This is a written arguement regarding ring gaps and ring gap staggering by a particular group of engineers. Very good arguement that i find hard to rebuttle.

http://www.triplesdownunder.com/Interesting_Stuff/piston%20ring%20gaps.doc

That was a good read.

__________________________________
-Ryan

There is no rebuttle, because it is true.

I've discussed this topic before but most people rather rely on their wive-tales knowledge of the subject.

I recall an excellent experiment where they put a radioactive tracer on a fresh ring set and then simply observed the movement of the tracer. The conclusion: Rings have a rotational rate of 5 rpm at idle.

So, and here comes the really juicy part- what does this mean in regards to the concept of "ring seating", new engine break-in, and the practice of honing?

Truth be told, rings don't seat in the view that they eventually wear into the cylinder walls and stop rotating. If you look at the surface of a cylinder with some good miles on it, it is completely smooth. This quality makes it a perfect surface to work with the ring in stopping gasses/fluids from passing by. It also means when you hone a cylinder, you are actually making the surface imperfect and causing nothing but wear. It's not until the cylinder wall has worn down into a smooth surface that the engine is "broken in" again and it stops eating oil.

And finally, what causes blow by on a worn ring? (hint, it's not the widened ring gap.) It's the lack of ring tension. Due to wear, the ring is not pushing against the wall of the cylinder with enough force to prevent blow by.

2gnt: '99 RS-T, killed by a toyota, pending rebuild...
Daily: Volt
Daily #2: '99 EVG ebike- STOLEN by PEDRO

Quite interesting. I think I'll keep staggering my rings on installation, but it's nice to know if I pull them out and they're not staggered it doesn't mean a damn thing.

Erik P.
Official 2GNT thread Hijacker
Some say that he's driven over more Covenant than he's shot, and that his grenades aren't where you'd expect them to be...
All we know is, He's not The Stig... But he is The Stig's Spartan cousin!

Ring seating has been known for years......no issue there and its been proven.

The day you can yank a piston and reset the piston back in the bore and get the same compression will be the day you have an arguement.

Please explain the mechanism

2gnt: '99 RS-T, killed by a toyota, pending rebuild...
Daily: Volt
Daily #2: '99 EVG ebike- STOLEN by PEDRO

Been so damn busy, but wanted to post up to the thread.

Yeah, curious info. Not fully buying in.

Ok, I've always felt that the rings do not stay in their place. I just did not know how far/fast they moved around. The idea of staggering new rings was, with the concept of starting at a "good" place. My thought process was that the rings do need to work the walls to seat. Now, in my thinking, I wanted to have the ring gaps as far apart as possible to give them the best chance of not aligning while they break in (this does not count the oil ring. I've always considered them a separate entity. Just don't align the gaps of the top and bottom half of the oil ring).

Now my official advice has always been the 120 degree rule so that nobody would come after me and say I blew their engine.

So my thinking was that the rings would spin but movement would be slower than the 5 mph quoted by ez. And I was figuring on the two rings to move at close to the same rate, so that the gaps would stay apart (not for the life of the engine, but long enough for break in).

So yeah, I would go with their assessment of the rings moving.

Sorry, can't buy the gap theory. Their findings would have to be repeated by others and then they would have to explain how I (and many others) have fixed smoker engines (or low compression engines)that had new rings put in, by putting in new rings with the correct gap. I have absolutely done that.

Who hasn't seen someone complain/post up about their engine with the new rings that smokes or has bad comp in a cylinder or two, only to find out they have ring gaps too large. Or the cylinder is past its spec. Hey, with their theory I wouldn't have to worry that much about spec, because the gap could be a .030 with a hone and I wouldn't have a problem, right?

As far as the gap difference between the top and bottom rings, you MUST have a larger gap on the second ring so that you don't basically use the second ring as your main compression ring. As they pointed out, there is compression between the rings (this would seem to contradict their theory a bit on the importance of gap size. It points out that indeed the gap DOES mean something). If you use your second ring as a primary compression ring, chances are you will run into ring flutter/chatter and possibly broken ring landings (those who want to buy in to their theory are welcome to try making a larger gap on the top ring and see what happens).

But who knows, this could all be some internet hoax with made up results, lol.

As for me, I'll continue to build the way I have built previous to this. Why? Because it is known to work and I have not seen any/enough conclusive evidence to the contrary. As a matter of fact, I have only seen emperical evidence that contradicts what they say.

Of course, they would say "That's what we figured an old engine builder would say" lol.

Captain Caveman

96 RS Turbo 11.414 @ 119.62 MSNS, Crower 2 NA cams, BW366, 10.5 comp, UDP, 60mm TB, W/A intercooler, 3.55 tranny 567.9whp 430tq
97 RS NA 13.188 @ 103.87 MSnS powered 12.5 comp, Crower 3's and 219.4whp with 175tq
98 RS DD 12.5 comp on stock ECU, LTH, Crower 2's, Koni, GC, Hypercoil, DG hats
99 OZ 5sp Stocker 15.856 @ 85.97
99 GS stocker auto 17.7@77mph!

wiki home page:http://www.2gnt.com/index.php?d=bullettdsm

2gnt: '99 RS-T, killed by a toyota, pending rebuild...
Daily: Volt
Daily #2: '99 EVG ebike- STOLEN by PEDRO

Actually the top ring has a larger gap than the second ring. Any piston or ring manufacturer will confirm this and this is how i have run my motors since i began building them.

As for staggering.....i have done both 120 Degree and 180 degree. Today i do 180 degree and will always do so.

Erik P.
Official 2GNT thread Hijacker
Some say that he's driven over more Covenant than he's shot, and that his grenades aren't where you'd expect them to be...
All we know is, He's not The Stig... But he is The Stig's Spartan cousin!

Erik P.
Official 2GNT thread Hijacker
Some say that he's driven over more Covenant than he's shot, and that his grenades aren't where you'd expect them to be...
All we know is, He's not The Stig... But he is The Stig's Spartan cousin!

Ha ha yea, I've noticed Terry does that a lot

2gnt: '99 RS-T, killed by a toyota, pending rebuild...
Daily: Volt
Daily #2: '99 EVG ebike- STOLEN by PEDRO

Captain Caveman

96 RS Turbo 11.414 @ 119.62 MSNS, Crower 2 NA cams, BW366, 10.5 comp, UDP, 60mm TB, W/A intercooler, 3.55 tranny 567.9whp 430tq
97 RS NA 13.188 @ 103.87 MSnS powered 12.5 comp, Crower 3's and 219.4whp with 175tq
98 RS DD 12.5 comp on stock ECU, LTH, Crower 2's, Koni, GC, Hypercoil, DG hats
99 OZ 5sp Stocker 15.856 @ 85.97
99 GS stocker auto 17.7@77mph!

wiki home page:http://www.2gnt.com/index.php?d=bullettdsm

Captain Caveman

96 RS Turbo 11.414 @ 119.62 MSNS, Crower 2 NA cams, BW366, 10.5 comp, UDP, 60mm TB, W/A intercooler, 3.55 tranny 567.9whp 430tq
97 RS NA 13.188 @ 103.87 MSnS powered 12.5 comp, Crower 3's and 219.4whp with 175tq
98 RS DD 12.5 comp on stock ECU, LTH, Crower 2's, Koni, GC, Hypercoil, DG hats
99 OZ 5sp Stocker 15.856 @ 85.97
99 GS stocker auto 17.7@77mph!

wiki home page:http://www.2gnt.com/index.php?d=bullettdsm

Here are a few ring specs

2001 PT cruiser
Top Ring .009-.020
Second .009-.018

94 LT1 z28
all compression .035

84-88 2.2L Dodge Shelby (daytona)
Top Ring .010
Second .009

97 Ford Cobra (shitbox)
Top Ring .25-.51
Second Ring .23-.49

Now granted I pulled specs of motors where the top ring is larger end gap........i know, i am selfish. Many others had Compression Ring gaps that were the same and some had top ring gap smaller. I think in fairness we could find examples at a 1:1 ratio.



Doug: I think your misunderstanding. No one here argued agaisnt recommended specs. Infact the point of increasign the gap based on application was mentioned previosuly if not here.

As for why the ring gap is based on Piston expansion rate....well I cant answer that (other that thats what the piston manufacturer tell you) but answer me this then. Why do you get the recommended gap from the piston manufacturer and not the ring manufacturer?

The recomended gaps are not consistant enough to say that forged pistons follow this rule and hyper eutectic use this rule. KB as far as I can tell, always recommend a smalled ring gap on the second ring regardless of piston type. Factory Pistons (aka manufacturer Recommended) tend to vary from car to car. Weisco appears to support a second ring larger end gap.

The whole point that Mark and I are hinging on is the the ring eng gap spec from the piston manufacturer must be followed and tailored to the application. most all aftermarket piston manufacturers do list for multiple types of applications.

how critical .001 accuracy actually is has yet to be proven in terms of Ring Gap. As you can see that is a discussion based on the post I initially started.

I have a very hard time accepting that ring gap is insignificant. As far as your choice of Ring gap size, I like most machinest in my area choose a smaller ring gap (within spec) on the second ring and i enlarge the ring gap proportionately to the application. I have not queried every shop in the area nor do i plan to. I have yet to have a ring sieze or have compression issues.

This is one of those things where there truely is not right or wrong answer but personal preference. Hence the whole idea of posting this.

What I really want to know is......do you think the rings were concerned with ring gap when Mark's timing belt decided he was too abusive and wanted a divorce?

I have also wondered what End Gap Noah used when he built the arc....Since Mark was there I expect he has the answer

Yes i have been waiting to make my jab.

Originally posted by Star Turbo Talon
What I really want to know is......do you think the rings were concerned with ring gap when Mark's timing belt decided he was too abusive and wanted a divorce? I have also wondered what End Gap Noah used when he built the arc....Since Mark was there I expect he has the answer Yes i have been waiting to make my jab.

Captain Caveman

96 RS Turbo 11.414 @ 119.62 MSNS, Crower 2 NA cams, BW366, 10.5 comp, UDP, 60mm TB, W/A intercooler, 3.55 tranny 567.9whp 430tq
97 RS NA 13.188 @ 103.87 MSnS powered 12.5 comp, Crower 3's and 219.4whp with 175tq
98 RS DD 12.5 comp on stock ECU, LTH, Crower 2's, Koni, GC, Hypercoil, DG hats
99 OZ 5sp Stocker 15.856 @ 85.97
99 GS stocker auto 17.7@77mph!

wiki home page:http://www.2gnt.com/index.php?d=bullettdsm

Doug, I have siad it already and i will say it again. I DO NOT KNOW.

Ring gaps are based on the piston not on the ring material. Apparently you are missing that point. Call anyone of your Piston manufacturers and argue with them.

Terry, I wasn't trying to argue with you. Just interested in a good discussion and hoping to learn something.

Captain Caveman

96 RS Turbo 11.414 @ 119.62 MSNS, Crower 2 NA cams, BW366, 10.5 comp, UDP, 60mm TB, W/A intercooler, 3.55 tranny 567.9whp 430tq
97 RS NA 13.188 @ 103.87 MSnS powered 12.5 comp, Crower 3's and 219.4whp with 175tq
98 RS DD 12.5 comp on stock ECU, LTH, Crower 2's, Koni, GC, Hypercoil, DG hats
99 OZ 5sp Stocker 15.856 @ 85.97
99 GS stocker auto 17.7@77mph!

wiki home page:http://www.2gnt.com/index.php?d=bullettdsm

That's what my understanding was initally but after reviewing some engineering discussions, ring gap size seems much more insignificant. I would guess something else was occuring in the situations you just described. Interesting topic

2gnt: '99 RS-T, killed by a toyota, pending rebuild...
Daily: Volt
Daily #2: '99 EVG ebike- STOLEN by PEDRO

The only problem i have with engineers making up the tests is that they always leave out real life situations that become a factor.

Fort example on the test above, they were able to prove in that motor with that particular bore, stroke, piston ring design ect that the ring gap didnt matter to some degree.

However since there are so many variables missing such as fuel type, cylinder condition (was this test taken on a set of rings broken in? or fresh out of the box?)

If these tests were taken with fresh rings that arent seated then there is blowby to start with and the ring gap will be less significant.

Without details on the limitations of the tests i find it hard to accept that you can file a set of rings to whatever you file them to and expect there to be no difference in performance. the other factor that i wonder about is that.....we have been driving cars since the 1900's.....it has taken engineers 100 years to figure this out? Bullshit.

Staggering them I understand, i see no way that the rings dont move. However i will stagger them just to keep my practices consistant.