How to tune for open BOV on MAF car

[DanNY]

So the set up is Turbo -> BOV -> MAF -> throttle body
the BOV dumps to the atmosphere so under heavy load the air rushes past the MAF again and dumps out of the BOV. When that happens the car runs a little rich and back fires.

is there any way to "fix" that? Basically to lean it out on deceleration

also when i turn the A/C on the car idles very low and it stalls...what i can do to fix that

Maxima VG30ET
Manual transmission

any input or suggestions would be appreciated.
thanks!
Dan

[skylinegtrhr]

what MAF do You have?

[DanNY]

what MAF do You have?

stock maxima MAF

[Matt]

Not really the ECU only injects based on what it sees from the MAF

[DanNY]

Not really the ECU only injects based on what it sees from the MAF

good point...but should the ecu still inject when there's 0 throttle?

any thoughts on the A/C? i see the AC switch signal on nistune when i flip it on but i don't see a jump in idle so it will just stall out.

[Matt]

AC controls the FICD (Fast Idle Control Device) solenoid which when working will increase idle RPMs by slightly increasing RPM. Some ECUs have air cond enrichment also (watch the injector time in Nistune when activating A/C)

Even on zero throttle if the MAF measures a spike on air it will tend to inject until the RPM cut limit is reached

[Mike_GruiZinga]

What BOV are you using, and can you adjust the spring pressure?

I use a Tial, which is fast enough to minimize this problem with the stock MAF in blow thru. I have to switched to the newer slot style maf (im using mustang HpX from vpn tuning) as these are not bidirectional mafs. They are much less sensitive to the reverse flow.

The installation was the same as a mustang cobra maf in terms of wiring, and nistune offers maf scaling for the HPX maf.

[jaqattack02]

How close is the BOV to the MAF? If it's too close it may mess with the readings the MAF is getting when it opens.

[Buddyworm]

I've had good luck with a combination of high spring pressure and fast valve action speed when venting to atmosphere. I run the Synapse Diverter Valve with the spring at full preload in a Push configuration. The fuel mixture doesn't seem to be severely affected, I've noticed no post-shift bog and my turbo comes right back up each time i grab a gear.

[enohand]

why don't you run your setup like mine?
this will prevent the ecess air from going past the maf again.

only issue is rich spot between shifts.

see the pic below

[88execvl]

with the idle problem when you switch on the AC the air feed for the FCID and AAC should come after the MAF/AFM.

[Adrian]

The solution for this BOV problem is quite simple. You have just set the max Tpulse wide between 0 and 1500 rpm as low as possible, without affecting the mixture under loud. find out the max possible pulswide to 1500rpm and set the max-tpulse slightly above. It's a 5minute job

[Matt]

Yes that would actually work quite well, it would limit TP overshoot at the lower end RPM scale, as long as it does not limit fueling in the same area required on acceleration