Leaking forge diverter valves caused months of headache

[phrenetiK]

People originally told me to check my diverter valves...I took it to a shop and had them test for boost leaks. supposedly they tested the entire system to 15 or 20 psi. i cant remember which. they found 1 torn vacuum hose and replaced it, and charged me 500 bucks. it didn't solve my problem.

i replaced spark plugs, had my intake walnut blasted, changed my intercooler to a vrsf 7"...nothing worked. i was about to save up 3 grand and take it to a shop and say just fix it.

tonight i did the DIY free BOV mod. after doing it, i could hear my diverter valves leaking from 1500 rpm all the way to 5500 rpm on my jb4 map 2. as soon as i heard them quit leaking, my boost PSI spiked up from around 5-8 psi to 13~psi and i had full power to redline.

if earlier on in the rpm band i am pushing more boost, they are leaking until the boost tapers down and they can handle it again, then i get a power surge and the car starts to pull. it has been doing this for months and no one has had a real diagnosis and i've been trying everything. if i hadn't done the free BOV mod I would have never heard them leaking...tomorrow im ordering yellow springs and a rebuild kit(currently have green springs). 90% sure this will fix my problem...will update after new springs are installed but do you guys think my diagnosis sounds right?

the leaking noise from the DV directly correlates with huge loss of power until i hear the leak completely stop.

[135Pats]

Certainly sounds reasonable, what's peak boost on the BMS map you run most often?

[phrenetiK]

should be 14.5 on map 2. map 5 should be even more than that.

[135Pats]

Originally Posted by phrenetiK

should be 14.5 on map 2. map 5 should be even more than that.

Though I think you're onto the issue, there's no sense in me playing mechanic outside of saying that you seem to be narrowing the potential list of problems down. The DVs should absolutely not be malfunctioning at 14.5 psi, that's really unfortunate. Even the stock valves should hold up for a good amount of mileage before leaking under that type of boost, and the forge kit is well designed. Bummer, but if that's the problem at least it's a (relatively) minor monetary issue.

[Cozy]

I think green springs are only good for around 9-10psi, there's your problem. Yellow I believe is good for around 22-25psi, blue and red I guess is reserved for BT.

I'm sorry you've had a ball ache finding your problem though but ALWAYS start with the simple stuff such as DV's, rubber hoses, clamps before the big jobs. My Dad taught me that (mechanic) and has saved my fortunes but on the plus side, you have a very clean intake now after those walnuts .

[phrenetiK]

i started with that but couldn't tell any of them were leaking, and i paid to have a boost leak test done and they specifically told me the DVs were good but they were caught in their lie lol.

[Freon]

I would start to suspect the manifold pressure line that goes to the back of BOV before the BOV itself. Blow off valves should need very little to no spring pressure to hold boost if the throttle body is fully open since there is manifold pressure trying to push them closed.

The spring needs only to be sufficient to take care of the pressure loss between the BOV piston and the line from the intake manifold. There's always a bit of loss through piping, even a fully open throttle plate, etc.

Spring pressure is an adjustment for when the BOV will escape are primarily under partial throttle situations. More pressure can lessen lag and improve throttle response in some circumstances.

A leak or impediment of air in the control line can cause serious issues with holding boost as there could be a reduction in pressure from the manifold to help hold the valve closed.

[phrenetiK]

added video. have to listen carefully. noise stops at 5500 rpm.

[135Pats]

Wow you can really hear the boost leak. Let us know how the yellow springs hold boost, assuming the problem has been diagnosed.

[shoepac11]

Its been a while, but is there any update on this? Mine is doing the same thing. But mine seals much quicker. About 4 or 5 psi. It seemed to start just after I installed my afe stage 2.