Contour Enthusiasts Group Archives Forums General General 91 Octane???

Originally posted by svt4stv:

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Originally posted by DemonSVT:

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Originally posted by svt4stv:

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i only use 87 in my svt.

i emptied my tank and filled it with 91 when i went to the track. per the butt dyno, no difference.

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Did you reset the PCM and let it relearn for the higher octane. EXACTLY!!!

Also the knock sensor ONLY pulls timing AFTER detonation occurs.


'nuff said.

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im not up too much on this kinda stuff. set pcm by disconnecting battery? would it make a difference really? in speed times? just curious. im not very smarts on performance stuff.

and what you said about the knock sensor is Chinese to me. i was only quoting what the manual said. please explain what you mean by "pulls timing after detonation"

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So you have a "CAI" and you use 87 Octane. If that isn't oxymoronic, then I don't know what is.

Deteonation is the uncontrolled, explosive, combustion of fuel/air in the combustion chamber (normally the charge should burn across the chamber like a wave, not a BANG!). It's basically destroys the combustion chamber internals by disrupting the cool boundary layer normally found around the charge, and thus superheats the head, valves, and pistons accompanied with percussive force which damages the wristpins, conrods and bottom end bearings = BAD!

Pinging/detonation sounds like rattling marbles in a can, and the knock sensor "listens" for this and pulls timing if it hears it (but it can only retard the timing so much) to try and diminish the detonation from occuring. When the ECU does this, you make less power.

Thus putting on a power adding modification (CAI) on, then using piss-water for gas in a car that has high compression (why it needs high octane fuel) is stupid.

Reminds me of the silly dopes who tried to dyno their modified SVT's with 87 octane and then were baffled why there car made even less power than a stock car!