I have had the b18b block bored out to 82mm and was gonna use rs machines ctr pistons along with a Gsr head. I dont know exactly how the compression calculators(c speed,zeal) are coming up with there compression numbers without knowing the flow characteristics of my motor. To any knowledgeable engine builders what will my compression ratio actually be? I am trying to build around the limits of 92 octane fuel.

 

You'd be looking at about 13.2:1, you're not going to want to use those pistons. Use the P30's or Pr3's. You'll probably run into clearance issues with the pistons slapping the head.

https://honda-tech.com/forums/showth...pression+ratio

 

what would the compression be with 82mm p30 pistons?

 

http://www.c-speedracing.com/

 

92 octane stay under 12.5:1

and a 82mm on a b18 will not last long you weakend the cylinder wall alot. anything over 81.25mm id recomend sleeve.

 

82mm is fine. It's a bad tune that will kill the motor here, or stock rod bolts in an LSv.

 

I was reading somewhere that the cspeed and the zeal autowerks calculators were innacurate.

 

only when using CTR/PCT pistons in the calculator is it really off. You're using P30's.

 

This is really confusing. What do "flow characteristics" have to do with the static compression ratio?

 

Quit repeating what you heard from other inexperienced people.
I'm driving a 81.5mm bore build with over 110k miles and another motor I built for my buddy is running a 82mm bore build with over 75k miles, and our motors are both on stock sleeves.

 

Flow characteristics have nothing to do with static. It has alot to do with dynamic. Why i was asking is what efficiency did they decide to base the static compression on?

 

CTR pistons should only be used in a B16 because their domes are so high. When they're used in a B18vtec they hurt the flame travel in the cylinder. Basically they divide the combustion chamber in half.

 

What if it's an LS or B20 vtec with a B16/ITR head? How is that any different than a B16B?

 

I build a couple of 82 set ups for years daily drive with no issues at all I can say anything over 82 is when u actually need sleeves.