Race Engine Forum UK

Hello Guy,

I’m coming back to the reading of the chapter concerning the CR in your first book (p22).
I calculated the effective CR for a camshaft opening up to 81° ABDC (GC stage 3), I found an effective stroke of 59 mm and so an effective swept volume of 330 cc (bore=84.4mm).
If I consider your yardstick CR = 9.5:1, I obtain an equivalent static CR of 14:1

Because you recommend for 98 octane gasoline and FI a CR of 12:1, what is it possible to do?
Rise the CR up to 14:1 to “stick” to the yardstick ? Is there pistons allowing this number ? What are the consequence in term of robustness ?

Keep a lower CR to the detriment of performance (??) ? …

Once again I thank you for your lighting on this subject.

Robert

What engine Rob?

G

Guy,

The engine being a 130TC 2l.

Robert

Ok - forget the calcs. You would be wasting your time in my exp going over appr 11/1 because the 8V TC burn rate suffers so much.

I know this from bsfc readouts on dyno test.

GC

Hello Guy,

In other words you mean that 11:1 is enough for any cams in the TC engine ?

Robert

8V - yes

GC