The setup is:
Hytech header, cat and exhaust
Mugen intake
Unichip (a "piggyback" system that controls fuel, timing and VTEC)

The tuner said that he would'nt change the A/F ratio, but only adjust timing and VTEC. That doesn't seem right.
What A/F ratio would you suggest?
I have already searched and found different suggestions like: "Whatever makes more power" and "around 12,8-13.5 :1".
We made a dyno run today, with just the mugen intake, and when VTEC hits, it gradually goes towards 12:1 at 8k rpm.
I Suggested an A/F ratio of about 13:1 but he looked suprised, and said that was VERY lean and that I risked engine failure.
The car will be tuned on Friday. Please let me know what you think.

 

Stock map on the ECU runs rich, so it is usually good to lean it out for basic mods.

BUT ......... it is best to tune it on a calibrated dyno, and with a wide band A/F meter to really get it right.

If there is one close, go get it done right. If not, lean it out a few percent, but that is entirely on you .......... it is your engine to blow ....

 

It was measured with a wide band A/F meter on a dyno just to get a baseline before the Hytech system and the unichip is installed. Around 12:1 at 8k rpm seems a bit rich. Would around 13:1 be "risky"?

 

13.8:1 to 14.1:1 with heavy track use... no issues.

Take a look at my charts. Stock ECU vs. VAFC'd ECU
https://honda-tech.com/zerothread?id=511707

 

yeah 12:1 is on the low end for NA.