Staffie Guy

On page 110 of the owners manual it says "always leave the PSM Sport switched off during 'normal' driving operation", yet later on in the page it says "always leave PSM switched on during 'normal' driving operation".

PSM is one of the 5 levers on the dash and has the "off" verbiage. I am confused as to the addition of Sport to PSM.

jlegelis

From the manual: In PSM Sport mode, the support provided by PSM is restricted in critical driving situations outside the ABS control range.

Translation: PSM Sport will allow greater slip angles (eg will allow the rear to step out a bit) under exuberant driving. I always run PSM Sport when doing DE or AX to help better understand the handling characteristics of the car, otherwise PTV, etc will kick in seamlessly at lower limits and keep the car from rotating (for safety). PSM Sport will also reduce rear brake wear at the track because PTV independently modulates the rear brakes to vector the car, IOW less intervention in PSM Sport means less track rear break wear. OTOH, for daily driving I use 'normal' PSM to stabilize the car in case of an emergency maneuver. Porsche prez here

VarTheVar

I don't get what you mean here. PTV is for reducing understeer and PSM is for controlling oversteer situations right? From my understanding PTV cannot be switched off no matter what. So how does going into PSM-Sport reduce PTV engagement?

VarTheVar

Yeah the wording is a bit confusing. But surely this can't be your first car with stability control. Every modern car is basically the same. Short press gives you more wiggle room and long press is the "all the way off" mode (which is never really all the way off).

When you start the car it will be in PSM normal mode.

Short press of the button puts you in PSM sport.

Long press of the button turns PSM off (allegedly). This is for when you want to really drive the car yourself, drift, etc.

jlegelis

>> So how does going into PSM-Sport reduce PTV engagement?

PTV helps vector the torque distribution on the rear axle. At the track I find it mostly engages at the rear, likely due to my (clumsy) driving style. PSM Sport simply reduces that amount of automated torque vectoring 'stability ' that PTV will do, allowing the car to move around more. Clear? Take it to an open parking lot and play around... 91 description here

VarTheVar

Yeah I've read all the literature but it still doesn't add up to what you're saying. I also drive with the systems completely off most of the time. PSM and PTV are not interconnected in any way that I know of. PTV does not increase stability. It decreases stability by helping the car rotate more and a car that is more willing to change direction is by definition more unstable. PSM increases stability by helping the car stop rotating. They do the opposite functions of each other. PTV = more rotation. PSM = stops rotation. That's my understanding of it. As far as I know there is absolutely no way to affect PTV function by any settings. The literature is not written very well. I've combed through all of it and tried to find discussions on the internet but no luck. I wish I could speak to an engineer, which funnily enough Porsche would probably provide if I pestered them enough.

jlegelis

>> As far as I know there is absolutely no way to affect PTV function by any settings.
Agree that it's not well documented. What I do know is that at the track using PSM Sport mode absolutely reduces brake wear and allows me to slide the car more....

From https://www.porschefremont.com/porsc...ue-vectoring/:
"With standard PTV, the rear differential lock is regulated mechanically. PTV Plus, on the other hand, offers fully variable torque distribution thanks to being equipped with electronic control. Joining forces with the Porsche Stability Management (PSM) system, Porsche Torque Vectoring increases stability on slick roads, in snow, and on roads with varying levels of traction."

Staffie Guy

Thanks for the explanation.

I reread page 110 and that key fact is so nonchalantly mentioned-should have been highlighted more in the manual.