# help with wastegate



## seximagtr (Feb 22, 2003)

My tial wastegate holds boost fine to 16 psi - holds fine further up too... 

At idle however, it will almost randomly open and vent exhaust. It does the same when cruising and when i let off throttle to shift. It seems that the opening is triggered by a vacuum difference. I've got the side port tapped to the turbo compressor outlet and the top port going to the out on the boost controller solenoid. The in on the solenoid goes to the brake booster vacuum source @ the intake manifold. I'm using the Blitz SBC-ID. Any ideas guys?

Another random question - i think i know the answer but i wanted a second opinion. I blew a gasket on the feed pipe to the turbo - i can hear the exhaust leak while driving. I'm getting a right bank lean code - This due to the leak right?...

Thanks for the help


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## lshadoff (Nov 26, 2002)

The wastegate and boost controller should use the same vacuum vacuum source. There is a pressure difference between the turbo output port and the intake plenum. I use the intake plenum for both, but it is just as good to use the compressor outlet. 

Here's how I installed my Profec B. 

Lew


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## seximagtr (Feb 22, 2003)

lshadoff said:


> The wastegate and boost controller should use the same vacuum vacuum source. There is a pressure difference between the turbo output port and the intake plenum. I use the intake plenum for both, but it is just as good to use the compressor outlet.
> 
> Here's how I installed my Profec B.
> 
> Lew



That still wouldn't explain why the wastegate is acting up.


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## lshadoff (Nov 26, 2002)

With normal driving conditions (no boost), if the sources of vacuum for the top and bottom of the wastegate are different, when the vacuum changes (due, for example, to a wind gust or hill) the plenum will see the change before the turbo outlet does. The lag is due to the restriction of the intake piping and intercooler and the volume of the section between the plenum and turbo. So the wastegate sees a temporary pressure difference across the diaphragm. If the difference is greater than the spring tension of the wastegate, it will open and close. 

What boost is the wastegate set for when the boost controller is off? Mine is set at minimum which is 4psi, and it is possible to have temporary differences in pressure this large across the wastegate with different sources top and bottom. 

I wouldn't have thought that there would be that kind of difference at idle, though. 

Lew


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## seximagtr (Feb 22, 2003)

lshadoff said:


> With normal driving conditions (no boost), if the sources of vacuum for the top and bottom of the wastegate are different, when the vacuum changes (due, for example, to a wind gust or hill) the plenum will see the change before the turbo outlet does. The lag is due to the restriction of the intake piping and intercooler and the volume of the section between the plenum and turbo. So the wastegate sees a temporary pressure difference across the diaphragm. If the difference is greater than the spring tension of the wastegate, it will open and close.
> 
> What boost is the wastegate set for when the boost controller is off? Mine is set at minimum which is 4psi, and it is possible to have temporary differences in pressure this large across the wastegate with different sources top and bottom.
> 
> ...


Spring is a 7.5psi spring.... i wouldnt think that a 1-5mm Hg difference would make make much of a difference as far as fluctuation goes


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## lshadoff (Nov 26, 2002)

seximagtr said:


> Spring is a 7.5psi spring.... i wouldnt think that a 1-5mm Hg difference would make make much of a difference as far as fluctuation goes


I agree. Is there a problem with the BOV? It responds to small fluctuations in pressure.

Lew


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## seximagtr (Feb 22, 2003)

nope it vents slightly under that fluctuation - but nothing out of the ordinary


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## lshadoff (Nov 26, 2002)

I'm out of ideas.

Lew


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## seximagtr (Feb 22, 2003)

Thanks though.


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## lshadoff (Nov 26, 2002)

There's a wastegate installation diagram on the Tial website. Click on the 'Technical' link and then on the 'Waste Gate Installation Diagram' link.

Lew


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## dmroberson (Jun 24, 2004)

seximagtr said:


> My tial wastegate holds boost fine to 16 psi - holds fine further up too...
> 
> At idle however, it will almost randomly open and vent exhaust. It does the same when cruising and when i let off throttle to shift. It seems that the opening is triggered by a vacuum difference. I've got the side port tapped to the turbo compressor outlet and the top port going to the out on the boost controller solenoid. The in on the solenoid goes to the brake booster vacuum source @ the intake manifold. I'm using the Blitz SBC-ID. Any ideas guys?
> 
> ...


Check your vacuum hoses for leaks.


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## seximagtr (Feb 22, 2003)

dmroberson said:


> Check your vacuum hoses for leaks.


no leaks. I still dont see how a vacuum issue is going to make it open - the only time it should open - even at 0 psi - is once it either hits the spring rating - or the boost controller senses that it reaches the preset level.


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