TB993tt:
...I would want a much smoother factory Motronic lump, 4 litre tuned to 420PS and reving to 7500rpm.
The factory Motronic 3.6L (with Varioram) made 285hp. The 3.8RS made 300hp. Going to be more than difficult to get an NA 4.0L with factory-type Motronic to make 420hp. More than likely this requires a significantly re-worked motor with individual throttle bodies, lightweight internals, etc. Getting 105 hp per Litre in NA Air-Cooled motor is way more difficult than the factory 79 hp per Litre.
The big displacement factory motors also had a pretty lazy character - I bet this Singer is fantastic and exciting in a way that Motronic could never dream to be...
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18 GT3 Manual, 73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs), 06 EVO9 with track mods. Former: 16 Cayman GT4, 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550, 79 635CSi