high comp pistons

[EGBOY]

been looking around for some really high comp pistons.. but i only find 12.5: 1 as the max...
are higher comp ( higher than this) custom one offs?
can anyone help me here or post up some links to places that make high comp all motor pistons ( off the shelf style)
thanks

[TODA AU]

been looking around for some really high comp pistons.. but i only find 12.5: 1 as the max...
are higher comp ( higher than this) custom one offs?
can anyone help me here or post up some links to places that make high comp all motor pistons ( off the shelf style)
thanks

Yes & no,
12.5:1 can easily become 13.5:1 or more.
Generally the comp ratio quoted is a nominal value or default value.
That is what you'd get with a std combustion chamber on an unmachined head, with a standard deck height block using x or stock gasket thickness.
In the case of the average b-series piston where the installed height is 30mm
The crown of the piston will be @ zero deck on a B16A
& 0.45mm below the deck height on a B18C
Removing this 0.45mm from the top of the deck on a B18C will increase the compression dramatically.
Same can be said for milling the head.
In any case, you need to measure & see where things are before you decide on X comp ratio pistons.
If you simpley go for the highest comp possible, it is likley you will exceed your compression expectations & significantly reduce the size of your tuning window.
Custom pistons are pretty much available from all piston manufacturers, with varying lead times for production.
Hope that helps.

[SeverAMV]

dont forget to factor in that cast iron pistons have a tendency to expand under heat and pressure. if you plan to push your motor past 7-8krpm, with a compression ratio above 12, i'd recommend getting forged pistons just so you dont shoot a piston through the head.

[fatboyz39]

dont forget to factor in that cast iron pistons have a tendency to expand under heat and pressure. if you plan to push your motor past 7-8krpm, with a compression ratio above 12, i'd recommend getting forged pistons just so you dont shoot a piston through the head.


B18c type R motors uses cast pistons with rev limiter 8600rpm. We've used cast pistons and rev to 8800rpm with no problems what so ever and thats with 12.x comp.

[fatboyz39]

Deck the block and head. That should yield some more comp.

[SeverAMV]

in a normal motor theres no problem with cast iron pistons, but when you mill the head and deck the block, it gets a lot closer to the head than normal.

[delsol9000rpms]

cast iron pistons will be fineat 12+:1... but forged will be better... i dnt think ive seen aftermarket hi-comp racing cast-iron pistons anyway most of them are forged

[Type R Positive]

Can you still buy cast iron pistons? I don't know why this was even brought up.....

[ralph_ef9]

i think the piston from a ek9 b16b is a great upgrage for any b16a motor....(b18c not sure)
and much cheaper than a custom pistons, also easy to buy!