Fiat 16VT piston ring end gaps

[ICI]

Hi Guy,

Today I measured my piston rings set end gaps, and they appeared as follows:

top ring gap 0,25mm, thickness 1,00mm
second ring gap 0,45mm, thickness 1,20mm
oil control 3 pcs ring gap 0,25mm, thickness 2,75mm

The whole piston set is made by Iasa pistons - Argentina, but the rings are made in Japan

Is there some performance idea to keep top ring end gap slightly smaller then second one? I mean not 0,25mm as now, but 0,35mm?
What is your recommendations about these end gaps?
The engine is Fiat 2.0 16V Turbo, expected 320 bhp

Regards
Iliyan

[Guy Croft]

I know those rings and the variance in end gap has more to do with the Japanese manufacturer's complete inability to impose proper ring gapping regimes at their factory than actual required dimensions.

I have queried this in the past with suppliers of their rings and been unable to impose any end gap dimensional protocols at all. In other words what you get is a lottery and yes, well done you have checked them. Others have fared worse. I think it's very poor practice and they have no business making them. Ring gapping in one-off quantities is an extremely painstaking affair and few aftermarket piston suppliers will devote the time to it that it needs, so you can get tight or loose depnding how well it's done. No piston manufacturer is going to throw away rings (which I sometimes have to do) because of an error by the guy adjusting them.

Ring packs from Total Seal, KS, Mahle, to name but a few were always made to flawless levels of concentricity and gap. And quite right too - there are few more critical components in an engine. One very good reason alone for using TS.

You are lucky they are tight because, yes the top and bottom rings need regapping to 0.4-0.45mm (14-16 thou").

I would not run 0.25mm in an 84mm bore block of that type. There is an article in GC V/W about gapping.

You did not buy from me but you have come to me for help and that is fine, but the least you can do is tell Iasa. If I had sold those I would have checked them.

GC[/i]

[ICI]

Hi Guy,

Thank you very much for you detailed explanation about the rings in a practice point of view.

I forgot to mention, the bore is 84,5mm , because of the rings size.
They are not available for 84,4mm bore.

I told to Iasa also, but at this moment just automatic confirmation of my e-mail received.

Regards
Iliyan

[Guy Croft]

Yes, I know that, 84.5 and 85mm, I have a source for them but I have learned that you still need to check them every time.

GC