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Testing wastegate

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amrbose14

New member
What's best way to test a wastegate? I was thinking I needed something special. Then I discovered that a bicycle pump, which has a rubber washer to grip the inner tube value, fits nicely over the air feed on the top. Does that sound OK?

If I pump the pump, the valve is gradually pushed down. A couple of pumps and it moves a little and a couple more and it is significantly open (I wasn't sure how far to push it). The valve only closes when I remove the bike pump from the waste gate. It closes very rapidly.

Is that good enough? Or is there a more quantitative test required to test it is fit for purpose?

cheers,
Chris

87 220T.


 
What you have done proves the diaphragm and spring are working.
Its a pretty tough device. Some-one may have a more quantitive test, sorry I don't
I would guess its fine, do you suspect its faulty?

George
944t
 
I bought it earlier this year. I haven't installed it yet but someone sensibly asked if I'd checked it.

So... is this a fair summary?
- it opens and stays open = diaphram not ripped.
- it shuts smartly = spring probably OK.

Presumably the remaining question is whether the spring is just a bit weak - perhaps leading to it opening too early. Is there any relatively simple way of testing this? A pressure gauge in line with the pump (this is where things get more tricky I guess)?

Chris

 
Well if it opens at around 1 bar pressure using an inline gauge then it it will be fine as a standard unit, presuming it stays closed on anything approaching that, the spring that holds it closed gets weaker due to heat (anneals) and flutters over time causing the lack of full boost.
 
Can you use an infra red thermometer to tell whether the outlet is heating up due to exhaust gas flowing through ut?
 
A waste gate only operates (in that it actually vents excess boost pressure) for a small fraction of the time in any given journey (maybe 3%), unless you lend the car to Hannu on the monte.........then its left foot braking and 95%[:)]

For the rest of the time the inlet system is in vacuum or static pressure (I can see this on my aftermarket boost gauge)

You can see if the car is making boost on the standard 951 boost gauge - anything above 1 bar on that guage is positive boost over and above atmospheric pressure.

So, its working if there is greater than 1 bar showing in a steady climb uphill at about 3000rpm as the spring is holding the WG closed in the presence of greater than 1 Bar boost.

Similarly, on the same hill if you floor the car and the boost goes to the top of the scale, and the overboost does not interrupt the engine, that proves the diaphragm is responding to the now excessive boost, and opening the WG to release excess pressure.

But you need to fit it to prove this.
 
if you use a foot pump wih a gauge you can see what pressure it opens at and shim accordingly if its weak. Also check around the valve seat for cracks.
Tony
 

ORIGINAL: 944Turbo

see also http://www.porscheclubgbforum.com/tm.asp?m=33373&mpage=1&key=wastegate
Click to expand...

Good link - thanks. I have a guage on my hand pump but have no idea if I should believe it. According to this guage It certainly opens below 1 bar. Of course, I do have a boost enhancer anyway!
 
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