Wastegate Valve Seat Removal

[twoqu]

I am a bit dubious as to how people have reconditioned the wastegate without knowing the critical valve stem clearance. Certaintly easy to free up the valve by either making the guide larger or the valve stem smaller.
I'll take a stab and say that the valve is some sort of stainless (214N?) with a chromium plated stem. Not sure whether the face of the valve is coated either.
Because of the application its difficult to assess what a suitable clearance should be other than a cast iron guide generally has a larger clearance than a bronze one in applications with cooling and lubrication. The wastegate of course has neither!
Had a reply from EFI Express. The valve and guide is $180 plus freight, about $200 to the UK the slow way plus an unkown tax/duty.

[diesel des]

Thinking outside the box here but could you find a big exhaust valve from say a truck that had similar key dimensions? For the guide you could start off with a tight tolerance and open it up if stickiness is a problem??

[EspenW]

I would think that some of the leakage and probably most of the type of leakage that would cause boost loss/taper would be due to the valve / valve seat interface, and that can likely be restored/improved with some old school valve grinding/lapping. in other words, easy with some very low cost stuff that many of us likely have in the garage already.

[twoqu]

Agreed! It has to be a reasonably cost effective method and within the capability of a Forum member.
The seat is also somewhat wider than the valve head so compared to the needs of a normal valve its all a bit sloppy.
I think the wear on this valve is due to it being cocked. Whether that is down to excessive clearance or perhaps a different wastegate spring I am not sure. I think I can see the corresponding wear on the bottom of the cast iron guide.
There would be a few options:
1: To rechrome the existing valve to an oversize and have the existing guide reamed or honed.
2: To remanufacture the valve in an oversize. This would allow a different material and treatment if there were benefits. Again either ream or hone the existing cast iron or replace guide with appropriate material for valve.
3: Use EFI Express kit of valve and guide.
There is obviously less chance of damage by reaming the existing guide in situ. I have uncucessfully tried to press out the guide from a 10V wastegate but it is clearly a different material. Might have another go later. I supported it on a piece of tube. In hindsight it would have been better to use a plate with a hole! Obviously MartinWS has extracted his cast iron guide so it is possible.

[EspenW]

I've never pulled the WG off my car, but I assume that it is rather easy?
Are the gaskets of the reusable type?

[twoqu]

For what its worth some pics!
A comparsion of the different valve guide material. A pic of the wear at the bottom of the guide and of the corresponding wear on the valve. This is effectively on the side nearest the exhaust ports.

[EspenW]

I assume that the WG assembly must be pulled off in order to remove the valve?

[twoqu]

Indeed! Hence the tips for the seat removal!
It appears the worst wear is in a position that cannot be seen without dismantling the wastegate completely to remove the valve.

[EspenW]

How tricky is it to unbolt the Wastegate? Does it require modding of tools or a curved (starter type) wrench?
Easier to unbolt the WG and flex pipe as one unit?

[K Simmonds]

How tricky is it to unbolt the Wastegate? Does it require modding of tools or a curved (starter type) wrench?
Easier to unbolt the WG and flex pipe as one unit?

The gate is easy to remove with normal spanners/sockets if you get the heat shields and solid boost pipe out of the way. The two three bolt gaskets for the flexi joint are not reusable and expensive, Andy (Rusty) can provide good quailty reusable gaskets for less than a pair of new OE one's.

[twoqu]

Well after an exhaustive internet search the only mention I can find of a valve guide/valve clearance is 0.3mm on a Porsche 911 wastegate which has similiarities with the Audi Wastegate but is not identical in design. It also looked like they used a bronze guide rather than cast iron or a stainless alloy based on the colour.
I was concerned that 0.1mm was too much!
The Audi wastegate probably shares some DNA with the Porsche 924/911 wastegate. The Porsche uses a longer valve (@25-30mm) with a seperate valve seat with a recess rather than the flat seat of the Audi. They may be some degree of interchangability evidenced by the one I linked to earlier!
Some pics to document the differences below.