Crank power to Wheel power

[jezze]

Has anyone found a conversion for the amount of power lost from a crank measurment of horse power to a measurment of wheel horse power due to drive train? Does that sound confusing? How much power is lost at the wheels due to drivetrain? I guess that sounds a little better. Okay, thanks.

[=Enigma=]

It seems to vary from article to article with numbers ranging from 3% - 30% so I don't believe there is a simple formula that can be applied to all cars and all dyno methods and results.

See the following for some more info:

http://www-unix.oit.umass.edu/~tcroy/articles/horsepower.htm

http://www.germanmotorcars.com/Dyno_load%20vs%20inertia_1.htm

[jezze]

That's good reading, thanks a bunch Enigma!

[Carl Beck]

I haven't seen too many of the stock "L" series engines actually measured at the crank, so I don't know about that.

However if you use the stated HP numbers for the 240-Z and 280Z... of 151 and 165 respectfully.. then they lose about 25% at the rear wheels. Most of the stock L24's that I've seen dyno'ed at the rear wheels put about between 110 and 115HP. Most of the L28's in stock form seem to come in around 120 to 130HP.

So it would seem that a rough rule of thumb would be 25% loss between reported HP and RWHP on the First and Second Generation Z's here in the US.

All this is at best - just a rough rule of thumb...

FWIW,

Carl B.

[Nigel1943]

I would concur, 25% loss.

[zguitar71]

I haven't seen too many of the stock "L" series engines actually measured at the crank, so I don't know about that.

However if you use the stated HP numbers for the 240-Z and 280Z... of 151 and 165 respectfully.. then they lose about 25% at the rear wheels. Most of the stock L24's that I've seen dyno'ed at the rear wheels put about between 110 and 115HP. Most of the L28's in stock form seem to come in around 120 to 130HP.

So it would seem that a rough rule of thumb would be 25% loss between reported HP and RWHP on the First and Second Generation Z's here in the US.

All this is at best - just a rough rule of thumb...

FWIW,

Carl B.

I have always heard that the 151 staed HP was not realy acurite and was closer to 135 (at the crank). Then the power loss would be closer to 15% but 15% sounds low to me. Who knows? At least I could add some confusion to the hole thing.

:stupid:

[Carl Beck]

I have always heard that the 151 staed HP was not realy acurite and was closer to 135 (at the crank). Then the power loss would be closer to 15% but 15% sounds low to me. Who knows? At least I could add some confusion to the hole thing.

:stupid:

I believe that 135 number was based on estimates or approximations - if you wanted to convert 1/4 Mile Speed/weight to HP numbers. Depending on what trap speed and which weight... the early road tests reported for stock cars.. it comes out between 130 and 140HP.

If you use the BRE C-Production 1/4 mile trap speed of 108mph and you guess that in racing form it weighted about 2300 lbls with the driver... the rule of thumb shows 243.8 HP... which is a little low.. but then it's a rule of thumb... just an approximation... The BRE engines were said to put out something over 250HP on the engine dyno's..

FWIW,

Carl B.

[jezze]

I was asking because I put a stock '83 L28et motor and ECU into my '71Z. It feels pretty fast. Today I put a dynomax super turbo muffler on it and it now is way quiter and even seems a little slowet compared to the open exhaust I was originally running.

Any idea how much rear wheel power the L28et's put to the rear wheels? I'm guessing 150whp with that restrictive muffler, but I really have no clue.

[Carl Beck]

I haven't seen a "stock" 280ZX Turbo on a dyno... but I'd guess that they would be in the 140 to 150 RWHP range. The Factory rating was as I recall 180HP.

I have seen a few L28ET's "mildly modified".. with the addition of intercoolers, free flowing exhaust, etc etc.... running boost limited to 10/11 lbs... They put between 215 and 235 RWHP down..

Carl B.