Advice on ring gapping for 99 Boxster 2.5l

[jbranch]

Purchased a set of Porsche rings for Boxster. The set must have been pre-gapped as I checked all of them and they were properly gapped. The only problem was that the spacer rings for the oil collector rings had a slight overlap when I checked them in the cylinders. When I install them on the piston with the collector rings, they hold the collector rings open much further than their allowable gap. My supplier checked the manufacturer data and said the manufacturer wanted them to be snug, but I did not understand his explanation of what “snug” meant. A tech with Porsche rebuild experience said I could just snip off the excess from the spacer rings with side cutters. That seems a bit coarse; kind of like cleaning your teeth with a chainsaw. I would like some advice on this. First, does anyone know what this “snug” recommendation from the manufacturer might mean? Second, I don’t have a ring grinder and do not want to procure one just for these spacer rings. Can you really just “snip” them off with side cutters? Third, why would the manufacturer sell a pre-gapped ring set without gapping the spacer rings for the oil collection rings?

The purple and white are the two ends of the spacer ring

The purple and white are the two ends of the spacer ring

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[four0four]

Purchased a set of Porsche rings for Boxster. The set must have been pre-gapped as I checked all of them and they were properly gapped. The only problem was that the spacer rings for the oil collector rings had a slight overlap when I checked them in the cylinders. When I install them on the piston with the collector rings, they hold the collector rings open much further than their allowable gap.

This makes sense - you aren't going to get useful information about the gaps without installing the rings in the cylinder. Put the oil ring assembly in the cylinder without the piston, fiddle with it and see if it makes sense then?

My supplier checked the manufacturer data and said the manufacturer wanted them to be snug, but I did not understand his explanation of what “snug” meant.

Possibly here expecting the ends to be snug against each other? Hard to picture. I searched around a bit, but I'm not quite sure what your oil rings look like. Does this help (I assume they're 3 piece)?

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From Mahle's little ring pamphlet.

[jbranch]

They are a 3-piece design, two oil scraper rings (with proper gap verified in cylinder) sandwiching a somewhat flimsy spacer ring. In order to better fit the spacer ring in the cylinder, I first slid a used center ring in the cylinder and leveled it. Then I placed the new spacer ring on top of it. This held the spacer ring level so I could check the gap. I could see a slight overlap. I have never heard that any ring manufacturer allows an overlap (there's a first time for everything) so I am taking the position that there must be a gap to allow for expansion ("snug" doesn't cut it). I've never worked with this stuff before so I am trying to make sure I am not missing something. I am clearly not fully understanding what these other folks are telling me, so I am just going to shorten the spacer rings. It won't have the precision of gapping the other rings, but it looks like (from the photo) I can just "snip" off two "tabs" from the spacer ring (chainsaw approach). And maybe that is just a bad way to go, and I need to get to a shop somewhere that has the correct tools. The only problem is I live in the middle of nowhere and I am not even sure where there is a qualified shop within a reasonable distance. It's decision time and I am looking for all the input I can get.

[four0four]

nonono!

Can you post a picture of the rings un-installed from the piston?

Assuming I was correct about the style of oil control ring:

The middle bit is intended to be under a bit of tension (along the circumference) when installed. You have to butt the ends together as shown in that Mahle pamphlet. This tension is necessary for the oil control ring to function!

Edit: some brief reading which partly covers this.

[Tom]

Regarding that overlap, this might help...

[jbranch]

I do appreciate the interest and help. I attached some pictures of the rings. One of the problems I am seeing is the spacer ring is shaped like a T. The oil collection rings ride on that T. You can see this in the above picture. This means that the oil collector rings cannot close in any further than is allowed by the T. This holds their gap open. I will never even be able to get them into the cylinders.

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[jbranch]

It's very clear now that I am going to have to gap them. I just have to figure out how much to gap them and how to do it without an expensive tool. I still don't know what "snug" means and is that really critical. I think someone was just making up their own terms.

[jbranch]

It almost looks like those two end tabs on the spacer ring were designed to be easily removed.

[four0four]

Thanks for posting pictures!

That's a very (to me!) odd looking expander ring, but poking around on youtube/internet (check out this!) seems to indicate that's the normal 986 type.

Anyway, I would still not trim the expander! All of the tension in the expander comes from compressing it along the circumference. You should be able to still fit it just fine, though sometimes it can be a huge pain in the ass to get situated in the compressor! I like using tapered adjustable type compressor (like this) and clocking the oil ring such that it's visible thru the vertical slot.

[jbranch]

If I understand correctly, the expander ring compresses by bending slightly the metal sections between what I am calling the tabs (the ring looks like a series of tabs connected by short strips of metal). The oil scraping rings themselves keep the expander ring from engaging the cylinder wall. Does this make sense?