Supertech Pistons, Wiseco rings....which ring gap spec to follow?
 

CLIFF NOTES:
Wiseco Rings on Supertech pistons. Run supertech or wiseco ring gap specs?




Hey all, I have some 84mm wiseco pistons on hand. I have two sets of ring gap instructions.

84mm = 3.30709"

For street/moderate turbo (is 20psi moderate?) Wiseco recommends a top ring bore-multiplication factor of 0.0050" which is identical to Supertechs recommendation.

Top ring recommendations
Wiseco : (3.30709*0.005)" = 0.0165" ≈ 0.017"
Supertech: 0.0165" ≈ 0.017"


The second ring, however, differs between both manufacturers.

Wiseco recommends a bore-multiplication factor of 0.0055"
Supertech asks for the first ring gap x 1.25

Second ring recommendations
Wiseco: (3.3079*0.0055)" = 0.0182"
Supertech: (0.0165*1.25)"= 0.0206" ≈ 0.021"


Since the rings were manufactured by Wiseco, I feel that maybe I should follow their 0.017"/0.018" gaps but when searching, I find folks running larger gaps on their supertech pistons. Does one anticipate the rings expanding more than the piston, and because there is slightly closer p2w tolerance, supertechs run a bit wider?

Any insight would be greatly appreciated. I'll be dropping my stuff off to the machine shop today, I just want to know what to tell them.

I can't really help with the specs since I've never mix and matched different brands like that before, but I will point out that supertech and wiseco use different alloys in their pistons, which have different rates and amounts of expansion, so be really careful with this. 4032 vs 2618

From Wiseco install guidelines:
https://www.miataturbo.net/attachmen...low-wiseco-jpg

Right, this is why I was a bit concerned. It seems counter intuitive, if the piston is expected to expand less, would one keep a tighter tolerance? Or if the rings expand more than the piston, does that force a user to run a wider gap?

haha, maybe I should average them and just run 0.019-0.020"

So when the ring gets hot it expands and this reduced the ring gap. When the piston gets hot it expands and this increase the ring gap. So by that logic if you went to a piston that didnt expand as much with the same rings you would want a larger gap.

Thanks for the input Leafy, that makes sense. Should I be considering a slightly larger top ring gap then?

No idea.

Poo

There is a thread somewhere that emilo explains what rings to use and why (including gap thoughts). Call them and ask them. he runs endurance cars and stuff. I heard somewhere that he's considered and expert or something :dunno:. If you search long and hard enough maybe you'll find the thread. Orrrr if we're lucky he'll just pop in here and get out his baby spoon and feed us.

Yeah sorry I tried to locate it but still couldn't find the thread i'm thinking of. It would be nice if emilio supplied a document on his webpage for installation of his products eh ;). I know this is a combo he sells. Maybe call and if nobody can answer your question e-mail. I bet sav knows the answer too.

If it were me I'd just go with the weisco spec sheet. I'd do Street-Moderate turbo. In fact that's exactly what I did now that I think about it.

There's some of this discussion in my build thread...including some input from Emilio and why he prefers the Wiseco XX rings

I'll dig through the thread, hopefully it has the answers I'm looking for.

The choice was made by following his suggestions. I just don't recall which gap to follow since the pistons themselves came with ring gap instructions. Had I received only one set of instructions, I wouldn't have known any better and this thread wouldn't exist.

I gave 949 racing a call earlier today and left a message. Had to drop stuff off at the machine shop. I guess I'll just update them as soon as I get a definitive answer.

Thanks for the input folks.

Sure do. If you bought the rings from me, just call and I'll let you know what gaps to use.

I didn't purchase from you :(

I'll give you an e-hug? (Or buy a bbk this winter)

The piston expansion has nothing to do with the ring gap in most instances. The rings when compressed into the bore still float in the ring grove of the piston. I would run the gap that the ring maker recommends for your power levels. A more important measurement is the gap between the ring and the ring gland. You need to make sure the ring groves are the same width between the two pistons. There should be a recommended tolerence on that measurement .

I responded to your IM but I'll put it out here as well.
I'm running 949's setup with supertech and wiseco xx.

I had to file top rings (which came out if the box around .012") to .017-.018" somewhere in there. The second rings were .019"-.020" out of the box so I left them alone. Also oil controls were .019" so I left those alone too.

Edit: I was shooting for .017 on the tops but went a tad over on one of them.

Both the low tension ST and near OEM tension Wiseco XX rings are manufactured by NPR in Japan. The piston material has virtually no effect on ring settings for a given ring. Use the Wiseco recommendations for the XX rings included in our piston kits.

Thanks Emilio, i appreciate it