compression ratio

hi guys , i would like to het your thoughts on compression ratio's in a turbocharged engines

to my understanding a higher compression ratio for example 9.0:1 has the main benefit of better combustion ,response etc while lowering the knock threshold of the engine and where the lower cr has the opposite effect , could you maybe share your thoughts on this

A higher compression ratio will improve engine efficiency, improve boost response and lower EGT. You need to be a little careful though as the compression ratio needs to be selected to suit the fuel you're running. If the octane rating is insufficient then you're going to end up retarding the timing to prevent knock and this is counter productive when it comes to power.

If you're running on pump gas then a CR of 8.5:1-9.5:1 is pretty normal. On a good fuel such as E85, race gas or methanol you can go higher and 10:1-11:1 isn't uncommon. On pump gas these sort of compression ratios would be detrimental to performance though.