As I mentioned in an ealier post on this thread I have the Forge recirculating DV(BOV). It is not as smooth as the stock set up and does exhibit a moderate amount of surge/stumble. George Orson at Forge is sending a stiffer spring and an assortment of shims for the standard spring to enable some adjustment. There is only one spring in this unit so it cannot be fine tuned in the manner discribed by Dan. I am guessing that the stiffer spring will only increase the sealing capability at full boost. Perhaps the lower price and plug-n-play convenience are not worth the savings in the end. Anyone have any experience or suggestions to smooth out the part-throttle/low vacuum performance when using this unit?

jfh

 

Everytime your car stubles, you damage your compressor wheel, as the air is backing up throught the turbo, it is called compressor surge and will kill a turbo. Keep the stocker for a while, or get a 1G BOV and crush it, it works like stock but holds about 25PSI, which is all you'll need for a while.

 

i dont know what u're talking about jfh... u're saying the Forge valve made the surge worse???.. i had the exact same jerky experience with the stock unit as with the Forge...

i'd say try out some different springs.. even softer ones (like the green or yellow spring).. and try out the shims as well..

 

I have recently installed the Stealth Fx BOV from www.gofastbits.com it vents to air and recirculates at the same time. You can easily adjust the amount of air that recirculates as well as adjust the spring rate of the piston. All in all its seems to be of very nice quality. Drives much better than stock with no surge.

 

Well after market BOV's have a trade off, they are stronger, so they create a perfect Vaccum (HKS SSQBOV) but since the spring rate is so much stronger, it won't open under partail boost or slight vaccum, which it needs to. So unless you make full boost, the valve won't open or open enough to vent the gas and so it is cramed back into the turbo, causes a stumble and damages your turbo.


Any metered air vented into the atmosphere is a big NO NO for these cars of any car running a MAF setup, it is very bad and causes bad fuel mixtures and ****s up your plugs not to mention you car does not run right, not good at all.

 

this is why i'm saying that the forge with some playing with the different springs (comes stock with the blue spring, which is pretty strong in comparison to the green or yellow spring) will work perfect!

 

That's exactly what I am saying. Stock unit was much smoother than Forge replacement.

What spring/shim combination are you using, or did the default Forge setup work OK for you?

George Osmun from ForgeUSA is rcommending that I install shims or go to the stronger red spring. Will this make matters worse?

jfh

 

Yes, if you are experiencing hesitation/stumbling due to the BOV you need a softer spring load on the valve, my original post explains why.

I have a wide band O2 permanently installed in my car (getting ready for mods), along with EGT, boost and oil temp. While this car does seem to run very rich under boost/WOT 10.0 at 5k and above, the part throttle A/F ratios are actually kind of lean. The factory fuel curves try to maintain a 14.7 A/F ratio even under light loads. This is why even with a completely stock car you can get some hesitation and adding a BOV with a heavy spring is enough to throw it over the edge. Every time I experience bucking/hesitation in my car I can see the A/F ratios are getting into the low 15's while I am trying to mildly accelerate with part throttle (light load).
When you lift off the throttle the injectors shutdown, (this is another common method to improve fuel economy), the reason you see flames on an open exhaust car is that there is a slight delay from the throttle plate closing (removing air from the engine) and the injectors shutting down. This causes a momentary rich condition sending un-burned fuel into the exhaust, there’s nothing wrong with this situation it happens with every car I have ever seen.
If you can accept and understand what I am trying to say in the statements above then I have to admit that running a BOV vented to the atmosphere should not cause any additional drivability issues. I think that people who experience problems with these valves did so for the same reason that people with re-circulating valves did (springs to heavy).

 

so basically you are saying that currently there is NO aftermarket BOV that is 100% plug and play without having to do any modification????

 

Well that's a pretty broad statement, I don't know if we can say that for sure. If you install an aftermarket BOV and your drivability gets worse then yes, you need to adjust the valve spring tension. Get yourself a hand actuated vacum pump with a gauge, (most auto part store's carry them for around $25), the stock valve starts to open with around 16" of vacum on the actuator (no pressure on the valve). You want to adjust your spring tension of your aftermarket valve so that it opens at 16" or less, I have my spring tension set to around 12" and it seems to work quite well, it also does not leak (tested up to 25PSI).

 

I have the HKS resurculating on my Evo and it still stumbles in stop and go traffic once in awhile....Why, I have no clue!

 

The feedback I have seen regarding the HKS valve indicates that the spring tension is to high for this application. When the spring tension is to high the valve does not open enough or in some cases at all under light load conditions. This causes minor surging in the intake system causing the MAF sensor to read inaccurately making the car run lean. That is why the car stumbles and hesitates under part throttle.
Cars with speed density systems (no MAF sensor) do not have this problem with after market BOV's.

 

Hey Silver Surfer guess who?

I am still on the DV/BOV thing and did some testing of the Forge and disassembled it. Didn't PM you this time though.

The spring in my Forge is green (99.9% sure). The forge is a very simple design. The valve uses no diaphram and is all aluminum except for the 2 o-rings that seal the piston. The Forge valve does not use anything but the vacuum line to the valve to control it. It can be installed in either orientation. I believe barb up seems to be a bit smoother though. The Forge valve opens at .5 to 1 inHg using a mightyvac pump.

What this means is that at idle, the valve is wide open (it only took 14 inHg to pin it open). Thereby bypassing the turbo inlet at idle. The filtered air from the inlet is allowed to go through the bypass and into the IC pipe. Once you lose vacuum say to zero the spring will close the valve fully. Once it starts to make boost the boost in the vacuum hose helps to keep the valve closed fully. As soon as you lift and the throttle is closed, the valve will immediately begin to open (.5 inHg) and will be pinned open almost immediately on high manifold vacuum.

This is an interesting design if I must say so. Instead of trying to keep the valve close at idle like stock, they let it be open cause it doesn't matter. Once the car starts to make boost, it is closed for good and stays there. A heavier spring is only going to be bad unless you need it to hold boost up top. Fact is if you install the valve with the barb up, it cannot be forced open by boost pressure because that is the chamber area. Therefore it may be better to install this way. The valve works the other way because the boost pressure in the vacuum hose can counteract the boost against the valve face and with the springs assistance, keep the valve closed.

I have a post of these results which I pretty much repeated here because no one seems to answer my posts, maybe too technical?

Never did come to a final answer on the dual DV post, still mulling it over. Given the design of the Forge it maybe an interesting proposition, now.

 

Okay I am responding to my own post.

I realize that if you mimmick stock install with the Forge, it will open a fraction sooner when the throttle closes. The problem is the design of the valve face causes that nasty squeak noise which would gewt really annoying. I may have to take the valve face and smooth it out to see if I can eliminate the noise. Hmm...

 

Hey SilverSurfer

I know the reviews on the HKS SSBOV isn't that great. Unfortunately, I've ordered it and will install it tomorrow. Can you kinda give me some advice? I'm not a very technical person. Also can one cahnge the Maf system to a speed density one???

Ben