gatorbait

Could someone remind me how to calculate drivetrain loss in converting HP at the flywheel to rearwheel HP?

I'm trying to get a sense of how much RWHP I have (without benefit of a dyno). I'm guessing that with APE chips, catbypass exhaust and cone air intake, I'm somewhere around 257 HP at the flywheel (stock is 217 HP for my '86 951). Don't know what that translates to at the rear wheels.

TIA

dand86951

If you have 257 at the Flywheel, then you would multiply that number by (1 minus the percentage lost in the drive train). A lot of people use 15% as the loss in our drivetrains, but some think it may be only around 12%. So you would have 257 * .85 equals 218 at the wheels for a 15% loss. OR 257 * .88 equals 226 for a 12% loss.

Ski

I think most people here use 15% for driveline loss. So if you have 257,,,that would be 218rwhp.

BTW,,Dyno's,,there is about 13% difference between a Mustang and a DynoJet; with the Mustang providing lower numbers.

gatorbait

Thanks guys. Much appreciated.

Danno

There was a thread a while back on this with dyno-charts: <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=18;t=000474" target="_blank">transmission losses on dyno run </a>.

Billy W

When I dynoed the APE stage 2 chips I had 220rwhp. You should have a little more since you do not have a cat. You should pick up Danno's chips, I gained 20hp over the APEs just by swapping chips. Stock chips I had 186rwhp. So that would be 14% drive line reduction.

Steve Lavigne

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by gatorbait:
<strong>Could someone remind me how to calculate drivetrain loss in converting HP at the flywheel to rearwheel HP?</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">This may help:
<img src="http://www.sciencecartoonsplus.com/miracle.gif" alt=" - " />

Chris Cervelli

Where does the 'lost' power go?

TonyG

Where does the 'lost' power go?

It's given to the Dyno Gods in hopes that they won't blow your motor while on the dyno.

Chris Cervelli

Tony,

Seriously, that is the best explanation I have heard so far.

dand86951

Chris I have to second that motion and Tony you must be on a first name basis with the Dyno Gods. What do recommend as the best sacrifice to offer for protection of your engine?

TonyG

The Dyno Gods have spoken to me directly:

"Thou shalt sacrifice 15% of thy horsepower or a fierce wrath shalt be cast over thy engine and thine engine shall engine meet thy maker"

DynoGod 15:30

TonyG

The best sacrifice:

I burn the first dyno chart right there on the spot.

dand86951

That sounds pretty reasonable to me. Better than say having to waste a drum of VP racing Fuel. I will be sure to call and get pointers the next time I go to the dyno.