weird boost issue

[kazuma]

Okay I have been experiencing a weird boost issue. During warm days I cant seem to hit full boost(currently running a tial 38mm wg with 7.5psi spring) I hit 5.5-6.5 psi but never full, now today its a little cooler day and I hit 9psi and it held it there! Iam completely confused as to what it could be, I thought at first its a boost leak issue and checked and fixed any leaks up to 20psi(I know overkill but wanted to be safe)and had the same issue then the creeping happened(Iam pretty sure its creeping)and now iam completely stumped.

The only thing I can think of is the Tial spring is broke or not working correctly.

Any suggestions on what else I can check?

[lrb_2000]

Where are you getting your vacuum signal for your wastegate? If it's before the intercooler, then 5.5-6.5psi sounds right, because there is a pressure drop across your intercooler..

[kazuma]

see I think I might've messed that up, there is a vacuum source from the turbo I plugged into the wastegate. Iam going to try to do it like it says on the tial website but then do I need to plug the vacuum source on the side of the turbo?

[Chezedik]

What is your vac at idle?

[kazuma]

vaccum at idle is 18-22 cold and then when it warms up it goes to 25. The car idles fine when warm but when its cold the rpms vary between 50-100(I guess its normal with the colder plugs).

[Chezedik]

Sounds about right. You say that you are pulling your boost signal from the turbo directly, so if you are boosting that little, but your gauge is reading from the mani (which must be the case if you are reading any vacuum), then you are good. As far as spiking, are you running an MBC?

[kazuma]

Sounds about right. You say that you are pulling your boost signal from the turbo directly, so if you are boosting that little, but your gauge is reading from the mani (which must be the case if you are reading any vacuum), then you are good. As far as spiking, are you running an MBC?

I have a ebc but I have not put it in.

just a quick question about the tial WG. there are 2 ports for vaccum the top and the one on the side, the one on top is meant for ebc/mbc right? and the one on the side is meant for just a vaccum source?

[Chezedik]

The one on the top is for a boost controller, yes. It is to allow the unit to be pressure compensating. So that when you divert 3 psi to the top, and have an 9 psi spring then you will have 12 psi.

[kazuma]

The one on the top is for a boost controller, yes. It is to allow the unit to be pressure compensating. So that when you divert 3 psi to the top, and have an 9 psi spring then you will have 12 psi.

k so Iam a 100% sure the issues isnt with my pipeing or bov anymore because when the car just hits idle temp I can hit full boost and hold it there no problem but after a while of driving it sems like I cnat go past 5.5-6 psi. I believe the issue is with the wastegate. would adding the ebc to the system help at all in terms of pressurizing it? How can I test the Wastegate for issues?

[Chezedik]

If it opens and at the same pressure, and you have the Fire Ring in, then it is fine. You could just have a psi spring, in which case you would get better pressure with the ebc.

[kazuma]

If it opens and at the same pressure, and you have the Fire Ring in, then it is fine. You could just have a psi spring, in which case you would get better pressure with the ebc.

What I did was I removed the vaccum source to the wastegate and it would boost just fine over 10psi so I figured the wastegate is not the issue and it must be a vaccum issue. The vaccum I was using was off the outlet of the cold side of the turbo but now Iam teeing off the big vaccum line thats under the throttle body(my boost gauge and bov are off the same line).

I went for a test drive and its not having boost leak issues anymore but boost creep! I hit 9 pounds in 3rd and I creeped upto 10 in 4. I know its not a gauge issue cause it felt wayy different than before.

now the weird thing is it doesnt goto 7 psi and slowly creep up it hits 9 hard and then slowly creeps up to 10. Should I be using a different vaccum source for the wastegate instead? I havent yet plugged the vaccum source on the turbo outlet and it hasnt changed the way the car runs but should I plug it?

[Chezedik]

You are using the line below the TB, I would use some manifold vacuum. See the difference is in the draw. If you use port vacuum, it can behave strangely by comparison to the more consistent manifold vacuum. Also, shorten the vacuum lines as much as you can afford. Personally, I love the idea of a turbo source, with an appropriate spring, that is what I would do. Helps a lot in preventing spiking.

[kazuma]

You are using the line below the TB, I would use some manifold vacuum. See the difference is in the draw. If you use port vacuum, it can behave strangely by comparison to the more consistent manifold vacuum. Also, shorten the vacuum lines as much as you can afford. Personally, I love the idea of a turbo source, with an appropriate spring, that is what I would do. Helps a lot in preventing spiking.

The way you mentioned, using a source off the turbo is what I had but I ran into the issue of the boost just slowly falling so I decided to use a different vacum source that I said above and it seems to be holding much better now. I'll try doing it the other way you mentioned as well with the vacum source off the manifold it self.