engine hp to rwhp HOW?

[subodh]

how do i count to get engine hp when ive just got dyno on rwhp?

read somewhere that i can count 1. 31 x "rwhp"

because i had my car in overdrive thats 1:0,69 right?

and then should i count with 1. 2 when i got like 20procent loss in my

auto transmission and drive train?



please point mi right here



my rig is a 2005 automatic



so if i read right i should take my rwhp x 1,51

but that sound to good to be true. .



but how?

 

[subodh]

btw what about my torque. . whats the torq in my engine then. . it cant be the same as on th wheels right?

 

[MChrist]

My understanding is that you take roughly 20% drivetrain loss into account. Since you are only looking for a rough #, I would take rwhp x 1. 2= engine hp. That should get you in the ballpark. Not sure if you do the same on torque, but maybe somebody with dyno experience could help out.

 

[AH64ID]

The several times i have dyno'd I have seen about a 15% drivetrain loss (based on OE specs), with my manual trans. So RWHP/. 85 will give you crank power. . ish

 

[RustyJC]

20% drivetrain losses for automatics and 15% for sticks is probably pretty close. You could divide chassis dyno horsepower by 0. 80 or 0. 85 respectively to come up with a reasonable estimate of flywheel horsepower.



Rusty

 

[cerberusiam]

Use 12% as the general loss thru both auto and manual transmissions given you dyno it to maximize your numbers. A lot will depend on the consistency and content of your dyno runs.

 

[AH64ID]

Use 12% as the general loss thru both auto and manual transmissions given you dyno it to maximize your numbers. A lot will depend on the consistency and content of your dyno runs.

12% seemed low, but I looked at my numbers again. 13% loss on hp and 15% loss on tq. This was at 2,700' on a 95% day.

 

[cerberusiam]

12% seemed low, but I looked at my numbers again. 13% loss on hp and 15% loss on tq. This was at 2,700' on a 95% day.

Mine came out to 12% and change on 2 different occasions on both. However, that may be the difference between the execution of the run and\or the transmission differences.

 

[Allnew2Me]

When I ran my truck on the dyno stock I had the following numbers



Stock HP 235

Rear wheels 209



Stock torque 460

Rear wheels 391



I lost just over 14% to driveline friction.

 

[AH64ID]

Mine came out to 12% and change on 2 different occasions on both. However, that may be the difference between the execution of the run and\or the transmission differences.

Thats really good for an auto, thou if you were locked it should be about the same as a manual.



I would think fluid, run, and ambient conditions will all effect that number. Really a very low %age loss for such a large drivetrain.

 

[cerberusiam]

I would think fluid, run, and ambient conditions will all effect that number. Really a very low %age loss for such a large drivetrain.

You look at an auto compared to the manual and whats going on there and it is not much different. The flywheel offsets the TC and the internals are pretty close.



It varies from truck to truck, dyno to dyno, and run to run. Those are the best runs, others are closer to 14-15% when I did the run different.



Maybe just good conditions and favorable Dyno accounts for some also. Trying compare gets to be problematic so anything between 12 and 15% is realistic on any given day.

 

[AH64ID]

Makes sense, and shows you just why tc lockup is good.

 

[cerberusiam]

Makes sense, and shows you just why tc lockup is good.

That and getting the boost up at the start of the run to get the ECU to think load all the time. Just rolling into the throttle jumped difference to 15% or better with no preload, same thing with a lockup switch and not loading the engine down at the start. The Dyno jet just will not load the engine hard enough to get all there is out of a run with a little trickery.

 

[AH64ID]

Very true, I did the same easy roll on all my runs to be the same. But I did it different on one run, and wow the curve really changed.

A pull down dyno would be cool, and give a better indication of the real curve.

 

[cerberusiam]

Very true, I did the same easy roll on all my runs to be the same. But I did it different on one run, and wow the curve really changed.



A pull down dyno would be cool, and give a better indication of the real curve.

Yes, a Mustang Dyno would be good to the ultimate out of the engine if the operator knows how to back out all the specific reductions that are default in it. We can't control the environment so throw that out for tuning purposes.

 

[NIsaacs]

Does anyone know if factory gas power ratings are gross and diesel is net? It seems like the gas powered rigs on the dyno loose a lot more then the diesels.



Nick

 

[AH64ID]

All modern rigs, since 04, have certain requirements for ratings. If you notice there were several engines in the 03-04 time frame that lost or gained hp with zero changes. It was due to new SAE standards, so anything since then is rated the same.

 

[NIsaacs]

I wondered about that. The '02 HO was rated 245/505 and the '03 HO was rated 305/555 seems like a big jump in power.



Nick

 

[AH64ID]

I wondered about that. The '02 HO was rated 245/505 and the '03 HO was rated 305/555 seems like a big jump in power.



Nick

That was also a severe enigne change, went from the VP44 system to the HPCR system, so that was a legit jump in power.