Hi I have a question regarding which is a better motor in swaping onto my car (S5 NA).
What are the pros and cons of each. I plan on using the stock turbo(?), engine but upgrading everything else in the future..fuel injectors,FMIC,BOV,Wastegate, etc...

 

For high boost applications, s5 manifolds on a s4 engine (port matched). For the stock turbo, full s5 motor. S4 has heavier/stronger internals.

 

how about other cons and pros

 

S5 turbo is better. Larger wastegate which will allow for even more porting, especially if you want to run the stock turbo with many modifications.

 

Do a search for the user name sledgehammer, he did an s5 na/turbo conversion, and said it's very easy using the s5 motor, in an s5 car.

S4 has lower compersion, asuming all things are equal allows for higher boost. It's mechical OMP, alows you to premix, or use an EMS that doesn't run OMP's. The E11 is the only EMS I know of that will run the electronic OMP of an S5. If you try to promix with an S5 on the stock ECU it will go into limp mode.

S5 has a better turbo/maniflod. Higher compersion, so it should make a little more torque. The intake is different, I think it's runners are a little bigger. The S5 AFM is said to be better flowing. Early s4 cars use low impeed injectors witch need a resister pack, while S4.5+ use high impeed injectors, that don't need a resister pack.


that's all I can think of right now. I did the NA/T2 conversion on an S4, and it wasn't as hard as everyone makes it out to be, the S5 one is said to be even easier. I know it's a huge PITA to use an S5 engine/harness/ECU in an S4 car, but don't know about doing a backwords swap. I would keep the car all s5 just keep it as streight forward as possible, the few dollars you save by going s4 IMO wouldn't be worth the head akes.

 

yes, stay with whatever series you have unless you are gonna use a standalone EMS. will make things nice and easy.