hi, I have a well modded s4 tII with a BNR turbo in a first gen car (300+ HP) and I am exploring the option of putting in an FD motor instead.
I am looking for a fun strong, reliable daily driver and I think that despite having to handicap the FD motor with a single turbo only, for chasis clearance, I want some advice about how much better (or not?) the FD motor will make the car perform.

 

I wouldn't bother. REWs have some advantages over S4 TII motors, but they're relatively minor at modest power levels. Certainly not enough to justify swapping if your current setup works.

 

I have significant experience with both and I can tell you that the biggest advantages of the FD engine are:

1) Crank angle sensor requires no adjustment (it bolts to the front cover). It's pretty hard to screw up the timing. As you know, on the FC you have to adjust the crank angle sensor according to the timing marks. If the crank hub and crank pulley are from the same engine then the marks are correct. If somebody swapped them, the marks will be wrong and you could potentially blow your engine from improper timing.

2) FD has much thicker casting at the dowel pin landings--this can be a big advantage.

3) FD has bigger ports from the factory, including the runner section on the side of the iron

4) FD has lighter rotors and higher compression (9:1 vs 8.5:1 on s4 T2), although I don't notice much of a difference in real-world terms from this. The s4 can rev to 8000-8500rpm easily if you can make power there.

5) FD upper intake manifold helps mid range torque some

I'll put it to you this way. If you put the same turbo on both engines, don't expect a real big difference. If your s4 engine is running fine right now I'd just leave it. You could also look into a stainless divided manifold and say a GT35R class turbo. At a given power level you may have better spool with that versus the BNR.

 

Thanks,
I have been having a tough time getting my older haltech E6K tuned properly - blaming the whole TII set up for the trouble. I am super glad to get some response on changing out the motor. Looks like I might change out the ECU if I can't get a good tune.

I thought the newer REW setup would tune easier and run much smoother than the tII setup. A lot of technology has passed between the time the tII came out.

I will consider any responses. super.

 

Haltech E6K is still a very powerful and tunable ECU for a Two-Rotor.
My car drives like an stock OEM daily driver. No hiccups, no bucking, under any throttle condition.

I was fortunate enough to have Crispeed tune my car..

As long as your E6K was properly installed - try another Tuner if you aren't getting the results you want.

 

the FD basically has a bunch of small upgrades to handle the 25% increase in power over the stock t2.

the bigger front thrust bearings, better oil pump, the competition style multi window bearings. bigger dowel lands, etc etc

the port timing is almost the same though, FD makes a sharper turn at the lower intake too, so as far as power is concerned, they are about the same.

if you are having problems getting it to run right, the FD motor won't help