[tekenaar]

Static vs. dynamic CRs . . . my recent build-up

Calculated, static compression ratio does not take into account the closing point of the intake cam lobe or other variables that affect the compression that the motor "sees" when it is actually running. That is why Dave ("Nobody") has been able to utilise a CR of near 11:1 on pump gas by installing a suitable, long duration cam (As RallyBob so rightly said could be done!).

Have a look at www.kb-silvolite.com and see their Tech articles on "Dynamic Effective Compression Ratio" and also the compression calculators that are on that site. All extremely interesting and puts a whole new light on CR's

Taking cam profile into consideration when estimating (calculating) dynamic CRs certainly helps explain why my 10.7 CR, domed piston, large valve, stroked engine runs on 87 RON without any pinging or resorting to retarded ignition.

Brief specs:
'72 ported head with 45mm Opel intakes, 38mm Opel exhausts, 224°@.050"/.465"/110°LDA cam/solids, matched Opel single springs, 8 Opel intake retainers (lighter) and valve locks, rockers and lock-nuts from my 2.4.
'71 (stationary pump) block bored to 3.701", forged 94mm Venolia pistons with .100" domes, moly top rings, no-gap seconds, 3-piece oils, stock '71 forged rods bored for .912" Ford LW pins, .010"/.010" 2.2 crank, everything "zero balanced".
'73 timing cover with new timing chain and tensioners, OP relief spring tensioned 2mm additional.
'75 distributor with locked, mechanical only advance and Pertronix, advance weights resprung, set at 10° initial, 35° total all in at 3000RPM, 6500RPM rev-limiting Bosch rotor, MSD5 multispark, Bosch "red" coil, Bosch WR7BP plugs at .040" (1mm).
Steinmetz SSD welded and ported (48mm) intake, single DHLA48 carb with 15mm trumpets inside fabricated cold-air plenum, filtered by K&N 78mm filter.
Old style, 4 into 1, HT coated header into 2.25" exhaust, turbo muffler and gutted "stock", twin-pipe resonator.
Remote oil filter and T-stat controlled "Volvo turbo" oil cooler.

Result: Street sweeping TORQUE MONSTER!

 

[tekenaar]

Dome CRs

I thought it was a bit more than just 2 cc. R-Bob calculated 9.5CR for 94mm flat-top pistons with the 2.2 crank and a 1.9 head, and 11.1CR with .150" domes. I had the domes milled .050" (.100" domes) and extrapolated the CR from there mathematically by calculating volume of material removed. Couldn't locate my numbers, but it came to ~10.7CR.

With the small overlap cam I'm using, it's probably a bit lower when dynamically measured . . . perhaps ~10.3CR. With this engine's long stroke (77.5mm), it produces awesome torque from ~3000 to 6200 RPMs . . . EXACTLY why I chose this combination!

 

[tekenaar]

Or is it ?

The 2.2 crank is currently at the machinist right now getting wet-mag'ed, and if it passes that test, then it is going to get turned. Pretty much, everything is on hold because tuning a 2.0 is a world away from a 2.2, and I hate to invest too much time and parts into it, then have to change course (as I already have done repeatedly).

That and the holidays have kicked me in the neither regions.

UNLESS you're trying to tell us something else entirely, I think that's supposed to be "nether regions".