hacker-pschorr

Funny, we have almost the same gmail address....

AO

Heinrich's gmail is close to gaylover@gmail.com? Whodathunk...

Tampa 928s

Nice and so early in the morning

PorKen

NTTAWWT.

Have you tried disconnecting the O2 sensor? If the MAF is not/cannot be adjusted properly, then the idle correction will be bad.

Tampa 928s

I have a data logger on the car and everything is spot on, yes I disconnected it when I did the set-up a month ago. I have a custom made Maf with two trim pots that is very adjustable.
I am trying to find out where to place my Bov once I relocate my maf any suggestions?

PorKen

I forgot that your issue is part throttle, not idle.

Instead of relocating the MAF, how about making an airbox for it? Leave the MAF in place, and make a box like the original airfilter box, but smaller and sealed. Most importantly, have a bellmouth inside leading to the MAF inlet. Then the inlet pipe angle doesn't matter anymore.

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I suppose you could dump the BOV into the box, too.

PorKen

Wait, that doesn't make sense. I guess I mean you could put the BOV/recirc valve on the box.

In reading your x-post over at, I see that 'he who cannot be named' uses an airbox/plenum to feed the MAF.

Abby Normal

It's not just a box either, there are some specific features in the design of that box that make it work so well.

Fabio421

The BOV should be located as close to the throttle plate as is feasibly possible IMO.

Tampa 928s

Well as close works for me, so do I connect a tap for the BOV near the dummy maf?
Where does the air go, it would go rich everytime the pedal was let off under boost. Do I feed it back into the intake, I'm so confused

Tampa 928s

So where do I connect the Bov?

Per a ricer post(s): If you ahve a MAP then your cool. If you have a MAF then you have 2 choices. 1 you can vent to the atmosphere anyways and make your car run like crap, or you can re-route the blown off air back into your intake system before your supercharger after your MAF sensor so it still knwos its there.

The air bypass valve (ABV) serves two functions. The first is to provide a route for air to bypass the supercharger when it is not spinning. The second is to act as a blow-off valve when boost exceeds aproximatly 8 PSI. The blow off point varies significantly between cars from 8 to 10 PSI.

Everything depends on where you place your throttle body. If you put the TB before the S/C like most are factory designed then there is no need for a BOV. The internal bypass mechanism that mounts to the side of the SC will control the boost by "sealing" the chamber when you go off vacuum (hard on the gas) and open when you go under vacuum (cruise and idle). This will work perfect with the MAF as well. If the TB is located after the supercharger then you have to have a BOV between the 2 in order to vent the pressure when the throttle plate slams shut (letting off of the gas). If not this pressure will back up into the SC because it has no place to go (even though the SC bypass is now open and thus not making more boost) and apparently they really don't like that! The tradeoff is the fact that the closer the TB is to the intake the better for throttle response.
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Fabio421

I think its best to vent it back in line after the MAF since that air is already metered. If you put it in before the MAF it would be measured twice. Where are you getting your signal for the RR fuel presure regulator? At the plenum?

Tampa 928s

Shawn,

I don't understand your ? the FP Regulator and FMU is getting it from the same vacuum source.

Larry Velk

We have 4 factory turbo cars (old style, pre new style emissions). I think the main reason for the location of the air meters is to make sure you have crankcase venting without fouling the meter - the vacuum is taken between the meter and the blower. It always seemed stupid to me to have no crankcase evac. on many 928 supercharged cars.

Tampa 928s

I am getting some mixed messages as to my set-up, it was brought to my attention the by using the 4” to 3” reduction at the in and out of the Maf is going to cause turbulence. I have very little space to work with is there some type of formula as to how much straight 4” feed the Maf needs on both sides so not to disturb the air flow.