Single Turbo Setup Can't Reach Wastegate Pressure

[Arrtus]

Hey guys,

I originally had posted this in the N54Tech forum but got little to no help. I'm really stuck on and can't understand what is causing this problem.

This is a brand new DR700 setup and ever since making the swap, I am unable to reach more than ~9 psi (14 psi spring). The car is obviously way underboosting and I have no idea why. All the vacuum lines have been checked and are brand new. I have pressure tested from the turbo output all the way to the charge pipe and have found no issues. I also tested the compressor housing side of the turbo (and intake) and it did not leak whatsoever. I went through all the V-band connections and everything is on correctly and tightened to the max.

Symptoms: The car sounds different. I don't know if it's because of the single turbo but when going on WOT it doesn't sound like it's spooling. It's also very loud, like it just changes sound as soon as it starts building pressure.

With other maps, the wastegate (I think?) starts pulsing and sounding like it's hitting a rev limiter or 2-step while it's on WOT. It's most likely because of the mac that it's switching the air into the wastegate but it's not able to hold pressure or something. With maps aiming at higher PSI, it reaches ~12 PSI. What would cause the wastegate to do this? Can it be defective? It's a turbosmart gen V 45mm. I also checked the wastegate by putting some pressure on it and I can hear it open and closing. The MAC solenoid is also working just fine (which doesn't matter since it's not in use in map 0 and the problem is still there).

Log of a map 0 pull attached. Any advice or suggestions would be really appreciated!

 

[Arrtus]

Too small of a leak not to hit spring pressure on a single turbo setup, you can't even hit 14 psi when your building boost.

Any system will hit more even with a leak twice that size.

The leak wont help but that's not your issue.

Okay, that's kind of disappointing to hear.

If that is the case then we can rule out the main issue being from the output of the turbo to the throttle body.

I'm not sure what you mean by the wastegate being stuffed. It does freely open and close when pressure is applied to the bottom port. However, I do hear and feel air being released from the stem portion which feeds into the top part of the wastegate with the spring. I assume that is normal though.

I forgot to mention that when the car is on idle, I do feel some exhaust fumes coming out of the dump tube.

Is there a way to test if the wastegate is leaking while it's installed other than feeling around it with the car on (I did do this and did not feel any pressure for the record)?

Maybe using some seafoam will help show where it can be leaking from?

 

[martymil]

If the wastegate does not fully close and leaking exhaust gases you will never hit spring pressure boost.

At the very least you should hit 2 psi less than what the spring is rated for, unless your mistaken and have a 9psi spring, seen that happen.

 

[Arrtus]

If the wastegate does not fully close and leaking exhaust gases you will never hit spring pressure boost.

At the very least you should hit 2 psi less than what the spring is rated for, unless your mistaken and have a 9psi spring, seen that happen.

It should be 14psi. I never opened the wastegate since I've gotten it.

Just to confirm, there should be absolutely no exhaust coming out of the dump tube, correct?

Then something is not right since it's seated and I'm unable to push the wastegate any closer.

 

[martymil]

It comes with various springs, did you confirm it has the right one installed.

With the adapter or fire ring installed someone called it it shouldn't leak or very minimal.

The 9 psi wastegate comes with no springs and 14 does but you have to install it.

Just double check.

 

[Arrtus]

It comes with various springs, did you confirm it has the right one installed.

With the adapter or fire ring installed someone called it it shouldn't leak or very minimal.

The 9 psi wastegate comes with no springs and 14 does but you have to install it.

Just double check.

No way... I thought it was already installed.

That still doesn't explain why the MAC doesn't keep the WG closed on other maps though... Unless the MAC is messed up somehow.

 

[martymil]

are you running a motiv boost box or jb4 ?

 

[Arrtus]

are you running a motiv boost box or jb4 ?

Running a JB4 with MHD BEF. 3.5 bar TMAP.

JB4 does have the ST MAC firmware installed.

 

[martymil]

I've seen and experienced issues with the boost box, let's start by installing the correct spring and double check your mac plumbing.

 

[Arrtus]

I've seen and experienced issues with the boost box, let's start by installing the correct spring and double check your mac plumbing.

I looked at the WG documentation and believe the 14 PSI spring is already pre-installed since I don't have the blue one in the box. Regardless, I'll take off the wastegate and open it up to make sure the spring is seated properly.

 

[martymil]

and check you o ring on your charge pipe to tb, its a minor leak but still a leak

 

[Cruizinmax]

It should be 14psi. I never opened the wastegate since I've gotten it.

Just to confirm, there should be absolutely no exhaust coming out of the dump tube, correct?

Then something is not right since it's seated and I'm unable to push the wastegate any closer.

Correct, no exhaust should be coming out of the dump tube at idle.

Sorry if this sounds elementary but are you tightening the wastegate v band clamp all the way? It should be pressing the fire ring firmly against the wastegate valve and fully sealing. I have used some light oil, like wd40 on the tapered flanges of the v band to ensure they are sliding and pressing the flanges together firmly before.

Also if you take the fire ring and place it on the manifold where it should seat by itself, are the mating surfaces perfectly flat with each other or does the fire ring rock slightly on the manifold?

 

[Arrtus]

Correct, no exhaust should be coming out of the dump tube at idle.

Sorry if this sounds elementary but are you tightening the wastegate v band clamp all the way? It should be pressing the fire ring firmly against the wastegate valve and fully sealing. I have used some light oil, like wd40 on the tapered flanges of the v band to ensure they are sliding and pressing the flanges together firmly before.

Also if you take the fire ring and place it on the manifold where it should seat by itself, are the mating surfaces perfectly flat with each other or does the fire ring rock slightly on the manifold?

Yes sir. I checked again today and did not feel any exhaust coming out of the dump tube. I think the ring wasn't being pulled into the housing when the clamp was tightened before so I had the compressor hooked up to the bottom port and kept the valve open while I tightened it. I now know for certain that it doesn't leak and it's fully seated.

There is absolutely no play on the manifold side with the ring on it. It's perfectly flush so I don't expect it to have any issues.

Going to hook up the CP to the TB tomorrow using a coupler to rule out the leak around that being the culprit. After that... I don't know, I'm all out of ideas.

 

[Jeffman]

I once installed a new charge pipe and couldn’t boost more than 15psi even though WGDC was 99%… I forgot to install a meth bung blocking screw…doh!

 

[martymil]

Exactly the charge pipe leak he demonstrated wouldnt cause a 6 psi discrepancy it has to be the wrong spring or a major huge boost leak not to hit spring pressure

 

[martymil]

There is only one more thing that could cause that, the turbo is stuffed.

These are the only three things that would stop him from hitting 12 to 14 psi.

You have these to check out properly

Test the waste gate is closing properly with the boost solenoid disconnected not to interfere with the test to see if it hits close to 14 psi +/- 2 psi.

Major boost leak which you would hear if a 14psi spring is installed.

Turbo is Toast.

There is no more to ask until you test these out properly, keep looking you'll find it

 

[RuskiRacer]

What turbo are you running ? I'd find it very odd to have a precision thats defective out the box. In all my experience with precision turbos they will make the boost as long as your system is free of leaks. You put exhaust manifold gaskets in? There just can't be many more variables

 

[RuskiRacer]

What turbo are you running ? I'd find it very odd to have a precision thats defective out the box. In all my experience with precision turbos they will make the boost as long as your system is free of leaks. You put exhaust manifold gaskets in? There just can't be many more variables

Is your v band to the turbine housing completely seated and flush ?

 

[Cruizinmax]

Yes sir. I checked again today and did not feel any exhaust coming out of the dump tube. I think the ring wasn't being pulled into the housing when the clamp was tightened before so I had the compressor hooked up to the bottom port and kept the valve open while I tightened it. I now know for certain that it doesn't leak and it's fully seated.

There is absolutely no play on the manifold side with the ring on it. It's perfectly flush so I don't expect it to have any issues.

Going to hook up the CP to the TB tomorrow using a coupler to rule out the leak around that being the culprit. After that... I don't know, I'm all out of ideas.

Awesome. You're on the right track. I would also recommend connecting the boost reference to the intake manifold as well. This will ensure any pressure loss from the intercooler is overcome as well and ensure you are staying closer to target boost.

 

[martymil]

The problem is he cant even hit spring pressure boost.

The problem lays with

wastegate
boost leak
turbo

its that simple.

even with electronics disconnected until he finds the problem he should hit 12 to 16 psi on spring pressure and he is not.

 

[Arrtus]

Turbo to down pipe does not have an exhaust gasket. They connect with a v-band clamp and both surfaces are flat.

I checked the turbo for shaft play and did not feel any. Spinning the turbine also made no noise. No smoke coming out of exhaust to indicate seals to be blown. Again, it's a new turbo, I doubt it's bad but nothing is impossible.

Anyway, I ordered an ER charge pipe today so I can rule out that leak for certain.

Going to get a small camera to see if I can look between the manifold and turbo connection and make sure it's not open. I didn't feel any leaks with the car on idle but that may not show it.

Wastegate is mounted perfectly and clamped as tight as it can be. I had been in touch with Turbosmart trying to see if they had any ideas. They said they doubt the spring to be out of position because of the way the housings are made. At this point, I do not suspect the WG to be the problem. It opened and closed perfectly fine when it was tested. Even if it opens too soon, other maps should keep it closed regardless. I might take it off one more time to do one final check and feed equal amounts of pressure into both ports to make sure it stays shut to simulate how it would be when the MAC feeds air into it.

I will update this when I receive and install the new part or if I find something else. Sorry for dragging this on for so long.

Edit: pics of turbo to manifold clamp