Has anyone had the drive train loss of the ZF-6 C4 measured?

I've been told it can be in the order of 20-25% due to the IRS. Just looking for some confirmation... :cheers:

 

a manual trans car will probably be more like 15-18%...
but i'm sure you will get many opinions on this subject.

 

I think the drive train losses are much closer to a constant number than a percentage. I dont think if you were to bolt a 300 hp engine on to a drive train and then a 450 hp engine to the same drive train and seperately measure losses you not see that great a difference . On our Vettes it seems to be around 45+ hp.

I have seen coast down measurements on a dyno which try to approximate the drivetrain loss and they are similar to the above mentioned figure.

Hope that helps.....

 

Not thread jacking, but how much for a Th400? :confused:

 

Based on CHP from trap speeds immediately before the dyno pulls, my DT loss is 17%.

I have the stock 2.59s out back and a worked 700R/4. During the dyno pulls the TC locked up at around 120-130mph in 3rd gear (pulls were terminated at 145mph) though that doesn't happen on the strip. Since the pulls ended at about 5,400rpm, which was past the peak HP point, I don't think TC lockup biased the calculated DT loss.

I've heard that the Vette 6-speed has a little less DT loss...more like 15% or so.



[Modified by 65Z01, 4:31 AM 10/22/2003]

 

isn't the DT loss for an automatic solid axle car around 17%? if so, that would mean that no additional losses are caused by the IRS which can't be possible unless the 1/2 shafts are in perfect horizontal alignment with the diff and axle stubs ? :confused:

 

Does anyone have solid (ie, dyno) evidence of the losses with stock, and modified engines? Shouldn't be that hard to do for 1st, 4th (direct), and 5th gears at various RPM.

Also, does anyone have solid evidence for loss reduction with cryotreatment, coated gears, and synthetic lubes? If any of this stuff gives even 5% loss reduction in aggregate, the gain of net hp to the wheels would be worth it.

Finally, would be interesting to see "apples to apples" comparison of stock and modified engines with 6sp vs Auto trans to see how the loss compares.

Any takers?

 

:lurk:

 

danny kellermeyer told me personally that it was around 15% for a manual vette. he has dynoed many many engines in and out of the car and i think that he has a pretty good grasp on the subject (former GM engineer and now TCC racer).
:cheers:

 

I can see where type of trans and TC and effect DT losses as well as possibly some small effects from type of tranny & gear lube as well as temp of each.

But I don't think that engine mods would effect DT losses as the measurement is a percentage of drop from crank shaft to where the rubber meets the road (or dyno drums).

 

Drivetrain loss is an irrelevant factor. Regardless of wether you lost 5 or 500 HP through the drivetrain, the numbers at the wheels are what matters. If you have an engine that can produce 1000 HP, but the drive train uses up 700 of that, you still only put 300 to the ground. Will you be an faster than someone with a 350 HP engine that only lost 50 from the drive train? No. The only reason I can see that you would need to know engine/flywheel HP is if you wanted to sell the motor.

FWIW, I saw a T56 and a GM 10 bolt get mounted to an elctric engine on an engine dyno to determine excat loss through that combo. It took 38 HP to turn the whole thing, simultaing a 3600 lb car with zero drag. I would say that 45 is pretty close for a C4.

Think about this. Say my car dyno's 300. Considering 15% loss through the drivetrain, I would be making 345 at the motor. Or, the drive train absorbed 45 HP. Now I install an N20 kit and spray a 200 shot. The car then dyno's 500 RWHP. Again, 15% works out 575 at the engine, or a 75 HP loss through the drivetrain. How did the drive train eat up more power, when I didn't change any of its components? I don't think it did. IMO the % loss thorugh the drivetrain is BS.

 

About 1 month ago I scanned an article in ???? car magazine at a newstand regarding drive train losses.Can't remember the details but it compared some different rearends & trannys.

The jest of the article as I remember was that these losses are significant & something to consider when trying to maximize rwhp. Significant differences between different differentials & trannys. It included dyno results.

Sorry I don't have the mag, but as I recall it was very relevent to this thread.

 

I'd have to partially disagree. HP is determined by two things, torque and RPM. If you increase the torque applied to a drivetrain you will increase the pressure between gears, bearings, and whatever moving parts have to transmit or redirect that torque. That is going to increase friction and therefore increse power absorbed by the drivetrain. It would make sense to me that this would be a linier relationship. If you double the torque, you double the friction.

If you increase RPM you will increse the rate at which drivetrain drag must be overcome, just like increasing the speed of your car requires you to overcome more air drag. It would make sense to me that this would be a cubed relationship like air drag is. If you double the speed you multiply friction by 8.

So...
Drivetrain loss increases with the horsepower the drivetrain is being asked to handle. Is the drive train loss a fixed percentage? I doubt it. I think it depends on the toque and RPM.

Somebody please correct me if I'm wrong but after a year and a half of study for my mechanical engineering degree this is what makes sense to me.

 

What??? I'm not sure I would agree with that broad of a statement....also I think the losses of the drivetrain, increase as HP/TQ increase.

For what its worth, contrary to what I personally think with the IRS system, with all its joints etc. Its appears to be VERY efficient.

When I was on the dyno, they did a parasitic loss on my car. The guy was astonished, that it only lost the little bit that it did. I'm not at all familiar with how exactly this was done, computered etc, but he did it with the car decelerating, and the dyno computered out a number. He said it was the lowest reading he ever saw on his dyno. He made me do it SEVERAL times to verify its readings. Every time it returned the same number. I questioned the accuracy of the test, and he pulled up several tests of his buddies autocross VW someting or nothing they just got done unstrapping from the dyno a few minutes before and it made the same numbers it always did several times before....on different occasions, so he said its dead accurate on...however he was still amazed. what that all says, I'm not real sure. I was happy he wasn't telling me I was the worst. lol.

Anyways the only real way I suppose to tell is to have your motor dynoed, throw it in the car and have it dynoed again. But even at that its not going to be 100% accurate.

:cheers:

 

:iagree: I was about to post exactly the same perspective... :cheers:


[Modified by vette_tweak, 9:49 AM 10/23/2003]