Bench testing wastegate actuator

[Anthony P]

using the setup as pictured, I've been testing spring pressures and checking diaphragms for leaks using regulated compressed air.

stock actuators : test pressure at 20 psig, rod begins to move at about 8 psig

HD actuators : test pressure at 25 psig, rod begins to move at about 16 or so psig.

How long should the pressure hold at these levels during this bench test? 15 minutes? 30 or 60?

System pressure will gradually bleed down in any static testing. After an hour or two there could be a drop in pressure of 0.5 to 1.0 psig. The pressure drop would be much larger and faster if there was a problem.

Any insight in appreciated.

 

[wb_7354]

If you’re only getting .5-1.0 drop in a hour I would say that is acceptable.


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[Anthony P]

If you’re only getting .5-1.0 drop in a hour I would say that is acceptable.

Thanks for the confirmation. I'm hoping someone will chime in to specify some threshold pressure drop in such time period makes a replacement necessary.

The Buick service manual is of no help on this topic. Pages 6J21-22 discuss WASTEGATE/BOOST PRESSURE TEST PROCEDURE. But only to verify that at approx. 13.5 psig, the actuator rod moves 0.015 in. If not, replace it. OR perform a 0-40 or 50 mph acceleration at WOT and verify that the test gauge measured 13 - 14 psi boost during the acceleration test. If not, replace it.

To eliminate the potential for pressure loss through either the gauge or my isolation valve, I'll pinch-off the poly tubing at the actuator with hemostats and repeat the tests noting pressure drop at 15 minute intervals for one hour test.

I'll post an update tomorrow.

 

[Chuck Leeper]

If they are working, why mess w/ it?
Seriously doubt anyone drives around at those boost levels, for an hr at a time.

 

[pacecarta]

i doesnt matter ...the gate has a constant source of air at pressure when its required to be open
its good as long as it opens at the pressure you need

 

[1972chevy]

1/8 & 1/4 mile is over in seconds. Road course over in a few minutes and your in boost for seconds at a time.
So if it holds for 5-10 minutes that's a A++

We test home plumbing in hours because the system is being used for hours.
We test home gas system at 15 psi for about 24 hours. The actual use of a home system is not even 1.5 psi. So your golden if you pass that test.

 

[Anthony P]

Chuck, Paul, 1972Chevy,
I agree with you 100 percent before I even started this thread. If the diaphragm had an issue, it would leak down immediately.

I'm sorting out turbo parts. I've had this test setup at various events over the years - GS Nats, BPG and other Buick racetrack events. Some folks are curious and want to learn the test parameters (give out a copy of the two pages of the service manual) and make their own. And then there was this well known vendor who proceeded to make comments about pressure drop over x time period concluding that my actuators were bad, but he had brand new ones to sell. So, the unknowing customers bought new actuators "for peace of mind" rather than half priced used actuators that function perfectly to spec and have that functionality demonstrated in front of them. Pretty douchey move.

I did not want to begin a discussion about the gas permeability of the diaphragm material. I have a background in mechanical and electrical engineering and a few decades doing industrial projects for pharma facilities, powerhouses and boilerhouses. There is no comparison pressure testing a wastegate actuator to pressure testing pipelines for high pressure steam or high pressure nat gas feeding 5 megawatt turbines for cogen. But, sometimes you can't talk to stupid.

While all the actuators I have work fine on the bench and in real world on the car, I was curious if there is such a statement in a Garrett manual noting if, at a starting pressure of x, a pressure drop of y in z minutes would indicate a deteriorating diaphragm. While it may still work fine for that 10-15 seconds at WOT, it would be great to learn if it was in a deteriorating pre-failure state rather than experience sudden failure and potential damage from overboost.

 

[dank GN]

As long as you don’t have a big ass leak you are fine . The turbo is constantly forcing pressure in there so if it holds for a couple seconds you are fine . Also you have to Remember that the boost pressure is also pressing against the waste gate flap so if it starts opening at 16psi it would be completely open at 16psi with the boost pressure pushing on it

 

[1972chevy]

You can't sell to uninformed people either. People need to understand that actuators are open for seconds at a time. So why are they testing for hours at a time.
And to that vendor saying that your parts are bad.
Oh well just leave him, he is either uninformed himself or telling people what they want to hear to make a sale.

Either way my TR friend good luck with your information gathering. Hope you find what you're looking for.
Much respect to you..