2.5 class piston options

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Fairchildbr

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Aug 11, 2014
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Im looking at my options for pistons right now because im starting to build the 12v for my puller i plan to run 2.5 with. i was told by brian at hamilton when we decided on a 207/220 to keep my compression as high as possible until boost reaches around 100psi and i can no longer get rid of cylinder pressure. which i probrobly wont see. he told me to use the mahle S41518 from cummins for the wide bowl and high compression.now i always tought the lower compression was better thoughts guys?
 
Higher compression makes more power but you lower compression to improve reliability in heavily modded engines is my understanding of it
 
I've heard, but never thought about, that higher compression will also mean less total air/fuel you can squeeze into the cylinder. You have to draw the line somewhere between compression and stuff that goes boom.
 
A lower-compression piston will have more air in it than a higher-compression piston at a given cylinder pressure. More air in the cylinder will make more power as long as you can put enough fuel into it.

The down-sides of low compression is that it starts to run like absolute crap under low-boost operation, making lots of smoke, hard-starting, et cetera... Correct me if I'm wrong, I understand low compression is the main reason you see pullers with 1000+ hp engines spraying ether and spending several minutes to get them to start.

The question is, are you going to be pushing so much air into it that cylinder pressure is really going to be the limiting parameter?

At a good-flowing 100 PSI, the answer to that is probably "yes"...
 
Lower compression will have more DEAD air than higher compression.. less VE% as well
Higher compression and smaller quench equals better volume efficiency.. Means more HP.

Also higher the CR easier it is to get on top of a turbo.. Now a days only reason to lower CR is if there are not hard parts that can handle higher CR like 17-19:1 at given hp
 
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I cant say I totally agree with more compression always makes more power. In certain application's it is definitely an advantage. For all out performance you start to compromise combustion chamber design the higher you go. I have seen some really nice lower compression bowl designs that offer great throttle response once up to opperating temp. Start obviously can require a touch of ether. I also believe higher compression can limit high rpm hp potential. There comes a point where it starts to work against you imo.
 
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