Jay and all,
Firstly let me point out to all that I'm calculating this purely as an
interesting exercise and not taking physical measurements from the motor -
which I will do at a later stage. This spreadsheet I did up was purely to
see if the calcs worked - after seeing they didn't with the B data I
entered, I figured I must have missed something. I knew about the piston
dome/dish issue but didn't bother including that in the calculation at this
stage because the difference to the overall result would be very slight - I
guess. I know it's important in reality but not while I'm just playing with
the spreadsheet. I just wanted to get 'into' the 'ballpark'. Y'see I have a
'totally std' engine, never been decked or had the head skimmed (we've owned
it for ages). So I guess I have something good to start with.
>Neil, how are you measuring your combustion chamber volume? You need to
Well, this sounds like the problem going from Harlan's post. I was just
taking the 42.5cc figure from the Bently book. I didn't figure the
"..Combustion chamber CC plus the volume from the top of the piston to the
top of the block at TDC (deck height) " part, I just assumed the piston went
to the top of the cylinder - doh. I guess if I add that figure to the CCV I
will end up with a closer figure. I guess it adds about 15cc to it, as I
think I worked out 57-58ish cc's got to the 8.8.1 ballpark.
Questions:
Can someone tell me what the dish CC is and also the deck height on a
totally standard - theoretical - engine (18GJ)? I also guess where the
stroke of the piston stops is where the deck height volume starts - surely I
don't have to subtract the deck height cc from the Swept Volume figure as
well as adding the deck height volume to the CCV? I would say not because
the stroke figure in the swept volume calculation only goes to where the
deck height figure begins..?
I'm going to do all these measurements on the motor when I have the $ to buy
the equipment I'll need. Performing the actual measurements looks quite
difficult. Very interesting stuff this. :) Thanks everyone for the help.
Cheers,
Neil.
--
Neil Cotty - Sydney, Australia
1970 MG B GT / 1959 MG A 1600 Mk1
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