Great formula for comp. ratio !
Although I do have a question relating to this topic.
What would be the maximum compression ratio that you could run with LRP (lead replacement petrol) in an A14 without having a cranky pinger of an engine ?
This is assuming that the motor is fresh & well tuned, electronic ignition & a decent exhaust system.

edit: If not LRP what about 98 octane Premium?
Any opinions would be appreciated.

phunk
it won't be legal but atleast i can pull the charger off if need be to make it legal rather than an engine change

cheers for the info fella's

Using a15 pistons in an a14 is the same as putting an a14 crank in an a15, (same conrods, different pin height)
I was going to go down this road, but after giving it more thought, and speaking to an engine reconditioner, I now think that a better trick would be to get the a15 pistons, (in an a15) and machine the eccentric dish so that it is concentric, but still leaving the squish ring in place. This will lower compression enough to allow for the type of boost you would likely create safely with a 4agze s/c , without completly sacrificing the motors off boost power.

plus of course the volume between piston crown at TDC and top of block if pistons don't come right to the top, which when you're aiming for low comp is highly likely.

Hey yup.
the C/R is determined thus

Capacity of one cylander+capacity of the headgasket+capacity of the combustion chamber (+ or - any piston dish or pop top)
divided by
Capacity of the headgasket+capacity of the combustion chamber (+ or - any piston dish or pop top)

So, for example...

a 1608cc engine with a bore of 80mm and a stroke of 80mm, a 1mm thick headgasket (5cc) and a 40cc combustion chamber running flat top pistons..

402cc+5cc+40cc+0=447cc
divided by
40cc+5cc+0=45cc
is a C/R of 9.3:1

hmm, might actually be 0.5cc, could have a decimal in the wrong place but you get the idea!!

I know its not an answer to your question, but why cant you register it with an A15 but yet you can with a supercharged A14?

I was wondering if anyonew knows a link to a site to work out comp ratio

I will soon be building a engine for my wagon
i was thinking A14, a15 pistons and the h72 low comp head, with a 4agze supercharger. don't really won't to run a head shim, but wont to get the comp as low as possible.

i've thought bout a15 with a14 crank but can't register with the a15

any other idea's ?

cheers