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Not able to maintain desired boost


Wenier

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  • Member For: 14y 2m 10d
  • Gender: Male
  • Location: Christchurch, New Zealand

Hi all,

 

Been trying to sort and tidy up the Tune on my BF XR6T ute.  Now previously the turbo had managed to pull 20psi quite happily, eventually the original turbo gave up and seized.

 

With this I got a standard replacement 3582 core and refitted to the housing as they were undamaged.  However decided to upgrade to a turbosmart IWG75 12psi actuator which I have also built a strong bracket for as it was flexing the original bracket a lot when actuating.  After the rebuild I found the original turbine housing had worn where the wastegate arm goes through and this was causing it to randomly jam open which wasn't very helpful.  Because of this I replaced the turbine housing with a GCG 1.15 housing with the very large wastegap flap.

 

Now we come to the current issue.

During tuning it is targeting 20psi but only managing 15-16psi at the manifold.  The tuner started measuring the boost pressure at the turbo and manifold and has found the in the higher RPM it has a pressure drop of up to 6psi which is quite excessive, down lower it is as expected from 1-2psi drop.  He has also mentioned that it seems to be 1000rpm late getting onto boost.  He has checked for leaks in intake piping etc and come up with no leaks.

 

Today I took the BOV valve off to see it it was loosing the pressure and found it would boost to 18-19psi but then fall back to 15psi which is wear the manifold keeps settling to.  I am wondering if the preload I have put on the wastegate is not enough (2mm approx) and is allowing the exhaust gases to push the gate open when it isn't commanded.  The tuner has also questioned whether the dump pipe is a restriction, it is a Xforce twin pipe style and now I see they only sell the large bellmouth style.

 

Hopefully that all made sense, bit tired while trying to sum this all up and just looking to see what other peoples thoughts on the issue might be.

 

Even with the lower than targeted boost it is make 370rwkw and approx 900nm.

 

Cheers in advance

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  • less WHY; more WOT
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  • Member For: 15y 11m 18d
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1. I wouldn't bother using one of those actuators... they're cheap and nasty (as you found out) and hard to setup the preload properly.

 

2. the 1.15 rear housing needs to go into the bin... another cheap and nasty item. Just get a replacement garrett 1.06 rear-housing.

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  • Member For: 6y 10m 27d
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  • Location: Brisbane

Nothing wrong with the turbosmart actuator if set up by someone who prefers or uses them regularly. Put another spring in it so its 15psi. Exhaust should be ok but getting close to 3.5 or 4" dump territory. The rest who knows.

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  • Member For: 8y 11m 6d
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You could try pressure testing the piping between the turbo outlet and the throttle body . You can diy a test kit with some PVC pipe end caps and installing a tyre valve in one - then hook up a compressor and see if it holds pressure. I found I had a couple of spots that looked and felt ok but actually leaked slightly. Hopefully the tuner has already tested this properly and not just had a quick glance.

If you disconnect the wastegate line you should boost to the moon. Maybe try this first (but be ready to jump off the throttle before you go sky high) if you make heaps of boost this way you know you have some sort of wastegate or wastegate control problem but no boost leaks.

I spent a lot of time last year chasing a low boost problem. Turned out I had a piping leak AND a failed wastegate which made testing and tracing a bit confusing.

Edit: just took a pic of my boost leaks tester so I'm making more sense!

03a03e9a7df2a400e26d070cae288dd6.jpg

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  • Member For: 14y 2m 10d
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  • Location: Christchurch, New Zealand

I'll give the boost to the moon a go as at least that tests the preload of the gate.

 

The Tuner had done a pressure test of piping but I could redo at home just to be sure.

 

Cheers for the info.

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  • Puff
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2 hours ago, Wenier said:

I'll give the boost to the moon a go as at least that tests the preload of the gate.

 

Be very careful if you try this. All it takes is one decent detonation event north of 20psi on stock pistons and you can say goodbye to your ring lands.

Edited by Puffwagon
Low carb beer edit
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  • 7 months later...
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  • Member For: 14y 2m 10d
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  • Location: Christchurch, New Zealand

Long time getting back to this.   Luckily my pistons aren't stock.

 

Added a fair bit more preload to actuator and that sorted it.  So yea Turbosmart actuators appear to need extra preload in this instance.

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