911 engines by Mike Piera 1/00

Here are some charts that I put together, of various 911 engine torque curves. Many are factory curves from the shop manuals, others are from actual dyno runs. Dyno runs in Ft Lbs were recalculated to MkP, and if done on a chassis dyno, they were increased by 15% to compensate for the drivetrain loss.

The 2.8 RSR engine is a home-built engine with twin plugs, customs cams and head work, pistons, etc. Others are from the factory manual. Note the strong high end of the 2.4S, and how the 2.7RS, though it has S cams, has a torque curve shaped more like the 2.4E.

These are all from the factory manuals. Note that the 2.7CIS is a killer down low!

The mod 2.7 is close to RSR spec, the 2.8RSR is the same as the chart above. I dyno'd my 2.7RS (this curve is with a home-made "sport" muffler) and it parallels the factory curve but seems a bit stronger down low and weaker up high. Maybe due to my cam timing. I have no idea why mine is higher than the factory spec, maybe dyno error, or the SSI's and exhaust helped. This curve does not show my dip at 4700 as it only has data points at 500RPM intervals.

Dyno runs comparing mufflers.

Run1 : Supertrapps with 12 or so disks.
Run 2: Warmed up (was a bit cold)
Run 3: remove disks
Run 4: advance distributor a bit
Run 5: Stock muffler
Run 6: Sport muffler (home made, just added 2 outlets).

Note that supertrapp disks are EVIL! The factory sport muffler is real close to open supertrapps in top end power, and even better for autocrossing (though it is a lot heavier...).

The 3.0 and 3.2 were run on a dyno, the 3.0 is stock while the 3.2 has SSIs, special muffler, and other tuning like most F class race cars. Note the 3.0 is like a larger 2.7S engine. And it is interesting how the 2.7RS has similar low end torque to the 3.2, and a stronger top end. But the 3.2 kills the 2.7RS through the meat of the powerband.

Here is a chart of my old 2.7RS engine and my rebuild 2.7RS engine VS a 2.7"RS" with E cams which people used to think were the best cams for the RS engine.

You can see that the E cams are pretty good from 3000-3750. But if you are below 4000 RPM you really need to downshift as you are making VERY little HP, so this RPM range is meaningless. Even my old worn out engine with S cams has a big improvement at only 4200 RPMs. It had a bad tuning DIP at 4750 but has been tuned out after the rebuild. My minimum RPMs at a racetrack is about 5000 RPM.

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