bov help

gorf · Feb 15, 2010

I have been fighting a rich condition on my car for a while, I think I finally have it under control.
However, I am now having trouble turning up the boost. I am running a 20g with a holset actuator and with a tube running from the compressor to the actuator I pull 20lbs boost and the car runs great, no knock no bov flutter.

When I install a MBC and crank the boost up to 25lbs my BOV sounds like it is getting blown open (fluttering under full throttle). Needless to say, when this happens I my knock counter starts going up.

The BOV is a 1g with the dodgemod, fast release is open to atmosphere. Reading other threads, it seems like 25lbs should not be a problem for a DM 1G BOV.

Any suggestions what to look for? Or do I just need to buy a better BOV?

GRAVEDIGGER · Feb 15, 2010

I have a 1g crushed BOV and it holds my 25psi just fine. :idontknow:

Dewayne Waldron · Feb 15, 2010

Worn blow off valve seal ?

gorf · Feb 15, 2010

The BOV was brand new when I got it. It was mounted on a Dave Brode uicp. I did the dodgemod because a number of people claim they can hold 25 - 30 psi without crushing.

Guess I need to try crushing it.....

donniekak · Feb 15, 2010

Mine was blowing open at 23 psi, i barely crushed it and it holds 30+.

Jimmyskrew face · Feb 16, 2010

gorf said:
I have been fighting a rich condition on my car for a while, I think I finally have it under control.
However, I am now having trouble turning up the boost. I am running a 20g with a holset actuator and with a tube running from the compressor to the actuator I pull 20lbs boost and the car runs great, no knock no bov flutter.

When I install a MBC and crank the boost up to 25lbs my BOV sounds like it is getting blown open (fluttering under full throttle). Needless to say, when this happens I my knock counter starts going up.

The BOV is a 1g with the dodgemod, fast release is open to atmosphere. Reading other threads, it seems like 25lbs should not be a problem for a DM 1G BOV.

Any suggestions what to look for? Or do I just need to buy a better BOV?

That flutter sounds like you have a compressor surge issue..

gorf · Feb 22, 2010

Jimmyskrew face said:
That flutter sounds like you have a compressor surge issue..

Please enlighten me..... I am not sure just exactly what compressor surge is, I thought was more evident when you backed off the gas and you can feel the turbo jumping. I am using a holset actuator which holds 20 lbs when directly connected to the boost source. Runs great when configure like this.

I only have a problem when using a MBC to get 25lbs and under full throttle, it sounds like the BOV is fluttering. It may have to do with the MBC, but I just don't know.

I pulled the BOV and noticed one side of the BOV was pushed down like it might have been dropped. I put it in the vice and crushed it just enough to even out the top. It still does the same thing - flutters under full boost and knock count starts going up.

gorf · Apr 4, 2010

STILL STUCK!!!

Installed a Synapse BOV which can not blow open. Did BLT up to 30 lbs.

with actuator directly connected to turbo source, 20lbs no knock.

When I install a ball and spring MBC I get 25lbs but under full throttle STILL sounds like bov being blown open. Could this be something simple as the MBC? is there another one that I should try?

Boosted98gsx · Apr 4, 2010

Jimmyskrew face said:
That flutter sounds like you have a compressor surge issue..

Was thinking this also.

gorf · Apr 4, 2010

Boosted98gsx said:
Was thinking this also.

from another thread:
http://www.dsmtuners.com/forums/turbo-system-tech/357281-true-compressor-surge-info-elimination.html
"Like has been said before your turbo is flowing too much air for the engine to ingest at your operating points. If you have surge at WOT you need to increase the amount of air your engine can flow with a certain displacement and engine speed, aka increase your volumetric efficiency/eliminate flow restrictions post compressor outlet."

My mods 2.5 inch fmic piping from turbo to throttle body. Throttle body is 1g n/t with 2g intake manifold ported to accommodate throttle body, so no restriction all the way to the intake manifold. 6 bolt block with 100mm crank (2.3), 264/272 hks cams.
So I don't think a 20g could out-flow my engine?

romeen · Apr 4, 2010

Sounds more like a boost leak that only starts leaking air as you approach 25psi. Do a proper boost leak test.

Boosted98gsx · Apr 4, 2010

gorf said:
from another thread:
http://www.dsmtuners.com/forums/turbo-system-tech/357281-true-compressor-surge-info-elimination.html
"Like has been said before your turbo is flowing too much air for the engine to ingest at your operating points. If you have surge at WOT you need to increase the amount of air your engine can flow with a certain displacement and engine speed, aka increase your volumetric efficiency/eliminate flow restrictions post compressor outlet."

My mods 2.5 inch fmic piping from turbo to throttle body. Throttle body is 1g n/t with 2g intake manifold ported to accommodate throttle body, so no restriction all the way to the intake manifold. 6 bolt block with 100mm crank (2.3), 264/272 hks cams.
So I don't think a 20g could out-flow my engine?

There's your restriction. Invest into a SMIM, so you can make use of those cams.

gorf · Apr 4, 2010

Boosted98gsx said:
There's your restriction. Invest into a SMIM, so you can make use of those cams.

Damn if its not one thing its the next.......

I am running the 2g head also, which is not ported. But my understanding is that should not be a problem.

So even though I have a 1g throttle body and the manifold intake is ported to match, you are suggesting that the 2g manifold may be the restriction?

romeen said:
Sounds more like a boost leak that only starts leaking air as you approach 25psi. Do a proper boost leak test.

BLT to 30lbs and it holds. The first time I ran it up that high, it would start leaking at about 17, but that has been resolved.

Boosted98gsx · Apr 4, 2010

gorf said:
Damn if its not one thing its the next.......

I am running the 2g head also, which is not ported. But my understanding is that should not be a problem.

So even though I have a 1g throttle body and the manifold intake is ported to match, you are suggesting that the 2g manifold may be the restriction?

Well the 2g plenum is quite small and is designed with a t-25 in mind. You are more than doubling the amount of airflow that manifold is designed to distribute, so yes, it's a very real possibility that the manifold is causing the restriction.

You should have upgraded to a higher flowing manifold at anything larger than a 16g in retrospect.

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