I've been trying to figure this out for a while heres what i've got:

the compression height of the b7 is 30.7mm
the compression height of the a6 is 29.025mm
the crank displacement difference is 5.5mm so the b7 pistons will end up 2.75mm higher if they're put on the a6 crank (thats at tdc)
The a6 rods are 137mm and the b7 are 134 a difference of 3mm

If you add all that up you'll end up with a piston that goes 5.75mm higher than it was going in its 9.2c/r setup. How can i figure out the compression ratio of the pistons in the a6 engine with the information given?

 

I believe i figured it out:

I did compression height of b7 minus the compression height of the a6 (30.7-29.025 = 1.675mm) and since the a6 piston sits .02mm below the deck of the block to find the piston deck clearance i gotta subtract the original clearance from the new clearance. I ended up with -1.655mm, which means the piston will sit 1.655mm out of the block at tdc. When i did these calculations on the c-speed site i ended up with -1.7695921354063943:1 cr. I figured thats wrong so then i did it on the Honda D Series site (http://www.flashcow.com/dseries/compression.html) and came up with 12.026042047727056:1. So now I need to find out if The valves will end up kissing the piston or not. Heres a pic of the piston btw:



Lemme know what you guys think


[Modified by EE4, 12:43 AM 2/6/2003]

 

The valves aren't your problem, the piston will contact the cylinder head if it's sticking 1.6mm out of the bore. It'll turn over and create great compression for one glorious moment, then sling metal everywhere.

 

haha yeah i was worried about that, you actually think 1.6mm is enough to nail the head? I was going to buy one and clay it and see how it turned out. its something like .06", not too much sticking out

 

clay it and see whats up/!

 

nah it won't work, i keep thinking the combustion chamber is as large as the bore, and its not, so it'd nail the head, and compression would fart out the top of the head

 

Exactly. I've never seen a Honda with true open chambers, they're all closed.