Piston to Deck height difference
Turbo Mini Forums

So got out the DTI today and measured the difference between the top of my piston and the top of the block was 1.02mm can anyone tell me what this means in cc for my compression ratio please :)

Cheers

Craig

4.08cc

Edited by bennyy on 4th Apr, 2012.

Audi s4 b5 - 470bhp & 486ft lbs

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble

Depends on bore size. But probably around 4cc or so.

WWW.TURBO-MINI.COM

Compression Ratio.
The ratio is calculated by the following formula:


where
b = cylinder bore (diameter)
s = piston stroke length
Vc = clearance volume. It is the volume of the combustion chamber (including head gasket). This is the minimum volume of the space at the end of the compression stroke, i.e. when the piston reaches top dead center (TDC). Because of the complex shape of this space, it is usually measured directly rather than calculated.

He's 1310cc

Audi s4 b5 - 470bhp & 486ft lbs

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble

As benny says bores is 1310cc

so do you just multiply it by the overbore size? so in my case 0.40" so 1.02 * 4 = 4.08cc

??

Thansk guys :)

1.02mm is 0.040" of an inch, I know because I have a good memory lol. I think its on phils site iirc?

Audi s4 b5 - 470bhp & 486ft lbs

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble

Phils site goes up to 0.020" down the bore

CR works out as 9.17 : 1

should be good for about 10psi with an intercooler?

0.020+0.020=0.040?

That should be ok if fueling and timing are good, why not lower it a tad more for more boost? Do it now while its being built because the crave for more boost never ends.

Audi s4 b5 - 470bhp & 486ft lbs

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble

Been building it for a year already and havent got the money for head work, besides going form standard 998 to 1310 turbo is going to be a big jump anyway :)

Iirc to work out the area of the piston to deck height it would be the same as working out the cc of an engine
Radius(cm) x radius(cm) x stroke(cm) x 3.14 if phil hadn't already kindly listed it for everyone.

Edited by wez on 4th Apr, 2012.

one day boost will be mine!

Yes it's only listed on my site to 0.020", so for 0.040" just double the figure. :)

WWW.TURBO-MINI.COM

1.02 / 25.4 = 0.040 :)