Supertech forged pistons 9 or 8.5 @ 1?
 

Purchased this forged piston set from Adam
adam@nolimitmotorsport.com
631-363-8659



Do these pistons look about right for 9@1 SuperTech pistons?

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According to the serial number they seem are suppose to be 9@1, but who knows if it was packed incorrectly.

By the way, the pics were taken with a Nikon D1H with a NON/AI 55mm macro lens, no PP.

Look like 9:1 to me, but what do I know.

Here's my 8.6:1:
http://i34.tinypic.com/i5rp1c.jpg

They aren't 11:1, so you're on the right track. :P

They look just like my 9:1 pistons... but so do Hustler's. This has me wondering now too. :confused:

Do/did you guys take something to the edges to smooth them out?

I think they are 8.6@1...

I got the Miata cast 10@1 and have a very high dome, the Kia Sephia cast 9.5@1 have a slight more conservative dome. The Ford Escort GT or Mazda Protege LX (cast) 9.0@1 are FLAT and thats when I think these are really 8.6.

I have seen Mazda DX 1.8 SOHC casted 8.5@1 and are a little bit deeper on the bowl.

One of the things I find strange is the guy told me the 9@1 were back-ordered and all of a sudden I got them within a week or so.

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I will give them a call to see if they can provide pics of both.

Looking at the chart they do make 8.6 84mm.

The only minor difference between the two is the center circle of the alleged 9@1, the 8.6 does not have it, but that could simply be a change in the mold.

I bought a set of Supertech 9.0:1 from emillio@949 last week. I was told they were back ordered also, several days later they showed up at my door. I've already taken them to my builder, so no pix, but from a casual glance they look very similar.

The 8.6:1 and 9:1 *could* have the exact same dish but with the only difference being the 8.6:1 being a bit vertically thinner.

It looks like that Supertech spec table Dome/Dish column is wrong for the 84mm 8.6:1 since it's saying it has a dome rather than a dish. Looks like the 84mm 11:1 and 8.6:1 have that Dome/Dish column data point incorrectly swapped.

If this is true then the 84mm 8.6:1 and 9:1 have the same Dome/Dish of -4 with only difference being the Comp Height of 30.5mm for the 8.6:1 and 30.7mm for the 9:1.

I second Tim's question: Should the sharp edges be smoothed? Or does the surface of the piston have a special finish that shouldn't be removed? Obviously this wouldn't be done if it was already ceramic coated.

Anyone else notice the intake valve "pocks" are larger than the exhaust? Oh well, I'll keep driving.

When you say pocks, do you mean reliefs? Intake valves are bigger:dunno:

Let me see if I can upload a pic of the cast 10@1 side by side with the forged 9@1. the height is the same. I got cast 9@1 from a spare block, but they are not outside the block and those are nowhere close to the forged ones.

I ordered 9.0:1

https://www.miataturbo.net/picture.p...&pictureid=727

About smoothing out the sharp edges, feel free to give a call to SuperTech.

http://www.supertechperformance.com/

Supertech Inc.
3580 Charter Park Dr, San Jose CA 95136
Ph. 408-448-2001 / Fx 408-448-3700
www.supertechperformance.com

I sent SuperTech an email about smoothing the sharp edges. We'll see if they respond.

Any smoothing would probably have to be done by hand. This would make it very hard to do consistently. I'd be afraid of ending up with piston weights that are unbalanced. Or ending up with a few sharp edges that would be more detonation prone than leaving the big sharp edges. So this is not really something I'd have done.

Not to keep bleeding out this thread, but I have made some and some not progress.

Called Nolimitmotorsports and they guy stated there is no visual difference between the two. To me that is total BS, I can tell which is which by a quick glance from 10,9.5,9 and 8.5. The funny thing was he would be it is not .5 difference is .4. That by the serial number it is the correct one as if typo errors never happened, by the way it is not that it is engraved on the piston, just a sticker in the packaging.

Well, called Supertech as NoLimit was a waste of time. Tech support immediately agreed to send me a picture of 9-1 f pistons, so here they are...

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Immediately the first difference is the center ring on the face of the piston that is missing, unless castings or whatever in design change from time to time. It does look more like 8.6 as all the ones posted here missing the center circle are that compression. The tech agreed to send me today pics of the 8.6, and he also said there is no visual difference (once again). He stated the pin is slightly different between the two something like .02 or W/E machine shop talk he threw out.

Is that a typical trend, To change compression by placing the piston higher or lower by moving the pin location?

That is pretty common actually. When you really boil it down, the difference between 8.6 and 9 to 1 pistons is very small. Going from dished to flat faced valves can give you a similar change in compression. I'm far too lazy to actually do the math at the moment but I'm betting the volume change between the two compressions is on the order of <10 cc.

Moving the wrist pin is pretty weak, I guess I could have run a fatter head-gasket if all else is the same. Next time I'll run a different piston and get better quench.

Supertech email reply:

"We currently do not have any of the 8.6:1 on the shelve, there fore I can not get you a picture."

-Martin

For those who say that there is no visual difference:

http://www.liptonius.com/miata/missi...ncompareTN.jpg

Before the link to that picture would maximize, but AOL closed the link and this is the one I could find.

From left to right; 9.0,9.5,10. Even on such small image the differences are noticeable.

VanMSM:

Just talked to Willy from the technical department about the valve pockets sharp edges. Rumbling through ideas/suggestions more or less concluded to use emery cloth with WD40 or with valve lapping compound. He stated it WILL NOT affect warranty, in the contrary it is a very good idea to smooth the edges to minimize hot spots.

Also stated NOT to touch the outer diameter of the head of the piston, ONLY concentrate on smoothing out the valve pocket edges.

that picture is retarded small.