Help me understand C/R

[blue72s]

For our 911's nobody recommends higher than 10:1 C/R for pump gas, but the new Porsches have much higher C/R:

Cayman S - 11.1:1
997 Carrera S - 11.8:1 !!!

Please enlighten me.

TIA.

[Steve@Rennsport]

Hi:

These engines have:

1) VERY sophisticated Engine Management systems with active knock-sensing.

2) These engines use 4-valve, pent roof chambers with a centrally located spark plug that are FAR more detonation-resistant than the air-cooled engines.

3) These engines are all water-cooled which brings FAR greater control off those all-important cylinder head temps.

All these things permit these engines to operate safely on pump premium while using over 10:1 CR.

In short, apples-to-oranges (compared to any air-cooled engine),....

[blue72s]

Thanks for this.