Hello, I posted awhile ago stating i wanted to swap in 89-91 s5 TII engine into my 88' NA convertible. I can't remember correctly but someone recommended me from this forum to, install an s4 TII engine instead of the s5. My question is could someone tell me why? I thought the s5 TII engine has power overall, not much more but still. Is there any custom fabrication involved, or is an easy drop-in affair? Thanks.

 

Swapping an S5 engine into an S4 is the same mechanically, but it is a massive pain electrically. Much of the wiring is different, which is why using an S4 TII engine is so much easier. The power difference (200 hp vs. 187 hp) between the S4 & S5 is almost completely due to the fact that the S5 runs 2psi more boost in stock form. A simple boost controller on the S4 engine settles that issue immediately. Click the link in my sig. for details.

 

I understand. Thanks. Have you taken your car to the dyno yet? If yes, could you post the specs of your car, your car is amazing and simply gorgeous.