How much does octane affect HP?

[lookin4luey]

With an `02 Z28, I know that the computer pulls timing automatically to prevent engine knock when you use a low or mid octane gas. How much would that really affect the HP and TQ?

With 89 octane, my Z put down 285 HP and 295 TQ to the rear wheels. I was a little dissapointed that I didn't break 300, but would the higher octane (93 or 94 @ $2.10/gal ) make enough difference to put me over that mark?

Thanks for any input.

[gurrzt]

Your numbers (if stock) are fine, although the torque is a little low. Using higher octaine gas would allow the PCM to advance the timing, however no difference that the dyno would actually record.

I dyno'd with a tank of 100 Octaine unleaded, and had lower numbers than when I used 91 Octaine (same dyno). I have an 01 Z28 with bolt on mods, here are my numbers:

293.5RWHP/345RWTQ (295RWTQ @5400RPM)

Don't get hung up on the numbers, how does the vehicle run? Some very strong quarter mile cars do not dyno high.

JMHO

[Chevyracincamaro]

changing the octane is not going to put you over the 300 mark. in reality, using too much octane can actually hurt performance, as gurrzt has mentioned. if its the difference between going poor cause of gas prices or trying to squeeze a couple more ponies out of the engine, stay mid-grade...

[lookin4luey]

On a related note, does anyone know an average amount to expect in drivetrain loss in the stock fourth gen?

[Dober89]

When we had our dyno day in june there was a stock 00 Z28 and he made basically the same power as you but maybe a little torque.

They did some tuning on it also with a laptop and were able to get some more out of it.

[Deadcarny]

on an LT1 and LS1 premium is recommended due to compression. Put some premium in there and you will see a slight jump. an 02 with low miles should have just over 300 hp at the wheels and at least 320ft-lbs at the wheels.

Gurzzt, you got lower numbers with the 100 because that is too much octane for a stock motor.

[gurrzt]

Originally Posted by lookin4luey

On a related note, does anyone know an average amount to expect in drivetrain loss in the stock fourth gen?

For automatic the equation is RWHP/.85=FWHP
For stick shift the equation is RWHP/.80=FWHP

Hope this helps you out.

[Savage Messiah]

uhh i think he was looking for rwhp. from flywheel hp.

[Savage Messiah]

oh wait or is that 85% and 80% the same? but that doesnt make sense if manual has more loss... nvm

[Chevyracincamaro]

not necessarily, a torque converter is a torque multiplier. it actually increases the amount of torque being transferred.

but 20% loss on the manual seems high, but ill run with it...

[Dober89]

Ive always been told that manuals loose less power through their drivetrain. the torque multiplication on an automatic is only large at low rpms.

[Deadcarny]

he is backwards. the Manual is said to have a 15% minimum loss, and the Auto is said to have between 18-20% loss.

so, Saying his car is an Auto with 18% loss:

285/X=83/100
X=343.73 HP at the Flywheel

295/X=83/100
X=355.42 FT-LBS at the Flywheel

[gurrzt]

If you gentlemen use my equation just say with the RWHP being 300, you will see that the manual transmission makes more FWHP. When you use the equation above (by X) the number is different.

[Chevyracincamaro]

technically the equations you gave are the same as saying 15% loss and 20% loss, only technically though. ofcourse ive always maintained that you can not calculate horsepower with equations. you can come close, but there are too many variables to accurately compute a horsepower through mathematics, just sayin is all...

[Genopsyde]

i hate math