HP vs. RWHP

[CJFusco]

In stock form, what does the 951 put down to the pavement. If they are rated at 225hp at the crank, this would translate to, what, 200hp at the wheels? Is there an equation to figure this out?

[chitown944]

The 86' is rated at 217 and I dynoed mine at 174 at the wheels.

[pozican]

My '86 dynoed at 227.2hp / 254.5 tq at 13lbs, with shims, LBE, and 3bar FPR

Is 217 really the rated number?

[chitown944]

217 is the stock number as far as I know.

[AaronM]

Non-S cars are rated at 217 at the crank.

The S cars are rated at 247 I believe.

The dyno sheets on my '86 (K26/8 turbo, 3.0 bar FPR, Guru chips, shims WG and accuboost) show 274 HP and 297 ft/lb at the rear wheels.

[nynor]

Originally posted by AaronM
Non-S cars are rated at 217 at the crank.

The S cars are rated at 247 I believe.

The dyno sheets on my '86 (K26/8 turbo, 3.0 bar FPR, Guru chips, shims WG and accuboost) show 274 HP and 297 ft/lb at the rear wheels.

damn! maybe that's what i need to do... what is your MPG with that setup?

[pozican]

He's on the K26/8 turbo -- Not sure that '88 has that one stock...

I thought even the turbo S had the k26/7...

[nynor]

IIRC, turbo S was the k26/8. i am sure mine has the k26/6, but i think it was rebuilt with different internals.

[AaronM]

Originally posted by nynor
damn! maybe that's what i need to do... what is your MPG with that setup?

It's not as fast as it sounds, there's no real power until 3,000 and it doesn't punch until 3,500+ because the K26/8 takes a little longer to spool. Off the line I get taken out by Geos.

In my commute, about 21 mpg, but the commute is stop-and-go running between 0 and 30 mph on a packed freeway. In non-commute driving I average about 26-27 mpg.

It's a pretty simple setup, 15PSI of boost and the chips and hardware to handle it. Oh yeah, and the K26/8.

[nynor]

you get better mileage than me. i need to go through the whole intake, vacuum hoses, etc., and see what is going on.

[ae1969]

Once you get over 300rwhp....... things really wake up.

[AaronM]

Originally posted by nynor
you get better mileage than me. i need to go through the whole intake, vacuum hoses, etc., and see what is going on.

Well, remember that when just cruising down the freeway I'm not getting into boost, so at cruise pretty much any 951 should give the same mileage.

Now, when I really get into things I can burn through a tank pretty quickly, but even in BC with the other Pelicanites for the weekend I managed about 24-25 mpg on the trip.

[nize]

this is kind of a trick question, as no two dynos produce the same numbers, even on an identical car.

[AaronM]

Originally posted by nize
this is kind of a trick question, as no two dynos produce the same numbers, even on an identical car.

No one car will dyno the same numbers on the same dyno on a different day either.

It's enough of a confidence window to be within +/- 15 RWHP though.

[nynor]

er... 15 RWHP is nearly 10 percent on a stock 951, which still equates to a trick question.

[AaronM]

Originally posted by nynor
er... 15 RWHP is nearly 10 percent on a stock 951, which still equates to a trick question.

It's enough to get a comparison.

[nize]

same car, same setup, different days;

on one brand of dyno (dynojet), i got 270whp.
on another (mustang) i got 245whp.

that's a pretty damn big difference, and enough to tell me that dyno numbers are far from real world numbers.

use a dyno for tuning and comparing to other cars on the same dyno, not to figure out street hp numbers.

[Techno Duck]

Typically you account for 15% drivetrain loss. So take 217hp at the crank, multiply by .15 and you get 32.5hp. 217 - 32.5 = 184.5hp. So figure a completley stock, perfectly running 944 Turbo making the same as stock power puts down 184rwhp.

Some cars are more efficient, some are less. But 15% is the general average i think.

[CJFusco]

Come spring, I think I might attend a dyno session (PCA has them sometimes) just out of curiousity. By then I would have added a bigger FPR and a straight-exhaust to my current upgrades, the 951Max chips, LBE, and a custom-built BOV.

Any guesses on how much power my car is putting down? It is running about 13psi on the LBE.

[AaronM]

Originally posted by nize
same car, same setup, different days;

on one brand of dyno (dynojet), i got 270whp.
on another (mustang) i got 245whp.

that's a pretty damn big difference, and enough to tell me that dyno numbers are far from real world numbers.

use a dyno for tuning and comparing to other cars on the same dyno, not to figure out street hp numbers.

If those numbers aren't corrected for temperature and humidity, that could be enough to explain the variation.