Why 18 to 1?

[Billman]

I understand the concept of lowering the compression ratio to 18 to 1.

Does everybody who goes this route also replace the turbo with a more efficient model? Why increase boost levels to 20+ only to have your backpressure in the exhaust increase as well.

What are you gaining?

What are the other benefits of lower CR pistons?

[More Power]

The advantages of a lower compression ratio (in the context of the 6.5 engine) is, that a lower CR improves durability - durability primarily of the head gaskets and pistons.

More durability allows for more boost and fuel = more power with less risk.

This applies for either a factory GM-series turbo or an aftermarket hi-flow version. The factory turbo has backpressure issues above 14-15 psi, while the non-wastegated aftermarket hi-flow varieties allow for as high as 20. The trade-off with the non-wastegated versions is more turbo lag - good for pulling, but not so good for a city truck.

MP