Robin W.

I'm doing an engine swap and I'm just wondering how much torque the 951 tranny take? Depending on the total package I'll have between 300 and 460 ft-lbs of torque, the "problem" here is that it's available instantly, off the line, tires not turning yet so the torque doesn't build or ramp up gently it just sort of hits (unless I tweak software to allow a more gentle ramp, but what's the fun in that??).

The other question is how much torque can the stock 951 clutch hold? In a way I would like the clutch to be the weaker link and slip before snapping axles or destroying gears. But I don't want to be replacing the clutch very often either.

LS1Porch

450whp seems to be about the breaking point, but some live longer than others.

Then there's the weak axles...

Darwantae951

If you're going to have between 300 and 460, I'd suggest upgrading to a higher clamping pressure plate.

xsboost90

my upgraded cup clutch only held 350 rwhp before slipping. Now w/ a KEP i have more clamping force- 600ft/lb - i would do a solid trans mount or trans brace to keep from killing axels.

Robin W.

Thanks for all the input guys, looks like I'm under the HP limit but torque could be a problem. To give you a little more info it's an 11" series DC electric motor.
So I won't actually need to use the clutch to start out, as the motor will start with full torque from 0rpm. I would like to keep the clutch for shifting, even though many do without it. I will also likely be starting in 2nd gear and not use 1st at all since the electric motor has more low end torque than any gas engine that would fit in this car. I would just rather not have to replace transmission parts. I'm ok with upgrading a clutch if necessary but I would like to stay within the limits of the tranny. It'll just be a fun daily driver that might hit the autocross or drag track once in awhile.

SirLapsalot

Whuuuaaaaaaaaaaaaat? Explain. What exactly are your plans? More info please sounds cool if you are serious!

MN944S

Recognized you from the DIYEC board.

Thought you were set on the WarP 9?
WarP 11 or a Kostov now?
This thing is gonna be a hoot either way.

I'd rather replace CV's than a clutch...

Robin W.

I am serious, I'm less than a week away from ordering the motor. I just have to decide the level of power (and expense). The conversion is going to be expensive regardless so I thought why not go all the way with the warp 11 or 11-HV (similar to what CroDriver is using on DIYEC, his motor is modified though)
The Warp 11 would have the most torque, but the 11-HV would have quite a bit more power with a bit less torque.

SirLapsalot in short, I'm ripping out everything gas related, cooling system, fuel system, exhaust system, computer, engine, swap to a manual steering rack, and replacing it all with a BIG electric motor, electronic motor controller and a fairly small pack of high current batteries. The pack voltage will be 288v and capable of 1000A continuous discharge. I'm hoping to come within a couple hundred lbs of stock weight, but going electric it will gain some weight. I just have to be careful to keep it balanced.

http://www.youtube.com/watch?v=iOo1TnWKVCg

The above green bmw is really my inspiration to go a little bigger with my project. I'm not looking for that type of performance, just something better than any stock/mildly modified 944 turbo. (mine is starting out with as a stock '86 944 NA but it has a 951 tranny)

The bmw is capable of 0-100km/h in 3.7 seconds or less. I will be using street tires though, and have a bit less battery and motor current so in the end I'm shooting for 5ish seconds.

SirLapsalot

Wow thats cool. Id love to know/see more of your project specifically as it progresses. You should document it.

Robin W.

I am actually documenting the process on one of my blogs.
http://electricporsche.rwaudio.com/
Most of the progress other than engine removal is me flip flopping about what parts I'm going to use. It has changed weekly as I switched from medium cost to low cost to higher cost etc. But in the big picture it's only a variance of 15-20% of the total project cost so why not just go a bit bigger which will provide quite a performance increase.

SirLapsalot

Oh ok cool thanks for the link, that's the kind of thing I was hoping to see. And I would agree why not just go bigger with a 15-20% difference in price? Do it once the way you would really like it and be proud. Best of luck man

V2Rocket

try adding a voltage chopper for the first 2 gears, you will still have plenty of grunt to get going quite quickly but with less chance of damaging the box.

Robin W.

The controller is there to do that and is software configureable. I will be able to set maximum battery current, motor current, motor voltage etc, as well as the slew rate on the current ramp (IE how long it takes to reach 1000A when you put the "electric pedal" to the floor) I'm just curious if I started to max out the settings if I would start breaking things.

How well does a stock 944 hook up? Is it easy to break traction with too much power?

pontifex4

It's quite easy for me to break traction in the first two gears with less than half a tank of fuel on my fairly stock Turbo with LSD, for what it's worth.

V2Rocket

a stock NA with an NA gearbox can break the tires loose if you take off from 3000RPM and up. hell, my NA with a turbo gearbox could break the (fatter) tires loose. 137 ftlbs of fury...

i think itd be neat to program the controller with the transmission ratios in mind; it could be cool to have essentially the same amount of axle torque in every gear. maybe boring, but smooth...

like, if you have 400 ftlb from your motor...
951 gearbox ratios // programmed motor output
3.5:1 // 114 ftlb
2.059:1 // 195ftlb
1.4:1 // 285ftlb
1.034:1 // 386ftlb
.829:1 // 400ftlb