compression calculation......dont shout!!!
Turbo Mini Forums

I know this topic has been covered millions of times, and I have tried loads of different compression calculations on the t'internet but cant get it to work out right always get some stupid answers.

Basically its a standard metro turbo engine - standard bore (70.625), stroke (81.3), pistons (12cc), 28cc head and bk450 head gasket.

I was looking for around 8.5, i think im under it, but what would be the best way to rasie it slightly - skim a wee bit of the head and how much?

Edited by bertieboo on 10th Mar, 2008.

I make it 8.39:1.

Skimming the head is the easy way to raise it a tad.

A 27cc head will give you 8.57:1.

Bear in mind those figures are close but not 100% accurate, to get the accurate CR you need to measure deck height and also take into account the ring land volume.

Edited by Tom Fenton on 10th Mar, 2008.

Is that right. Cheers tom your a star.

How much of a skim would be needed to get 27cc chambers?

whats the cross sectional area of your chambers?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

How much of a skim would be needed to get 27cc chambers?

I dont know, i dont have the head near me at the minute

Roughly 40 thou as an educated guess, but you'd really need to get maybe 20thou skimmed off and then measure the chambers.

1cc is approx 12"thou on a standard chamber.