funny idle after venting....

[Guest Silvrbmw1]

So here's the deal. My buddy has a 2g tsi, 99, w/ a 1g bov. after turning the boost up and veting the bov, the idle would very quite dramatically. w/ the idle set at even 1200 rpm, the engine will die after a rev and you let the motor roll down the rpms, and sometimes it will catch itself before the motor dies, but not all the time. it only does this when venting. we capped off the tube in the intake were the pipe would had gone and it was sealed well. any idea why this is happening?!?! it average's 15 psi, and spikes at 17. on the t25.

[Guest Silvrbmw1]

oh yeah, i may have not made it clear that the motor does die, 50% of the time on decel.

[timmy43016]

sounds like a vacuum leak of some sort...i dont have a turbo that big, but thats my guess.

[MrMeanGreen]

Off to Tech...

[SupraGlue]

This is on a mass airflow equipped car, correct? If so, he is venting metered air. This causes the car to run very rich when venting from the BOV -- hence the attempts to stall. Very common problem.

 

You need to either route the BOV vent back to the intake, like stock, or you need to use some sort of fuel controller that compensates for the BOV venting.

 

"Doctor, it hurts when I go like this."

 

"Don't do that, then."

[Guest Silvrbmw1]

dremel, i got ya. my other buddy, who also has a tsi runs fine when venting though. he's got a few more little mods, nothing out of the ordenary. 3 inch cat back, and greddy bov. its the one car not running right because it's more moody than the other?! the one having the problems is a 99 compared to a 95. still a 2g but still...

[SupraGlue]

Different BOV. Your other friend might have the Greddy adjusted tighter, so that not blowing off so much during light deceleration. The stock BOVs have pretty soft springs, which is why people do the crushed top mod, or drill them to make them adjustable.

 

It can be hit or miss with the mass air cars, too. My Supra never stalled with the Greddy vented, but when we took it off my car and put it on another Supra, that one stalled every time he came to a stop. *shrug*

[20G TSi]

has your friend drove the car much with the BOV vented? Any time you go up a hill and approach 0psi, the BOV opens and the car bucks like a $3 whore (due to running rich). Unless you've got some type of VPC, like dremel said, its not going to work well. Why vent anyways? So you can sound like you've got a fast car or something? It does nothing positive for performance... infact (again, like dremel said) it will make the car run rich and like shit. Tell your friend to quit trying to rice his car out and route the BOV back into the intake.

 

I've been using a 1G BOV, and with a K&N and the BOV routed into the intake, and BOV dump tube cut, its quite audible....

 

 

edit: the idle is like shit since the BOV is open during idle letting some metered air out. Stock 1G BOV's leak at anything above 17psi, so he's likely getting worse performance at WOT also.

[Guest fooked]

I thought I had read a lot of people having bad luck when trying to vent a 1g bov. If he really wants it vented, I would get the HKS or the greddy. I've got the HKS vented to atomosphere, and my car runs as good as it did with the 1g bov routed back to the intake. The only problem i have is the smallest amount of hesitation when I only build like 2 or 3 psi on the freeway and then let off the gas.

 

I have a friend with a vented Greddy type S, and he has similar problems as me. It's hardly noticeable, and it doesn't happen very often.

[Mr. Jones]

"I've got the HKS vented to atomosphere, and my car runs as good as it did with the 1g bov routed back to the intake."

 

While that is not technically possible

 

I have heard good things about venting the SSQV on MAF equipped cars with fewer symptoms than the rest.

 

 

You'll still be running rich regardless of which bov, if its vented.

[Guest fooked]

I meant to say "almost as good as the 1g bov..."

 

There....better?

[20G TSi]

Originally posted by Jasons TSi:

edit: the idle is like shit since the BOV is open during idle letting some metered air out.

correction, its running extremly LEAN at idle, due to vacuum pulling unmetered air in through the BOV. And it dies because its going from a rich condition to an extremly lean condition every time you boost and lift off the pedal.