decompressed pistons

Also am curious of this also! I have a custom cut cam and my motor is decompressed 15.1 with fly cut pistons! But i really havent seen it hurt my power, its hard to start when cold and very luggish between 1500-2100rpm but thats all i have noticed!
 
Mine is 15.5:1 and its a little harder to start during winter(with no grid heater) also its smokes white on initial start up and goes away when warm but I've also got my ring gap set pretty loose. I think that that is alot of the key to keeping these motors alive at high temps from the heat expansion. Mine is Ross forged pistons,top fuel coated,fly cut and I removed the dome out of the bowl. To me the biggest reason for dropping compression ratio was making more room for more fuel & more air. If its was on a pretty stock daily driver I would say don't do it but with what he's after I would say go for it. More fuel,more air and less cylinder pressure is a good thing when trying to make a high HP motor for pulling stay together.
 
so what is the conclusion? i recently found out i have 2 bad pistons and if those are needing to be replaced then i will replace them all. my main curiousity is keep stock or go with say a mahle? decompress or not? coat them or not? i just want it done right so i dont have to do this again for a long time these lasted only 42000 miles only about 15000 miles modded. you guys know a lot more about this than i do do i am open to all advice!! thanks again
 
You need to grow a set and do it on your own or you won't learn anything! My pistons are flycut and the comp ratio is 13.3-1 no so called hot spots here just one big one LOL
 
Tuning is the key with the common rail. Duration makes lots of heat!
 
zstroken said:
Tuning is the key with the common rail. Duration makes lots of heat!
Click to expand...

found that out the hard way, lol. too much with tst and bullydog on there and the high rail pressure probally didnt help much either. oh well you pay to play i guess.
 
Fly cutting can creat hot spots. Using some sort of ceramic coating on the piston crown can only help. The hot spots could pose a problem if water/meth is being used, other than that I wouldn,t worry too much about it. One thing to remember with fly cutting vs a flat milled crown, the tighter quench area of the fly cut crown will creat more combustion turbulance. This in my opinion would help burn more of the fuel air mixture due to better mixing. And should make more power. Be advised I have no proof of this on a diesel, but these rules apply to most gas engines.
 
Gasser Nitrous guys take all the sharp edges off their pistons to keep from having hot spots.

Jim
 
Here is hot hotspots occour on a flycut. Take a cutting torch & cut a flat piece of metal. If you start your cut in the middle it takes longer to heat up than if you move your torch to the edge of it.
 
Need the who fragged there ride with the TST thread......LOL Been there, done that.....

I thought hard about reducing the compression, have a buddy with a 15-1 and what a dog off boost. BUT if you want to put the screws to it, is the only way to go.

If your going to run a lot of water, your going to be dynamically increasing CR, so thats another reason.
I'm a little reserved running a lot of water with stock compression.

In the end I didn't lower compression, and this thing is STRONG off idle and low boost, but the ZZfab intake helps with that too.

Keeping the head on.....we'll see I guess.
 
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