2.0 to 2.3 Build Plan

[B D]

I wanted to run the specs of my planned upgrade to a 2.25 from a 2.0 by the experts and get some opinions on compression ratios.

The case is an Al 2.0 with all the oil upgrades, 66mm crank, std rods and bolts, recently rebuilt no issues. Mahle cylinders bored to 85mm and JE pistons with CR of 9:1 to 9.8:1 not sure? Rebuilt 2.2/2.4 heads to S pecs ported and polished 46/40 valves 36/35 ports. Running L cam (same as E) topped off with Webers. In conclusion a 2.2 with "S" P/C and heads with an "E" cam.

My first thought is to run a CR of 9.8:1 same as the 911S. But I want to ensure that's the best choice with 91 octane street gas in CA. JE Pistons offers a 9.8:1, 9.5:1 and a 9:1 option.

TIA

[BURN-BROS]

Bret,

The Dynamic compression of the E cam is higher than the S, that is why the E had less static compression than the S. Stay below 9.5 /1 with the E cam. 9.0/1 would be the safest route.

[jpnovak]

Overall this sounds like a great build.

In my opinion that intake port size might be too large for that cam and displacement. I think the low-end would suffer more than you would gain in the top-end. If the car is primarily street driven I would err on the small port size to increase intake velocity. This will also help the metering signal on the webers. My numbers would be a 33-34mm intake diameter and this would close to max out the intake velocity at peak TQ and HP around 100 m/s gas speed.

YMMV.