FUEL
Senior Member
Joined: May 2001
Posts: 136
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so lets say, for example, i were to bring my compression ratio from 10-1 to 11-1 with a 50-75 shot of nitrous a decent set of cams, cai,exhaust etc.... would i need to use a higher octane and what kind of power gains would i get?
Super Moderator
Joined: May 2001
Posts: 11,851
Likes: 2
From: Rancho Palos Verdes, CA
Vehicle: 2008 Toyota Prius 2006 Suzuki SV650S
El Tiburon-
The only way you are going to raise your compression ratio is to..
Install domed pistions
longer rods
Shorter throw crank
mill the block/head
Nitrous oxide usually likes higher octane fuel, simply because the increased oxygen/fuel content ignites more readily at a given compression ratio. Cams/headers have no effect on CR and should NOT affect your octane requirements.
One last thing to point out here while we are discussing octane.
Low Octane fuel ignites easier than high octane fuel. Thus high octane fuel is HARDER to ignite, and the flame travel is actually slighly SLOWER with High octane fuel rather than low Octane fuel. Thus, you could LOOSE POWER due to a slow moving combustion event using High Octane fuel/octane booster products. Usually to compensate for High Octane fuel, you Advance the spark event, so that the combustion event happens sooner, to compensate for that slower flame front (sooner also usually = more power, but that's a timing discussion not an octane discussion). Since our ECU's cannot Advance timing based on the *lack* of ping, it does not compensate for the High Octane fuel, and you can loose power.
In short, since our ECU's can't detect it, or compensate for it, don't use it unless it's needed (pinging...)
The only way you are going to raise your compression ratio is to..
Install domed pistions
longer rods
Shorter throw crank
mill the block/head
Nitrous oxide usually likes higher octane fuel, simply because the increased oxygen/fuel content ignites more readily at a given compression ratio. Cams/headers have no effect on CR and should NOT affect your octane requirements.
One last thing to point out here while we are discussing octane.
Low Octane fuel ignites easier than high octane fuel. Thus high octane fuel is HARDER to ignite, and the flame travel is actually slighly SLOWER with High octane fuel rather than low Octane fuel. Thus, you could LOOSE POWER due to a slow moving combustion event using High Octane fuel/octane booster products. Usually to compensate for High Octane fuel, you Advance the spark event, so that the combustion event happens sooner, to compensate for that slower flame front (sooner also usually = more power, but that's a timing discussion not an octane discussion). Since our ECU's cannot Advance timing based on the *lack* of ping, it does not compensate for the High Octane fuel, and you can loose power.
In short, since our ECU's can't detect it, or compensate for it, don't use it unless it's needed (pinging...)
