Blow Off Valve question...

[eclipsefan98]

I was wondering if there is any way to have a bov that vents to atmosphere and not have the ebgine run real rich at the same point. i know a bov that vents back to the intercooler would accomplish this but i love the chirping or wooshing that they make when shifting gears. i have heard that switching your MAS to a MAF or blow thru unit will solve the problem, can anyone confirm this? thanks

[-Jayson-]

umm thier is a whole section dedicated to forced induction. . .

[eclipsefan98]

well i thought that people around here may know more, and have had more experience with it.

[JekylandHyde]

Cars run rich when the valves blow off because they are venting air that has been metered by a AFM (Air flow meter) or MAF (mass air flow sensor) and the ECU has already sent the proper amount of fuel for that amount of air.

How to get by this?

Get rid of the AFM or MAF.
You can do this with the HKS VPC (not available new anymore) or go to an EMS (engine management system) that works on speed denisty to measure the air.

[nissanfanatic]

I've heard that you can use the S-AFC to tune the idle and make it a lot better. I don't think it fixes the problem completely. There is also a Turbosmart BOV that vents to atmosphere and to the intake. Not sure on that last one.

[JekylandHyde]

The SAFC allows you to tune at 2 different throttle positions. You choose which two.
Choosing "idle" (zero throttle) as one of the points to tune at would be a waste of a tuning point IMO.

[eclipsefan98]

would a recirculating bov still make the whoosh sound when i shift?

[JekylandHyde]

Recirculating the air significantly quiets it down.

[TatII]

having experienced this many times before myself in the past, i can help. i also have a apexi SAFC. i use to try to run a turbo XS RFL blow off valve. however my car ran like shit and stalled everytime i let off boost, even if i'm only making 0 psi on the boost gauge. before it stalls, it will be acompanied by a hugh back fire. now i drove it like this for a mile before i got soo annoyed at it that i put the turbo XS type H34 bypass valve back on. now after reading the instructions for the AFC carefully, and figured out how to use the function that prevented the car from stalling when you let off boost. i decided to run the RFL again. this time the car would not stall when i vent off, however the car will back fire everytime you let off. so cruising down the block i would backfire atleast 3-5 times. also what really killed it for me was the throttle response went to shit. part throttle is impossible. it would have such a delay then all of the sudden the would jump forward. it doesn't do it all the time but it does it enough to get annoying, and driving in stop go traffic becomes very dreadful, and my fuel economy went waaaay down. also another draw back is that when you start the car up cold, the idle would be very erratic until the car warms up.

now there is another alternative, get a Greddy Type S and bypass the thing back into the intake, it is still pretty loud with being recirculated. y ou can still hear it from out of the car pretty loudly. after i've switched to the type S BOV i'm very happy with the car, the car now runs super smooth, and i get great fuel economy again, and you can still hear the whistle when you shift on boost.

not all cars act the same. like my friends 2nd GEN MR2 runs pretty smooth with a RFL on, and Eclipses runs okay with it on. but for a 240sx, it runs like a nightmare.

[nissanfanatic]

Good. I wasn't sure how it would sound being recirculated. I heard one on my friends 1gen DSM and that thing was hella-loud to atmosphere.

[TatII]

in order for you to hear the bypass valve you need a free flowing intake. this is becasue the stock intake box and resonator muffles the boost being rerouted back.

[nissanfanatic]

I do. I'm using a K&N cone filter.