can't boost more than 4psi

[Hoffbrohaus]

I have been chasing this problem for a while now and can't figure it out. With my wastegate connected i can't get more than 4psi to the manifold, even with a 6.5psi spring. Since i have a dump pipe I can hear it opening pretty early. I have taken the boost source for the wastegate in 3 different locations with all the same results. FPR line, nipple right after turbo, and same line as Megasquirt. Since it always stays the same, close to the turbo or far, I don't think it's a boost leak. Just to be sure I bought a smoke tester and have eliminated all boost/vac leaks i can see. Still 4psi.

I should mention when running the smoke tester, I am getting a small amount of pressure out of the pcv tube I have open to atmosphere (no catch can). That should be happening correct? by that point I'm past the intake manifold and it's relieving pressure in the engine since it's not running?


I'm thinking it might be emap/pre-turbo pressure pushing the WG open too soon? But If this was the case my EBC should be helping to hold it shut from the top right? I adjusted the duty cycle of the EBC from 0, to 10, to 50, then to 90 and the WG still opens around 4psi. I verified power to the EBC which is a DIY auto one btw. Also with the WG boost ref disconnected it does not open, so maybe it's not an emap issue.

So I'm stumped. I could put an even stiffer spring in but I still think the EBC should be holding it shut.

screenshot from Tuner Studio "Feature list showing i/o pins", this means it sees the EBC right?

[Panici]

Remove the boost controller from your setup until you figure out how the gate is working with spring and boost reference alone. Will make troubleshooting easier.


What kind of wastegate are you using? I wouldn't trust cheap ones or the springs they came with.
Try a genuine Tial spring (if it will fit in your model)

[Hoffbrohaus]

I'm using this summit racing copy of a tial. So a genuine spring should work.

https://www.summitracing.com/parts/sum-260072

I have taken the ebc out of the equation and went direct, always opens early. 6.5psi spring with boost ref after turbo compressor or at the back of the intake mani I get 4psi. No boost ref I get all the boost I want.

I can double up the spring to about 10psi and see what I get.

[Hoffbrohaus]

I just put a 6 and 4 psi spring in and went for a drive with wg only, no ebc. Only got 6psi to the mani. Doesn't make sense to me though, the wastegate and MS boost refs are both off the back of the intake mani. So if MS sees 6psi then so should the wastegate and not open.

With the wastegate off I used compressed air to actuate the valve. Opened when it was supposed to. I then put air in the top port and pinched it, added air to bottom and it didn't ooen. So the wastegate and springs seem fine.

[varg]

Is anything coming out of your wastegate tube with the car idling? Valve seat sleeve installed? I use a port on the turbo to reference my wastegates. As long as it's hooked up in the typical fashion and the wastegate is sealing properly, there's not much that can go wrong, I have a similar (probably the same just rebranded) wastegate on my wagon and haven't had any issues.

[Hoffbrohaus]

Is anything coming out of your wastegate tube with the car idling? Valve seat sleeve installed? ...and the wastegate is sealing properly

This has to be what's going on. The "fire ring" valve seat sleeve is installed so I will do some troubleshooting. At idle I do not feel anything coming out of the dump tube, but I'll do some more more definitive testing. Thinking i'll run a tube off it from my shop vac and see if it can blow up a bag on the end :)

[Hoffbrohaus]

100% what is going on. I hooked up my smoke machine to the exhaust side of the turbo, after it built a little bit of smoke pressure I could see smoke seeping out of the dump tube.

So I disconnected the WG and inspected the valve seat sleeve, put it back on making sure all was lined up. Tightened the vband clamp and tested again. Still smoke. I noticed when attaching, the valve seat sleave doesn't seat all the way in and when you tighten the vband clamp it presses the WG valve in a little. To test this I loosened the vband clamp so the valve seat wouldn't push on the valve. Sure enough, no smoke out of the dump pipe, but now i'm getting a little from the vband clamp since it's not tight.

Is there a trick to this? Like make the clamp tight but not too tight? get a gasket or use copper gasket for the vband connection?

[varg]

That's unusual, and hard to visualize. When a wastegate is attached the valve seat is supposed to push against the valve, which should seal against it under spring pressure preload. Usually it's quite difficult to install a wastegate because of the spring pressure so you pop it open with an air compressor and put the clamp on, then take the air supply away and torque the clamp down.

[Hoffbrohaus]

Yea after reading your post I took off the wg to see if I could take pictures to better explain it. What happened is I saw how it really works and it should be fine.

This flange sticks out a little and when I apply air it seats correctly. I thought it was seating and pushing the valve open but I saw it pushes it and keeps a seal.



So I bolted it back up applying air to make sure it lined up nice, re ran the smoke test and still got smoke. I put the smoke tester on a pressure gauge and saw it makes more than 10psi over time. But not right away.

I plugged in the smoke tester for 2 seconds, so it didn't build up more than 6psi. After turning it off I could see a slight haze in the dump pipe, I counted 30 seconds and clearly saw smoke.



I don't know how or why that smoke made it out but at this point I'm thinking I just need to try a different wastegate. I really don't want to spend $450 on a tial though.


edit: i'm now convinced that puff of smoke is just a little that leaks through, not like it has a massive leak that is keeping the turbo from spooling.

[Hoffbrohaus]

Because I didn't want to shell out the money for a Tial yet I decided to put a block off plate on my external wastegate flange. So I ran the car with no wastegate at all, turbo should be getting all the exhaust to spool, megasquirt cuts fuel/spark at 14ish psi.

Still building boost slowly. Peak near 4100 rpm, There is nothing visibly wrong with the turbo, the turbines spin freely with no shaft play. So back to the drawing board.

Either the turbo is crappy or maybe I'm still losing boost somewhere, so the turbo itself is building like 20psi and I'm only seeing 13 of it? I'll see if I can measure right after the compressor somehow (where I have a 90 degree silicone coupler).

[Hoffbrohaus]

Should I be able to hold pressure into the intake manifold with the engine off? I don't think I should be able to since a few of the valves would be open and the air would push through.

I corked the icv hoses, propped open the throttle body and measured pressure from the fitting I made where the brake booster line was. With my air compressor at 2 bar, 29psi, I see about 10psi at the TB fitting and then start hearing air come out of the pcv hose.



Before this, btw, I capped the IC piping before the throttle body to verify that holds pressure. It did.