The Engine

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.


 

 

Press a Porsche through a turn, and the rear-mounted engine's low center of gravity creates uncanny handling precision. The low mass of its aluminum-alloy block, heads and pistons also contributes to its remarkably efficient performance.

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?
 

Varioram.


 

 
 

 

A lesson in Porsche engineering. Think of an engine as something that, like you, needs to breathe. The demand for air at rest or when walking is different from when you're running at full speed.

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 a resonance
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.

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