just a quickie
Turbo Mini Forums

anyone know how many cc's it would be if the pistons sat 1mm down the bore? or does anyone have the formula to hand?

cheers, Nick :)

just a simple cylinder formula mate

3.675^2 x big fat pies

all that multiplied by 0.1

should do the trick. assuming that is you went for the 1380!


edit: did it in metres! too used to frigging engineering calcs!

Edited by iain on 21st Aug, 2006.

cheers mate, just found it via google aswell.

i get 1.07 cc if that sounds right?

i did 73.5 x 73.5 x 0.01 x 0.01996 = 1.078...

Edited by Nick on 21st Aug, 2006.

Area = (Pi x D^2 ) / 4

(use cm to make sife simple)
So (3.142 * 7.35 ^2 ) / 4
= ( 3.142 * 54.023) / 4
= (169.72) / 4
= 42.43 cm^2

This is just an area, hence to turn into a volume we need to multiply by a depth (0.1cm)

42.43 * 0.1 = 4.243 cm^3 = 4.243cc


isn't it?

Edited by turbodave16v on 21st Aug, 2006.

same as me except for i arsed not putting the radius in! lol!

Its a monday!!!

well i got around 4.2cc at first by using

73.5 x 73.5 x .039 x .01996

the 0.039 being 39 thou, then i thought you couldnt mix imperial and metric in a sum so i used 0.01 for 1mm, then i got a bit more confused.

i'm looking at buying an engine so i need to work out what the Cr will be with my turbo head.

bore: 73.5mm
stroke: 84mm
deck: 1mm
piston: 11cc
head: 29cc
gasket: 3.8cc

just using alexF's CR excel thing and i get it to around 8.3:1 with 4.2cc as the deck, and 8.8:1 with 1.07 as the deck.

anyone want to check my maths for me please? :)

By my own spreadsheet, I get 8.82:1 for a BK450 @ 2.8cc or 8.64:1 for a 3.8cc gasket with the pistons 1.00mm below the deck

excellent, cheers dave :)

When doing math of any sort, you should use absolute values. 1mm being an absolute value.

Well this has been discussed before but is the BK450 2.8cc???

I measured a compressed one and got 0.8mm, the chamber size was roughly 73 x73.5mm, average that and its 73.25mm so i work out the volume as 3.37cc

A new gasket is 1mm so thats 4.21cc

Who worked out the cc on the BK450 and got 2.8cc, other than Minispares saying thats what it is??????????????????????????????

Edited by Sprocket on 21st Aug, 2006.