First I would like to apologize for my bad English. I come from Denmark.
And i really need some help.

I am having big problems finding out what my compression is going to be on my Engien.. :/ I have tryed most of the Honda B-sereis Calulators on the internet. And they can not help me.
It is because i think i have gotten the wrong pistons from "cp"

My enginen is a b20b3 whit b16a Cyllinder head whit Oem head gasket.
And i have baught an Brian Crower 92mm Lw stroker kit
And i have ordered the Cp pistons so the compression should be 12.5,
if my head og blok is like stock and not milled

But there is certainly something wrong whit the pistons.
Because i had 12.5 i compreesion when it was 89mm stock stroke and running whit the old Cp pistons in my old setup. And over the deck the old pistons is 3-4mm taller then the new pistons.

So now i have to calulate how much compression the new pistons will give me so i can be 100% sure that the dealer i baugt the Pistons from can change them to the right pistons.


The Data sheet is:
Crank 92mm
Bore Diameter: 3.347
Clearance 0.0040
Piston gauge point 3.343
Compreesion height: 1.024
Intake valve Relief: -0.21
Exhaust valve Relief: -.150
Dome Height 0.063
And the rod size is 1.7710
and Main size: 2.1646
Ans Something called Rod C-to-c: 5.512
And Oem Head gasket.

And that is all the data i have from the sheet.

I really hope there is someone who will help me whit the calulations

 

hope this helps
https://honda-tech.com/all-motor-nat...r-kit-3233511/

 

It did not help me :/ I have tryed to calulate all.
And every time i does something wrong..

 

do u bought an new set of the stroker kit? a complete kit with crank,bearings,rods,pistons? where did u bought it? because a b20b have not a 87mm crank. it have a 89mm crank

 

Yes i have bought a compelte 92mm kit. And the old one was original 89mm
It was a mistake that i wrote 87mm.

 

You have not offered up a dome volume in the above data sheet which is critical to calculate compression. The only thing that suggests anything about the piston is the dome height, and at .063", this suggests that your pistons do not have a huge mountain in the middle of them but in fact, a smaller dome. What we don't know is how wide the dome is, how broad the dome is, and the amount of edge relief. We also do not know the total volume loss for the valve reliefs.

The piston box should have a job number, build number, or customer number on it. I suggest you email JE Pistons with that number and request a "net dome volume" for these pistons. With that, you can calculate the compression.

 

Also, remember that when you increase bore and/or stroke... the dome volume is reduced to maintain a similar compression value. So comparing your older piston with a bigger/taller dome to your new one with the flatter dome is misguided... I suspect you are worrying for nothing.

I calculated a 1.5cc dome volume, 5.512" rods, 92mm crank, 85mm bore, .030" head gasket thickness and a 212mm deck height = 12.48:1 compression. I suspect that when you get a response back from JE, the total net dome volume will be between 1 and 2cc's.

Now, with all of this said... my worry for you is that your deck height is actually LESS than 212mm, which means that the piston will stick up out of the block. B20 blocks are typically more like 211.6mm... less if it has been cut. If the block has been decked, it will be worse than I think. This will increase the compression and the danger of valve to piston contact will also be increased. The easy solution will be to increase the gasket thickness to make up for this deck height difference. You MUST get the block height accurately measured.

 

Cp just rode back to me. And the said: The piston CC is +.90cc Hmm?

And the pistons doesn't stick over the deck they fit 100%

 

With a net dome volume of .90cc, the compression calculator shows a compression ratio of 12.45:1 with the piston sticking out of the block .007". You say that it is flush/flat... so assuming that your statement is true, I modified the calculations to reflect that detail and came up with an effective compression ratio of 12.23:1

I hope that helps.