[aeroscott]

Originally Posted by eleven

i find it very hard to believe that the diff. alone is losing 20-25% since that's more than most people consider "normal" drivetrain loss. usually for RWD vehicles you can count on about 15% drivetrain loss, FWD and mid engine RWD slightly less, and AWD slightly more, some in the neighborhood of 25%

but, a salesman said it loses 20-25%, so it must be so...

just look at the site please ! then tell me he is just a salesman. if we as a group can do 10% of what he has done I would be happy! for more then 20 years I have been asking about this , the dyno guys all seam to confirm high losses in the rear end . same for my "x"

[mattW]

Couldn't you just compare the horse power and brake horsepower of various cars to give you the efficiency? I'm sure there would be plenty of cars with measures of power at both the engines and the wheels.

[eleven]

i did look at the site. that's how i determined he was selling something. selling something makes you a salesman by definition. Maybe he's totally right that the BMW rear ends lose 25% but that would mean a stock E46 M3 would lose 83hp through the differential alone, let alone whatever is lost through the transmission, weight of the driveshaft, and the unsprung weight (brakes, wheels, etc.)
it may be that it loses more due to it being an IRS as opposed to a solid axle, and the limited slip as well, but i find it hard to believe that BMW can't accomplish today what Ford has been doing since the 60's, which is make ENTIRE DRIVE TRAINS that lose less than 25% of their power


and for the record, I typically consider myself the resident hater of Blue Ovals

[eleven]

Originally Posted by mattW

Couldn't you just compare the horse power and brake horsepower of various cars to give you the efficiency? I'm sure there would be plenty of cars with measures of power at both the engines and the wheels.

the hp at the wheels will encompass more than just differential loss... there will be transmission losses, driveshaft losses, wheel losses, brake rotor losses, etc.

plus, the atmospheric conditions as well as wear and tear not only on the engine, but all of the drivetrain will give several variations in the dyno results. i guarantee no one has dynoed, then pulled the engine and put it directly onto an engine dyno

[jeffey]

OK, we've established the fact that there is a loss! May be 10% or even up to 25%. The question is how to minimize or eliminate that loss.

The origional question was direct drive, eliminating the transmission. If the transmission were eliminated and you could achieve the correct ratio would that work and what other obsticles would you have to deal with?

BTW, This ( http://www.sunrise-ev.com ) is not my site. When I said "I found the perfect solution" I ment I found a site with the perfect solution. Although it probably isn't perfect. Just Better!

[eleven]

Originally Posted by jeffey

OK, we've established the fact that there is a loss! May be 10% or even up to 25%. The question is how to minimize or eliminate that loss.

The origional question was direct drive, eliminating the transmission. If the transmission were eliminated and you could achieve the correct ratio would that work and what other obsticles would you have to deal with?

BTW, This ( http://www.sunrise-ev.com ) is not my site. When I said "I found the perfect solution" I ment I found a site with the perfect solution. Although it probably isn't perfect. Just Better!

you could probably reduce SOME loss, but obviously not all loss. most of the drivetrain loss is actually noticed from the unsprung weight of the wheels and brakes. you could do a custom Independent suspension setup with dual motors, CV joints and custom half-shafts to the rear wheels (or front if you really wanted FWD for some reason) but you'd still need some sort of reduction gear to make the power useable, otherwise it would be like driving a regular manual transmission vehicle in 4th gear at all times

[jeffey]

Holy Moly!!! Based on this calculator it would take a rear end ration of 20:1 to go 50mph with an 84" circumferance tire at 4000 motor RPM!!

http://www.free-online-calculator.co...lculator.shtml

Input Parameters Are the Following:
Differential Gear = 20.00 to 1
Transmission Gear = 1.00 to 1
Tire Diameter (Inches) = 84.00
Engine RPM = 4000
Computation Results:
Computed Vehicle MPH is 50

Does this seem right?

[eleven]

Originally Posted by jeffey

Holy Moly!!! Based on this calculator it would take a rear end ration of 20:1 to go 50mph with an 84" circumferance tire at 4000 motor RPM!!

http://www.free-online-calculator.co...lculator.shtml

Input Parameters Are the Following:
Differential Gear = 20.00 to 1
Transmission Gear = 1.00 to 1
Tire Diameter (Inches) = 84.00
Engine RPM = 4000
Computation Results:
Computed Vehicle MPH is 50

Does this seem right?

the calculator asks for diameter, not circumference... that's your error... try something more like 21 inches

[eleven]

here's mine...

Input Parameters Are the Following:

• Differential Gear = 4.00 to 1
• Transmission Gear = 1.00 to 1
• Tire Diameter (Inches) = 21.00
• Engine RPM = 4000

Computation Results:

Computed Vehicle MPH is 62

with these figures, you'd probably need a pretty massive motor to propel the car from 0-62 in 4000rpm with no transmission... it would take a LOT of torque down low

[SuperChuck_A11]

Originally Posted by jeffey

I have been wondering the same question, Why use a transmission with gears and fluid (oil, grease) = DRAG???
Then I found the perfect solution, even 1 or 2 steps farther than I could have imagined. Check out "Drive system" here: http://www.sunrise-ev.com/specs.htm. Then "Transaxel" here: http://www.sunrise-ev.com/kit.htm.

i looked at those specs and they say:
Transaxle:
A Ford 8.8" differential from the donor car is used, with new gears for a 5:1 ratio. That is a really steep rear gear.

This is a very strong part, often used in drag racing. ahhh usually it is ditched for a 9 inch. But it is pretty strong.

Dry sump lubrication is used with lighter weight oil to improve efficiency.
I hope they are directly lubing the outer bearings on the axles.....and i wonder if the oil pump they use is mech. or ele. ??