davidc1

Hello everybody, OP here...

So, back to one of my original questions.....when I've heard that running lean can damage an engine, especially at the track, is that because of knock and/or preignition? Or because of the the extra heat that running lean produces only?

And then, does running a higher octane fuel, such as 99 or 100 found at the track help at all?

And if so, does putting an octane increasing additive from the auto parts store work the same as the higher octane fuel?

davidc1

Hello everybody, OP here...

1. So, back to one of my original questions.....when I've heard that running lean can damage an engine, especially at the track, is that because of knock and/or preignition? Or only because of the the extra heat that running lean produces?

2. And then, if it's because of knock, does running a higher octane fuel, such as 99 or 100 found at the track help at all?

3. And if so, does putting an octane increasing additive from the auto parts store work the same as the higher octane fuel?

4. And, as an aside, it appears that our stock ECU, via the OBDII link, does not report the AFR, correct?

dan_uk

I don't think they come near to running lean until you increase the exhaust piping size
With my 03 on the stock exhaust it was very rich.
With a VAFC and testpipe we took about 10/15% fuel out over 6000rpms to make power.

Once I went to a 70mm exhaust the AFR's where about where it made most power so we took the VAFC out.

takchi

I have a graph showing what happens when you go from stock to HFC to testpipe. It just gets leaner by 0.5 pt each time...

yonson

Yeah, the engine is programmed to run at stoich. or 14.7:1, the fuel trims are how much fuel is being added or subtracted in order to reach 14.7:1 So if your fuel trims are 5% the PCM is sensing a lean condition and adding 5% fuel to reach 14.7:1.

yonson

Knock is mainly caused by not running high enough octane fuel. If you have a stock AP1, you shouldn't be having any knock issues. The leaner your mixture is (to a point) the easier it is for detonation to occur. If you are having actual knock, higher octane fuel will help. The only octane booster I have had success with is Torco. Correct the stock lambda is a narrow band, so it is only accurate ~ +/- 1 AFR from stoich... If you want actual get a good wideband and install it before the catalyst.

Togobox

Knock , running lean or preignition can damage an engine track and street. Not enough fuel to cool the combustion camber cause lean running. Low octane or low quality fuel cause knock and/or preignition.

Higher octane fuel have more stable burn rate. It might not help since stock engine is tune for premium gas not race fuel.

Not sure octane booster works the same as race fuel. If i have to guesss, i would go for race fuel.

I think the Honda HDS/MVCI only shows target a/f not actual a/f. I belive the target open loop a/f ratio is 12.5.

Pull a spark plug out and you can pretty much be able to tell the condition of the engine by it's color. Is your engine running lean?

Togobox

Knock , running lean or preignition can damage an engine track and street. Not enough fuel to cool the combustion camber cause lean running. Low octane or low quality fuel cause knock and/or preignition.

Higher octane fuel have more stable burn rate. It might not help since stock engine is tune for premium gas not race fuel.

Not sure octane booster works the same as race fuel. If i have to guesss, i would go for race fuel.

I think the Honda HDS/MVCI only shows target a/f not actual a/f. I belive the target open loop a/f ratio is 12.5.

Pull a spark plug out and you can pretty much be able to tell the condition of the engine by it's color. Is your engine running lean?