so whats the real main differences between the S4 and RS4 engine.. the V8 (new) ones.. if i was going to get like a 05 S4 could i get RS4 internals and would everything from a RS4 work on the 4.2? or maybe even R8 internals haha.. just kinda curious...

 

the R8 is the RS4 engine....no difference other than the computer.

as for the s4 v rs4, the cam is different, the pistions are lighter and make a higher compression, higher flow intake mani/heads, different fueling, better exhaust, etc.

 

could you put an RS4 cam into the S4??? ...to bad it's way too much freakinwork to replace the camshaft...this V8 ain't no honda.....

 

my guess would be that you can do that....but you will probably want an engine tune with it just to keep the audi smoothness there

 

Just changing the cams probably wouldn't help, might actually hurt.Cams are ground to work within specific parameters. Air flow, compression, RPM range, gearing, fueling,etc. I bet you'd lose bottom end, too. Like Blue_S4 said, there are lots of differences that all work together to make more power. I've seen many people put in big cams, only to get smoked by people with smaller cams, in better combinations.

 

^^^^agreed!