998 Cooper raised D pistons

[Vegard]

Does anyone know the size of the raised D in cc? I'm trying to work out the CR on this engine.
I've heard 4cc but it does seem alot.
There are infact three levels on these pistons, the squishband around the "D" is higher than the lowest point. I guess including this, 4cc might be true.

I can calculate and estimate, but if someone once did a proper measurement....???

[dutchacme]

Hi Vegard,

did some checking on a Hepolite Powermax Cooper piston

outer diameter 64,8 mm
D shape diameter 58,3

D shape area is 21,765 cm2
C ring shpae area is 4,38 cm2

the height D shape top down ontop the C ring shape is 0,7 mm
the height of the D shape top downtop onto the squish is 0,8 mm

this makes
D shape + C shape times 0,1 mm => 0,26093 cm3
D shape time 0,7 mm => 1,52355 cm3
Total crown volume 1,785 cm3

If one would make a decimal mistake in the first volume one could get approx 4 cc

[littler]

i deal with raised crown pistons all the time as pretty much every aston engine i build has them!

basicly what i do is drop the piston down the bore a known amount and work out the volume of the area from the squish band up then CC the area with a burette.

you then remove one form the other and youre left with crown area

most of our cosworth race postons have about a 66cc crown!