RED04Z06

Hey guys, this isnt really a kill story, but it relates to street racing. Well I live in California where at the pump the highest octane we have is 91. Well I have a friend with a 01 Z28, before he goes and races, he doesnt put in any gas until it gets really low then goes and adds 2 gallon of 100 octane and 2 gallons of 91 octane. Considering there is still some 91 in the tank before he adds gas in again so im guessing it would be all togther 2 gallons of 100 octane and 4 gallons of 91. Well he says it helps him out alot. I was wondering what you guys think??? He added all the octane numbers from the 6 gallons and divided them by 6 and it came up 94 and he is telling me that it is equal to 94 octane???

necrocannibal

iTrader: (5)

Only if hes running boost or nitrous do I see it helping him, it could actually hurt him. Of course if he is detonating now for some reason it would help him.

Sparetire

Kinda a tech thread but....

In a stock NA car thats pretty useless unless you have some serious problems like improperly gapped plugs causing detonation or something. I saw a recent test where a new BMW M5 (which has a friggin supercomputer to run the engine..ugh) basicly got nearly the same power on everything from the recomended gas to high octane. And thats on a high winding high compression V10.

However, in FI cars and NO2 cars, higher octane is damn good to have. It allows you to run more boost and hotter intake air temps without detonation, meaning a lot more power. But the real benefit is that the ECU can advance spark timing a lot more even at a normal pump gas boost level. This is huge for making power, as any tuner will tell you in any motor.
The sooner you set off the mix (advance the timing) the greater the amount of the burn that is acting at the point in the pistons travel where it produces power. Of course there are limits to this, advance it like 90 degrees and your basicly blowing up, since you are inducing detonation. They call it advancing the timing becuase you are setting off the compressed fuel air mix sooner in relation to where the crank is positioned. So 10 degree advance is setting it off when the crank is 10 degrees form the point where the piston is at top dead center. So 10 degrees in 'advance' from TDC.

What I dont know is how the LS1 ECU handles timing. Does it advance it according to certain parameters and knock? If it does then the LS1 will get this benefit.

BLKWS.6

Higher octane gas has less chemical energy. Unless he is detonating or getting knock retard, he is making LESS power.

VORTECFCAR

iTrader: (2)

for fun I tested this theory using a bomb calorimeter and found no significant difference in energy between the common three grades of fuel.

you would not notice a difference in how the fuel performs, unless, of course your car requires the use of high octane fuel.

BLKWS.6

Vortec, addatives are used to retard the combustion of fuel in higher grade fuels, any way you slice it, whatever volumn of addative there is, it subtracts from the volume of FUEL there is.

VORTECFCAR

iTrader: (2)

I don't really want to get too carried away with specific gravities of octane boosters and whatnot, so I'll concied that if you're increasing octane of a fuel by adding ethly alc. then yes- you will lower its BTU. It all comes down to the method of 'octane boosting'.

My little experiment proved what it proved though, out of the pump there was no significant difference in thermal energy released between the grades tested.

FWIW - there may be a larger study that says otherwise, but if the difference in BTU is there, it isn't much (and by isn't much, I mean you would need to do 100 trial bomb runs to see it).

moving on....