1G compression ratio

[4G63Tlove]

Hello guys I was just wondering about your guys opinion and experience on compression ratio depending on my goal, well here it is. I am rebuilding my 1g 6 bolt, my goal is to make around 400 to 500, the car will be a street car mostly city driving. I have a Mitsubishi 20g, I also have a extreme turbo systems Intercooler. Fuel pressure regulator, full turbo back exhaust, Hks wastegate. Apexi Boost Controller. I will be getting wiseco pistons and manley rods wich will be installed by a machine shop, and all the rest water pump, new belts, gaskets arp studs felpro headgasket etc... Bit I cannot decide on CR since it's going to be mostly city driving I was thinking about 8:5 maybe 9:0? What do you guys think

 

[94awdcoupe]

I have experimented greatly with comp from 7.5 to 11. including some comp only changes to my setups. its really a fuel used related question. for pump gas you want to stay in the lower comp ranges. between 8.5 and 9.0 to one there is about 2-2.5psi boost difference between the two. meaning for 8.5 to one at 20psi boost will equal power at 9.0 and 18psi. the lower comp setup will be slightly less fussy to tune, slightly more reliable. there also a quite noticeable off boost feel to engine with this small comp change. with 9.0 feeling more lively. not really an issue with 16g/20g size turbo but becomes a bigger factory with laggier red size up turbos.

 

[RipperXX]

I would say just go 8.5:1 unless you want to squeeze everything you can out of the 20g (which has apparently become a generic term since there are so many flavors) then I'd consider 8.8:1 evo pistons or 9:1 forged. IMHO on a street machine that wont be doing anything insane Mahale makes a damn good forged piston that tends to weigh less and expand less than the other offerings out there due to a different (though more brittle but still much stronger than cast) alloy. Which allows for tighter piston to wall clearances. There what I'm going to install if I can ever get back to Georgia where my car is.

 

[4G63Tlove]

Alright thanks for the reply guys I think I'm going to go 8.8:1 I'm going to be running on pump gas all the time because e85 is not available where I live I think it should be pretty good for my setup and not to hard to tune and responsive off Boost.