In depth the new Porsche Boxster Engine and Transmission

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Photography by: Porsche AG
981 Porsche Boxster transparent technical view
981 Porsche Boxster transparent technical view Source Porsche AG
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981 Porsche Boxster transparent technical view Type 981 Porsche Boxster Engine and Transmission Type 981 Porsche Boxster Flat-Six Engine Cutaway 981 Porsche Boxster dynamic transmission mounts 981 Porsche Boxster redesigned 7 speed PDK

The Boxster’s mid-engine concept has been a decisive reason for its outstanding agility ever since the roadster has existed. In addition, the flat-six engines with their economical performance, located forward of the rear axle, make the two-seater Porsche a model of performance and efficiency.

The new Boxster models have opened a whole new chapter here. With direct fuel injection, thermal management, electrical system recuperation and auto start/stop function, both models’ engines are even more powerful than before on the one hand while being more than 15 per cent more fuel-efficient

The new Boxster models have opened a whole new chapter here. With direct fuel injection, thermal management, electrical system recuperation and auto start/stop function, both models’ engines are even more powerful than before on the one hand while being more than 15 per cent more fuel-efficient irrespective of model on the other hand. Comparative figures:

Boxster

new

before

Δ

Displacement

2,706 cm³

2,893 cm³

- 187 cm³

Power

265 hp at
6,700/rpm

255 hp at 
6,400/rpm

+ 10 hp

Torque

280 Nm at 
4,500/rpm - 6,500/min

290 Nm at 
4,400/min – 6,000/min

- 10 Nm

Fuel consumption 
with manual transmission 
with PDK


8.2 l/100 km 
7.7 l/100 km


9.4 l/100 km 
9.1 l/100 km

-1.2 l/100 km (-12.8 %) 
-1.4 l/100 km (-15.4 %)

 

Boxter S

new

before

Δ

Displacement

3,436 cm³

3,436 cm³

+/- 0 cm³

Power

315 hp at 
6,700/min

310 hp at 
6,400/rpm

+ 5 hp

Torque

360 Nm at 
4,500/min – 5,800/min

360 Nm at 
4,400/min – 5,500/min

+/- 0 Nm

Fuel consumption 
with manual transmission 
with PDK


8.8 l/100 km 
8.0 l/100 km


9.8 l/100 km 
9.4 l/100 km

-1.0 l/100 km (-10.2 %) 
-1.4 l/100 km (-14.9 %)

The Boxster’s engine has been derived from the Boxster S machine according to the downsizing principle and has a displacement of 2.7 liters – 0.2 liters less than its predecessor. Both bore and stroke have been reduced. In the standard model, increased performance, higher revs and the specific design of the combustion chamber for direct fuel injection with higher compression resulted in a change to the light alloy pistons. On the intake side, both engines feature variable valve lift and variable valve timing (VarioCam Plus) with the range of adjustment increased from 40 to 50 degrees. Moreover, the engines breathe through an especially flow-optimized and thus efficient air intake system. The main reason behind the reduced breathing resistance is that air is now drawn in from both air intakes on left and right. Moreover, a pressure sensor measures the intake manifold pressure instead of a conventional hot-film mass air flow sensor, which is located in the air flow and thus acts as an obstacle. In the 3.4-litre six-cylinder engine of the Boxster S, a controllable resonance flap further improves the charge level, thus providing high torque at low revs and an even torque curve.

Intelligent efficiency: Electrical system recuperation, thermal management, coasting

The Boxster with PDK transmission is borrowing the principle of only drawing on engine power when it is actually needed from the new 911 Carrera: so-called coasting

To increase efficiency, the boxer engines feature electrical system recuperation and map-controlled cooling water thermal management. In terms of electrical system recuperation, the battery receives an increased charge during the braking or coasting phases. Reducing the generator charging current with a full battery in turn reduces the load on the combustion engine during acceleration phases as the combustion engine does not have to sacrifice so much power for charging the battery. Thanks to the intelligently managed cooling systems shared by both engine and transmission, both of them reach their operating temperatures more quickly, meaning better combustion under partial load with less friction. To avoid any disadvantages under full load, the map-controlled thermostat – as required by the driver – very quickly reduces the temperature under full load even below the level of the predecessor model, thus ensuring an optimal charge and maximum performance. Moreover, Porsche is introducing the start/stop function for PDK and manual transmission in the Boxster as well.

The Boxster with PDK transmission is borrowing the principle of only drawing on engine power when it is actually needed from the new 911 Carrera: so-called coasting. What is meant by coasting is rolling along without power, with the engine idling and with low fuel consumption to match. In practice, that means fuel savings of up to one litre per 100 kilometres with a forward-thinking driving style in everyday driving. Coasting is initiated by slowly taking one’s foot off the accelerator or by a manual upshift command if the highest possible gear given the driving situation already happens to be engaged. Coasting is ended by accelerating, braking or by manually changing gear. Coasting is better for fuel consumption because it enables the vehicle to harness its kinetic energy and convert it into forward motion.

Standard equipment: manual six-speed gearbox

The gearbox is critical to driving performance, comfort and fuel consumption values. A six-speed manual gearbox is fitted as standard in the new Boxster models, the gear ratios being optimally matched to the engine characteristics.

The Boxster’s new ergonomics and the more precise shift characteristics now offer the driver even better prerequisites for fast and effortless gear changes: The upward inclined centre console, as in the Carrera GT, and the driver’s seat position ensure a very short distance between the steering wheel and gearshift lever. The new gear indicator in the rev counter indicates which gear is selected, the upshift recommendation in the instrument cluster acts as a guide for the driver assisting with consumption-optimized driving.

Optional equipment: Redesigned Doppelkupplungsgetriebe (PDK)

The extensively redesigned Porsche Boxster PDK, available as an option, offers seven gears, gear changes without interruption to the power flow making for faster sprints and lower fuel consumption

The extensively redesigned Porsche PDK, available as an option, offers seven gears, gear changes without interruption to the power flow making for faster sprints and lower fuel consumption. The latest generation PDK has been rigorously enhanced for performance but with fuel consumption and comfort characteristics being improved as well. The driver immediately realizes that the optimized shift points are significantly quicker in accommodating his wishes. The new Boxster models are tangibly more responsive; even in normal mode they reach higher speeds more quickly, thus providing increased agility. Overtaking is also supported by a PDK function: When the driver presses the accelerator pedal briefly but firmly, the PDK understands that a sprint is imminent and selects the lowest possible gear to ensure the fastest possible overtaking maneuver through high acceleration power.

Heavy braking is supported by faster downshifts at higher engine speeds, which are started earlier and are punctuated by intermediate acceleration – accompanied as ever by highly emotional sound. This retains higher revs and thus performance. This provides increased power output coming out of bends, thanks to the optimization of the shifting programs, and the significantly reduced shifting times, the latter especially in manual mode as well. For example – subject to a suitable stretch of road – a controlled drift is possible with Porsche Stability management (PSM) deactivated: detection of the yaw angle and steering wheel angle prevents upshifting thus permitting this very special driving fun. Pressing the sport button, now fitted as standard, provides a further increase in the performance, with regard to both the engine’s fuel intake and the shifting strategies of the PDK. In combination with the features relating to the chassis and the engines, the new Boxsters with PDK deliver a completely new driving experience.

This is in no way at the expense of comfort – quite the reverse. The change to more comfortable and more economic engine speeds after a dynamic driving phase is also effected faster. The drive-off behavior has also been optimized, providing the very highest performance while remaining comfortably relaxed and also extremely agile.

The new Boxster models now offer a sport button, featured as standard, which allows the driver to choose between a sporty setup and a comfortable setup optimized for fuel economy. In sport mode, the electronic engine management system controls the engine with more bite. This makes the engine dynamics even more direct. On vehicles with Porsche Doppelkupplung (PDK), upshifts take place later and downshifts earlier in automatic mode. Moreover, the start/stop function and the coasting function are deactivated.

New: Sport Chrono Package for the first time with dynamic transmission mounts

The optional Sport Chrono Package, which now includes dynamic transmission mounts for the first time, makes for a very wide spread between a sporty setup – for example for the race circuit – and driving comfort in everyday use

The optional Sport Chrono Package, which now includes dynamic transmission mounts for the first time, makes for a very wide spread between a sporty setup – for example for the race circuit – and driving comfort in everyday use. In conjunction with PDK and the Sport Plus button with the Launch Control function, it supports the best possible starting acceleration. The vehicle thus requires 0.2 s less for 0 to 100 km/h than in the normal mode. The Sport Plus button also activates the PDK “racing track” shift strategy; the lowest possible gear is engaged at all times, braking downshifts are performed already from around 4,000 rpm with the fastest possible downshifting, optimal shifting points and torque enhancement during the shifting operations.

To further improve the driving dynamics as well as the driving comfort, the Sport Chrono Package also comes with dynamic transmission mounts. These change their rigidity and damping characteristics according to the current driving situation. The Boxster’s engine-transmission unit is mounted on three points of the body: the front engine mount and the two rear transmission mounts. The dynamic transmission mounts significantly reduce the transmission of vibrations from the entire drive train and in particular from the engine to the body. The system does this by using a damper fluid with magnetisable characteristics and an electrically generated magnetic field. In the process, the magnetisation of the particles in the fluid is increased or decreased. This changes the viscosity of the fluid and the transmission mounts are made harder or softer.

Type 981 2012 Porsche Boxster The dynamic transmission mounts significantly reduce the transmission of vibrations from the entire drive train and in particular from the engine to the body.

With a sports car, the damping characteristics of the power unit mounts have a considerable influence on handling. When entering a corner or negotiating S-bends at high speed, for example, hard mounts significantly reduce the power lag caused by the inertia of the drivetrain, thus minimizing a pushing of the vehicle’s rear end. As with racing cars, in which the power unit is rigidly bolted to the body, this results in more stable and more precise handling. Disadvantages are discernible power unit vibrations and reduced practicality when driving with comfort in mind. However, these vibrations are filtered by means of softer mounts. The dynamic transmission mounts combine both of these advantages at the same time and reduce vertical power unit vibration during acceleration at full throttle. The result is more uniform and higher propulsion force on the rear axle with better traction and acceleration. The system thus ensures that the power unit is optimally in tune with the body in every driving situation, thereby contributing to improved handling characteristics accompanied by a high degree of driving and vibration comfort.

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