Wastegate air leaking into exhaust

[S2central.net]

Isn't a "shagged" WG spring in the same category as "wastegate chatter", hobgoblins and other mythology ?

Seen plenty of torn WG diaphragms and yes the valve itself is not completely air tight. The latter worsens with age thru wear. It would be great to agree a simple test on the WG that determines if it is leaking ok or leaking too much.

Ages ago I played with an rs2 WG and an airline to try and get a measure of when it opened. I think I videod it too - will take ages to find results and such. Might have to do it again.

[driftin jo]

http://www.youtube.com/watch?v=FJ_W6g04xso

http://www.youtube.com/watch?v=dpUsJoqRAg4

http://www.youtube.com/watch?v=bvOljR6s0V4&feature=related

[ian4455]

ok, now it makes sense.

Would be interesting to do a test and measure exhaust pressure so as to be able to simulate the gases passing up through the shaft and lifting the wastegate.

Looking at getting my wastegate reconditioned none the less!

Better design would be with the valve seating the opposite way

[prj]

http://www.youtube.com/watch?v=FJ_W6g04xso

http://www.youtube.com/watch?v=dpUsJoqRAg4

http://www.youtube.com/watch?v=bvOljR6s0V4&feature=related

Those first two videos - the descriptions are incorrect and misleading.
If you pump air into the lower chamber, it is obvious that it will open.
Also, boost creep is when boost keeps creeping up, meaning the wastegate has trouble opening.

If the wastegate is sealing properly, the spring does not do much when boost is controlled electronically.
This is because on a correctly working wastegate when the N75 valve is ON, the lower chamber is sucked into vacuum by the turbo.

Of course the more play and wear there is, the more the exhaust backpressure contributes to opening the thing...

[Christophski]

So what causes the following symptom - Boost guage is fluttering around 1.3 - 1.4. It will hit that then float back and fourth between the two marks.

[prj]

That's normal - it's how boost is controlled.
It also depends on the gauge.

If it's floating slowly back and forth (overshoots at start, goes down, then goes back up), then that usually means that WGDC could be mapped better...

[Christophski]

Its more of a flickering and someitmes the it will only boost to 1.1 or 1.2

[prj]

Its more of a flickering and someitmes the it will only boost to 1.1 or 1.2

Is this the regarding your post you made a long time ago?
Did you pull the codes from the car?
Did you fix your boost leak?

[driftin jo]

Some gauges are damped better than others, there is also a difference in where you take your reference from with regards to pulsing in my experience, for instance if you tee off at the front of the inlet manifold at the line that goes to the DV you tend to see more gauge flutter, the best place is to tee off at the ECU as this seems the most stable with regards to pulsating pressure. Where is your gauge plumbed to ? There is always high frequency oscillation in pressure due to the inlet strokes of the pistons, if it is high frequency (fast flutter) on your gauge you are seeing it is most likely your gauge can't cope with the I5 pulse frequency in boost pressure.

Have a look at this video at 4 Min 10 sec , is this the sort of flutter you are seeing ?

http://video.google.com/videoplay?docid=6369021561677387492#

[Christophski]

I fixed the leak so it holds more but it still isntt right. My car wont read on vag com for some reason. It worked a year ago when I plugged it in out of curiosity and drew no codes but the leak has appeared since then.

It not as violent as that in the video and I have seen my guage hit and hold at a solid level as last night was the first time I saw it flutter. It only moves very slightly up and down but its still not right. I dont know where it was plumber into and I havent tried chasing it back on to the tee.

[Lloyd]

I fixed the leak so it holds more but it still isntt right. My car wont read on vag com for some reason. It worked a year ago when I plugged it in out of curiosity and drew no codes but the leak has appeared since then.

It not as violent as that in the video and I have seen my guage hit and hold at a solid level as last night was the first time I saw it flutter. It only moves very slightly up and down but its still not right. I dont know where it was plumber into and I havent tried chasing it back on to the tee.

Is it possible you have an adjustable wastegate that has been screwed down a bit too much or, is there a stronger spring in your WG than your map is expecting?

Just a hunch, because my boost gauge will also flutter (oscillate up and down slowly compared to the video above) if there is too much pre-load on the WG spring.

[Christophski]

I wouldn't have a clue as it is as I brouht the car and I was not told of anything then and I have not done anything since having it. It looks like it's standard though from the outside

[prj]

Then open it and see if the spring is standard and if the diaphragm is okay...
And get your car connecting on VAG-COM. If needed, tap K-Wire and L-Wire directly... and measure their continuity.

Provided the fact that it's not connecting is not user error in operating VAG-COM or a bad cable.
Anyway, talk about it in your other thread you already have...

[madpugger]

Interesting thread.

I agree with PRJ, the spring cannot 'leak'. If the valve guides are worn and the valve is operating slightly sideways and not seating, increasing the spring pre-load is likely to help it seat, but this does not mean that 'air' is passing through the spring.

Also, putting vacuum on the top of the diaphragm does not 100% test the diaphragm, it could be leaking below it between itself and the lower casing!

However, I too have an issue with excessive play in the guides. My problem is that i get initial boost fine then it slowly drops. With a bigger spring it spikes too much as the N75 cannot open it quick enough as the 'air' leaks to the exhaust rather than opening the valve. (Spikes to 2+ Barg.) I was going to get a new WG but don't know whether to get an OE or a Tial one. Is there a direct fit Tial one?

Cheers

[A80Avant]

marc swanson makes replacement parts for the original wastegate. I recently had a new piston and we made a guide to fit.I had excessive side to side movement and its now cured.