air/fuel ratios

[kyles_r32]

Hey im just wondering whats everyones a/f under full boost. Im running .85 bar and im hitting like 11.7:1 and the leans out at higher rpm(5500 and up) at about 12.7:1...is this too lean?

Thanks

[love_boost]

yeah thats to lean, i think it should be closer to 11.7 at the top end.

[BrianV8]

thats untrue, with the amount of boost your running 12.5 would be prime, so your almost bang on, your don't need to get into the really rich number until you start dumping 1+ bar of boost IMO from the research i've done

As long as you never see 13 you should be fine, just an agressive tune. Keep an ear open for knock but i would not be overly concerned

[Skym]

Also depends on ignition timing your running that can cause unstable combustion (knock).

Max A/F ratio for stock engine is 12.0:1 at peak boost (around 2500rpm on stock engine) to peak hp at higher rpm (6400rpm) with 98 octane pump gas.

Safe A/F ratio is 11.6:1 at peak boost to peak hp at higher rpm. Why, if exhaust manifold or intake manifold leaks, can make engine go lean and with advanced ignition timing, could knock and result in engine failure. So having a safety margin with A/F ratio, ignition timing is worth it.

13.0:1 A/F ratio would be more for a NA engine.