I asked about this in the middle of another thread of mine but did not get much feedback.

For those who know or have used just a WG alone to regulate boost, I have a question

With my 5.8 psi spring I consistantly got 5-5.5 psi of boost. With the down pipe open I got over 6psi. So the WG spring did a pretty good job

Now with my 10 psi spring I get 7-7.5 psi of boost. With my new 3" cut out I get 9psi of boost.

Is this normal? From how my 5psi spring performed I figured I would get 8-9 psi normally and 10-10.5 psi with the cut out open.

My exhaust set up is 3" down pipe, 3" test pipe, 2.5" cat back. I know the cat back is a restriction, which makes sense that I got a little bit less boost than the 5psi spring and even less with the 10 psi spring. But with the cut out I would think I would at least see the full 10psi.

Is this normal, as in the larger the wastegate sping the less percise it is?

 

Bump???????

 

where are you reading boost pressure the manifold or the turbo?

 

where is the wastegate getting it's boost reading from?

 

The manifold

 

Right off one of the vacuum hard lines under the TB area. I had an unused one capped off that was not needed when I put a 97 maxima auto motor in my 96 5spd I30.

 

Thats wierd. Both spots you tap from are the same. So the WG is seeing manifold pressure, it should build boost close to the spring rate in the manifold no matter what.

In my set up the WG gets boost pressure from the turbo. But I have my gauge/EBC tapped to the manifold. I usually see ~1 to 1.5psi of pressure drop when the EBC is off and the WG is doing its thing based on turbo out pressure.

What turbo? What exhaust AR? Perhaps its too small? which is why the open dump pipe helps.

 

That's odd like matt said. That's where my delta gate gets it's reading from and it was dead on. Like 5-7 psi depending on where the screw was set.

I know your tial has no screw, but you should see +/- 1 psi of the spring.

hmm..

 

Garret straight T4 .7 exhaust AR IIRC.

 

.7ar should be fine. this is wierd.

 

I need to get a boost controller anyhow so it is not that big of a deal, but it just bothers me that I don't why it is doing this.

I have a small intercooler, maybe it just can't flow that much. I forgot the ccm's that it flows. I have some crazy intercooler piping, maybe that contributes. I have removed the wastegate and checked the gakset. It is a no brainer on the spring install. So I don't know...

 

This is a shot in the dark but it coulld be a boost leak. When my car was on the dyno last week we found that at full boost a leak would develope around the gasket on the HKS BOV. The shop owner said that the HKS's are bad about that. The spring was allowing 7psi but the intake only got 6psi.

 

i have a 2 psi leak when i get above my stock spring rate at the end of my rpms. and i have an hks also oh its a 7psi spring and i only get 5.5psi