2.2T Piston Ring Set 84 85mm

[strictly]

Im slightly confused on piston rings on a 1970 2.2T with Mahle pistons.

The piston ring sizes from the book, are 84mm 1.5 x 2 x 4, except the piston rings availble seem to be written 85mm on the box.

The part number is 911-103-901-01 which cross references to 0831950010

For example 1 supplier :

- 91110390101 / 0831950010 - Goetze - Engine Piston Ring Set
Single Cylinder Set; (1.50 x 2.00 x 4.00 mm)
Standard; 84 mm
Brand Goetze Condition New
Part Number 911 103 901 01 / 08 319500 10 / 91110390101 / 0831950010

But Goetze box states 85mm....it also states 911E so, is the 91110390101, the incorrect part number?



P.s dont f'ing worry im not just chasing the piston rings lol. I want to measure my ring lands, and end gaps before the pistons and cylinders go to the machine shop

[Trackrash]

Interesting that the package also states 2,1 L. The part number seems to check out for a 2,2.

I would test fit. Since we are talking about 45 year old stuff here, who knows?

Just don't fudge up the packaging or rings in case they need to be returned.

[strictly]

Thanks for the reply. I haven't actually bought the rings yet, presumably if they were "85mm" instead of 84mm, they would have no or 1mm less end gap than "84mm" rings?

I was searching for mahle rings, but they don't seem to make them, in any case a lot of the different rings some specify 84mm and some say 85mm, so I thought I would ask the question if it matterered, as long as the ring end gap is correct, and the thickness is correct (1.5mm/2mm/4mm)

Luke

[strictly]

Further to my reply/question above (still need help with that)

Tech specs below (for next three questions)

----- Piston Ring Side Clearance ----

There is a wear limit specified for piston ring side clearance of 0.2mm (.0078"), and a piston ring side clearance. With a NEW ring in a used (clean) piston, say #1 ring, the clearance is .075mm to .107mm (.0029" to .0042").

Q1) So is the piston junk with a new ring, if the side clearance is more than .0042", even though the wear limit is 0.0078"? Assuming that the new rings are within the specs below for thickness

Q2) When do you use the wear limit? I.e with a new ring if you cant achieve .002" to 0.004" then its okay to exceed 0.004" provided that it cannot exceed 0.0078" when HOT, even though it would be difficult to measure that. Same for ring end gaps, below (next question). Wear limit is 0.1mm (0.040")


I know about the other measurements on the piston/cylinders, I just want to investigate the ring clearances first.

---- Piston Ring End Gap ----

Q3) The piston ring end gap (new ring, good cylinder, inserted and measured near bottom of cylinder), should be .15mm to .45mm (.006" to .012")?

[Trackrash]

From my experience, the piston ring side clearance is critical. With new rings there will be more "bite" or friction on the cylinder walls. Therefore the ring side gap will typically get pounded and enlarge during break-in. So the rule of thumb is more than 0.004" side clearance with new rings and the piston is done, not worth re-ringing.

0.006" sounds a little tight for end gap, but I will defer to the experts.

[strictly]

Ok thanks, that reinforces what I've read before as a general rule of thumb as otherwise the rings will just break.

End gap I'm sure I can google/use the search function.

That really only leaves the okay to use the "85mm" piston rings question...

I'm the meantime I might just buy a box as at least I can see if the pistons pass the ring land 0.004 and then general dimensional tests

[ed mayo]

The 85 would seem to be for a normal 1mm over bore. As to the ring gap, usual 'rule of thumb' is .003" per inch of bore. I don't think I've ever seen a new set of Mahles or Goetz that measured at the low end, usually new they tend to be at top of new installed tolerance.

[strictly]

good rule of thumb Ed, thanks. I have bought 2 sets from different suppliers and will see how they measure up