Replaced stock BPV with EVO 8 BPV now boost hits 20psi

[hellraisin']

I preformed a boost leak test on my 98 talon tsi awd. I found that my stock 2g plastic bpv started leaking at about 10psi. I replaced it today with a metal EVO 8 bpv which bolts right in and now the car hits 19-20 psi in the lower rpms but falls to a steady 14psi afterwards. It doesnt have an MBC that I can see. The car is stock other then a boost gauge and now an EVO 8 bpv.

The car freakin flys like mad but I think I can hear the stock T25 turbo giving all its got. Almost like a vibrating whistle sound in thr higher rpms at wot.

 

[AdR]

I agree in that the BPV was probably already masking the issue. With oem BPV they have the pressure equalizing transfer tube to the bottom of the diaphragm that cancels the boost reference pressure going to the top of the diaphragm. This leaves you with only the spring pressure holding the BPV closed limiting the amount of psi it can hold open. In a 2g the spring is set to blow much lower than an Evo which would explain why the spikes are there with the new BPV.

A way to test this theory is to block off that small hole in the 2g valve and see if the boost spike happens with that setup. Then the boost spike issue will probably be at your wastegate control or somewhere else.

 

[Mauispyder]

I had the same issue when I changed to an evo metal bov with my T25. I kinda liked it. When I changed to a T28 with new wga the issue went away.

 

[2gmitsueclipse]

A way to test this theory is to block off that small hole in the 2g valve and see if the boost spike happens with that setup. Then the boost spike issue will probably be at your wastegate control or somewhere else.

Since we all know this, why test it? The OEM (plastic) bypass valve bleeds off around 10 psi. Use the time to test the other likely causes since it is unrelated to the problem.

 

[JusMX141]

Common....the boost control solenoid is toast but you never know with the stock BOV because it becomes a wastegate at 14psi or so.

Run a hose directly from the boost source on the cover to the actuator and see if the pressure stabilizes.

 

[hellraisin']

I apologize for the delay. I haven't been able to work on the car until tonight.

I took the wastegate off and tested it. It opens at 10psi but only about half way. At about 14-15 psi it opens almost fully and at 16-17psi it opens far enough to almost hit the mounting tab.

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20161014_18081


I found that the boost gauge is installed in the correct location. In vacuum line B in the above diagram. The T fitting isn't very appealing I know. It's the same fitting from the previous owner with some zip ties to make it secure and keep it from leaking. I need to redo this soon.

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20161014_183156 by

I haven't preformed a boost leak test yet. I have a digital tire inflator this time which I didn't have last time. So I will be able to preform a good boost leak test.

I'm suspecting that the wastegate is bad and I'm looking for a replacement.

Also, the flapper moves freely but when turned as far as it can go counterclockwise (the tab all the way to the right) it gets stuck and requires being tapped with an extension to flop back down. Just something I noticed.

 

[hellraisin']

A little update.

I disconnected the boost control solenoid lines that go to the wastegate actuator and intake tube. Then I connected the wastegate nipple to the nipple on the turbo housing. If the BCS is faulty this should reduce the boost down to about 10psi from what I've read. I haven't test driven the car yet.

I checked the turbocharger. 6 months and about 2500 miles ago the T25 had zero shaft play. Now it's about shot from running too much boost. Not surprised.

I'm currently sourcing a used 14b. There isn't a new replacement T25 wastegate actuator with the correct DSM flange within the universe. My plan is to send the 14b off to Turbo Lab of America to be rebuilt then throw it on the car with the help of an ExtremePSI install kit. Wastegate actuators for the 14b are abundant and the turbocharger it's self is said to be more durable.

While I was at it I cleaned the MAF. It wasn't very dirty. And installed a new Mann air filter.

I suspect either the wastegate actuator or the BCS is what's causing the boost spike. The BCS has been eliminated. As far as I know, the culprit of the boost spiking has been narrowed down to a faulty wastegate actuator or a boost leak. I will be preforming a very thorough boost leak test tomorrow.

The c-clip on the wastegate actuator shaft was so rusted that it broke in half. So I've ordered several replacements.

Thanks for the help everyone. You guys are the best.

 

[hellraisin']

It was the BPV. I'm now at 10psi. No more boost spike. Thanks for the help everyone.