does my compression ratio calculation look right
Turbo Mini Forums

ok ive just measured and worked out, just looking for some clarification (sp?) that im not a million miles away with my measurements or calculation

spec
+0.020 thou overbore to make 1293cc.
18cc dished pistons
bk450 gasket
standard head

measurements
head chamber 22.5cc
stroke 82.35mm
bore 70.90mm
piston dish 18cc
top of piston to top of block 0.85mm
head gasket bore 70.90mm
head gasket thickness 1.03mm

i get 7.74;1

is it looking right?

thanks in advance

Edited by Carl on 5th Sep, 2007.

no longer a series, but still 1.3 turbo.

your calculations work out ok,

but isn't + 20 71.15mm and std stroke 81.33mm

Yeah I would re-check bore/stroke values..

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1/4mile in 13.2sec @ 111 terminal on 15psi

hmmm stil turns out at 7.7;1 seems a little low so not sure if its right.

no longer a series, but still 1.3 turbo.

Using standard stroke and 71.1 as bore I make you CR to be 7.82:1. :)

So looks like your on the right tracks.

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1/4mile in 13.2sec @ 111 terminal on 15psi

one reason its low is the deck height, .82 is about 3 1/4 cc

on a properly decked build you'd be up to about 8.2:1

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1/4mile in 13.2sec @ 111 terminal on 15psi

is the deck hight from top of piston to block with the piston at the top?

these are avonbar/accralite pistons so perhaps they sit a little lower down the bore?

the block had a very light skim as well on the build

no longer a series, but still 1.3 turbo.

IIRC the accralite do sit slightly further down the bore...stand to be corrected though?

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1/4mile in 13.2sec @ 111 terminal on 15psi

well thnks for the help.

my measurements may not be spot on but even if i use the figures what ive found on here i can deduce my compression ratio is some where between 7.7;1 and 8.0;1 i think lol

no longer a series, but still 1.3 turbo.

I cant believe youve only just bovered. LOL
Seems lower than i thought it wouldve been.

Saying that youve ran some stupid boost wit no gasket troubles (until now)

Back once again like a renegade master

http://www.afracing.com/cr.xls

:)

Edited by AlexF2003 on 6th Sep, 2007.

AlexF