Improving a piston: porting, polishing...

[100mphlambrettaclub]

This was a wiseco we used in the sprinter less weight more revs less strain on the conrod. Needs to be balanced and dont take any weight out of the critical areas.

[sean brady scooters]

general tidying up and flowing is a good thing ,but highly polishing the surfaces can actually be detrimental ,and so is a great waste of time and effort unfortunatly..
and be very careful if considering (as someone has suggested) thinning the piston skirts/knife edging
as strength could be compromised by doing so.especially on the inlet side.

the way that stu and jason have done theirs is the way to go,this is also how i do them.....

[100mphlambrettaclub]

Yes polishing may look pretty but isnt needed and can weaken. Thers was a few hours work in that piston which was a nightmare as they were changed every 25 miles or there abouts.

[J1MS]

general tidying up and flowing is a good thing ,but highly polishing the surfaces can actually be detrimental ,and so is a great waste of time and effort unfortunatly..
and be very careful if considering (as someone has suggested) thinning the piston skirts/knife edging
as strength could be compromised by doing so.especially on the inlet side.

the way that stu and jason have done theirs is the way to go,this is also how i do them.....

I was in no way suggesting anyone knife edge their piston skirt. Somthing I tried once was somthing read in a two stroke tuning article about putting an angle on the inside of the inlet skirt 30 or 60 degree. Can't remember now it's that long ago. But whatever angle I noticed no diffrence.

[sean brady scooters]

Ive a mate who knife edges the inside of the piston skirt, dont know why, i,ll have to ask .

Think its got something to do with turbulence and eddy currents, knife edging or cutting a chamfer on the back end of the skirt was or is supposed to reduce this... Done it myself in the past...dont know if it made any diffrence.

sorry Jims,
it was perhaps a bad choice of words by me matey....
i should have said "mentioned" as opposed to suggested.

[RICSPEED]

Polishing can have advantages for things like con rods as a polished surface improves their strength but I dont see any advantage in polishing a piston

[100mphlambrettaclub]

One thing i never disclosed in the articles on the secrets of the sprinter and it may be just that i forgot was about cryogenic freezing. Originally we did it with the gear box and yes it stopped it breaking teeth . The thing is we did it to the whole engine piston crank the lot everything that moved. At the time 2001 the technology was new and we got the idea off a bloke who was doing it for indy car engines in America. He told us that every part of the engine was done and it had helped stop parts failing to a certain degree. So the whole lot was done in my engine. When i missed a gear which did happen sometimes the engine would rev to 12,500 and most of the time it ran between 8,000 to 11,000 rpm anyway. In all that time i never broke a conrod or cracked a piston. While the evidence is not 100% as we changed components at regular intervals it does make you think. Im not saying go and strip your engine and get it frozen but evidence suggest it does work ,well it did for me.

[Avantone]

One thing i never disclosed in the articles on the secrets of the sprinter and it may be just that i forgot was about cryogenic freezing. Originally we did it with the gear box and yes it stopped it breaking teeth . The thing is we did it to the whole engine piston crank the lot everything that moved. At the time 2001 the technology was new and we got the idea off a bloke who was doing it for indy car engines in America. He told us that every part of the engine was done and it had helped stop parts failing to a certain degree. So the whole lot was done in my engine. When i missed a gear which did happen sometimes the engine would rev to 12,500 and most of the time it ran between 8,000 to 11,000 rpm anyway. In all that time i never broke a conrod or cracked a piston. While the evidence is not 100% as we changed components at regular intervals it does make you think. Im not saying go and strip your engine and get it frozen but evidence suggest it does work ,well it did for me.

I'm sure this is something a few people are doing in the scooter sport world but keeping quiet on

There's a great description HERE on how and why the process works that's worth a read - the bit on Aluminium is interesting too.

The process is also used for aluminum, he continued. “It’s fantastic on aluminum. Not only is it tougher and more durable, but it machines so much easier. We treat bare metal for machinists, and a lot of times, you get a more true machining, because when it heats up, it doesn’t bend and warp, because all the stress is gone.”

“All of the aluminum pieces can now be treated to be as comparable strong as steel, while still retaining their lightweight advantages. One example of this is the cryogenic treating of cylinder heads. This stabilizes the aluminum, so the racer gets less deflection and distortion in the head, and even heating across the combustion chamber to help with consistent power from start to finish".

[Fred_64]

Thank you for your numerous feedbacks.

What sort of smoothness should we achieve on areas submitted to air / fuel mixture ?
Should it be P240, P400, P600?

I know some of the fresh mixture must get “trapped” on the transfer walls, and the rest of the mixture is supposed to flow over that layer.. in French we call it “couche limite”

To summarize;
- Everything flowed nicely and smoothly; helps preventing cracks, helps mixture flow, prevent hot points were oil residues get trapped….
- Maybe a P240 grit keeps fresh mixture and oil on the bottom of the piston and helps cooling?
- Then a bit of Cryogenics to make it tougher…
- Then a few layers of Ceramic coating on the piston dome as a heat barrier….
- Do not forget some graphite coating on the piston skirt to reduce friction…
…Then a bank loan to pay the final cost !

For psychiatrists, here is my little workshop….


And for sean brady scooters…

you must have really spent some time and effort on that,but what difference did it really make...?
cosmetically it looks fantastic,but who is ever going to see that again...?

It does not matter nobody will ever see it, it must be nice if it is inside my engine, for my peace of mind!

I know I am weird… quite fan of Bugatti T35 engines; where every nut and bolt is labelled, you can nearly use any element and put it on your coffee table, looks like art to my eyes…

Otherwise on my balance a TS1 Asso piston weights 336 grams, I had some Peugeot Formula 1 V10 pistons that were 231 grams each, for an individual displacement of 350cc…
Someone sold a matched set of 10 for 290 euros; quite a deal hey, I forgot to mention the bore is 91mm and it is four stroke….. look at this lovely short skirt:

[100mphlambrettaclub]

Just to add another little thought on this crogenic thing and this isnt proven either. At the time (2001) they were starting to use it in the Karting world as well. The 100cc Tonykart class was ultra competative and every engine that was built for the class had identical performance . We were told that to gain a slight advantage some of the top drivers were having the whole engines frozen and were getting a 1-2 bhp improvement just from this process. Wether or not it works and why it works i dont know but they were doing it . I wish i hadnt stopped developing at the end of 2002 because there is so much out there that can improve performance .