So, below are the torque curves from 2007 and 2009 997 Owner's Manuals...

Questions:

1: In the 2007 diagrams, the base is noted as an M96/05 engine, and the S a M97/01, Please explain this nomenclature (both diagrams were on subsequent pages of the same 2007 manual).

B: Why the goofy concave arch to the torque curve between 2500 and 4500 RPM on the 2009?

3: Why is the 2009 torque curves have such a darn flat spot? How are they doing this?

D: Why or how is the 2009 torque so much higher than horsepower under 5K rpm compared to the 2007? The delta between years is striking to me

4: Why can't I write in parallel construction using numbers and letters?

This 2009 engine looks pretty odd to me (and I'm and internet French model!). The only diagram that looks like engines of old is the 2007 Base graph... looks typical to me.

Peace
Bruce in Philly

 

Ok, I'll start...

Yup, the 3.6L 997.1 engine is a M96.05 whereas the the 997.1 3.8L is a M97.01. There are a lot of common parts with the 996 series but the engines do have differences. Take a look at the end of the PET docs for the 997.1 and the 996, specifically in the V-pages sections. Here's a sampling of the engine models:

996 Series
1998-99 220 KW M96.01
1999 220 KW M96.02
2000-01 220 KW M96.04
2002 232 KW M96.03 +2 KW, (why did the revision go backwards?)
2003-05 235 KW M96.03 minor bump in power again

997 Series
2005 235 KW M96.05 3.6L base models same power as 996 series
2005 261 KW M97.01 3.8L 'S' models
2006-08 239 KW M96.05 3.6L base models (minor bump in power)
2006-08 261 KW M97.01 3.8L 'S' models

No idea. But the flat spot right after it is interesting. It looks like clipping, as if the engine is capable of producing more torque in this region but is either being held back artificially or there is something else downstream preventing the car from producing more torqure (trans? differential?).

edit: I guess I'm commenting on 'C' here, not 'B'. Or is it '3', not '2'?

 

Guessing it's to meet EPA noise regulations. Most sport bikes also have that dip in that rpm regions which is at 55 MPH or so in top gear. That's why a good tune gets rid of that dip and increases the torque in that region.

 

The 9A1 torque curve has no flat 'spot' It rises to 4500RPM and has a flat peak (a good thing) from 4500 to 6500RPM. Look at the power curve - its derivative d/dt is almost constant.

 

+1 here it not uncommon to have these dips engineered in.


Also this is why a lot of aftermarket mods claim or 'feel' like a big HP boost as this is the part of the torque curve you tend to use the most around town and a lower speeds. You can have a larger gain here and minimal maximum and still feel like your car has picked up a lot of power.


As confirmed by your calibrated butt dyno

 

Two things are important: total area under the torque curve; and as flat as possible at peak. Peak spikes are not real useful or meaningful if not flat at or near peak . . .