Working Out Comp Ratio's With Alternative Pistons To Make An Xu5j4

[welshpug 1,661]

just a topic to see if my calculations and methods are correct really.

 

Starting with the STD XU5 data they would be 1580cc, 9.1 comp ratio, head combustion chamber size of 32cc, piston dish of 9cc, and gasket cc of 7.8 (total clearance volume of of 48.8cc)

 

Working on the fact that they sit flush or nearest dammit at TDC (is that right?) and is 37.5mm tall

 

Working on the fact that an Mi16 piston is 0.38mm shorter at 37.12 (which adds 2cc, D6C pistons I should add) BUT has a smaller dish of 2.8cc, you get total of 4.8cc compared with 9cc for the 8 valve configuration.

 

so if the mi piston has adequate clearance for the 8v head's Valves you'd have a clearance volume of 44.6cc for a compression ratio of 9.85-1

 

bolt on a gti6 head with a bigger chamber volume of 36cc and use Mi16 pistons you get a clearance volume of (36+4.8+7.8) 48.6cc, for a compression ratio of 9.12-1.

 

so, ready to be shoot down in flames

 

p.s using this info to work it out - http://www.pumaracing.co.uk/CAPACITY.htm

Edited May 20, 2008 by welshpug

[Sandy 191]

GTi6 head has a smaller chamber than the Mi16.

[welshpug 1,661]

yeah, 36cc compared to 40cc of the Mi, I was meaning 36cc being bigger than the XU5's 32cc.

[Sandy 191]

Right, i'll be in my shell