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Discussion Starter #1
This one should be quick. I have been noticing that everytime I fix a boost leak, my PSI goes down instead of up. Is this the correct reaction in terms of PSI/CFM?

Thanks,
Chris
 

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Im assuming you have a gauge that reads boost and vaccume pressure.

If you have leaks fixing them will make you have more vacume pressure (negative pressure that is), because you engine is trying harder to suck air in. And under boost since you dont have air escaping thru a leak your boost pressure will go up.

got it?
 

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Discussion Starter #3
well, I agree with you on the additional vacuum, but I want to hear more opinions on the boost pressure. My car does have additional vaccuum pressure now, but my boost is lower. The only explanation I can think of is that the turbo does not have to work as hard as before to flow the same amount of air, producing a cooler charge. Since the air is not as hot, it is not under as much pressure as before. With this reasoning, the same amount of air is being moved at less pressure.

Is this in the ball park?

Thanks,
Chris
 

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Probably not. What boost gague are you going off of? If you are talking about the factory gauge, then you need to know - it is NOT a boost gauge, at best it is a very poor airflow gauge. It never measures boost at all - just displays what the ECU thinks is happening based on airflow and barometric pressure at the MAS. If that's what you are reading then yes, it should go down slightly since you are flowing less air to get the manifold pressure the same, and wasting less metered air.

If you're seeing these results on an aftermaket gauge though, I dont' know any good reason it should happen.
 

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Discussion Starter #5
I am using an SPA dual digital boost/egt gauge tapped on the FP vacuum hose. My ball/spring boost controller is tapped on my 20g turbo outlet nipple and routed to my tial external wg. I have been scratching my head on this one, but it has happened three times now with the same results.

Thanks,
Chris
 

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It sounds like you were running a higher Psi at the time correct? When you get the leaks fixed, the vacuum is sealing better so it's running more efficient. You're going to have to adjust your boost pressure again to set it correctly. Atleast this is what I did when I fixed mine. I was leaking like a sieve. Come to find out, I was running roughly 18psi when I should've been doing 14psi.

Rob
 

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well, I agree with you on the additional vacuum, but I want to hear more opinions on the boost pressure. My car does have additional vaccuum pressure now, but my boost is lower. The only explanation I can think of is that the turbo does not have to work as hard as before to flow the same amount of air, producing a cooler charge. Since the air is not as hot, it is not under as much pressure as before. With this reasoning, the same amount of air is being moved at less pressure.

i really doubt that is whats going on, the only think i can think of is a seperate problem with your boost controler, it may be acting differently,

OR you fixed a leak on your wastegate line, the wastegate needs a certain amout of positive pressure to open and stop your turbo from increasing boost. So if you had a leak that means that more pressure was needed to open up the wastgate actuator since some was leaking out, and now that you fixed it, This is why you would run unlimited boost (as much as your turbo can compress) if your wastegate actuator hose ever fell off or broke.

I dunno maybe its just a coincidence or its in your head, otherwise im out of suggestions.

Personally i would just re adjust your boost controler and forget about it
 

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Discussion Starter #8
turbofwdtsi, can you explain more about your experience? It seems like you had the same psi reaction as my car.

cheezoto- this time the boost leak was at the TB gaskets and TB shaft seals. No leaks on the WG lines. Thank you for the suggestions though.

Thanks,
Chris
 
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