edwardsuen

Hi everybody, do not know if any of you have experience installing supertech pistons? I have two questions below:

#1) The wrist pin comes with supertech piston is 20mm, and the original eagle rod Wrist Pin Hole is 0.787 in. after I installed, the piston is not moving freely, from the size it read, it should be fine, but why so hard to move? will this cause problems after installed?

Here is the new wrist pin that comes with supertech piston, measure 20mm

Here is the center measurement from old eagle rod wrist pin

Here is the side measurement from the old eagle rod wrist pin (not likely to have wear)

Here is what the piston clearance difference between normal piston and supertech piston installed:

Normal piston feelings:



#2) The curclip that comes with supertech piston is without the curl part as listed in pictures below, I wish to use the old curclip as it both read .02mm, or maybe supertech pin are slightly thinner, but from the design of the pin, will it be causing something different after the piston got heat up, expand that will need these hard to install pin (without curl part) is actually needed?

The left side of the curclip is from supertech, the right side is from miata (stock)
see curclip

Miata stock lock curclip measurement

Supertech lock curclip measurement read

Thank you for any experience sharing, I am now need to decide on installing the old wrist pin or keep using new ones that come with supertech pistons, second is to will I face any problems if I use all old curclip from miata...

Thanks again..

edwardsuen

Okay, I found that there is two types of wrist pin, which is semi float and full float, guess this could explain that installations will be fine with only piston area moving with rod fixed, guess what comes with supertech belongs to semi floating wrist pin:

semi floating wrist pin - would be the rod is heated, and interference fit wrist pin is fitted so that when the rod cools, the pin is fixed in place. The piston "floats" on the pin, while being fixed to the rod

full floating wrist pin - would be the wrist pin is held in place with small clips on the ends of the wrist pin cavity in the piston. The wrist pin "floats" in both the rod, and the piston.

full floating is superior.... but it really depends on the application as to how much of an advantage.. (incremental... to significant)

edwardsuen

Finally, found that the pin with supertech piston will not match eagle rod, I found out after installing the curclip on both sides, both rod and piston will not "floats" on the pin.


Eagle CRS5233M3D ESP H-Beam Forged Connecting Rods
Here are some particulars:
Length 5.233 in.
Rod Journal 1.770 in.
Housing Bore 1.8850 in.
Wrist Pin Hole 0.787 in.
Big End Width 1.8900 in.
Pin End Eidth 0.8570 in.
Thickness Above Pin 0.200 in.
Typical Weight 535g
http://enginetuning.hk/images/93_mia...upertech_2.JPG

Supertech piston
BORE (mm): 79.00mm 1mm +
COMP. RATIO: 10.6:1
DOME/DISH VOLUME CC's: -1
HEAD CC'S: 36
COMP HEIGHT: 1.260″(32mm)
STROKE: 3.287″
SKIRT STYLE: Round
ROD LENGTH: 5.228″
PIN DIAM: 20mm (.787″)
WEIGHT GRAMS: 258
PIN WEIGHT: 73.4
PISTON PART NUMBER: P4-MA790-N1

Although both pin diam is .787", but it just will not match, solutions is either take pin to machine shop for modify the pin, or, which the solutions that I took is, to install the old original miata rod back into the engine, save me lots of trouble.. now the supertech back to full floating system without any friction lost.. or risk of any damage due to friction if install the eagle rod!
Below is the wrist pin difference.
http://enginetuning.hk/images/93_mia...upertech_3.JPG

ftjandra

iTrader: (6)

You just needed to hone the small end of the Eagle rods. I had to do the same thing on some M-Tuned rods. Any engine shop would have told you this - this is very common.

Quick search turned up this thread:
https://www.miataturbo.net/engine-pe...-honing-42619/

--Ferdi

edwardsuen

Oh, this is that simple, but it's hard to find a machine shop in Hong Kong to have line honing the rod parts, will keep looking for machine shop that will do this in the future!
Thanks for your info!

NiklasFalk

iTrader: (1)

Since you don't pay for top notch QC, you have to do it yourself, made possible since the hole is a little tight.

edwardsuen

This is what I am thinking, maybe this is from machinery tolerance, so little that I cannot measure correctly to find out the difference is in, but I believe in future will buy stuff in sets, so nothing will be wrong, not mix and match parts.. Simply say is to stick to the same manufacture parts~

NiklasFalk

iTrader: (1)

Paying twice the price and "trust" supplied tolerances will never work. You will never find all related parts from one supplier, and even then you should never trust the tolerances.

Finding a builder that can check/correct supplied parts for your installation is the key.

But then we have the "front fender sticker" installations...

edwardsuen

I see, then I have to find very good measurement tools to start learning how to tackle tolerances myself, before I going into this, I have wrong concept that supplier always have the finest figures measurement sold to end users, with pro engine builder, they even have more experience to fine tune those figures to even closer match with manufacture spec., so that engine will work better, or last longer in the long run, but without the fine tune, I may still get by with better then stock engine results, these were my understandings before...

So, I may buy a small honing tools 20-30mm, 30-60mm, to slowly hone the rod to make it fit, is this the correct ways to do it? since I have a dream to build a track car in coming future, I should be able to tackle the task myself so that engine can perform the toughest conditions through out the track period. Since Hong Kong do not have race track, cars need to apply and ship to China for given period of time to have fun in track, therefore, I cannot rely too much on machine shop local as their main jobs are rebuild commercial vehicles with stock parts, no mod!

Thank you for experience sharing, very useful~

noname4me

Honing the small ends of the rods should be an operation that many engine machine shops should be able to do. This isn't a "race only" type operation, but is also done when rebuilding engines with stock new and used parts.

edwardsuen

that is good, thank you~

Corky Bell

Establish a 90 degree angle and touch it with a brake cylinder hone. Use some light oil and go very slowly.

corky

edwardsuen

Thanks, now is the second time I break this engine apart, and felt more confidence in touching these myself now.. there are always many should do OR not to do during the installations process. for this miata, since all had already installed into the factory rod, I will leave it.. awaiting to experience the additional HP the High compression piston is giving me..
Guess I will not be able to feel the difference with slightly heavier rods compare to last mod (eagle rod with factory pistons).
Treasure the experience from all of the track members here! Bravo~