Hey guys, i know that the new trend in boost now is higher compression motors, but im up in the air about which direction i want to go with pistons and compression for a JRSC b20b application. Im expecting between 6-8psi of boost on this b20 setup, but im not sure whether or not the b20 on stock sleeves will be safe running higher compression for better low end response to turn the supercharger drive system easier. A couple people suggested that 11:1 to 11.5:1 compression would be no issue with low boost and proper tuning, but my concern is the monosleeve under that kind of pressure in boost. Granted I will be running a progressive methanol system from 2-max psi but it still is a concern to me regardless of knock or not. Should I air on the safe side of 10-10.5 compression or should I push it to the max with 11's.

Im looking for maximum throttle response, low end power, since this car makes 2psi off idle with the blower, and it will be running on a non vtec setup with an auto trans. for daily use. (trans will be getting upgraded at a local trans shop, higher stall converter, modified shift solenoids, LSD)

 

honestly i wouldnt push too far past 10-10.5 on 6-8psi. Anymore than that and you run the risk of cracking a sleeve. but honestly its up to you.

 

Whts your head set up like? and wht blower do you have??

 

P8R non vtec head, port and polish, crane powermax FI cams, supertech single springs, and a M45 blower with a 2.8 pulley with a fluidampr crank pulley

 

I hate to be the bad news bear but the stock auto trans won't hold a whole bunch even with work. Might want to rethink that path

 

Im considering an SC for my b20b p8r at the moment too, a 2.8' pulley is crazy! where did you find that?
General rule of thumb is a lower compression is a happier engine...

If your concerned about the cylinders there are a couple options. You could post the cyls, or you could add a gsr/aftermarket girdle which add rigidity to the bottom of the cly's. Just be sure to properly dowel and line hone the girdle.

 

Let me worry about the issues with the trans.

we are gonna make the pulley ourselves

 

My setup for over the last year and a half was a b20 block with rs machine 84.5mm USDM ITR spec pistons, eagle Ibeam ls rods, with a stock gsr head. I have the lht aftercooler, and i was running the b20 crank, custom stepper(MVM size), and a custom 3.6 snout pulley. I was getting 9psi, and running e98 for fuel tuned on Neptune. Never got the car on the dyno but it had to be getting towards the 300whp mark. I drove this daily, drag raced it, and auto-x for a season and a half with no issue. Setup for next year is a sleeved block and spray on top of the blower. My compression would have been around the 12:1 mark, a little higher than what I wanted originally but I had limited choices trying to stay with a cast piston.