Low vs. High silicon pistons. Also Diamondyzing.
 

Guys,

I'm in the throws of finishing my shopping list for my build, and am at a fork in the road with piston choice.

CP or Supertech?

I've read TONS of info/posts detailing the differences, but I'd like people to chime in with some real-world (sexual) experiences.

I'm aiming for about 350hp in an ultra-reliable road/track car, and at the minute I'm leaning towards the ST's due to the more "daily" nature of the high silicon pistons. Am I missing a trick? Is there something super awesome I've missed about the low silicon pistons, considering my application?

Also, to steer this away from an OMG SEARCH NOOB replies - I'm thinking about having them Diamondyzed. Admittedly this is about 20% because it looks awesomesauce and might be epic and 80% because I can have them pink ^^. I've yet to see anyone mention it here. Let's discuss.

http://www.techlinecoatings.com/hi-p...iamondyze.html

Diamondyzed:

wtf does this do that the teflon coating already on the STs doesn't?

The high silicon pistons should be better in a streeted car since they can use smaller piston to wall clearances. However they arent as strong as the other alloys. I'm not too familiar with the ST alloy but some High Si Al alloys are quite abrasive which would mean that theoretically you'd have increased cylinder wall wear on the thrust side.

I have super techs in my engine. I have no idea if they were hand finished. But if I was going to re-do the build myself they would get hand finished since the pistons come with some sharp edges as delivered. Theoretically the 949 pistons are going to use the same alloy but with better piston top geometry I have no idea if it will be worth the price difference vs hand finished ones.

Coating wise. The more I learn about piston coatings the less I'm able to decide if I like them or not. DFL on the skirts seems like a good idea in theory, in practice it seems to wear off quickly. Thermal coating on the piston tops seems like a good idea in theory, or it seems like a bad idea in theory, either way it seems to wear off. DFL on the rest of the bearings in the engine, I've been told by a couple different spec miata builders that it isnt worth any power at all (you know they tested it, its spec miata), but if you suddenly loose oil pressure with DFL if you instantly kill the car and push in the clutch you might be able to salvage the engine without any rebuild.

Brian Crower steered me away from having a thermal barrier coating put on some 4G63 pistions (1000hp build) . They said the coating causes the rings to overheat

That's an interesting view. What was you thinking of coating them with? The diamondyze is only about 10% efficient as a barrier so it isn't at all a total heat blocker.

I was actually thinking about it to help the rings. There would be no degradation around that area as the process makes the alu super tough and corrosion/wear resistant.

Interesting about the DFL too, I was thinking about using this as I'd heard good reports! I may still have a go for the money involved - it isnt expensive.