How much does octane affect HP?

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.

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

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...

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

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.

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.

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.

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

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

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...

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

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

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.

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...

i hate math

well im an electrical engineer, so unfortunately math is my life...

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.

Other than the fact that my equation used 17% loss instead of 18% [oops, I can work formulas but cannot subtract 18 from 100..LOL], The number is different for a reason. Given the Accepted 15% for Manual and 18% for an Auto.....If you have an A4 car and an M6 car that make the SAME RWHP, that would mean that the A4 car is making More Power at the Crank/Flywheel.

If you look at your math above:

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

You are saying a Manual car has more Driveline Loss than the Auto, which is wrong [Sorry]. You are saying a manual has 20% and an auto has 15%. If you were to plug in the .85 for the Manual and a .83 for an auto, your Equation would come out the same as mine (Answers come out the same).

285/X=82/100
X=347.56 HP at the Flywheel

295/X=83/100
X=359.76 FT-LBS at the Flywheel

285/0.82=347.56 HP at the Flywheel

295/0.82=359.76 FT-LBS at the Flywheel

I used a more basic equation to show the Correlation [sp] that the Rear Wheel Power/X (X=Crank power) is equal to the percentage (82%=82/100). It is a basic Cross multiplication Formula.

that's still assuming 13% power loss. arent we trying to figure out the power loss through the driveline?

that's still assuming 13% power loss. arent we trying to figure out the power loss through the driveline?


13% loss would be 0.87 or 87/100

This is to find Approximate HP at the crank with a given acceptable value for DL loss (15% for Manual, 18% for auto).

The ONLY way to easily determine true DL loss would be to Dyno an Engine on an Engine Dyno, then to Dyno the Engine in comparabe conditions at the wheels with a Chassis Dyno. Then RWHP/FWHP for the % that made it to the wheels.

sorry i cant subtract today, thats assuming 17 and 18 percent loss...

well lets just say that adding 91 or 93 octane adds .. oh for the sake of argument 5 hp.. over here 87 is $2.00 a gallon and sometimes 91/'93 can reach $2.40 a gallon.. now for a full tank (16 gallons) thats 32$ compared to $38.40 thats $6.40 difference... not bad for 5 hp... but if u always use it.. For me i go through a tank about every 3 days ( i drive alot) and i average 17-20 mpg. Figures into a little more than 100 a week.so about... $400 a month for gas almost $5000! a year for gas... on basic.. still getting about 290hp. now add in the high test. $120 a week thats $570 a month($170 difference) and for a year $6840 a difference of $1840 all for 5 hp... in a month you could save enough for a cold air intake (which would add about 20 hp) or in a year you would have almost $2000 for mods.. you will get alot more power out of $2000 then you would out of 93 octane. just my figures of course.

Finally something on this thread that makes sense

:) :):)

goddamnit why can I never see smilies or avatars here. Only twice since I started posting have I seen em... but every time im at work or school i can. Wtf.

well, the lower octane can cause Detonation. Detonation is not good for your engine. The PCM does sense it and retard timing, but it (Detonation) still has to be there for the PCM to retard the spark advance. After the PCM corrects, it resets after a little while and picks up Detonation again and starts the whole cycle over again. The repeated Detonation on the Crowns of the pistons can eventually cause problems.

THis is enough reason in my mind to spend the extra $0.30/Gallon on 93 octane. It really equates to about $54 extra a month on fuel filling up 3X a week in a 4 week Month. The best way to cut the gas prices is to Drive less....Stay at work during lunch breaks, let your buddies Drive when you go places, etc...

Do you regularly go out to the bars/clubs, or out to eat? If you do, I bet you spend more than $54/Month on those things....

what if ur friends want to do the same thing... let their friends drive... do we all walk? :)

what if ur friends want to do the same thing... let their friends drive... do we all walk? :)
split the gas bill...it is still cheaper...if theys till do not want to drive...Take a CAB, WAY cheaper than a DUI if you are going to the bar!

(for the sake of arguement) i never fill up completely. gas weight approx. 7 lbs per gallon, which adds up in a 15.5 gallon tank. so lotus can cut his figures in half. bottom line is ive forgotten what the point to this thread was...

Use the octane that allows you to run the max timing. The LS1 will pull timing out if you have a lower grade fuel in it. With my car, I bumped the timing up 2*more than what I usually run and I made a consitant 20 HP gain just from 2*. This is to just give you an example on how much timing affects HP

now if you had only come around 28 posts ago...

my name is Kris :wave:

Use the octane that allows you to run the max timing. The LS1 will pull timing out if you have a lower grade fuel in it. With my car, I bumped the timing up 2*more than what I usually run and I made a consitant 20 HP gain just from 2*. This is to just give you an example on how much timing affects HP

Right now I'm running 89 octane in a stock 02 LS1 with the LS6 intake. Do you know how much timing is typically pulled at that octane? Would 93 octane allow full timing and 94 slightly advanced timing?

How exactly did you change the timing on your car anyway?

A little more detail on the condition of the car when it was dynoed: running 89 octane, the left catalytic converter needed replaced and the SES light was on, ambient temp ~89*F.

Thanks.

93 octane will bring you to the programmed timing. If you had LS1-Edit access, you could add a couple degrees of spark without problems, but the PCM does not advance timing past the set specs.

now if you had only come around 28 posts ago...


Sorry, crap has hit the fan at work.


Right now I'm running 89 octane in a stock 02 LS1 with the LS6 intake. Do you know how much timing is typically pulled at that octane? Would 93 octane allow full timing and 94 slightly advanced timing?

How exactly did you change the timing on your car anyway?

A little more detail on the condition of the car when it was dynoed: running 89 octane, the left catalytic converter needed replaced and the SES light was on, ambient temp ~89*F.

Thanks.

As far as how much timing is pulled, it depends on the conditions. There is no set ammount of timing it pulls out, it a progressive system using the knock sensor to measure the severity of knock and pulls the timing out accordingly. If it is a cold night, you might be able to run full timing on 89 octane. On a warm day, it will pull out some, on a hot day it will pull out more. It also depends on your barometric pressures (Altitude) Your knock sensor will detect knock before you even remotely hear it. If you can hear spark knock, it is already in the danger zone.

I can control my timing by using a Translator plus. I know they make a Translator for the LS1 cars (controlls fuel only) but I do not know if they make a translator plus for the LS1 cars (controlls fuel and spark)

Like it was said, unless you have LS1 edit or something like that, your timing is capped. It can only go up so high. It won't matter if you put in 93 octane or 100 octane, you timing will be the same for both. The car does not sense octane, it pulls timing based on the knock sensor outputs.