3sge (3rd gen) Octane? Options

[czwalga]

3rd gen 3sge does anyone know the recommended octane? Or most likely RON since it's not a US engine? I've been bashing my brains in trying to figure out this problem and refuse to go to another race with it. After about 30 hard miles 5k RPM.... the engine starts cutting out lower and lower in the RPM range until I cant rev over 4k RPMS.

I've been running 87 octane, i'm thinking the knock sensor could be detecting something and slowly pulling timing.




If this is the case i'm an idiot, and created a lot of headache for a stupid easy fix.... just sucks cause there's no easy way to test it.

This post has been edited by czwalga: Jan 31, 2013 - 8:10 AM

[Special_Edy]

CR, fuel/air ratio, octane and ignition advance are all codependant factors. Most ecu's will retard the ignition until the predetonation stops. If you put a higher octane in the car the ecu will actually advance the ignition. to utilize it until it detects detonation.
Its similar to how the engine determines the fuel trim, it constantly fluctuates between lean and rich to pinpoint the best trim. The ecu is constantly testing the limit of the ignition advance for maximum performance without detonation.
Putting a lower octane in shouldn't negatively impact an EFI motor except for a slight loss of torque. Raising the octane will marginally increase output.

Check the plugs for color, if they are pitting then you have a problem.

This post has been edited by Special_Edy: Feb 1, 2013 - 12:46 PM

[czwalga]

CR, fuel/air ratio, octane and ignition advance are all codependant factors. Most ecu's will retard the ignition until the predetonation stops. If you put a higher octane in the car the ecu will actually advance the ignition. to utilize it until it detects detonation.
Its similar to how the engine determines the fuel trim, it constantly fluctuates between lean and rich to pinpoint the best trim. The ecu is constantly testing the limit of the ignition advance for maximum performance without detonation.
Putting a lower octane in shouldn't negatively impact an EFI motor except for a slight loss of torque. Raising the octane will marginally increase output.

Check the plugs for color, if they are pitting then you have a problem.

Not many people run their car as long or as hard as I do. Starting out for the first 20 miles above 5k rpms you dont notice anything. Around 25 miles you start to sense something. 30+ you know something is definitely wrong.

If it's continually detonating, the ECU is going to keep pulling timing until who knows... i'm just assuming there's a point where it jsut wont accelerate anymore, but who knows. It's either that or a super lean condition, caused by some hangup in the fuel system.

The lean condition, doesn't make much sense to me though just because I would think if something was clogged, not high enough fuel pressure etc, it would just do it all the time... which would make my life a hell of a lot easier.

This post has been edited by czwalga: Feb 1, 2013 - 3:20 PM