911R vs GT3RS engine difference
 

I'm not a technical person so I appreciate if anyone here can explain to me the need for the different compression ratio on the R vs the GT3RS? The R runs a slightly higher compression ratio than that RS but with a lower rpm redline. Why? :confused:

Wild guess, MT (which has 6 gears) versus the PDK (which is 7 gears)?

As a very general statement, more compression gives more torque and power from a given displacement. And lowering redline makes it less likely for the high compression to cause detonation (the main risk of high compression). So if you're forced to lower redline, may as well bump compression...

Agree with Grant. If you are trying to reach the RS headline power numbers with out the Venturi/ran effects of the side mounted air intakes perhaps this is one method you can achieve that....