Discussion on how bypass valves can affect LTFTs.

[BuddySpeed3]

Originally Posted by Sacrilicious My hypothesis is that our ECU is programmed to expect a low release point, since the stock BPV has a relatively weak spring holding the valve shut. I think that this stock Release Point is expected to be DURING the operation/learning range of the heavy throttle LTFTs. This is the same LTFT that is used during WOT (Open Loop) operation. When you add an aftermarket BPV which raises the Release Point of the BPV such that it puts it out of the operation/learning range of the heavy throttle LTFTs, which means that the ECU will learn these LTFTs with a fully shut valve (vs the slightly leaking recirc of the stock weak spring), which means that more air would actually get into the engine, making the ECU calculate higher LTFTs, since it sees more air in the system than it's used to (making it add more fuel).

Could this be why people are getting rich throttle tip in conditions in between shifts?

My LTFT's are on point at part throttle/closed loop. But during hard acceleration, in between shifts, as I step back on the gas, and boost builds again, I keep getting a rich throttle tip in condition (10:1) that quickly settles out to my target AFR (11.5:1).

Tweaking the MAF CAL in those specific MAF voltage regions doesn't seem to fix this rich throttle tip in condition.

Is it possible that the ECU dumps fuel during throttle tip in between shifts on purpose to protect the engine? Or is it caused by the after market BPV being set too stiff?

Thanks.