i had a question aboutthe new 4.2l r rs4 engine. this person i was talking told me thathe 4.2l in the rs4 is a completely differnt engine from the 4.2l
s in the s4 a6 a8 ect, they only had the same displacement. i was always under the conclusion that they took the s4 4.2l and reworked it and modified it and in fact it was the same engine just tune and tweaked better. so does anyone know who is right and has some website or magazine proof?

As far as i know, being a big fan of the S4 & RS4, i was in an Audi dealer the other week in the UK, and was speaking to a echanic their, and he said the engine is the same except for power output and the fact the RS4 has the FSI system.

This is what i was told by a mechanic at Audi, so i should beieve it to be true.

And as for the 4.2 V8 in the A6, A8 models, again its the same V8 again.

appreciate the response. and thought i was right all along.

--------------------- B7 S4 Fuel Injected V8 ------ B7 RS4 FSI V8 ----

Here are the similarities

Bore ---------------------- 84.5 mm --------------------- 84.5 mm
Stroke -------------------- 92.8 mm --------------------- 92.8 mm
Spacing ------------------- 91 mm ----------------------- 91 mm
Displacement -------------- 4163 cc --------------------- 4163 cc

Here are the differences

Horsepower ----------- 340 @ 7000 rpm ----------- 420 HP @ 7500 rpm
Torque -------------- 302 lbs ft @ 3500 rpm ---- 317 lbs ft @ 6000 rpm
Compression Ratio --------- 11.0:1 ---------------------- 12.5:1
# Valves ------------------ 5V -------------------------- 4V
Intake Valve Diameter ----- 27 mm ----------------------- 33.85 mm
Exhaust Valve Diameter ---- 30 mm ----------------------- 28 mm
Intake Cam Drive ---------- Belt ------------------------ Chain
Exhaust Cam Drive -------- Chain ------------------------ Chain
Fuel Injection ------ Manifold Fuel Injection ------- Direct Injection

On the RS4 the following additional engine components have been modified:

Cylinder Head
Crankshaft
Pistons
Connecting rods
Intake Manifold
Exhaust Manifold
Red Line 8250 rpm

In addition, the entire engine block is a new casting.