well i was reading a previous issue of " sport compact car" and they mentioned the rx7 as one ofthe top ten best buys under 10k..well long story short

they said that the s5 was made with better engine components..so if u plan od doing any mods..and s5 would be better..now my question is,is it just the apex/corner seals that make the diffrence,,or could a s4 that was rebuilt hold upgrades as well as the s5 engine..and ya i already know the s5 has more power,,,but i dont see that as grounds for saying its a better engine to upgrade...

 

The s5 has higher compression on the N/A rotors and the turbo'd s5 has a better turbo than the s4. Also the s5 has more electronic components than the s4 where as most s4 components are mechanical. Are are only a few subtle differences, I'd prolly say the s4's are easier to work on since they have more mechanical components which are easier to diagnose than s5 electronic components. Also there are cosmetic differences.

 

the S5 also has a re-inforced engine (stronger bigger ribs)

apparantly the S5 can handle more abuse and take more power without coming apart or breaking...

but the S4 is a lighter car then the S5 and is generally more reliable, and has a higher build quality

 

Bah, but I always hated that the s5 has plastic end links, and non-replaceable ball joints...

Oh, and engine wise, besides whats already been said. Most of the internal gears were factory hardened if I remember correctly. Anyone?