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.

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.

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.

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

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.

Originally posted by bullettdsm
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.

Let's take that exact scenario you just explained and put a different understanding on it. You saw that the old rings on a smoking motor have a large gap. You put on new rings with a "proper" (smaller) gap and the smoking issue is fixed. You then conclude that the large gap caused the smoking. But was this really the explanation??? Here is an alternative view:

Consider *why* the old rings had a large gap. It is because that ring was wearing down on the outer circumference. Over time, the friction between the ring and the cylinder wall slowly wears down the outer surface of the ring. Essentially this leads to a thinner ring. If you wear down the outer circumference of a ring, and that ring's outer circumference is always trying to push outwards towards the cylinder wall, what *must* happen to the ring gap? It will enlarge. The more you wear down a ring, the larger the ring gap will become. But it is not this larger ring gap that is the cause of smoking and reduced compression.

An old, worn down ring will have reduced spring tension. The thinner ring has a reduced ability to press against the cylinder wall, thereby allowing gasses and oil to pass by the ring with ease.

My argument is that everyone notes the obvious characteristic when tearing apart a smoking engine (enlarged ring gap), but the ring gap is not the culprit. It's a red herring. The true issue is one of ring tension.

I would like to support all this discussion with literature, but I'm having trouble finding that radioactive tracer study.

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.

Originally posted by Star Turbo Talon
Actually the top ring has a larger gap than the second ring.

Huh?

Originally posted by RoninEclipse2G

Originally posted by Star Turbo Talon Actually the top ring has a larger gap than the second ring.

Huh?

look at any piston manufacturer recomendations regarding ring gaps.

For Example KIeth Black Hyper Eutectic pistons used in a 383 Mopar.
(taken directly from the spec sheet)

Top Ring Gap factory for N/A Street is 0.0065
Top ring example - 4.000 bore x .0065 gap factor = .026 total top ring gap.
second ring: set second ring end gap at .004 per inch of bore minimum.



Reason being is that the top ring and top edge of piston see the greatest value of heat in the cylinder and will expand far more than the second ring which sees less heat and expansion.

Originally posted by Star Turbo Talon

Originally posted by RoninEclipse2G

Originally posted by Star Turbo Talon Actually the top ring has a larger gap than the second ring.

Huh?

look at any piston manufacturer recomendations regarding ring gaps. For Example KIeth Black Hyper Eutectic pistons used in a 383 Mopar. (taken directly from the spec sheet) Top Ring Gap factory for N/A Street is 0.0065 Top ring example - 4.000 bore x .0065 gap factor = .026 total top ring gap. second ring: set second ring end gap at .004 per inch of bore minimum. Reason being is that the top ring and top edge of piston see the greatest value of heat in the cylinder and will expand far more than the second ring which sees less heat and expansion.

Nice Admin ninja edit. My HUH? was in refrence to your original wording.

How it was originally worded

Originally posted by Star Turbo Talon Actually the top ring has a larger gap than the top ring.

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

Originally posted by Star Turbo Talon
Actually the top ring has a larger gap than the second ring. Any piston or ring manufacturer will confirm this

Huh? Um, no....Where you going with this? Just a quick google to grab something from JE;

http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc4032.pdf

The top ring has always been smaller gap than the 2nd ring ???

Originally posted by bullettdsm

Originally posted by Star Turbo Talon Actually the top ring has a larger gap than the second ring. Any piston or ring manufacturer will confirm this

Huh? Um, no....Where you going with this? Just a quick google to grab something from JE; http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc4032.pdf The top ring has always been smaller gap than the 2nd ring ???

JE has been the only one as of now that ihave ever seen do that. KB and venolia are both the opposite due to expansion rates. Perhaps JE expansion rates are so rediculously large that they need the seconds ring gapped huge.

Edit: Wiseco are the same way as JE. Cant say that is becuase of the forged piston because liek i said Venolia pistons i have do not require the second ring to have nearly as large of a gap. The KB pistons have a very large expansion rate and are not like JE either.

Factory ring gaps had the top ring gapped larger than second ring on all the motors i worked on as well.

It is obvious the main point of this is that to say the second ring is ALWAYS gapped larger than the top ring is obviously and without a doubt WRONG.

Ring end gap is dependant on the piston manufacturer specs and failure to follow those exact specs may result in excessive blowby.

Originally posted by Star Turbo Talon

Originally posted by bullettdsm

Originally posted by Star Turbo Talon Actually the top ring has a larger gap than the second ring. Any piston or ring manufacturer will confirm this

Huh? Um, no....Where you going with this? Just a quick google to grab something from JE; http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc4032.pdf The top ring has always been smaller gap than the 2nd ring ???

JE has been the only one as of now that ihave ever seen do that.{/div} KB and venolia are both the opposite due to expansion rates. Perhaps JE expansion rates are so rediculously large that they need the seconds ring gapped huge. Edit: Wiseco are the same way as JE. Cant say that is becuase of the forged piston because liek i said Venolia pistons i have do not require the second ring to have nearly as large of a gap. The KB pistons have a very large expansion rate and are not like JE either. Factory ring gaps had the top ring gapped larger than second ring on all the motors i worked on as well. It is obvious the main point of this is that to say the second ring is ALWAYS gapped larger than the top ring is obviously and without a doubt WRONG.

So trying to make me think are ya, lol? Aight, I'll give you that damn word ALWAYS (its so all encompassing. All you need is one negative to prove it wrong).

Stock DSM's, stock Neons, stock Honda's, stock VW's, Mahle's, Je's, Aria's, Wiseco's many etc. I'm trying to think back to my Mustang and Pontiac builds (long time ago) but I'm sure that they followed the generic rule of thumb of smaller gap to the top for the reason's I mentioned. I've just never run across any rings that called for a larger gap on top.

BUT I see where you are going with the expansion rates. I do know a builder (as you know every builder has there own way of doing things) who build's some of his race motors with identical gaps. His theory is the same as you mentioned. With the top gap getting more compression and more heat. He came up with this through trial and error (and again noting the importance of gaps sizes. I did mention to him about the engineers arguement and he about fell on the floor laughing. So many engine builders have come up with their gap numbers based on experience. Certain gaps worked better. Too small a gap and you lock up, too large a gap and you get a smoker - or lose power. Just proven over and over again) Inevitably after warm up, you would end up with the same situation of the smaller gap up top.

Originally posted by Star Turbo TalonRing end gap is dependant on the piston manufacturer specs and failure to follow those exact specs may result in excessive blowby.

Yeah, I'd agree with that. Again falling back to the importance of gaps. I'm still wondering if this is all an internet hoax posted up.

Originally posted by Star Turbo Talon JE has been the only one as of now that ihave ever seen do that. KB and venolia are both the opposite due to expansion rates. Perhaps JE expansion rates are so rediculously large that they need the seconds ring gapped huge. Edit: Wiseco are the same way as JE. Cant say that is becuase of the forged piston because liek i said Venolia pistons i have do not require the second ring to have nearly as large of a gap. The KB pistons have a very large expansion rate and are not like JE either. Factory ring gaps had the top ring gapped larger than second ring on all the motors i worked on as well. It is obvious the main point of this is that to say the second ring is ALWAYS gapped larger than the top ring is obviously and without a doubt WRONG. Ring end gap is dependant on the piston manufacturer specs and failure to follow those exact specs may result in excessive blowby.

How are the piston RINGS affected by different PISTON expansion rates? I'm not following you on this. Can you explain?

I'd like to say that I don't think there's a huge difference in temperatures that the top and 2nd compression rings are exposed to. Definitely not enough that I'd open up my top compression ring end gaps to intentionally be larger than that of the 2nd rings.

Personally, I set my top compression rings as tight as possible for the application. Ideally, you don't want a gap at all, in the name of compression and making horsepower... but you have to make sure that the ends of the rings never touch or overlap during the life of the engine. I set my 2nd compression ring end gaps the same as or <i>slightly</i> larger than the top compression ring end gaps, because I believe that trapped gasses can cause ring flutter. Everyone does things differently, and unless you have lots of experience building, modifying and testing engines... it's best to follow the ring manufacturer's specs, and leave the engine voodoo up to the pros. }(

Also, I've been building lots of racing engines the last couple years... LOTS... and I have not seen a single problem with rings binding up when following the ring manufacturer's minimum ring end gap for the application. Remember guys that the manufacturer specs are supposed to be MINIMUM recommended gaps, and it's always a good idea to open them up a couple thousands more just for good measure.

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.

LMAOff........cocksucker.

Yeah, its one thing to come up with a theory that goes against the grain, its another thing to go against real world trial and error proved over and over again. While I'll give them rings spinning like a top (I think most builders are aware of that), I can't give them "gaps don't matter". Its just been too important a dimension.

Originally posted by Star Turbo Talon
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?

I don't think I'm misunderstanding anything here, and I know that no one was arguing against recommended end gaps... I was simply adding my personal practices to the conversation. Just wondering why you think ring end gaps are dependent upon piston expansion rates.

The only connection that I <i>can</i> think of between the piston and the ring end gap is that different aluminum alloys have different thermal conductivity (transmittance) properties. This means that one alloy may transfer more heat to the piston rings than another alloy. In some cases, I think that the top compression ring gap would need to be increased due to it transmitting more heat from the piston to the ring.

Maybe you meant to say piston thermal conductivity instead of thermal expansion. After all, the more thermal conductivity, the less the piston will expand.

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.

Originally posted by ez
You put on new rings with a "proper" (smaller) gap and the smoking issue is fixed. You then conclude that the large gap caused the smoking. But was this really the explanation??? Here is an alternative view: Consider *why* the old rings had a large gap. .

Nope, this is new to new. New rings installed, that were installed with the gaps too large. Fixed by changing gap. Has been seen and done many times.

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 :thumbsup

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.