Alright so here's the deal. I want to see what I can get for HP out of an N/A 2.0L DOHC. My first upgrade is going to be pistons, since the old ones were all scratched and need to be replaced anyway. I know that the 2.0 and 2.4 use the same bore and basically the same head. I may have the opportunity to get ahold of some 2.4 pistons for very cheap. I was going to order high compression aftermarket pistons, however, if putting in the pistons from a 2.4 will increase the compression ratio, then I will probably do that since it will end up being way cheaper for me. So basically what I'm asking is, will the pistons from a 2.4 increase the compression ratio in my 2.0, and will there be any problem with clearance of the piston to the head? Any advice or even solid numbers on this would be greatly appreciated.

 

if you're going turbo you want a lower compression, and the 2.4 pistons will lower your compression

 

[:@]He says N/A = NATURALLY ASPIRATED= NO turbo

 

and my post says if you're GOING turbo... learn to read.

 

I forgot to mention that the engine I could get the pistons from is a non-turbo 2.4L, will those ones still lower the compression?

 

You'll need the piston Rod length to compare the two ... the 2.4 may be shorter rod length to get the extra displacement with the same bore

 

Actually the rods are longer, 5.47" for the 2.0 and 5.945" for the 2.4L. The extra displacement is acquired by lengthening the stroke of the crankshaft, thereby pulling the piston further down the cylinder. Although it doesn't make much sense to lenthen the crank stroke and then lenghen the rods, after looking up some numbers, I figured out some differences. 0.708" difference in stroke and 0.475" difference in rod length leaving a total difference of 0.233" which I think would make the 0.4L of overall displacement. But anyways, I'm thinking that because the 2.4 pistons are dome top and the 2.0's are flat, that would leave less space in the combustion chamber thus increasing the c/r (compression ratio). But, if the 2.4 pistons are shorter, then that would make up for the dome top and you'd end up with the same, or possibly less c/r. I guess it's really hard to know if swapping the pistons would up the c/r until you actually try it, which I think I'll try anyway, even just to get an answer to this question so that other people can benefit from this knowledge. But if someone has done it or knows a solid answer, it would be appreciated. And thanks to all who replied and will reply to this post, everyones input counts!!

 

Or crashing the domes directly into the valves ...

 

lol, ya, that could happen, but I'll check for clearance before I try turning it over. It'll be a while before I can get my hands on the pistons cause they are recall engines from PT's and Sebrings. The crank was moving too much front to back and would pop out the front seal. But the main bearings could be re-machined and then the engine is still good. So Chysler has to decide what they're going to do with them. I'll update when I get more info for us.

 

if you use 2.4 n/a pistons on a 2.0 engine, you will get a really high compression, 12.5:1