First Look
SuperTech Pistons

PN# P4-MA8350-N4

Bore Over Size Comp Ratio Volume CCs Head CCs

83.50mm +0.5mm 8.6:1 -4cc 50


Height Stroke Rod Length Pin Diam Weight

1.201"(30.5mm) 3.346" 5.228" 20mm 293g


Ring P/N Note
P4-MA8… GNH-8350


I have a set of factory sealed pistons for a turbo build on a 1.8l



Open the box and this is what I see, pistons still sealed in there bag with wrist pins.



I see a nice label on each piston with the pertinent info.
Part Number checks with what is on the box.
Proper bore size listed.
Piston weight listed at 278g
On all 4 pistons, We will see.

On the Supertech website,
http://supertechperformance.com/cata...ection=pistons
They are listed to have a weight of 293g
15g difference between posted info and what is in the box.

Now to get them out of the packaging and give each a quick look over for any shipping damage.
Top looks good

So do the bottoms and the ring lands.


Now to weigh each one.



Piston #1

This piston was jumping between 279.0g and 279.1g

Piston #2

278.8g

Piston #3

278.3g

Piston #4

This one bounced between 279.4g-279.5g

So piston #3 is the lightest at this point.

Next is to weigh the wrist pins.
As you saw in the above pic, the wrist pin was packaged with the piston.

Wrist pin #1

98.7g

Wrist pin#2

98.3g

Wrist pin #3

98.4g

Wrist pin #4
Sorry, no pic
99.4g

The weight difference is rather wide for wrist pins.

Now , to weigh the combo and get the combined weight of the piston and wrist pin.

Combo #1

377.8g
Combo #2

377.2g
Combo #3

376.6g
Combo #4


378.8g

So we have a range of weight from 376.6g lightest to 378.8g heaviest.
The average weight is now 377.5g

Now since the wrist pins have such a variance of weight, I will swap them around some and see if I can get them closer.

Piston #1 with wrist pin #2

377.4g

Piston #2 with wrist pin #1

377.5

Piston #3 with wrist pin #4

377.8g

Piston #4 with wrist pin #3
No pic, Sorry
377.9

Well, now this is a whole lot better, Now the weight difference from lightest to heaviest is .5g

Now to check the wrist pin clips and see how close they are.



10 for 10 C clips weigh .8g each.

They can be hung on the rods at this point, But I want them closer.
My lightest now is 377.4g

With a touch on a belt sander, on the lip by the wrist pin boss, I will remove some weight.


I buffed on 3 pistons to get a matched weight of 377.4g

Piston #2 needed .1g removed

Piston #3 needed .4g removed

Piston #4 needed the most removed with .5g

So you have an idea how much a gram weighs, Hold a dollar bill in your hand, That is 1g

A nickel weighs 5g

My over all opinion of the pistons is not too bad, the fit and fish looks good to the naked eye, but the out the box weights need to be checked.

As far as the website posted weight of 293g being off by appox 15g

The label weight of 278g being off by appox 1g

Supertech needs to update its website.

The label weight is close enough to work with.

 

What is your opinion of the sharp edge by the exhaust valves? I have seen several supertech pistons that were burned or melted there.

 

The ones I have in my hand have a slight champher on all the valve reliefs, and the reliefs do not extend into the edge of the piston like I have seen on some others.

Have pics or links to the melted pistons you speak of?

 

https://www.miataturbo.net/engine-performance-56/built-motors-detonation-42072/

 

He means this:
Any comments on the intake "eyebrows" and how little meat there is to the edge?
They like to fail there. Granted this one probably detonated but...

 

If you look at Pic #2 in this thread..
https://www.miataturbo.net/showthrea...349#post861349

A milder form, yes, but still the start of it.

If I need to hand touch up the valve reliefs, I will.
I will have to look into what the pistons are coated with.
I rather avoid a burnt piston from another form.


I would agree with too much inginion timing under boost,
With the commonly used tuning device of the board, Does it have an active role in ingtion retarding?

Or even a boost refrance that will pull timing? Think MSD 6BTM.

Also what are most you guys running for ring end gap?

 

Megasquirt ECU is popular here.

"roll in retard" - do you mean tip-in acceleration retard?

My AEM ECU FWIW has it.

 

How does ring end gap affect detonation?

 

Do not freak me out in this thread, please.

 

Jason, What I ment was does the knock sensor have an active role in pulling timing, based on the knock count the sensor picks up.

By the time your ear can hear the knock, it is too late.

Fae, That was an after thought question to see what the fourm tends to use.

I tend to like a tad wider ring gaps for a little padding insurance.

Most of the time cracked/busted ring lands are from the ring gap butting, then the ring flexes and breaks the land.

This happens from a lean condition, or a non-boosted engine going boosted.

Husler, I will try not to freak you out.
Just hug your teddy bear and all will be ok.

 

role vs. roll.

many of the ecus have active knock sensing. the megasquirt 3 is a work in progress. a few beta testers are running the knock code (e.g. me) but it's not mass-market.

Until I got the hardware to sense knock, I didn't know for sure if there was any. Now I know there is and I've addressed it by trimming fuel to each cylinder and backing off timing.

Even an active retard is still waiting for detonation to occur at some level before it pulls timing.

 

y8.. Sorry for the misuse of words.. I was I bit wore out last eve when I wrote this.

I am used to to reading about DSMLink, But what I know about ECU tuning would fit in a thimbel, and have room left over.

But what I have learned about link is that it can pull timing out as low as 1 or 2 counts.

I did not know if the setup that the Mazda was as sensitive or not.

Now on my Ford TC, I use a Vortec SC boost refrance ingnition box, it will remove 1-3* of timing per lb of boost to a total of 20*, The old EECIV does have a knock sensor, but is very crude in its use.

 

lemme ask a stupid question...
i have pistons that are also 83.5mm...
what's the clearance between piston and wall supposed to be?

 

Philly, What pistons? Cast? Forged?

Pistons come with the PTW clearance built into them.

But that tolerance can be changed depending on the build and use of the engine.

Most forged pistons want about .0035 PTW

But if we use a mazda BP-ZE engine for a base, Std Bore is 83mm/3.268"

Then add a .50mm/.020 over bore

The bore in the block will now be 83.50mm/3.288"

The forged piston should mic out appox 3.2845-3.2850

The pistons should have come with a spec/info sheet.

Looking at the info that Supertech has in the box they want .00276/.07mm

At the botom of the paper they have a disclaimer saying....

"Some applications may require more clearance. Correct piston installation is the responsibility of the customer."

So with that being said
Supertech pistons should measure out

3.288 - .00276 = 3.28524 call it 3.285

(I will post pics of the paperwork later)

 

How bad is it if you don't weight match the pistons and rods?

 

dgmorr.... hard to say, depends how bad off they are in the box.

If you look at the starting weights I had at first, then how he become closer with just swapping wrist pins around. To me they were rather far off.

The closer the balance the smoother the engine idles and revs

 

You ever see a break dancer do the worm? It's just like that....

 

What's your opinion about the supertechs? Some finishing work on them, match the weight and balance the rotating assy, think they're good to go? Any sort of finish on them from supertech?

 

Ok I just called Supertech, to find out about the coating on the pistons.

I spoke with *****, He told ne the coating is a dry lube coating to help oil absorbtion.
Also asked about removing the coating on the crown of the piston, by grinding to help remove sharp edges, He told me there will be no issue with doing that.

So yes you can polish the sharp edges on the supertech piston crowns.

Supertech Performance Inc
3550 Charter Park Drive
San Jose, CA 95136
(408) 448-2001
www.supertechperformance.com

 

What is your opion of piston coatings, top and skirts. Stuff like swain.

Do used coated pistons you see look better than uncoated?