Ebay wastegate - I think I am forcing it open

Finally got around to finishing v3.0 of my hot side. It looks really good this time around, and runs/sounds better. Its still a log style though, just with much better logs and actually has some length to the primaries. Pics later.

So I switched to a 60mm ebay gate so I could give the racegate back to its rightful owner. Its rated at 12psi, and on the air compressor actually takes a bit more than that to open the valve more than just a hair.

I am only seeing 10psi - adjusting the MBC does nothing. Pulling the line from the intake does nothing. I cranked the adjustment screw all the way down and it seemed to spool a bit quicker, and maybe .5psi more, but not much.

Heres my thought...

60mm = 2.36ish inches
So area of the valve is @ 17.5 in^2
They say a bad log system is 2:1 backpressure - a good tube header setup on a turbo is 1:1. Seeing 10# of boost we will look at either option.

Assuming 1:1 - Best case - Thats 175# of force against the valve trying to push it open. Worse case its 350#..... I think I am just forcing it open. I am going to try to use a longer set screw in the top, or shim the hell out of the spring with washers.

I think I've got a lot of backpressure because of the little t70, or so I hope. I have no major leaks on the charge pipe, turbo still feels solid, exhaust after the turbo could be better, but its not horrible - sweet thunder muffler, Blow off valves are not leaking. Motor feels strong but with 8.5ish compression 10psi just doesn't cut it. I dont' think the turbo is out of steam, I have seen as high as 18psi with the other gate and a much worse log setup.

Thoughts?

have you torn the gate apart and checked for debris in it? I have an xo2 44mm wastegate from ebay, and it works great for me.

Run a smaller wastegate.

People run the big wastegates for lower boost on big turbos. Needing a 2.5" pipe to dump all the exhaust from hitting the GT42R so they can run 5 psi.

Gate is clean on the inside and functions smooth.

I think its too big for sure, but I am going to see what I can do to hold it closed longer. Hell I wonder if I could run this little setup without a gate. The turbo will max out lower than what I would percieve as a danger level.

Shimming the spring sounds like a good place to start.

-Scott.

Boost controller?

Bleed the boost before it hits the valve. It might be enough to keep it closed until you want it opened.

EDIT: I see you have a MBC. You have tried to pull the line from the wastegate and run it full closed?

Aye, no line on the gate and it still opens up about the same spot.... well I don't make any more boost rather. Its not an intake side leak, and my hotside is the best its ever been.

Grabbed a stage 8 bolt that was about twice as long and cranked it down just a few turns past the max on the old bolt and got a steady 13-14psi out of it with no boost controller. I think I will add my controller for the last 4-5psi and head to the dyno.

My air/fuel is about right, but I have no idea where my timing is.


Lesson learned.
Low boost = use big gate
higher boost = smaller gate