Well, had our little dyno day. Mine was the 3rd one to go. It was a bit humid, low 80's not too bad.

Well, here were my numbers Max Power= 253.9 and Max Torque was 294.1

My ratings for the car are 275 bhp and 325 lbs/ft. So according to simple math, that leaves a 7.6% drivetrain loss through hp and a 9.5% though tourque. It was at Unlimited Motorsports in South Windsor. So I guess my auto drivetrain loss isn't so bad, unless I got a factory freak

All and all, I am quite happy with the base numbers that I put down today. And all with just a K&N.

 

if you really think you have 9.5% drivetrain loss...



if you have 253RWHP and a 17% power loss you have 304rwhp...

intresting

I am going to say you have a freak or its not SAE corrected or a mod. what dyno?

 

253/275 = 92% efficiancy .

Not bad at all! Sounds like your car is strong . Any track mph numbers?

Ryan

 

If you really only have 9.5% loss I'd like to buy your tranny and rear

 

I'll go out on a limb and say you have neither a freak or low drivetrain loss. Sounds about right when you look at what the numbers are. I believe Fred dispelled the 17% loss when he dyno'd his motor engine and chassis, and it only lost around 13%, and I think he has a fairly large stall as well. With a tighter stall, you could expect 1% less I'd guess? So, 253 RWHP and a 12% loss gives you 287 FWHP. Your sig says you have a K&N, which adds around 10 dyno tested RWHP. Convert that to FWHP and you would pick up roughly 11.5, and add that to the 275 rating you get 286.5, which is right in line with the 287 you should have. Sound more reasonable?

 

You can't just assume your car makes exactly the 275flywheel HP that GM rated it at many years ago. There is a fairly wide variation among factory production engines. To suggest this indicates 7.5% drivetrain loss is a bit of a reach.

I've got ACTUAL engine dyno vs. chassis dyno for my setup with an M6, and the losses ranged from 12.6% at 500HP to 12.1% at 762HP. Hard to believe a 4L60E, even with the convertor locked up, could have 5% less loss than a T56.

Not sure where "brain" got his numbers from, because the only auto trans numbers I have are for a TH400 with a sloppy, non-locking convertor, and those range from 19.8% at 500HP to 21.3% at close to 800HP. No way that can be compared to a 4L60E.

 

My bad Fred! I thought the 12.6% loss was with the auto and big stall! So much for thinking. Curious, did you have a 9" rear? Was the manual dyno on that? Also, I've heard that slicks will rob some power as well. What tires did you dyno with?

 

anything that is heavier (ie slicks) will create more drivetain loss. think of it as adding a lead driveshaft (ok a bit dramatic)

also there will be slightly more loss if the tires are "stickier" on the dyno.

 

My T56 runs were done with a steel flywheel Street Twin, stock T56, 3" chrome moly DS, and Strange 12-bolt/3.73 gears. Tires were 315/35-17 Drag Radials.

TH400 runs were done with a B&M flex-plate, non-locking convertor, more than 10% slip, 5Krpm flash at 800ft-lb, same 3" DS, same rear axle, gears and tires.

The typical GM rear... 10-bolt or 12-bolt is good for about 6 to 7% loss.