I just gapped my rings yesterday (wisecos for d16), and I'd have to say they package the pistons with NA guidelines. The slip in the ring bags recommends .004" per 1" of bore for both top and bottom. Then when you look at laskey's info, it is .006" and .0065" per 1", but they have "for turbos only" in bold above.

I really don't know if I'd trust CP on this though. While the may have the most acurate pistons, a good look at the FI archives shows they didn't do their homework on how low to place the ring pack. [Mind you I know most CP failures are precipitated by other problems, but you typically want some room to play when it comes to 150hp per piston] I would definately be suspect about their endgap guidelines as well. They tend to design stuff to the beat of a different drum.

 

Which is exactly why they redesigned their pistons....

I have a new set in front of my now. 81.5mm too (the two that needed the redesign was the 81 and 81.5mm versions 9:1 and 9.8:1)

 

I gapped my top to .012-.013 with my endyn pistons. The bottom was about .016 with no filing. Endyn recommends .011-.013. Seems a little tight but I went with what the sheet says.

 

Now on to the oil rings. Apparently the gaps on these arent really important, as long as they arent smaller than .015". But what if you have 2 different gaps. What is the most logical order? should I put the tightest ring on top or the bottom?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">Now on to the oil rings. Apparently the gaps on these arent really important, as long as they arent smaller than .015". But what if you have 2 different gaps. What is the most logical order? should I put the tightest ring on top or the bottom?</TD></TR></TABLE>

I'd put the tightest one on top, because the motion of the oil ring tends to 'scavenge' the oil in and through the return holes on the piston, so it would make sense to put the tightest ring on top to minimize anything getting past the oil ring.

 

im boosted pushing 30psi and i run mine 18 top 20 bottom

 

Mr. Hyde, are you talking about the top and second compression rings or the oil rings?
And what piston/ring brand are you running?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr HYDE &raquo;</TD></TR><TR><TD CLASS="quote">im boosted pushing 30psi and i run mine 18 top 20 bottom</TD></TR></TABLE>

None of this info helps since you havn't said what size piston you are using....

 

Yeah hes prob 81mm (3.189") bore to be running those specs.

 

Oil rail gaps are pretty meaningless (within reason).Many ring manufacturers use the same rails for a couple bore sizes.There is very little heat at the oil rings (and they are oil cooled).They grow very little.I wouldn't worry about .015" to .050".

 

Actually those are the exact numbers that were recommended to me by Laskey Racing for my 81.5mm build.

 

Everyone needs to remember these numbers are just used as guides. As the "engine builder" we have come to use what we know works. You really have to decide exactly what the motor is going to be used for and that can dictate how to gap the rings. If the rings are are slightly over what you wanted...we are talking thousandths here...its not going to kill you. A motor is pretty dumb and I personally do not think .022 vs. .023 is gonna make any such noticeable difference.

I have seen a motor run with too tight of end gaps and either the ring breaks or it bends up the ring lands and also tears the block up.

 

the only time the ring gap really matters is if its too small

 

If thats true and it doesnt matter that much, then just make one size for each bore. Nobody would needs to file them, everything is loosey goosey and nice and safe. That seems to be the case anyways since half of my rings are too large out of the box to run the tighter specs.

When a manufacturer includes a formula for NA, Race, and FI ring gaps, and then manufacturers rings that are too large to even meet the NA and Race specs, why even bother including different formulas?

I know 1 thousandths isn't going to be the end of the world, I know that. The point is the unfiled rings were bigger than they should of been. CP tried to tell me my bore was too big and it was my fault. I asked CP to exchange ring sets but they would not. So I bought another ring set and magically those were good as I had to file them to get the gaps I wanted. With that being said, now I have the gaps I want but I had to waste another $100 bucks on rings and I shouldn't of had to do that.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">If thats true and it doesnt matter that much, then just make one size for each bore. Nobody would needs to file them, everything is loosey goosey and nice and safe. That seems to be the case anyways since half of my rings are too large out of the box to run the tighter specs.

When a manufacturer includes a formula for NA, Race, and FI ring gaps, and then manufacturers rings that are too large to even meet the NA and Race specs, why even bother including different formulas?

I know 1 thousandths isn't going to be the end of the world, I know that. The point is the unfiled rings were bigger than they should of been. CP tried to tell me my bore was too big and it was my fault. I asked CP to exchange ring sets but they would not. So I bought another ring set and magically those were good as I had to file them to get the gaps I wanted. With that being said, now I have the gaps I want but I had to waste another $100 bucks on rings and I shouldn't of had to do that. </TD></TR></TABLE>

Who did you buy them from? If you had gotten them from me, I would have exchanged them for free Glad the 2nd set you got worked out for you.

 

First set came with the piston set (SC7020 with rings CPN3307) which I purchased from your dad about a year ago. Second ring set came from RaceEng. I know you would have replaced them and I appreciate that. But I dont want to stick the vendor with the cost, its the manufacturers problem.

If anybody needs rings. I have 4 unfiled ring sets - CPN3307

 

we have tried it all and it really dosnt matter, as long as the 2nd ring gap is bigger than the top you're good.

does everyone go by the piston-wall specs they tell you.. if everyone did then you'd have alot of motors with scuffed pistons. a small difference in bore can have a big effect on the ring gap. i have built motors with ring gaps to hte piston mfrs "specs" and built em looser than **** and there is no difference in the performance of the engines.

 

I noticed on my last build with loose ring gaps that it always had low compression test results. 170-180psi range. With tighter CP ring gaps it was ~190psi. Maybe just a coincidence.

 

i havent seen any consistent results with bigger ring gaps, hell my buddys 84mm b16 with wiseco -18cc pistons and big chambers (around 8:1 maybe a hair less compression) has 190psi compression, we set the top ring to 22thou, the bottom to 28thou.

remember cams and cam timing can play a big role in static compression. also, the quality of the hone can be a big factor as well as proper break in with said hone. if you have a rough hone and break it in hard youre compression will be low, if you have a fine hone and break it in easy you will have lower compression number, there are tons of factors and you have to take them all into account.

somethings dont matter enough to worry that much about.. now if i got some rings that were like 0.040 or some garbage id deffinatly get a new set.. hte last replacement set i got from wiseco came out perfect, i told them the finish bore and the ring gap i wanted, they sent rings that were spot on.