Discussion on how bypass valves can affect LTFTs.

[dadasracecar]

Sac, I appreciate your efforts with this but I think your logic is flawed. You're basically describing a boost leak that happens all of the time. The air is being recirculated in your theory so it's already been metered by the MAF. It recircs right back in to the turbo.

Also, the stock bpv is a pos plastic hunk of shit and there is no way the ecu actually uses it to accurately calculate fueling. Sorry man, but your theory just doesn't hold.

[Sacrilicious]

Originally Posted by dadasracecar Sac, I appreciate your efforts with this but I think your logic is flawed. You're basically describing a boost leak that happens all of the time. The air is being recirculated in your theory so it's already been metered by the MAF. It recircs right back in to the turbo. Also, the stock bpv is a pos plastic hunk of shit and there is no way the ecu actually uses it to accurately calculate fueling. Sorry man, but your theory just doesn't hold.

yes, it's being recirculated, but by diverting the air like that back to the turbo, you end up pulling air from the intake manifold, because what you're doing is delaying how soon that air gets into the intake manifold. just because you recirculated that air back into the turbo inlet, does not mean that the air gets into the intake manifold in time to run the AFRs that your expected.

another way to think about it is that the valve is moving compressed air back to a point before it was compressed (requiring it to be recompressed by the turbo), which would stand to reason that you're actually pulling enough air from getting into the intake manifold...corrupting what you thought you knew using the MAF sensor readings.

like i said in my post, dada, it just does not make sense that i have gone back and forth between spring settings and essentially toggled this rich/backfire problem on and off just by changing out the spring of the valve. i understand that this air is already metered by the MAF, but when you play tricks with the system by pulling compressed air and shooting it back into the pre-compression area (turbo inlet), you are definitely keeping air from reaching the engine cylinder when your ECU calculated it would be there...making the resulting combustion richer than you intended.