The stock BOV works fine. I think I posted that way back at the beginning of this thread. All of you trying to run 30 psi or something are just asking to rebuild your motor...

 

You could always sell or return the valve. I am not being a smart ***, but it is not that good of a valve for this application.
There is no reason to change to speed density, the MAF system is actually more accurate.

 

It is plastic and does not seat well so it tends to leak. Some one also already split one open.

 

Is this after they put a boost controller on and started getting wild??

I have a lot of mods, my car runs perfectly (the tach idles at 900rpm without even wavering) and nothing sputters, stalls or otherwise.

I think people have been playing too much Gran Turismo and expect to boost their car to 600hp and not have any problems...

 

I think he was stock, but regardless.
A DV will not cause an idle problem because the metered air is not being vented. The stock DV can be open a bit at idle, but it doesn't matter. The Forge is wide open at idle and idles just as well as stock. The problems you described are attributed to BOVs not DVs (properly adjusted).

 

tried the types S mod and it works fine car feels better only thing though is that it really sounds gay and its leaking at idle so its whistling at idle.....i also added a boost controller at the same time but its boosting 21 and going down to 14lbs and about 5krpm.....can this be because of the type S leaking.,....??? by adjusting it will it fix the problem...???? how much should i tighten it..im kinda new to this so if u guys can help it would be appriciated

 

oh by the way its a greddy something B electronic boost controller

 

At idle the valve should be open (with this spring tension), but the amount of airflow from the engine at idle should not cause any sound, I know mine doesn't. I suspect you may have a leak in the actuator chamber area, it should be air tight/be able to hold vacuum. This could also keep the valve from closing under boost, causing your other boost problem as well.

I am not sure what can be done about the sound from part throttle lifts, it doesn't bother me but if your actuator chamber is leaking yours might sound differently. With a full 3" exhaust I don't even hear the DV valve anymore. I suspect that other valves, that do not make this whistling noise is due to one of three things:

1. The spring tension is very light so the valve opens faster and higher and does not hit resonance. This will give you the whoosh sound even on part throttle, drivability will be good maybe even better, but the valve will not close as fast (and might even leak on boost if you go too soft), possibly compromising performance. More testing may be needed, Timzcat?



2. The spring tension is so high that it does not really open under part throttle, which causes the drivability issues. Under high load lifts the higher pressure to vacuum transition causes the valve to open quickly, preventing resonance.

3. If the valve leaks a little even when fully closed (like the stock one), it should prevent it from resonating at partial opening. I am beginning to suspect the stock valve may have been designed to leak a little for this reason??

I was simply concerned with setting it for the best possible performance without affecting drivability (stalling/bucking), the noise does not really bother me. I am sure with enough time and effort some one can and will find a combination that does not really compromise performance and doesn't whistle.

Hey Timzcat, I have been meaning to get back to you regarding the Forge, I do appreciate you fielding questions on this thread. It sounds like a good option although I am not sure you have the optimum spring tension yet. The light spring sounds like it maybe a little too light, and I am not sure installing it backwards would not cause surging under high load transitions?


Kind regards,


Eric

 

I really don't know anything about the Evo BOV,however, I have played around with the 1g DSM valve on my 1g DSM.

I believe that the 1g is thought to open at 17-18 psi based on that if you use a sping scale that is the pressure it takes to start to open the spring. the 1 inch wide opening is not 1 square inch though. My 1g valve opens at 17lbs spring pressure on .78 sq inches. This means that it will take 21.6 psi to start to open the valve.

as far as vacume to open the valve remember that IF it takes 16 in to open the valve on the bench with no boost. the valve should then open at 8in or less with 11psi boost. At 17psi the valve would open at at 4 in vacume.
Actually I believe these vacume numbers would be to high since on the 1g DSM BOV there is a hole going from the boost side to the lower upper chamber. This would prevent the manifold boost from holding the valve shut at higher pressures. This ballances that force. This air also helps to open the valve at a lower vacume number. If you disconect the manifold hose on a 1g valve it will not hold more than 12psi. This means 9lbs of pressure on the piston and8 lbs on the upper chamber. In reallity it is probably an even split.

the jist of it is if you are over 12psi (maybe 10) on a 1g DSM valve the bov is going to open when the throttle plate is closed enough that there is no boost but also no vacume in the intake manifold.

It is likely that in the aftermarket valves that this second upper fitting serves the same purpose as the passage in the 1g valve. This is to allow a higher spring pressure to hold the valve closed to boost while helping to open the valve faster when there is a differential in the manifold to pre throttle pipe pressure.
I beilive that on th 1g DSM valve if I pluged this passage and vented the lower upperchamber to atmosphere the valve would hold up to 40psi of boost but it would take much longer for it to open under throttle transition. I have thought about taping and venting the lower upper chamber with a manual boost controler to make my 1g BOV tuneable, but, I never run more than 20psi so there is no need. one time I accedently left off the boost controll vacume hose I hit 22psi with my 16g.

Kent
91 eclipse GSX
Test drove Evo 8 thurs night.
Might purchase next week.

 

Well i put the second spring back on so it fixed the leaking problem and i inverted the electronic boost controller vaccums so now its holding 20lbs all the way up trough the rpm range.......but im having a little bit of bucking or stalling and compression surges on 5th gear at about 1-4 lbs of boost.......the adjustment screw is almost all the way out but gots a few more threads to go, im gonna try and adjust it some more later tonight

 

any ideas on how to address the problem....what should i do?

 

With both springs installed the poor drivability you described is common, that is why I recomend removing the lighter spring. With one spring in the greddy type S, it does not make noise at idle and can hold more boost than you could possibly make with the stock turbo.
The fact that you are having problems with this configuration tells me that there is ethier somthing wrong with your valve or you some how installed it incorrectly.

 

AHH, I never understood why people were claiming that the 1G leaks at higher boost pressures, until now. With this opening between the chambers, spring tension is really the only thing keeping the valve closed under boost. The stock EVO DV (and most of the after market ones that I have seen) do not have this passage, I know this because applying vacuum to the upper actuator chamber will hold the valve open all day.
BOV/DV's that do not have this opening (most from what I can tell) do not require a large spring tension to stay closed at very high boost pressures. They only need enough to over come the pressure differential from the turbo to intake manifold, (intake tubing, throttle body, and intercooler pressure drop). Testing so far on a modified EVO with a stock intercooler (325 WHP/22PSI) shows this to be around 2-3 PSI at WOT, so you do not need a lot of spring tension to keep them closed, 4-5 PSI should be plenty. The stock EVO valve will hold a lot of boost, accept that the valve seat leaks like a siv, and apparently the plastic cannot handle too much stress. I try to use the highest spring tension I can simply to get the best possible throttle response, you can use less and still have it hold under WOT, a lower spring tension may also help the whistling under part throttle.
Your post also made me realize why the after market BOV's use a lot more spring tension then they really need to stay closed. I initially thought it was for better response, but with these units vented to the atmosphere they use high spring tensions to keep the valve closed at idle. This is probably the best reason to use a DV instead of a BOV, unless you want to lower the spring tension of the BOV and put some kind of air filter on it.

Thanks for the info, it was enlightening.

Regards,

Eric

 

I think that car companies do this as an extra safety precaution. With a light spring but the boost ballanced on top and bottom the
bov/dv would not open no mater how much boost you ran. The factory wanted this so that if the vacumeline fell off the wast gate the bov would open and keep the engine from blowing up.

Iguess technically my language was maybe not correct the 1g uses a diverter valve. On the old talon digest everyone refered to it as a BOV. It really was only a BOV if you ran more than 21psi boost.

I made a mistaken statement above also. If the hole in the 1g valve were sealed and the passage vented with a small hole the boost on top and bottom would balance and I don't think it would open under any boost pressure until the gasket separating the two parts of th upper chaimber failed. I have no idea what level this would be at.

I recall reading a post on this site that the Evo 8 valve was the same as the 2g valve. The 2g valve though was commonly expected to not hold more than 12psi. I wonder if it only looks like the 2g valve or is it just that the 16g turbo overcomes the leakyness where the small 2g t25 would max out with this leak.

Kent

 

The only problem with this possability is that the vacum line for the DV/BOV is completely seperate from the waste gate lines. If they were tied to gether it would make a nice safety though.

I noticed this also, but 40 PSI practically is infint for most of us. Assuming you had a big enough turbo, the pressure differential would eventually over come the spring tension, but again it would be at a riduculously high boost.
I can now see how the 1G would leak at higher boost, but with even a five pound spring in a valve like the Forge, Greddy, HKS, there is just no way they will leak (assuming everything connected and working properly), even at very high boost levels (25-30PSI).


The EVO DV does not have this passage you mentioned with the 1G, so if the 2G only leaks at high boost then it is not the same. The EVO DV leaks just a little all the time, it is not enough to prevent the turbo from making full boost, but it does appear to eat 2-3 WHP. Unless of course it splits open like the one I saw posted, then you might lose a little more .

Kind regards,

Eric