Does everyone run 93 or higher octane?I always have but ive read lately (including here on the Forum) that higher octane is not always a power booster and in some cases of lower compresion motors the higher octane gas cost the motor power.So I am wondering if maybe the 9.0 1 L98S would run any better on 89 octane?

 

Depending on compression ratios, don't reallly think we need higher octane than 91 Octane.
Anyway out here in Southern ,CA, cannot find anything better that the good old 91 octanes.
Good Luck
tony



[Modified by oldace84, 4:28 PM 9/3/2003]

 

For maximum power you need to find the lowest octane rating that doesn't detonate in your engine under the worst possible conditions.

 

where do you live in cali oldace? The highest octane I can find in the Riverside/Corona/Orange County area is 91. And that really really blows. My engine is running 11.2:1 compression now, and I really want to find a gas station that sells 93. Know of one in my area?

 

91 Octane, at chevron stations. At least thats what my mines eye saw. Oh.,OH!!!!
Down by the beach, in Huntington, Beach CA.
Or as they say SURF CITY.
Ha. Ha.
Good luck
tony

Think that I totally blew it. Sorry only 91 Octane.
Crap.


[Modified by oldace84, 4:25 PM 9/3/2003]


[Modified by oldace84, 4:27 PM 9/3/2003]


[Modified by oldace84, 4:29 PM 9/3/2003]

 

in huntington huh? so is it an arm, or just a leg for the gas there??

 

Does everyone agree with this theory ? I have heard this a few places before.
I have also seen dyno results that showed higher numbers when using significantly higher octanes. I once saw a guy get 20 more rwhp on his SC Stang going from 93 to 100 octane.
But I also know that top fuelers spray 89 octane in the carbs to start their motors. (lower burn temp)
I'm not skep or religious in either school and am willing to try both. Just looking for some more input.

FYI my dyno run was with 2 gallons of 93 and 3 16oz cans of B12 Chemtool (almost pure tolune (or however you spell it) (aka octane booster) ).

 

The reason this would happen is because he was able to give it more timing. Although the car ran on 93 it was not able to run it's full spark advance. To visualize this take it to the extreme. Assume that there is 0 spark advance, the spark occurs when the piston is exactly at TDC. Now remember no matter how fast it may seem, fuel still takes time to burn. If the burn is initiated when the piston is at TDC it will actually burn as the piston is getting pulled away, creating a larger space for the gasses to expand to. Well that's good, except that if they are expanding into a void they are not pushing down on the piston very hard!

As you start advancing the timing you are actually starting the burn before the piston hits TDC. This allows the burn to apply the most force to the piston on the downward stroke. Advance the timing too far (or use too low an octane) and your burn will actually begin to press down against the piston while it is still moving up. Now you've got the engine fighting itself, this can be heard as pinging or detonation and if bad enough it can do serious damage.

The Mustang got more power out of 100 octane because it allowed him to time the spark better while not detonating. When using 93 it would still run but the timing had to be retarded to the point that it cost him power. Clear as mud? :cheers:

 

Big thanks Nathan. :thumbs:

So from this we can also theorize how a slightly lower octane, say 89 to 91, might actually help make more power right ?

 

Right. So long as the car is not having to pull any timing out to make it run. You can run a slightly lower octane in your car and it may not cause any pinging or knock that you can hear, yet it may still pull timing.

The best would be to put some kind of data logging device on the car and see what kind of timing advance it is using. If you go with a lower octane and it starts pulling timing you know you need to go back up. If you put lower octane in there and it still runs at full spark advance then you know you are fine. BTW, be sure to test it under some bad conditions. While you might get away with it on a cool day you might have more trouble on a hot day under heavy load.

One word of caution, modifications can raise the octane requirement. Just like the supercharger, a camshaft allows more air and thus more fuel to be put in the cylinder. This effectively increases cylinder pressure and your octane requirement along with it. I've never tried it but I wouldn't feel safe putting anything other than 93 in my car just because of all the modifcations I've done.