Well I'm going to the drag strip tomorrow and I am wondering if I add 93 octain gas in my n/a will it make a difference? I know that I will have to advance my timming to get the benefit. Does it help any? Also how much will I have to advance my timming? Thanks.

It'll drain your wallet quicker, that's about it.





I may be wrong though. I'm just pretty sure that the higher octane is for higher compression, what with the higher flash point and lower volatility (is that a word?). Or something like that.

might wanna run a midgrade, 91 isnt needed though

runs great on 87, anything higher is a waste of money as long as you are n/a

but i was told that if you adjust your timming one way that it compensates for the higher octain. Just like people do when they run race gas. They have to adjust their timming to get the full use out of the fuel.

as i understand it, running a higher octane prevents pre-detonation, and lets you run a higher compression ratio (b/c the fuel is more resistant to diesel-ing or igniting off of a hot-spot). Its the higher compression ratio thats now possible that will give you the extra power, and require the change in timing. The s4 has a relatively low N/A compression ratio, unless you run s5 or RX-8 rotors (or do something else to raise Rc), you wont get anything out of higher octane besides a lighter wallet.

thanks, thats what i wanted to know

I can't say with certainty, but on a wankel, wouldn't dieseling be a non-issue, since we technically speaking have separate intake, cumbustion, and exhaust chambers, unlike any other gas motor.



This is why Mazda has been able to so easily make those new hydrogen RENESIS motors. Unlike BMW or Mecedes, who had to do alot of work to prevent "dieseling" in a hydrogen setup.

yep, combustion takes place in a different location....

dieseling is when the temperature and pressure of the mix of gas and air is enough to ignite it without a spark, like the combustion-ignition that occurs in a diesel engine. The only place this could occur is during the compression stroke before spark, because thats when the gas is rapidly getting compressed and shoved into the hottest part of the housing. It doesnt have to do with where the intake is.



The problem with the hydrogen was that, in a piston engine, during the intake cycle the hydrogen would heat up too much, too rapidly, because it was in the same chamber that just experienced combustion. Since the rotary does have the intake cycle in a different location than combustion, this wasnt as much of a problem, but this AFAIK isnt dieseling.

^^^ I still think this sounds like a very subtle difference between the two.... Maybe not quite the same thing, but they have got to be related like third cousins at least....

they are similar, both are problems of the fuel igniting earlier than desired. dieselling happens during the compression stroke, and the other one happens during the intake. The different configurations of the engines determine how they will react

Dont ask me why, but the few people I know that REALLY know these cars all say that they make more power on 87 octane. One guy dynoed with 87 and then with 93 and lost 12hp. Granted he may not have lost any power if the timing was advanced more but i cant see that you would gain much either.

Thanks for that clarification topless. That makes perfect sense, didn't think about them just being the same kind of thing on different strokes.

octane = resistance to detonation.



Use the lowest grade possible as long as your not detonating.



If you detonate increase your octane.

changing the timing will make the motor run like ****, i've tried it a million times on a dynojet. I got about 3hp out of a few degrees more advance, but the motor was soft and peaky above 7k rpm.



use 89 octane and stock timing at the drag strip, and 87 when cruising around