Today, 12:24 AM
The BMW M3/M3 and Porsche 911 have quite a bit in common this generation. Why? Because both have twin turbocharged and direct injected 3.0 liter six-cylinder powerplants. You can also get either with a dual clutch or manual transmission with power sent to the rear wheels.
Let's look over the specifications of the motors:
9A2 3.0 991.2 Carrera
Torque: 332 lb-ft
Boost Pressure: 13.1 psi
Bore x Stroke: 91mm x 76.4mm
Redline: 7500 rpm
Compression Ratio: 10.0:1
Intercooler: Air to Air
Turbos: 49mm compressor/45mm turbine
Piston Speed FPM: 3759.842
Torque: 406 lb-ft
Boost Pressure: 18.1 psi
Bore x Stroke: 84.0mm x 89.6mm
Redline: 7500 rpm
Compression Ratio: 10.2:1
Intercooler: Water to Air
Turbos: 51mm compressor/43mm turbine
Piston Speed FPM: 4409.449
Obviously, we all know the S55 engine is highly underrated by BMW. Recently, when Porscheboost was doing some testing at VF-Engineering on their Mustang dyno the opportunity presented itself to overlay a stock S55 with the stock PorscheBoost project 991.2.
Here is the result, both dual clutch examples stock on 91 octane pump fuel:
What is interesting to note is that the spool on the 991.2 Carrera 9A2 is much better than the BMW S55. The Carrera is spooled by 2400 rpm and the S55 has more lag by roughly 1000 rpm. That is significant.
You will notice once spooled the curves are fairly similar. The S55 does have more peak torque and horsepower but the difference is not as large as one would expect.
The difference in torque is only 3 lb-ft at the wheels. A wash. Not bad for what on paper is supposed to be 74 lb-ft. The 911 is making more torque than Porsche is letting on by quite a bit.
The difference in peak horsepower is 15 at the wheels. This is attributed to the S55 making power to 6850 rpm while the 9A2 is tailing off past 6400 rpm. Both torque curves are dropping hard but the S55 maintains a top end edge from 6400-6800 rpm.
Revving either engine out to their 7500 rpm redline does not gain anything and short shifting is preferred for maximum performance.
It is interesting that the 9A2 engine with less boost and slightly lower compression is so close. It is also interesting the spool is so much better but Porsche likely concentrated very hard on quick spool down low to appease naturally aspirated purists who would complain about lag. The engine comes on strongly and quickly. It is no wonder the 9A2 knocked out the S55 in its category at the 2016 International Engine of the Year Awards.
In an ideal world we would be able to toss a Carrera S and a GTS onto this dyno to see how Porsche is really separating their 9A2 motors. We do have Dynojet numbers posted for the Carrera and S but the GTS is the variant we are all eagerly awaiting to see. This is the difference between the turbocharged 991.2 Carrera S 3.0 and the naturally aspirated 991.1 Carrera 3.4:
BMW of course has the Competition Package version of the S55 and now the CS version in an even higher state of tune essentially doing what Porsche does in offering the same motor in different flavors. The main difference though is that Porsche changes the turbochargers and not just the software offering greater differentiation and tuning value in this respect.
What is clear is that the turbo era is elevating power and torque to heights we have never seen and it will result in a far greater proliferation of tuning for Porsche and BMW models than ever before.