Audi 20V Wastegate Cap ID

[twoqu]

Having had my own troubles with over boosting and knowing that the wastegate cap appeared to be an adjustable one, I searched through my spares to find a 20V one.
Having eliminated one cap as a 10V one, I used what I thought was a 20V with an original 20V spring. Having fitted the cap and spring, the car demonstrated the standard boost characteristics so I was satisfied.
However subsequently, I have advised Andy P and indeed declined to buy a wastegate cap from add on the basis that the one I used was a 20V one. That was not the case. So apologises to both!
So if you need to ID a 20V one then see the pics below. Indeed the 20V is in effect adjustable with a seperate perch. The dimension of the spring perch to the bottom of the wastegate cap is @18mm if you need to get back to stock (At least on an AAN!).
The screw is obviously sealed so you would need to remove the seal from the top and possibly heat the sealant to break the seal to release the adjustment screw. Hey Presto! An adjustable wastegate!

[UrS4boy]

AFAIK, the 10vt and the 20vt wastegate caps are exactly the same, down to the extra, unused, nipple on the upper side of the caps. (I am running a 10vt Audi 100 cap on my 93 UrS4 AAN right now.

You are right about the adjustment: drill a small hole in the protective center cap. Insert a small metal self-tapping screw in the protective center cap and pull it off. Using an Allen head socket (5 or 6 mm, I can't remember), and a 3/8" rachet, try turning the screw. IF necessary apply heat to soften the thread locker. Standard "rule of thumb" is a maximum of 6 turns in with a stock WG spring. If running a 1.9 bar WG spring, you will likely need to turn the spring perch ALL THE WAY UP in order to avoid the ECU going crazy on WOT.