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1,056 Posts
Discussion Starter · #1 ·
Well I’m still having compressor surge after the new tial q-bov install. I’m not sure if it's because of the vacuum line or the spring rate. It opens fine when I put it in park rev the engine and chop the throttle. As soon as I get on it and take it to 1bar and chop the throttle it surges. My vacuum is coming right off the manifold and I’m starting to think the line is too small. I had also cut the spring 2 coils because I had gotten the 11psi spring. My turbo is a sp74gtq w/o a anti surge housing, so it is barking the turbo a bit and I want this turbo to last me.
 

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Highway Demon
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2,897 Posts
Hmm chopping the spring is not a good idea. Buying the proper spring would be. I understand the method behind chopping it but you have no idea of the spring rate on that spring now. Here is a chart as follows to differentiate which tial springs that should be used for each application according to your idle vacuum pressure. I think it is a lot smarter to know exactly what the rate is and be sure that it matches your needs. Piece of mind in knowing that it will not fail you and that you can rule that out as a problem when trying to diagnose your issue is what you are buying. not cheap for a freakin spring though I know. I have 3 of them personally a 7lbs a 9lbs and a 11lbs. The 11lbs is just a tad too heavy a spring still so I am running the 9lbs and the 7lbs is way too light of a spring. Yes I am on stock twins but when trying to find the right spring for your tial it does not matter what kind of turbo setup you are running because it is judged by your vacuum pressure not your turbo setup. Good luck happy boosting and I hope this turbo lasts ya ;)

12 lbs. -22 to -23 in/hg
11 lbs. -18 to -21 in/hg
9 lbs. -14 to -17 in/hg
7 lbs. -10 to -13 in/hg
 

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Silent
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1,412 Posts
increasing line size sure won't hurt. I'd be surprised if the proper spring and bigger line didnt solve it.
 
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