Porsche PSM, PASM & Sports Chrono Plus

PSM = Porsche stability Management

(Button Marked “PSM OFF”)

PSM, which comes as standard, is an automatic control system that stabilises the vehicle at the limits of dynamic driving performance. Sensors continuously monitor driving direction, speed, yaw velocity and lateral acceleration. Using this information, PSM computes the actual direction of motion. If this direction deviates from the desired course, PSM initiates braking interventions targeted at individual wheels in order to stabilise the vehicle.

Under acceleration on wet or low-grip road surfaces, PSM improves traction using the ABD (automatic brake differential) and ASR (anti-slip regulation) functions, giving an agile response.

When ‘Sport’ mode is selected on the optional Sport Chrono Packages, the PSM intervention threshold is raised to enable greater driver involvement – particularly at speeds of up to approximately 70 km/h (45 mph).

The integrated ABS can further reduce the braking distance.

For an even sportier drive, PSM can be deactivated.

However, it is automatically reactivated for your safety if either of the front wheels (in ‘Sport’ mode, both of the front wheels) requires ABS assistance.

ABD remains permanently active.

PSM has been enhanced and now includes two additional functions: precharging of the brake system, and brake assist. If you suddenly release the accelerator pedal, PSM automatically readies the braking system. With the braking system having been precharged, the brake pads are already in light contact with the brake discs. Maximum braking power is therefore achieved much sooner. When sudden braking is detected, the brake assist function applies maximum brake pressure to all four wheels.

Porsche Active Suspension Management (PASM)  (option 475)

(The button with the shock absorber image )

Optional PASM, the electronic damping control system actively and continuously regulates the damping force for each wheel according to the road conditions and driving style. In addition, the suspension is lowered by 10 mm.

Forward thrust | Chassis The driver can select between two different modes: ‘Normal’ which is a blend of performance and comfort, and ‘Sport’ where the setup is much firmer. Depending on the mode selected, therefore, PASM can be both sportier and more comfortable than the standard chassis. The PASM control unit evaluates the driving conditions and modifies the damping force on each of the wheels in accordance with the selected mode.

Sensors record the body movements that accompany powerful acceleration, braking or uneven road surfaces. This enables intelligent adaptation of damper stiffness for the selected mode, optimising contact between each individual tyre and the road and reducing pitch.

The image below shows the manner in which PASM works.

…it should be noted that some Porsche models have the option of 3 modes within PASM.

The following is from the Macan manual (2017/2018 year):

Porsche Active Suspension Management (PASM)

PASM is a system for the active adjustment of shock absorbers. The variable shock absorber system individually selects the relevant shock absorber stiffness for each wheel depending on the driving situation and driving conditions. Driving safety, agility, and comfort are optimized.

Three different chassis setups can be selected at the push of a button:
– “Comfort”

Comfort mode ensures comfortable chassis tuning.

The SPORT chassis setup offers very sporty shock absorber tuning.

SPORT PLUS mode offers particularly sporty shock absorber tuning (e.g. for race circuit driving). Apart from the manual mode selection, the PASM also adjusts the shock absorber setting toward more sporty or more comfortable depending on the driving situation.

Sport  button

Select the Sport mode by pressing the Sport button on the center console.

Throttle response becomes even more direct, the rev limiter is adjusted to a harder setting, and engine dynamics are tuned for performance driving.

The Auto Start Stop function is also deactivated. Coasting mode is also deactivated automatically.

With the optional Porsche Doppelkupplung (PDK) transmission, the shift points
are reconfigured to operate at higher engine speeds. Shift times are reduced and gearshifts become firmer and more immediate, while throttle blip downshifts are accompanied by an emotive engine sound.

PSE (optional Sports Exhaust) and PASM are also enabled.

Sport Chrono Package including dynamic gearbox mounts  (option 639)

Time is precious and every hundredth of a second counts. The optional Sport Chrono Package provides an even sportier tuning of throttle response and handling characteristics.

The package comprises dynamic transmission mounts, a performance display, a digital and analog stopwatch, and the Sport Plus button.

When this is pressed, optional Porsche Active Suspension Management (PASM) offers more intensive roadholding, switching to Sport mode for firmer damping and more direct steering.

The trigger threshold for the Porsche Stability Management (PSM) system is raised. Agility is perceptibly enhanced when braking for corners with PSM, allowing even sportier braking and exit acceleration. For even greater dexterity, PSM can be set to standby while the car is still in Sport Plus mode. For safety, it is set to intervene automatically only when ABS assistance is required.

In conjunction with the optional PDK, the Sport Chrono Package comes with two
additional functions.

The first is Launch Control, which is designed to optimize acceleration from a standing start.

The second function is a motorsport derived gearshift strategy. Using this, Porsche Doppelkupplung (PDK) is geared up for the shortest possible shift times and optimal shift points, while torque boosts during gear changes provide the maximum acceleration available. This involving experience is further enhanced by overrun downshifts and the throttle-blip function for uncompromising driving pleasure.

An additional display in either the steering wheel or the instrument cluster indicates the Sport or Sport Plus button—and, with PDK, Launch Control—has been activated.

In conjunction with the optional Porsche Communication Management (PCM), a special display enables you to view, store, and evaluate lap times or other driving times. It shows the total driving time, lap distance, lap number, and lap times recorded so far.

Understanding Rev Limiters:

A rev limiter is a safety device that cuts fuel, ignition or both at a specified RPM to prevent an engine from continuing to rev beyond safe mechanical limits. Because hitting a hard rev limiter can be uncomfortable for the driver and hard on the car, 981s come with a ‘Soft Rev Limiter’.

A Soft Rev Limiter reduces power output by adjusting ignition timing as the engine approaches the cut off RPM. As the ignition timing is retarded and power drops off, the resulting feel of power loss signals the driver that it’s time to shift. If a driver ignores this, ignition timing is retarded further until the rev limit is reached, at which point the resulting cut off is much ‘softer’ because the engine is not being cycled on and off between full power and no power.

A Hard Rev Limiter does nothing until the engine reaches the predefined engine speed, at which point fuel and ignition are shut off. This can be very abrupt and hard on the power train as the engine cycles on and off, but this type of rev limiter will provide the most power and acceleration, all the way to redline. This is how the rev limiter behaves when SC Sport mode is selected.

SAB 9/6/2019

NB information relates primarily to Porsche 981 models for 2012/2013 model year.

It should be noted that newer models, including the 718, now have 3 sport button options, including boost function, which have different characteristics based on other options on the vehicle.