Wastegate actuator pressure vs extension data

[acannell]

Just measured some data

I'm 99% sure this WG actuator is from FWDP and is about 7 years old.

pressure	extension
3	0.003
4	0.04
5	0.08
7	0.155
10	0.265
12	0.34
15	0.46
16.5	0.522
18	0.58
19	0.622
21	0.655
22	0.659
25	0.665
30	0.665

So looks like the maximum extension is 0.65" and it gets there at 20 psi.

Its quite linear up to that point.






- - - Updated - - -

I suppose I could also measure "pull out" extension to see how much force pulls it how far out....although I think that information is contained in the above measurements, but we'd need to know the diaphragm diameter to calculate spring rate..

[acannell]

0.65" on my swingvalve (biggest non 3" one for 2.5) opens the flapper maybe 30 to 40 degrees from fully closed

So....what does all this mean.

Lets see. In actual usage, there will always be positive pressure on the flapper.

That will tend to push the flapper open and pull on the WG actuator rod.

So the extension/PSI curve above will be shifted to the left somewhat. Not sure how much. Maybe insignificantly.

But if there is a pulling force on the rod from exhaust gases, then its going to take less air pressure to get the same extension as when there are none (like my bench test).

But something to keep in mind is that the actuator doesnt necessarily see intake manifold pressure. With ECU control, there is a variable pressure sent to the actuator depending on solenoid PWM. With a grainger, a pop off valve and a bleed hole combine to create some sort of non linear curve of intake vs actuator pressure.

So we can only look at the limits really, the middle has more to do with boost control "dynamics" than what happens when things are maxed out.

What would be interesting is to now measure actuator pressure vs. boost pressure. That could tell you alot about your engine and turbo setup. I think it might tell you how close you are to maxing out your turbo. If you see the actuator pressure barely increase then your wastegate is barely opening...turbo max out is occuring? And if the actuator pressure skyrockets at low psi then you are sending way more exhaust flow than required to get to the boost level you're targetting.