Does anyone know the differences between the 991 and the 997.2 DFI engines? Or a source which describes the differences? Thank you.

 

The main difference is actually in the air intake-- much less restrictive in the 991 version. Also less outflow restriction. In the 3.8 anyway, also increase in h.p in the 991., by tuning. The engine block is essentially the same though in the 3.8 engine in the 991 and 997.2.

 

The fuel injection has redesigned injectors. Both have the same stroke (77.5 mm). The 3.4 has 97 mm and the 3.8 has 102 mm.

ChuckJ

 

Googling "differences between the 991 and the 997.2 DFI engines?" brings up plenty of posts here and elsewhere also

(via 6SpeedOnline iOS)

 

The 997 engine has a much lower peak torque point, 4400RPM vs 6500 for the 991 engine. Is that mainly due to the exhaust, airflow, and injector differences?

 

thats a good catch i wonder if anyone with an aftermarket exhaust and intake could chime in with a dyno graph