tires.
Ahh, so the ring and pinion mounting is the same? I assumed the 3.25 would be smaller... Good news if true!! I just need to find a 3.25 ring and pinion.
 

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Most EV setups dont use a transmissions because the parasitic loss through the tranny is bigger than what you gain by having gears.
 

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Thats not necessarily true. The Tesla was originally a 2 speed, which allowed it to be more efficient and faster as well, but they had some issues and decided to keep it simple.

Most EV conversions dont have much power, so it makes sense to minimize drivetrain losses and gear it for the low speed that it is capable of.


Earlier I was trying to picture how to ditch the gearbox in a FWD conversion, like a Civic. Perhaps a chain driven differential, or maybe something like a Ford 8.8 IRS diff with the motor mounted longitudinally. The latter could probably be done cheaply (other than the custom CV axles), but it would be a shame to gear the motor down just to gear it back up again.
 

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Discussion Starter #11
Most EV setups dont use a transmissions because the parasitic loss through the tranny is bigger than what you gain by having gears.
Most OEM EVs also have AC motors that can spin to 12000 RPM too... Those kind of motor aren't easily available at a price I can afford, hence the use of DC here. The only guys who run DC without a transmission, or more accurately just a fixed ratio differential, run really big motors or dual motors. I can't run either of those in a Civic...
 

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Yea, my EV friend has been trying to get me to convert my CRX to EV. Apparently a Nissian Leaf drivetrain has quite a bit of modding potential, like 200+hp and 14k RPM if you know what you are doing.

I was crunching some numbers last night and with the ~8:1 final drive the leaf comes with and 205/50/15 tires that would give a potential top speed of 120mph at 14k.

I am curious about how much more weight and parasitic drag a d series tranny would add over the leaf fixed final drive, and how much friction could be saved by using a low weight, low friction synthetic oil in the transmission.

My thinking was if you didnt have to shift regularily, and simply used the transmission as a speed range selector, IE: 2nd is around town gear, 3rd is freeway gear, 4th is long distance freeway gear, you wouldnt have to use a higher friction oil that allowed syncros to work properly, because you basically wouldnt need them.
 

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Looks like it would be a bugger to mount up a tranny to though..... Possible, but probably not worth it.


 

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\/Your Mom Was Here\/
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You can also eliminate 5th gear by using some of the stuff from a 4spd L3 box. This would make the tranny lighter and have less friction, they do this on some of the drag racing trannys. There is a blockoff cuff or something in them 4spd trannys so you can't move it to 5th. Bone could elaborate more as I am sure he has built these before.
 

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Discussion Starter #15 (Edited)
Yea, my EV friend has been trying to get me to convert my CRX to EV. Apparently a Nissian Leaf drivetrain has quite a bit of modding potential, like 200+hp and 14k RPM if you know what you are doing.

I was crunching some numbers last night and with the ~8:1 final drive the leaf comes with and 205/50/15 tires that would give a potential top speed of 120mph at 14k.

I am curious about how much more weight and parasitic drag a d series tranny would add over the leaf fixed final drive, and how much friction could be saved by using a low weight, low friction synthetic oil in the transmission.

My thinking was if you didnt have to shift regularily, and simply used the transmission as a speed range selector, IE: 2nd is around town gear, 3rd is freeway gear, 4th is long distance freeway gear, you wouldnt have to use a higher friction oil that allowed syncros to work properly, because you basically wouldnt need them.
I've never heard of higher power potential from the Leaf motor... It ships at 107hp/200ft-lbs so 200+hp is a big jump. I'm not sure it can handle that kind of power. If you can share a link or reference to those numbers, I'd be interested in studying it.

I know some folks that are trying to use all the parts of a Nissan Leaf for various conversions. This video shows one of the local guys I know that has taken the complete guts from a Nissan Leaf and mounted it on a garage wall so they can isolate and analyse all the various modules to try to bypass or remove any one of them. Many are using just the batteries, but I know one guy that is swapping the entire drivetrain into a Dodge Rampage.

Finding a good motor and gear reduction is number one in converting to EV. Everything else needed is kind of dictated from there... e.g. the pack voltage is dictated by the motor controller, which is dictated by the motor. Choosing a motor is based on the wheel torque you want for acceleration, and the fixed gear reduction. Top speed will be dictated by the max RPM of the motor and gear reduction and if the motor has the torque curve you are looking for to even reach those top speeds. The gear reduction is kind of a compromise for both cases, off the line acceleration and top speed.

Then swapping this gear reduction and motor into the car will likely require some custom axles...

The AC motors that are available to someone like you or I doing a conversion at a decent price are all pretty low power, and there would be the need for custom axles. I just stuck with a DC motor, which has many affordable options in pretty much any power level you can fit in the car. I highly doubt any of the EV gearboxes have a LSD, which is another concern.

The battery pack is kind of dictated by the motor selection. Since AC motors have many more switching components, they are generally limited to around ~500A, so to reach the power levels needed will require very high voltage. A DC motor is kind of the opposite... There are options that can handle some really high current but are generally lower voltage. The motor controllers will generally support higher voltages than the motors, but they are not far from the motors needs in overall power output

Long story short... A DC motor is what is available now at a reasonable price point, that allows a LSD, existing axles, and some flexibility in gearing to tune the car for your needs. Where money is no object, go AC (these are nice, I wish!).

 

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He works for a company that builds EV motorcycles out of California, mostly designing the battery packs.

The claim was actually 300hp out of a Leaf motor, and I have never known him to lie. From my understanding it takes a completely custom controller and 480v. He didn't say how long it could maintain the 300hp for, so I don't know if it could be autocrossed at that level.

Would be sweet for a street car though.
 
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