Oil Expander Gap for Mahle Pistons

[TurboHawkTSI]

I'm having an issue with the oil ring expanders for my pistons. Now I have measured the end gaps for the oil rings and they are good but when I put the expander in the bore and try to butt the ends together is is way too tight, actually doesnt fit. I put the expander on the pistons and they fall out, way too big as if they were for a bigger bore piston. So I read every forum and piston mfg support page and most of them say they ends of the expander need to butt together. Great, but problem! Obviously I need to trim them to fit but,,,,,how do I determine how much to cut? DO I trim enough to where when I put the expander on the piston, then the two oil rings, should the expander be putting pressure on the two thin rings against the cylinder wall or should the expander be cutt just enough to leave the exact amount of gap that was measured when I put them into the cyclinder bore? I have two set up right now and not sure which to go with. I have one piston that has the oil rings and expander installed, when you squeeze the two oil rings together to where they butt against each other the expander gap is just a hair shy, not enough for the expander to put pressure on the rings themselves. Second piston, when you squeeze the two rings together the most you can sqeeze puts them at the exact gap they measured when checking clearance, expander putting pressure against the rings so they are pressed against the bore wall. The last seems that it would wear the piston wall out faster but not sure. Any thoughts would be greatly appreciated. TSI Mahle pistons, 20 over.

 

[crimsondragon]

You measure end gap with a feeler gauge when the rings are in the cylinder and square with the wall. You file as little as possible and recheck each time till you get the desired gap. You can either use a ring filer or take a file, put it in a vice and file the ring down.