Horsepower lost at the wheel

[Ctriton20]

Hey Guys! I want to know. How much engine horsepower is lost at the wheel on a big block mopar with a 727 trans and 3.91 gears?

 

[Steve340]

I understand the drive train of an automatic car can loose estimated 25% from the crankshaft figure.

 

[Chryco Psycho]

Easily 25-30 %
Also dynos read very differently so it is best to test on 1 dyno for comparison & tuning , Dynojet is very optomistic for example , Mustang is a reality check reading 15% lower than a Dynojet

 

[moparleo]

Anything is a guess. So many variables. Is the engine stock ? What type of fluids do you use ? Is the transmission, torque convertor stock, Is the engine tuned properly ?At what rpm ?and on.....

 

[Ctriton20]

Anything is a guess. So many variables. Is the engine stock ? What type of fluids do you use ? Is the transmission, torque convertor stock, Is the engine tuned properly ?At what rpm ?and on.....

I posted my engine dyno sheet in our forum. It made 665hp at 5800 and 691tq at 4500. Put the car on the dyno with full trim and it only made 480hp at 5800. That's a massive lost guys! 400/512 stroker with trickflow 240 heads 10.5cr.

 

[Chryco Psycho]

Roughly 25% loss as expected , 665 x .75 is 498

 

[Ctriton20]

I’m going to do some tuning and follow up on the same dyno.

 

[moparleo]

Low stall, lock up convertor ?

 

[Ctriton20]

Low stall, lock up convertor ?

10" 3400-3800 Stall

 

[moparleo]

There is where it is going. TC slippage.

 

[6PKRTSE]

Seems about right to me. +/- a few horsepower.

 

[Ctriton20]

I'm going in for a followup dyno Tuesday. Before number 6 wasn't

 

[Ctriton20]

Before number 6 wasn't firing. I also installed new tti headers and exhaust. (2'-1/8" step headers and 3 exhaust). Got a better tune setup. I'll let you guys know how it goes.

 

[Ctriton20]

Went to the dyno today! This shop had a Mustang Dyno. Not sure why it made more torque than horsepower. The AF ran around 12.5-14. I was running 38 degrees of timing. I added new tti step headers and 3" exhaust since the last dyno. I guys at the shop think that my converter is killing the horsepower. I have a 3800 stall. (524 ft-lbs/445hp at 5850rpm)

 

[Steve340]

The way to know is to look at the MPH of the rollers and see if the MPH slows down but the RPM continues to rise.
A dud converter will show up like a slipping clutch would with a manual transmission.

 

[moparleo]

Slippage kills power and shortens transmission life.
High stall convertors were designed for limited track use like most other high performance parts. Not daily street use.
Street cars are not good race cars and vice versa.

 

[6PKRTSE]

Slippage kills power and shortens transmission life.
High stall convertors were designed for limited track use like most other high performance parts. Not daily street use.
Street cars are not good race cars and vice versa.

Depends on the whole package. I run a 9" PTC 5600 nitrous converter and drive it all over on the street. Back and forth to work, to the stores, cruise nights, car shows and race it as well.

 

[Ctriton20]

Would it be safe to say that using the horsepower to torque calculator that my dyno reading of 525 ft -lbs at 5850 rpms equals 584.8 hp at the wheel?