phase12gsr

Does anyone know the ring-end clearance for 81mm 9:1 CP pistons? On the sheet supplied with the pistons it only states "clearance: 0.0035" which is probably for the piston-wall clearance isn't it?

Flamenco-T

CP has zero clearance for piston to wall specs, the pistons are machined exactly to the bore size minus the needed clearance. For example, if you purchased an 83mm pistons and require .0020 clearace, than your actual size of the piston diameter is 83mm minus the .0020.

as far as the ring end gap, it is usually the static number multiply by your bore size, typically around .0015-.0018. Check with Earl for the exact static number.

stan

earl

CP does not give ring gap clearance specs because they feel it is the engine builders call rather than the piston builders call. When I really stopped to think about it, they were correct. CP told me a number to use for my builds but I didn't like it and continued to use what worked for me in the past. I use the .006" per inch of bore for the upper and .0045" per inch of bore for the middle. This is the current JE specs and they always worked in the past so I keep using them. Current thought has the second ring a little looser that the first but I just can't swollow the logic of that.

phase12gsr

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">I use the .006" per inch of bore for the upper and .045" per inch of bore for the middle.</TD></TR></TABLE>

Is that .045 per inch for the middle ring or .0045 per inch? .045 seems like a lot

dennis

I just asked Rocket the same question:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
Quote, originally posted by dennis »
exactly what I need to hear - thanks rocket! I'm gonna have to get ring gaps from you at some point as well.

Turbo right?

Do like .017 top and 0.019 second for your size bore for turbo. (85mm bore right?). Use honda gap orientation.
</TD></TR></TABLE>


Modified by dennis at 1:36 PM 10/20/2003

earl

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by phase12gsr &raquo;</TD></TR><TR><TD CLASS="quote">

Is that .045 per inch for the middle ring or .0045 per inch? .045 seems like a lot</TD></TR></TABLE>Oh, ****, I should not post at 2AM.
I meant .0045" per inch of bore.
Sorry

93LSivic

Earl, what is your reasoning behind not using the JE current 2nd ring gap of an equivalent top ring gap? I have used both and had luck with both gaps.
After seeing that JE updated the revision in the ring gap sheet i was baffled and quickly made a call to JE tech support. They said they get lots of feedback from engine builders and thats why they changed the spec recommendations.
Im using a .0019" for top and bottom right now. I havent had time to do a leakdown test, but all seems fine.

earl

You do mean .019", not .0019", correct? I did not even know about the change of numbers by JE. I don't think that it makes their old numbers wrong. It is just a change in building philosophy. I just go with what I know has worked in the past but I may start to rethink the numbers a little.

93LSivic

Heh, yeah .019 After talking about piston/wall clearances in another thread I got used to adding that extra 0.

I guess if it works, then why change it I guess it really comes down to paying attention to leakdown then disassembling and examining piston ring grooves etc. and taking into accounts the duty that the engine went through. After that is all taken into consideration then maybe looking into changing specs around.

Suprdave

Clearance depends on the use of the motor and things like that.

Also depends on piston material and how much it expands when heated.

Can be as small as .0028 and as large as .0060. It depends on application.

Suprdave

hpfsi

Ok I'm gapping some rings tonight so of course this thread had me thinking about things when I first read it a little while back.... and so I did some more reading. Why gap the second ring a bit looser than the top ring?

Well here is what I found - basically it serves the same purpose as gas-porting (for the top ring) of a piston. You don't want to rely on the second ring for compression purposes, as this will counteract the function of the top ring. Obviously combustion pressure is used to force the top ring downward and outward so that it seals against the bottom of the ring land and the cylinder wall. If (or when rather) any amount of pressure gets by the top ring, you don't want the second ring to completely trap this pressure, as it can cause the top ring to flutter up and down because there is now pressure coming from below the top ring as well as above it.

So basically attempting to eliminate blowby by running a tighter second ring end gap is counterproductive. The only way that would work would be if you had a truly gapless ring. Total Seal tried making one for the second ring and the results were disappointing. Apparently they have or are changing their design to a gapless TOP ring instead based on race team feedback. But basically the whole gapless ring design is somewhat flawed and better results can and will be achieved from file-to-fit rings. From what I read, many NASCAR engine builders have settled on second ring end gaps looser than the top ring (this has been working better than gas-porting even), and GM is starting to use this theory on their new V-8's as some concepts do trickle down from race engine development to mass-production.

The only hard number I could find for second ring gaps was .004" more than the top ring. So if you are running .019" end gap on the top ring, you'd want .023" for the second ring end gap. We'll see I guess - I'll probably go with something a tad less dramatic

*edit* Just checked honda specs for the b16a2, and the upper end of the range was .014"/top and .022"/second.



Modified by hpfsi at 5:06 AM 11/9/2003

earl

I agree with everything you have posted but here is the flaw in the logic...
The upper ring is made from a different material than the second ring. The upper ring sees way more heat than the second ring. As the motor is at operating temperature under a strong boost, I feel that the gap has already tightened more than the second ring therefore giving a smaller gap than the second already. Starting it out that way at the build may throw the gaps way out of kilter under extreme use. This is my thought process of why I don't use a larger second gap than the first...I could be wrong.

Johnyquest

I was under the impresson that the easiest way to do this (if going stock bore size) is to just buy honda rings (pre gapped). I think I read on teh endyn website that that's what he does.

As far as gapping aftermarked rings, I wish I could be of more help.
...when me and my dad were rebuilding the camaro's 350, we just threw them in and said ****-it. It worked

earl

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnyquest &raquo;</TD></TR><TR><TD CLASS="quote">I was under the impresson that the easiest way to do this (if going stock bore size) is to just buy honda rings (pre gapped). I think I read on teh endyn website that that's what he does.</TD></TR></TABLE>Stock rings will not work on an Endyn piston. Larry uses custom made rings.

quickergixxer

hey earl howmuch extra to fit my new je rings i allready sent you the block and pistons

Rick

earl

Just send them or I will teach you to do it yourself,

Johnyquest

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">Stock rings will not work on an Endyn piston. Larry uses custom made rings.</TD></TR></TABLE>

my fault-- thanks.

93LSivic

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">Stock rings will not work on an Endyn piston. Larry uses custom made rings.</TD></TR></TABLE>

Forgive me, I have no first hand knowledge of Endyne RW pistons. Now, to get to the truth, are these Wiseco pistons that Larry only simply touches the top or are these actually custom made for him.
Secondly. Why do they use a custom ring? Does his pistons have a different side/back clearances than the industry standard?? Or does he use a different type of ring material for top/bottom rings?

Im interested in this due to the fact im in the market for a different piston in my motor again. Im looking into CP but I may be willing to try RW's.

Thanks Earl.

hpfsi

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">I agree with everything you have posted but here is the flaw in the logic...
The upper ring is made from a different material than the second ring. The upper ring sees way more heat than the second ring. As the motor is at operating temperature under a strong boost, I feel that the gap has already tightened more than the second ring therefore giving a smaller gap than the second already. </TD></TR></TABLE>

That is how I had always figured things as well... The little bit I found about nascar engine builders using a larger second ring end gap apparently resulted from rather extensive research with big budget toys (ie thermal imaging and ultra-high speed camera work). More than one way to skin a cat I guess .

BodyKits NW

I would also like to know why people recommend a larger end gap on the bottom ring? This is a real good topic for those looking to start engine building.

earl

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BodyKits NW &raquo;</TD></TR><TR><TD CLASS="quote">I would also like to know why people recommend a larger end gap on the bottom ring? This is a real good topic for those looking to start engine building. </TD></TR></TABLE>Not the bottom ring (oil ring) but the middle ring.
Here is the reason, right or wrong. Boost (pressure) escapes past the top ring. It can collect in the groove between the upper and middle ring. When that groove is filled, the pressure goes down to the middle ring. If it cannot escape there, it will push it's way back up to the top ring and try to unseat it or unseat the middle ring causing oil control problems. By having a larger gap in the upper ring, it makes it easier for the pressure to go back to the combustion chamber, neutralizing the problem.
If anyone has a more clearer explanation, feel free to help me on this. I don't think I have a good grasp on this.

dennis

Okay, speaking of CP rings - Is there a difference between the top and middle rings and if so, is there a "top" or "bottom" of the ring? Don't have them in front of me, but I thought I remember reading such a thing. If so, how can you tell? thanks.

93LSivic

To clear up some confusion....or the possibility of confusion. I generally speak of rings in terms of top & bottom, or 1st & 2nd. Both of these being the compression rings. Oil rings I never talk about in in reference to this thread's discussion simply because these dont get altered ever...altered meaning filed to fit.

Now. I under stand what you are saying Earl. Basically you dont want positive boost pressure caught in between the rings causing upload (or download) on either the top or bottom rings. This puts pressure on ringlands, and being honda people we all know that oem honda ringlands are the first to go after FI is added to the engine-----not related to do with the strength of aftermarket pistons, but a simple example of what happens to ring lands.
Fact is that blow by is needed in a FI motor. I experiment with my engines and have found that equal gap or a larger top gap is ok.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dennis &raquo;</TD></TR><TR><TD CLASS="quote">Okay, speaking of CP rings - Is there a difference between the top and middle rings and if so, is there a "top" or "bottom" of the ring? Don't have them in front of me, but I thought I remember reading such a thing. If so, how can you tell? thanks.</TD></TR></TABLE>

YES! There is a difference in the CP rings, mostly all rings for that matter. Bottom ring is a different material and is far easier to file---be careful when fitting this one especially after filing the top ring first!. Actually they are 2 different sizes in thickness, so you cant really get them confused.

Scott - 93HB Si

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93LSivic &raquo;</TD></TR><TR><TD CLASS="quote">
Now. I under stand what you are saying Earl. Basically you dont want positive boost pressure caught in between the rings causing upload (or download) on either the top or bottom rings. This puts pressure on ringlands, and being honda people we all know that oem honda ringlands are the first to go after FI is added to the engine-----not related to do with the strength of aftermarket pistons, but a simple example of what happens to ring lands.
Fact is that blow by is needed in a FI motor. I experiment with my engines and have found that equal gap or a larger top gap is ok.
</TD></TR></TABLE>


That pretty much explains it....You'll find that with the pressure building up in between the 2 rings you'll actually get the rings lifting off the wall a little. If you gap the 2nd ring bigger than the top one, this will allow any built up pressure to vent out.

I usually gap .004 per inch on the top and 0.05-0.06 per inch on the bottom.

Remember - Unlike Women, when it comes to gapping rings it's always better to be a little loose than too tight!

Suprdave

CP Middle Rings break really easy....Incredibly Brittle. Im talking about when putting them on the piston, heh.

Suprdave