Elcoete

How can I tell if it's a s4 or s5 just by looking at the motor? No car
Do I need a t2 CAS or can I use a N/A?
Are the coil exchangeable between a t2 and N/A?

DC5Daniel

iTrader: (10)

The AFM and OMPs are the dead giveaways. S4 AFM is large and boxy compared to the tubular S5 style. S4 will have a rod attached to the throttle linkage which goes down to the mechanical OMP on the front passenger side of the engine.

misterstyx69

iTrader: (142)

CAS and coils are the same between the series and engines.NO difference.

blk88t2

iTrader: (5)

This, the S5 afm is a black tube, and the S5 OMP would have an electrical connection.

Another easy check is the Turbo if it hasn't been changed, an S4 has a rather large external twin-scroll actuator attached to the exhaust manifold, an S5 turbo does not have that.

misterstyx69

iTrader: (142)

fast way to tell the engine series is the thermostat neck on an s4 is 2 bolts(metal).and on an s5 is 3 bolts (usually plastic unless aftermarket).

85TIIDEVIL

iTrader: (2)

Series 5 has threaded knock sensor holes just above the Trailing plug on the rotor housings, Series 4 does not.

All these methods are dependent to no one changing anything over the past 35 years.