Timing for Octane

[mn_vette]

So you are supose to run the lowest octane that keeps your car from getting knock retard, but what about this. Is there a proper tune for different octanes? Can I tune my car to run on 92 octane then retard the timing X degrees and have it run just as well on 87 octane? Is there any reason to run the higher octane on a N/A, Nitrous, or FI motor? Thr reason I'm asking is because I'm starting to mess with my timing on my car and I'd like to know if there is a theroy(sp? mental block) to tuning with different types of gas and see if I can save myself a few bucks the pump this summer. 9.5:1 compression just to let ya know. I hope to get some interesting thoughts on this subject.

[mn_vette]

TTT - nobody has any thoughts or expertiese on this matter??? I'm like atleast an educated guess from you guys before I go blow up my engine

[lcvette]

MN,

octane plays a key role in how the car will perform with different tunes. to answer your question, yes you can tune per the different fuels available in your area.. once you finish the turbo project and have everything working properly you will also be able to adjust it for race fuel to run higher boosts and more timing. just like the gN guys.. they generally will have a "thumbwheel" chip which has about 5 tunes on it, some for different octane and boost settings. NA cars can also benefit from this.. generally speaking, with your compression ration and depending on your quench area and how your engine behaves in general, you can tune to the max for each octane fuel and run on the edge of detonation with proper fueling and make max power. so to answer your question... your on the correct path!

Chris

[GlockLT4]

If you're getting knock .. stick some 110octane in there and see if it goes away. If not, then you're getting false knock. If it does go away, add in more gas (87-93) and experiment with your overall octane rating ( simple(X+Y) / 2) until you get to where it causes knock again. Go back one octane level. This should (of course) be done with your highest performance timing.

I had to run 97octane in the 383 (had my timing too far in the hot Texas Summer).


[Modified by GlockLT4, 8:17 PM 4/28/2004]

[mn_vette]

Glock, how do you detect knock? Is there an easy way without having to buy a whole nother scan software setup? I'm running an aftermarket ECU that takes up the laptop and the serial port. I'd really like to not have to have two laptops to tune it right.

[GlockLT4]

Glock, how do you detect knock? Is there an easy way without having to buy a whole nother scan software setup? I'm running an aftermarket ECU that takes up the laptop and the serial port. I'd really like to not have to have two laptops to tune it right.

I use my laptop with DataMaster software. Does your aftermarket ECU require different software than normal?

[mn_vette]

I'm running an Accel DFI Gen 7. I has an input for a knock sensor but you need a special converter box and such for it, not cheap.