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

[gerg]

As a test it's a good idea, for regular running that would be a no. Get a long piece of bailing wire and feed it through and make a rats nest of a loop. Doesn't have to be pretty, just hold it shut. That being said I've never worked in that engine bay so I'm making light of your work through ignorance. A rare thing I know.

 

[mudgudgeon]

As a test it's a good idea, for regular running that would be a no. Get a long piece of bailing wire and feed it through and make a rats nest of a loop. Doesn't have to be pretty, just hold it shut. That being said I've never worked in that engine bay so I'm making light of your work through ignorance. A rare thing I know.

Agreed.
Wiring it shut will give more certainty to your diagnosis.
If boost is overcoming spring preload to soon, a wired shut WG will eliminate this.

Boost won't build any quicker with it wired shut vs having a good actuator on it.
You might see higher boost, but for testing, watch boost gauge and limit boost with your right foot.

 

[IanB]

So an update...I was gone for 2 weeks on vacation, new WG actuator arrived a couple days before but no time to install until this past weekend.

I wasn't able to get at the circlip holding the arm to the flapper with the turbo in the truck, so the whole manifold and turbo came back out. New WG actuator installed, put it all back together. Didn't get the actuator adjustment correct, with the MBC removed it's only set to 12psi, so that sucks. The noise is better, sounds like it's not leaking at idle and low throttle, but still slow to build boost, doesn't hold expected boost levels, etc.

I'm going to try shimming the actuator away from the turbo body this evening, and see if there's any improvement. If yes I'll pull the whole mess again and get the WG set properly. If not, the next step will probably be to put the stock turbo back in and make sure the issue isn't something unrelated to the new turbo.

It's about a 7hr job to R&R the turbo/manifold, I've done the job 2.8 times at this point.

 

[gerg]

Gahh that's crappy man. So before you go all out and take everything off you might want to try it with thethe man boost compensator on. Without it i would expect boost to build slowly as the flapper will be pushed partially open around 6lbs boost. Also it's a long shot, but take the downpipe off and check the wastegate flapper seat for cracks.

 

[IanB]

So before you go all out and take everything off you might want to try it with thethe man boost compensator on. Without it i would expect boost to build slowly as the flapper will be pushed partially open around 6lbs boost. Also it's a long shot, but take the downpipe off and check the wastegate flapper seat for cracks.

Sorry, I'm not following what you're saying about the boost compensator?

I have had a good look at the wastegate flapper seat, I originally expected to find something there that was preventing it from closing all the way, but it looked fine.

 

[gerg]

Manual boost compensators help turbos not only make grater boost but they will build boost faster.

 

[IanB]

Manual boost compensators help turbos not only make grater boost but they will build boost faster.

I did have the manual boost controller in place after I swapped the new wastegate actuator on, it made 16psi, but didn't build boost any better than before, or hold boost any better. I then removed the MBC to see what the pure wastegate setting was, and it's now making 12psi.

Tonight I added a washer between the wastegate actuator and the turbo body to add some pre-load, 2mm washer netted 1psi of additional boost, no other changes noted. I may try adding a 2nd washer another day, not expecting much though.

 

[gerg]

Hmm that does sound like it's maxed out.

 

[gerg]

I hate to ask this again but, did you pressurize and check for boost leaks? Even the intake manifold gasket could be the culprit. I'd pressurize it before I went through another 7 he re and re. Kind of running out if ideas sorry man.

 

[gerg]

Or even the oring that seals the compressor cover to the backing plate .

 

[IanB]

I hate to ask this again but, did you pressurize and check for boost leaks? Even the intake manifold gasket could be the culprit. I'd pressurize it before I went through another 7 he re and re. Kind of running out if ideas sorry man.

You and me both. I have no intercooler, so there's just the rubber coupler from the turbo to crossover pipe, and the crossover pipe to IM gasket (new when turbo was installed), and the IM to head gaskets (new last summer) that could be leaking. I've had the crossover pipe off and on a number of times now with no change. I've checked the IM nuts and any I could get at without removing the injector lines are tight, no signs of leaking there. Here's the issue though...it doesn't FEEL like a boost leak, it feels like the turbo struggles to make boost in the 1st place.

Or even the oring that seals the compressor cover to the backing plate .

Where is this, part of the actual turbo?

 

[gerg]

So I highly recommend a leak check. You could very well have more than one problem. The compressor cover has a back plate which sits on a large o ring. It's what allows the cover to rotate but still maintain a seal .I'll get some links for you.

 

[gerg]

So here is a link for you. Gives the basic idea. I drill a plumbing cap that plugs off a plumbing rubber coupler the diameter of your turbo intake and fit an air coupler fitting so you can hook up compressed air. Instead of taping or using silicone which both are fine I heated up the air line fitting and melted it into my cap. It worked but as long as it seals your fine. Some folks use their ear or soapy water but I find smoke shows you the slightest leak when it's distrubed. I use a cigarette . Don't inhale the smoke. It's toxic. Connect the whole thing to turbo inlet, pressurize to 20 lbs, use smoke stream to find leaks, fix one leak at a time and move to other connections. It seems time consuming until you compare it to a full days re and re ......gahh . How to Test for Boost Leaks – Modern Automotive Performance

 

[IanB]

I added another washer (total of 2 per bolt) to shim the wastegate actuator away from the turbo body and increase pre-load, seems each 1.9X mm washer adds 1psi, it's now holding 14psi, and driveability seems improved which is encouraging. It seems a bit more willing to spool up and holds boost at steady loads better than before (could be a bit of me seeing what I want to see though), the exhaust is quieter for sure. I'm having a friend make me up some 10mm spacers as any more than 2 washers gets very difficult to manage, and some longer bolts, and I'll do a final test and see if pulling the turbo back off to adjust the wastegate is warranted.

 

[IanB]

I had a bright idea that I could pressurize the intake tract to leak test via the vacuum nipple on the crossover pipe that provides the IP boost compensator with its signal, but if it was still attached to the turbo on the one end, that wouldn't hold boost, correct? It would just push the pressure past the turbo towards the air filter? The chance that the valves would all be closed and would hold pressure isn't likely to happen either, would it? I'm trying to figure out how I would be able to boost leak test the IM to head connection...

 

[remy]

I would try with smoke and/or vacuum in the intake.

 

[mudgudgeon]

I think gerg's suggestion is good.
With enough pressure/ volume of compressed air pumped in, it won't matter if some inlet valves aren't fully sealed

 

[IanB]

I think gerg's suggestion is good.
With enough pressure/ volume of compressed air pumped in, it won't matter if some inlet valves aren't fully sealed

You'd need to disconnect and cap off the turbo side though, correct?

 

[mudgudgeon]

You'd need to disconnect and cap off the turbo side though, correct?

Yeah, I think if you cap off the intake between turbo and air cleaner, you'd get enough air in to mimic boost conditions when the engine is running, even with air leaking past intake valves.
If the intake valves are open, exhaust valves will be closed, so at worst, you have to pressure a couple of cylinders as well as the intake tract.

 

[gerg]

When I pressurize mine all I do is disconnect the turbo inlet and hook up my pressure tester thingy. The volume of air an air compressor can provide is more than enough to pressurize the entire intake plumbing all the way up and into the cylinder head. It's actually a simple yet surprisingly effective way to check for leaks. I leave the compressor hose connected while I do the checks because you have leaks everywhere like rings and valves etc but your only concerned with fittings that shouldn't leak. Be like Ricky Bobby and don't be a thinker......be a driver!