RTH: GTurbo got lazy after highway drive, slow to build boost, lower boost levels than normal (1 Viewer)

[IanB]

If I punch it I can get a black cloud and boost does rise, but slowly. I'm pretty confident it's not fuel related.

 

[Tim-HJ61]

So I've tried 2 more tests, pressurized the WG reference line with a bicycle pump, the actuator arm moves as it should, pressure holds till you disconnect the pump and release the air.

I also tried driving with the WG reference line unhooked, same lazy turbo performance, but boost would eventually climb past the 18psi mark I've been stuck at since the issue began, I saw as much as 22psi for a second. I hooked the line back up right away after the test.

I'm thinking I'll try and pull the downpipe and dump tube off the back of the turbo, pressurize the WG reference line with the bike pump to open the WG, and see if I can see and remove whatever is keeping the WG flap from sealing.

Did you hear the waste gate disc clack shut when you released the air?

Your own curiosity won't be satisfied until you remove the dump pipe and check things, but it would seem to me that the waste gate is working as expected if boost did not creep up to 22psi after you reconnected the actuator rubber hose.

I had a custom turbo to exhaust connection made up and noticed the waste gate disc fouled the exhaust when it was quite a way open. Didn't seem to stick open though. GTurbo said they only need to open 10mm or so for them to manage the boost.

 

[IanB]

Got the dump pipe pulled off this morning, wastegate appears to be closing/sealing, and snaps shut when I release the pressure applied to the wastegate line. I'm at a loss here.

It does start to open around 12psi (should be 18?), but that doesn't really explain why it's so slow to build boost below that level, and the low psi at cruising loads.

Anything else worth checking in here before I put it back together?

 

[DancesWithMutts]

Damn. This is a tough one.

Have you contacted Gturbo yet?

 

[IanB]

Ya, Graeme agreed it sounded like a WG issue based on the symptoms, so I really don’t know what to look at next. It’s like 5AM there now so I’m hours from hearing from him if he’d even look at this kind of thing on the weekend.

 

[DancesWithMutts]

Ya, Graeme agreed it sounded like a WG issue based on the symptoms, so I really don’t know what to look at next. It’s like 5AM there now so I’m hours from hearing from him if he’d even look at this kind of thing on the weekend.

I had another idea. In the Subaru world, it's very common to "smoke test" your intake tract to find any boost leaks. They use a machine to send baby oil vapor into your intake, and the idea is to pressurize the whole intake to 7 psi or so. Any leaks are immediately apparent. My buddy actually made his own smoke tester, it's pretty cheap and easy if you already have an air compressor, plenty of vids on youtube about it.

I know your intake tract has an order of magnitude less places to leak than a turbo Subaru motor, but since we're grasping at straws here it couldn't hurt.

 

[IanB]

Big day!!

I added some washers between the wastegate actuator and turbo to increase preload, test drive was very promising! Sounded less like a tractor as soon as I turned the key, built boost just driving in my neighbourhood where you had to lay into it previously, held boost at constant load, boost spooled much better (not as good as before with just one washer for now), I’m confident I’m on the right track!

I’m going to add another washer for now, and pull the actuator out next weekend when I have more time, set it properly, and away we go.

I’m left wondering why/how it would have lost it’s pre-load though, and what I should be doing so it never happens again?

Pro-tip: using the bike pump to extend the actuator arm makes adding washers MUCH easier!

Thanks to all for the help and input, this has been a rough, stressful week. I love this forum!

 

[gerg]

Hmm.... broken wastegate spring?

 

[IanB]

Hmm.... broken wastegate spring?

That would be internal to the wastegate, right? That would be a replace thing rather than repair? How would you check for that?

With how suddenly the symptoms came on, that could very well be it.

 

[gerg]

Get a pic of the top (large) part of it. Often aftermarket controllers can swap out springs and are designed to be disassembled to swap them. If you get the make its just a matter of finding what weight spring you want.

 

[CruiserGord]

Easy way to find out if your waste gate actuator has failed is to unplug the hose at the actuator and go for a short drive around the block. Be careful because you won't have boost control but you'll know if your boost will climb fast or still lag when laying into the throttle. It's how I tested my actuator and misdiagnosed my leaking boost issue right before I discovered all the loose manifold nuts while reassembling the intake pipe.

 

[Dave 2000]

It sounds like you have it sorted Ian? Something I saw many years ago, I fitted a turbo on a 2.8 Capri, car went like a scorched cat. A week later customer returns symptoms as yours, checked everything that had been fitted, all good.

On a chancer I disconnected the exhaust, engine revved great and went well....complete with flames under the car from the open down pipe!

Turned to be one of the perforated tubes passing through a silencer had broken, this dragged down a load of wadding and virtually blocked the exhaust, it was passed it's best, new exhaust job done.

Regards

Dave

 

[IanB]

Easy way to find out if your waste gate actuator has failed is to unplug the hose at the actuator and go for a short drive around the block. Be careful because you won't have boost control but you'll know if your boost will climb fast or still lag when laying into the throttle. It's how I tested my actuator and misdiagnosed my leaking boost issue right before I discovered all the loose manifold nuts while reassembling the intake pipe.

That test exhibited no change, other than the boost would continue to lazily rise past the previous limit when the WG hose was attached.

 

[IanB]

It sounds like you have it sorted Ian? Something I saw many years ago, I fitted a turbo on a 2.8 Capri, car went like a scorched cat. A week later customer returns symptoms as yours, checked everything that had been fitted, all good.

On a chancer I disconnected the exhaust, engine revved great and went well....complete with flames under the car from the open down pipe!

Turned to be one of the perforated tubes passing through a silencer had broken, this dragged down a load of wadding and virtually blocked the exhaust, it was passed it's best, new exhaust job done.

Regards

Dave

Dave,

I have no muffler at this point, had it straighpiped a while back after the muffler developed a rattle. So with a leaking wastegate it's loud under load! When the wastegate was working properly it was much quieter until the WG opened at 18psi.

I'd say I have it diagnosed, but not sorted.

 

[IanB]

Get a pic of the top (large) part of it. Often aftermarket controllers can swap out springs and are designed to be disassembled to swap them. If you get the make its just a matter of finding what weight spring you want.

This one has an adjustable rod to the WG flapper, but doesn't appear to have any provisions to open it up and swap springs.

 

[gerg]

I'd contact gturbo for advice on a replacement. I'd be asking for the design and get a wastegate from kinugawa or something that's designed to change out different springs. You could find it out in your own by comparing pics but I've wasted a lot if money with trailing and error.

 

[IanB]

I'd contact gturbo for advice on a replacement. I'd be asking for the design and get a wastegate from kinugawa or something that's designed to change out different springs. You could find it out in your own by comparing pics but I've wasted a lot if money with trailing and error.

Waiting to hear back from Graeme now, the time change is brutal for dealing with his in a timely manner.

 

[CruiserGord]

If boost didn’t taken off when you took it for a spin, with the waste gate actuator hose off, then something else is leaking. Unless the waste gate is being forced open even with the hose disconnected on the actuator it might be upstream from the turbo.

 

[IanB]

If boost didn’t taken off when you took it for a spin, with the waste gate actuator hose off, then something else is leaking. Unless the waste gate is being forced open even with the hose disconnected on the actuator it might be upstream from the turbo.

I'm thinking the wastegate actuator is unable to keep the flapper closed under load. A broken spring in the actuator could explain the issues. Shimming the actuator away from the turbo body yielded definite improvements, but it's still leaking under load. The turbo, which should be very quick to spool like it was before the issues started, is very slow to spool, and doesn't remain spooled when you back off the pedal.

If this was a boost leak issue, the turbo would spool as normal.

 

[gerg]

Can you hear any exhaust leaks by chance? I blew out a manifold gasket once and it did some wonky stuff to performance. Just a thought. They usually give you some weird sounds associated with it though.