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Discussion Starter #1
I saw online some people hooking up air compressor lines (with regulator to the wastegate port to test when the wastegate opens. Is this the same as the pressure of the engine? It make sense that 10 psi from an air compressor is the same as 10 psi in an engine. If the wastegate opens fully at 10 psi using the air compressor I should expect the same from it when hooked up to the compressor housing on the turbo. I just want to make sure before I do it to know for sure it's accurate.
 

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I did this using a leakdown tester. I didn't do it for any reason other than I wanted to see when it would start to open vs how much pressure it needed to be full open. From what I remember it was a small variation in pressure.

But like he said, this doesn't account for the pressure already on the WG from exhaust pressures.

I could see doing this to see what kind of preload to set on an internal WG setup though.

Might also be a half decent way to check a cheepo WG against a nicer one. Or to get an idea of what pressure spring is in an unknown WG.
 

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Discussion Starter #4
I pretty much have a wastegate spring and don't think it's a real tial, so I want to check that it is full open at the correct psi. So if it's a 10 psi spring, doing this test I should see it full open at about 10 psi give or take 1 psi?
 

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I just did this with my wastegate! Took the 12psi wastegate off the DSM t25 turbo and put it on my DSM 14b turbo since the stock wastegate was only 7-8psi spring. Used an compressed CO2 tank with a regulator on it and did 2 tests ....1-slowly increased the psi up to 12. ....2- Did a test from a quick burst of 12psi and it seemed to work for me. I would say def take in account it could be off a PSI or 2 if the gauge isnt 100% correct. How the pressure is applied from the exhaust might be a little different then using an air tank but not far off (in my opinion)
 

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Yea it's gets you close to it.

If you have a 10psi spring get and you put 10psi on the wg it should open fully.

Not while it's in the car you will have some exhaust pressure under the valve trying to force it open. So it might only take 9 psi to fully open.

Also most valves will Crack open around 25% of the spring max pressure.
 

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Just try to get an accurate gauge. 1 psi off at 10 psi is a 10% difference. That can really add up if you're trying to be accurate and your gauge sucks.
 

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There are too many variables - heat, backpressure, pulsations, WG valve guide leakage, boost reference location, etc. It will also START moving the valve at just over the set pressure. It will try to fully open at pressure a bit over what it would target. During normal operation the WG will open just enough so boost doesn't get above it's set pressure. If it needs to open more at a different rpm/flow, it will do so to keep boost pressure the same.
 

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Discussion Starter #10
For example if it's a "10 psi" spring then if it doesn't start opening until 15 psi or opens at 5 psi I know something isn't right. That's my main objective, just to make sure it's not completely off before I install it. A few psi difference I would have to test on the car to know for sure.
 

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I saw online some people hooking up air compressor lines (with regulator to the wastegate port to test when the wastegate opens. Is this the same as the pressure of the engine? It make sense that 10 psi from an air compressor is the same as 10 psi in an engine. If the wastegate opens fully at 10 psi using the air compressor I should expect the same from it when hooked up to the compressor housing on the turbo. I just want to make sure before I do it to know for sure it's accurate.
thats not accurate but it does tell you if it works or not
 

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Discussion Starter #12
So I tried it out yesterday. I used my leak-down tester setup with a air fitting with barbed end on it so I could hook up a vacuum hose. I first tried it on one of my wastegates on my work bench. It started to open around 17 psi and was fully open at about 21psi, it had a 11 psi spring and a 7 psi spring in it. The seller told me he took the 7 psi spring out and put an 11 psi spring in, but he put both in...good thing I checked. I put just the 11 psi spring in, and right before 11 psi it started to open and at 15 psi it was fully open.

Next I tried it on the wastegate I have on my car. I just unhooked the vacuum hose and hooked it up to my tester. It had a 10 psi spring, and opened at 10 psi. I started the engine up and at idle I tried it again, it opened at 10 psi just like before. I couldn't try it under full load, but I know for a fact it opens at 10 psi or just before.

I think this is a pretty accurate test, as far as verifying the correct spring. If there is a boost creep/overboost issue, on a dyno and simply watching the wastegate open vs psi would be the best way to verify if it's opening correctly.
 
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