Does anyone know what the engine design differences are between the 997.2 and 991. Of course, I understand in the base model the displacement went from 3.6 to 3.4 and the crank power went up 5 hp. Are the heads and valves the same? What about air induction, injection system, ignition, and exhaust systems?

 

Completely different engine. New design no RMS. Closed deck block using alumasil casting vs locasil. Much stronger design now used in all models including turbo. Oil starvation in racing conditions cured. Lots more inprovments.

 

The old engines have the same displacement.
3.6 for the non-s
3.8 for the s

They grew when the 997 replaced the 996

The new engines are also DFI. Fuel economy is supposed to be slightly better.

 

Hi Steve. Very interesting. Can you point me to a source where I can learn more about the differences? Gosh, do you think the 997.2 engine will be largely ignored by the after market companies since it was in production for just 2 years? Thank you for your reply. --John

 

I count 4 years, 2009 thru 2012.

 

TPC already has a turbo kit ready for the DFI engine.

Don't forget that there are Caymans and Boxters running around with the same DFI engine too.

 

Is there a specific reason you are asking? That might help people here give you some better info.

 

Not sure you are correct. The OP asked about the difference between the 997.2 engine and the 991. I believe you gave the difference between the 997.1 and 991 engine.

 

+1

The 997.2 do not have RMS issues. Different engine design. The 991 engines are closer to the 997.2 but there are certain differences.

The new 3.4 has power anywhere from 325 in the new boxster s to 350 bhp in the new base carrera... I am assuming they are the same engine.

 

Sorry I was talking about the difference between 997.2 and 997.1
991 major difference is in the heads valve train and cam profiles I think, higher revs and flatter torque curve at higher rpm.

 

You can actually see the 997.2 engine, and the 991 is lost under to turntables.

 

Same engine design differences only in electrical and thermal management.

 

Hello everyone, thank you for your replies. I was just curious. I have recently read several books on the history of the 911, how to modify the older engines for better reliability and more power. These books stop at the end of the air cooled engines. Just learning about the water cooled engines for my general education. --John

 

Was a good question. I was interesed in the answer as well. Question now is which answer is correct. Answers suggest everything from a completely different engine to the same engine with minor support system changes. And it must have a RMS, just no IMS. I'm thinking slicky rick's amswer makes the most sense as Porsche generally gets more than 4 years from an major engine redesign.

 

It may well be a question better asked on the 991 forum, since many of us, having 997's don't really care what the 991 engine is as its not an engine I have nor factors into me keeping my car.