What's the difference between these two engines, I know there is a power difference but what causes this. I have a C18 but not sure which one. Is there any way of telling which i have except by looking at the engine number? My car behaves like 1.8 GSi owners on here say their cars do, ie. "waking up over 3500 revs" Or do c18xel powered astra sports act like this also? Is it just a different ecu? Any ideas?