Boost is gone.

wydra · Postby **wydra** » Wed Feb 11, 2015 9:23 pm

Hey guys,

On the weekend I was at a tuning session and it was seriously hot, 38degC+.
All was going well, the cooling system was pretty much keeping up but at the end of 3 laps the coolant was starting to creep above 100degC so I would pull in let it drop some temp while running in idle.
I did a few more runs like this and all was going fine. After letting it all cool down again, I took to the track and had very low boost. I thought something was going wrong with the boost controller so pulled back in to inspect but everything looked ok, so I threw in the towel for the day and drove home.

The boost will come on very slowly, only a couple of psi boost at 4000rpm under load and 6-7psi at redline.
It almost feels like the wastegate actuator is not connected and the flap is fully open (but it is connected and visually is working).

I thought maybe I had a serious boost leak, so I tested the system and found a leak. It wasn't huge but was there so fixed that up and tested again, same issue, no change at all.

So I know it isn't an induction leak, I know it isn't the wastgate actuator or boost controller.
I think I am at the point where I need to pull the turbo off for an inspection. I have a spare GT2560R so might need to swap over to that and try again. I have head of some people having the wastegate flap not sealing correctly and causing all the exhaust to vent past.

Anyone have any other ideas before I do the turbo swap?
I have also bought a new 100cell high flow catalytic convertor which I will have installed next week but think a blocked cat is unlikely.

Paulus · Postby **Paulus** » Thu Feb 12, 2015 5:41 pm

Most strange. Almost sounds like the turbo has no load to spool the turbo. Manifold leak? does sound suspiciously like waste gate stuck open. you're sure your clutch hasn't gone (meaning no load on the engine?)

wydra · Postby **wydra** » Thu Feb 12, 2015 6:49 pm

Yeah 100% it isnt the clutch

I am putting load on it, still getting down the road in a reasonable time, just not where it should be.
Feels like I have a massive turbo on the side (but no boost a the top end either)

I'll pull the turbo off on the weekend, I'll go from there.

Paulus · Postby **Paulus** » Fri Feb 13, 2015 12:46 pm

Good luck - post back if you find anything.

I've got superlate spool, but I think it's turbo size, turbine wear (according to a turbo shop) and a small zorst leak.

you could try without the MBC and see if you hit the wastegate spring's known PSI. Spring could've gone funky with the heat... it could've deformed or something happened with it's elastic limit. I'd inspect the spring for sure

wydra · Postby **wydra** » Fri Feb 13, 2015 7:05 pm

Some interesting findings.

Before I started the turbo swap, I wanted to double check the physical connections from wastegate actuator to wastegate. Visually it looks fine and when you felt it, it was solid and felt shut.
I popped off the retaining clip and lifted the shaft off, Problem found! The wastegate was not shutting firmly (actually quite a way from it).
I'm not sure how this has happened, the actuator is still firmly bolted up to the turbo inlet, the shaft cant back itself off as there is a locking nut but somehow, the shaft was too long.
I am using one of these adjustable wategate actuators:
http://shopping.kinugawaturbo.com/bille ... 25det.aspx

I have re-adjusted the shaft and it is now boosting perfectly again.
I'm going to take the actuator off the turbo and strip it down to see why this might have happened, the spring is still fine and diaphragm functioning correctly.