dynojet results and power loss thru drivetrain

69 Mach I · #1 (**permalink**) 05-03-2005, 07:34 AM

what percentage of hp does a C6 consume? If my car is putting down 300 rwhp on a dynojet and I have a C6, how much HP should I have at the fly? The shop with the dyno says I am losing 30% through the drivetrain on the C6. does this sound right?

marcocsx3121 · #2 (**permalink**) 05-03-2005, 07:44 AM

Sounds very high. The rule of thumb for automatics is around a 20% loss.

Toby · #3 (**permalink**) 05-03-2005, 08:12 AM

69 Mach 1,

The only way to get flywheel hp figures is to pull the engine and put it on a flywheel dyno. That sucks I know, but rwhp dynos can change dramatically because of a myriad of factors including operator,s. For instance, the same dyno could read different by just tightening the tie down straps looser or tighter! same car, same dyno! A change in torque converter could have big rwhp figure changes also. Been there, done that, got the tee shirt! I hope this helps you.

Toby

blykins · #4 (**permalink**) 05-03-2005, 01:00 PM

I had a 260hp Mustang GT put down 228 at the tires. That's a 13% loss with a 5-speed. I would assume an automatic would be more....probably guessing around 20%.

Zoom This · #5 (**permalink**) 05-08-2005, 07:09 PM

So, if I have a 450 flywheel hp motor, and deduct 15-20% for drivetrain loss, I'm at 360 rwhp using a 20% loss, right? If I plant a 600 hp (at the flywheel) motor in the same chassis, why would I now have a 120 hp parasitic loss due to the drivetrain? I've been having a hard time buying in to percentages in drive train loss.

Only real way to do it is to get your motor on an engine dyno, flog it and document the results. Then after you put the motor back in, go to a chassis dyno shop and record your drive train losses. Each tranny, automatic or manual, rear axle, gear lube used as well as type of chassis dyno will give you different results. Chassis dyno's are notorious for mixed results. Inertia, hydraulic, and electric/magnetic will all tell a different story on the same car. When using a chassis dyno, it's all relative as long as you use the same dyno in the same shop each time you measure improvements to your motor.

Cashburn · #6 (**permalink**) 05-08-2005, 10:22 PM

C6 is the hungriest of all auto transmissions. I'm surprised you would run that instead of a lighter C4 (if you have to stay automatic).

69 Mach I · #7 (**permalink**) 05-08-2005, 11:00 PM

Quote:

Originally posted by Cashburn

C6 is the hungriest of all auto transmissions. I'm surprised you would run that instead of a lighter C4 (if you have to stay automatic).

it was what came with the car. I will swap it out for an AOD with 4.11s when I can.