Few cars are as closely
associated with the engine that powers it as the Porsche 911. The air-cooled
"boxer" engine, mounted behind the rear wheels, remains essential to the
unique performance of the 911.
Tap on the throttle and you'll discover the instant benefits of a power-to-weight ratio few cars have ever equalled. The curb weight of a 911 Turbo, for example, is just over 3,300 lbs. Yet from its 3.6-liter, six-cylinder engine comes 400 peak horsepower and 400 lb-ft of peak torque. Translation: an astonishing power-to-weight ratio of 8.27 :1.
As you round the apex, the engine's dry sump lubrication, an ingenious system almost exclusive to racecars, ensures that high lateral g's don't rob your Porsche of its lifeblood, 12quarts of oil.
As you throttle out of the turn, hydraulic valve lifters in the tips of the rocker arms reduce engine noise, as well as eliminate the need for periodic valve adjustment.
And, if your 911
should ever come to rest, a dual-coil ignition system has been added to
help improve cold morning starts as well as idle smoothness. Of course,
who would choose to remain idle in such a machine?
In an engine, the volume and velocity of the air reaching the combustion chambers are determined by the design of the intake system. Typical systems are a compromise: with fixed plenum and runner lengths, the intake systems can't optimize performance over varying engine speeds.
Enter Varioram, Porsche's
innovative two-stage resonance induction system. Varioram literally alters
intake runner length and plenum volume automatically. At low and
medium engine speeds, the intake runners are relatively long and create
effect that enhances cylinder filling.
At speeds above 5,000
rpm, the intake runner lengths are halved by vacuum-activated sliding sections.
This creates a "ram air" effect where the air is forced into the combustion
chamber at slightly higher than ambient pressure levels. Above 6,000 rpm,
one of the resonance chambers is closed by a flapper valve located in the middle of the chamber.
Result: no matter what the engine speed, Varioram optimizes engine performance to produce maximum driving response. The torque curve of a Porsche engine is nearly ideal, with deep reserves of power available throughout the rev range, and especially at the high rpm levels at which a Porsche is often driven.