Hp question

[efnfast]

So Chevy advertised my my90 as 375 hp. Is that flywheel hp or rear wheel hp? Mine dynoed at 311.:dontknow:

:Eagle:

[efnfast]

So my math says about 357 flywheel hp. Acceptable?

[XfireZ51]

So my math says about 357 flywheel hp. Acceptable?

311/.85 = 366chp. Car is 20+ years old along w not knowing what has transpired or the state of tune the motor is in. Finally, you have the variability of dynos.

[efnfast]

Thanks guys. Xfire, I like your math better. I did 311 X 1.15 to get my 15% loss. 366 sounds pretty good. Now if I can just squeez another buck and half out of it.

Steve

[mike100]

My guess (which I mentioned on your other thread) was that you are losing 10-15 hp from exhaust restriction (your catalysts might be partially plugged)- or maybe from your intake boot collapsing. What rpm was your peak hp at?

There is always the possibility of loss from mileage, but I don't recall what you said about the condition of your car or the compression on the engine etc...

I'm sure different dynos will vary 10 hp or so. I've heard you will get a different number in 3rd and a higher reading in 4th gear. Certainly if you are at a higher elevation, that could also explain a few percent loss...like about 3% per 1000ft elevation.

[efnfast]

Mike, new exhaust is pending. Can't wait.
Peak hp at about 6k. Hood was open, never bothered to check the boot.
Car has 39,000 miles.
Dyno'd in 4th gear.
I would expect elevation around 750'.
This all started 'cause I stopped to look at a Vette and the sales guys said all hp since 75 or so is advertised as RWHP.
I'm happy.

[A1990]

Mike, new exhaust is pending. Can't wait.
Peak hp at about 6k. Hood was open, never bothered to check the boot.
Car has 39,000 miles.
Dyno'd in 4th gear.
I would expect elevation around 750'.
This all started 'cause I stopped to look at a Vette and the sales guys said all hp since 75 or so is advertised as RWHP.
I'm happy.
He was thinking Gross HP vs Net HP. after 1971, the engines had to have the accessories installed before the dyno pulls.

[mike100]

well 2% loss (about 700 ft elevation) is about 367hp (from 375hp) at standard elevation and temps. of course the temp and atm pressure are usually measured and corrected on the dyno calc. There might be a correction number on the dyno plot.

[efnfast]

Correction number was .96 as I remember. To convert to SAE.
He mentioned NH correction numbers are usually low.

[A1990]

SAE is corrected, whereas STD is uncorrected.

[XfireZ51]

Correction number was .96 as I remember. To convert to SAE.
He mentioned NH correction numbers are usually low.

Did he pull the .96 out of his butt or was that the correction factor for that time and day. Dyno should calc the CF each time. Also, on the Dynojets, there is a smoothing factor. It cuts off peaks and valleys. A setting of 1 gives you the actual peak number. Could be a diff of +/- 5 depending.

[efnfast]

No, he showed me on the screen what the correction number should be. Still , I think I'm happy with this number. Jones'en to get the exhaust done.

[SteelBlueZR1]

Also, the Corvette action center has a GM engineering document that states the drivetrain loss for ZF6 wheel HP calculations as 16%. My ZR1 1991 with chip only dynoed at 321 rwhp yesterday. 321/.84 = 382 crankshaft HP. A 91 zr1 with chip + exhaust dynoed at 340 yesterday, so all the numbers and power gains make sense.

[Bob Eyres]

Most stock 91's I've seen dyno in the 320-340 range. Mine with headers and 3" exhaust only did 336 at the wheels, (not great).
Keep it cool, open up the airflow, it'll scream.:thumbsup:

BTW, love that "Steel Blue"

[efnfast]

Headers and exhaust go on as soon as it comes back from Swaintech. It's got a K&N in the stock air box, I think I'll change to an S&L with the claw design and three filters, not sure if that is money well spent or not. Then a Marc chip once I know what mods I've made. I'm not going to dyno again untill I get all of this stuff done. Wish I could do it between every mod, but I'd rather invest that dough into hp.