AFs2k

What are the compression differences between the two pistons?

If I was to put 9:1 ap1 pistons in my ap2, what would the CR be in the ap2? It would raise it right? How much? Is there a formula to figure this out?

Take stock ap2 pistons and put them in an ap1, what would the CR be on that?
Stock ap1 pistons in an ap2... CR?

(ap1 with ap1 crank, ap2 with ap2 crank)


I have searched around and can't seem to find this info on here anywhere. Does no one have a difinite answer?

Breaking Point

The ap1 has a taller compression height.the guys who r building g23 setups are trying out ap1 and ap2 pistons.it seems to be that if we with an ap1 put ap2 pistons into our motors that it'd drop up a point in compression down to 10:1.figuring the opposite for the ap2 motor with ap1 pistons would be put to 12:1 but I fear p2v would be an issue potentially. If not then an ap2 motor with ap2 crank .using stronger lighter.ap2 rods and ap1 pistons and flat faced valves would be a fun na setup but idk if it'd work

innovation

there is a thread somewhere in s2ki about f22/f20 hybrid

f22 crank with f22 rods and f20 pistons give the highest CR for NA

https://www.s2ki.com/s2000/topic/732...en-s2k-motors/

wadzii

going from the 84mm crank to the 90.7mm crank will bump the compression about 0.8-1 point.

Breaking Point

He mentioned using ap2 pistons into a an ap1 Moor to drop compression would using the ap2 rods (being shorter )drop it more? Also has anyone tied here options out

chris_barry

AP2 rods and Ap2 pistons in an AP1 are going to drop the compression a lot, to around 4:1 compression.

Breaking Point

I don't see that big of a drop lol.cause the rods aren't that much shorter and the pistons aren't that different. I could see it bringing down to maybe 8-9:1 lol not 4:1 lmao

wadzii

ap2 rods are 3.35cm or inches shorter. lets do some comparisons here.

on an ap1 going from a +9cc piston to a -11cc pistons takes you from 12.5:1 to 8.8:1.. thats 3.7:1 lower with a 20cc reduction.

How many cc's would lowering the piston 3.35mm make.. reduce the chamber by 20cc. Now if you did that with a stock ap1 piston you'd end up with 7.3:1, if you did that with an ap2 piston it would be 6.3:1

Not only that but you would destroy any amount of quench and all efficiency of the motor.

You dont use rods to change compression. Use a different piston or mill the head.

the only reason to change the rod is to change the rod ratio or to make things actually fit in the block. The closer the piston comes to the head the better everything works (with out hitting things of course.. haha)