chops

Ok guys, just got back from my dyno. Details:

- 57 degrees (Houston weather)
- Mustang dyno (was told this is lower than the normal Dynojets)
- Stock 911 C2s, 5111 miles on her
- PSM turned off, but Sport wasn't engaged
- Pulls done in 4th gear
- She really screams (would love to hear how PSE sounds!)
- No external fans were used

2 pulls resulted in:
1) 281 whp/227 wft-lb tq
2) 277 whp/230 wft-lb tq

Normalized to a Dynojet result (using what the shop told me, a 1.15 multipler:

1) 281 *1.15 = 323.15 whp/227*1.15= 261.05 wft-lb tq
2) 277 *1.15 = 318.55 whp/230*1.15 = 264.5 wft-lb tq

So if we have 16-17% drivetrain loss, that means my best runs were:

323.15 whp * 1.16 = 374.85 crank hp
264.5 wft-lb tq * 1.16 = 306.82 crank ft-lb tq

Do these numbers seem reasonable? Is the car underrated then? Not complaining if it is!

pmgoodwin

I have a '05C2S that has PSE w/EVO headers, EVO intake and a GIAC flash upgrade. I had a run done on a Dynojet last spring and got 320.3HP and 272.0'lb.

I'm a little suspect of your results since I should have 25-30HP more than you.

chops

Will post the results when I get them scanned.

What were your baseline results, pmgoodiwn (i.e., before your mods)?

MLindgren

Did you happen to do a baseline run prior to your upgrades?

I'm a little suspect of the hp gain claims made by most aftermarket companies.

pmgoodwin

I bought the car with the Mods already done, so I don't have a baseline.

Below is the Dyno run I had done and a dyno from the Evoloution Motorsport web site. Their run with the same mods I have is about the same - 322.2 vs 320.3 - and shows a baseline of 303.4.

The baseline 303.4 * 1.16 = 352HP against a claimed 355HP.
my 320.3 * 1.16 - 371.5HP.

In anycase it's an academic discussion since one can only use about 20% of the capabilities of these cars on the street and on the track driving technique has more impact than HP.

YMMV.
.
.

MichaelL

Applying a 15% "comparative ratio" for different dynoes & then a 16 to 17% drivetrain loss factor on top of it will give you illusory power and torque figures.

Edgy01

It never ceases to amaze me in the number of owners who modify their engines and fail to baseline them BEFORE the mod with a dyno run. It's been theorized in the past that Porsche figures are conservative.

pmgoodwin

Would that be the guy who dyno'd a stock car or the one who bought a car with mods?

Edgy01

Neither of these guys,--I'm referring to others on Rennlist who started off with stock 997s and then changed them "for the better" but failed to baseline them first. Obviously if you buy a modified car it woud be impractical to reverse the mods simply to measure it.

Unfortunately, unless you are extremely diligent in your testing routine you can easily draw the wrong conclusions from these tests.

chops

I guess the best thing is to compare mustang dyno results to mustang dyno results on a stock 911s. Even then, as you guys have pointed out, its still not apples to apples!

Car feels pretty dang strong to me, and I guess that's what counts.

In a related note, what's this theory I hear about our beloved 997s getting even stronger after 10k miles

KeninBlaine

I don't know if it real or imagined, but I have found in both my 997's that they seemed to get better with age. I have just over 12000 miles on my Targa, and it seems better than when I got it with 5000 miles. But it could just be my imagination. I'm sure some of the variation is due to having a full tank of gas vs a half tank, or having the AC on or off, or the air temperature that day, etc.