seankrider

So I typically drive a boring 75 miles/day commute with all you other dilberts out there, in my '04 CTT. Probably average 14 - 15 MPG in boring old regular automatic mode. Occasionally get to pass someone... yippee. But traffic and freeways are pretty constraining.

So this week I went in later almost every day, decided to drive with PSM off, and did a little more spirited driving. Of course the shift-map is different, and the revs run up nicely before dropping into the next gear. Obviously a more fun way of tooling around, as the power is punchy in the 3s and 4s, vs the usual 2500 shift-point. Felt like a Porsche.

So I thought I'd pay for it in how fast I guzzle gas, but I ended up averaging 16 - 17 MPG. Am I missing something here...?

Mike in CA

Maybe I'm missing something, but from everything I know about PSM in 911's, switching it off should have no effect on throttle mapping, rev points, or simlilar performance settings. It's a stability management system which only engages when the car detects that the direction of motion is at odds with the steering wheel angle. IOW, if you're not understeering or oversteering the system is monitoring things but not doing anything.

Since I don't own a Cayenne (yet) I don't know if there is some interaction between PSM and Sport mode, where if you turn off the former the latter engages. There isn't in a Carrera. Unless that's what is happening, I don't see how turning off PSM would affect anything in normal driving.

Dennis C

Early Cayennes didn't have a sport button, so turning PSM off does change the shift points. The vehicle also starts off in "D1" instead of "D2". It's quite a bit different than turning PSM off in my 911.

Renn 951

Since you were dealing with less traffic at the later hours, that probably outweighed the more spirited driving in affecting your MPG.

seankrider

Good point - I should have held the other variables constant. False Attribution Theory!

So I will continue the experiment next week with PSM off during normal commute hours and see if stop-and-go is in fact the difference.

Mike in CA

Didn't know that. Thanks for the clarification.

jtpsocal

I can tell you for a fact that the 2009 Cayenne Turbo S is completely different with PSM off. It is literally three different cars 1) Sport off PSM off 2) Sport only 3) Sport on and PSM off. Shift points change dramatically with PSM off

seankrider

Lack of traffic was definitely the cause of my better MPGs.

But PSM Off is definitely sports-car mode if you leave it in automatic. Much more fun, as the RPMs seeme to get nearer to the 3s and even 4s before bumping up a gear. Though it did take me all the way to the redline once, which was a little concerning. PSM Off should be standard.

ozr

Is above also true for 2011 Cayennes?

"Sport ON" does change 2011 Cayennes response/shift points/driving maps.

"PSM off" on 2011 Cayennes seems like does not change driving response, it may does something else and behaves similar ( "no engine response change") to 911, described above.

What are your "PSM off" observations for 2011 Cayennes?...


OZRacing

mellowyellow-atlanta

PSM off should be standard? You are kidding right? Or perhaps you are Patrick Long?

Just because the shift points are different with it off doesn't mean that 99.999% of people don't need PSM. The real value of PSM is the slip angle detection and protection from (a) you being stupid (b) other people being stupid or (c) the road having some unexpected stuff on it.

user 83838290

there used to be times when cars were driven by drivers and not computers... good driver always thinks a step ahead and always leaves himself some safety margin so he can resolve the unexpected.
nowadays, most sports- and even supercars can be driven to 7-11 by 70y old ladies which is just plain wrong IMO. don't know about the US, but over here most new cars don't even let you turn the stability control completely off... what's the point in having a 400+ hp car when you can't even drive the way you want.

I leave mine on only when I have my daughter in the car, otherwise it stays off.

mellowyellow-atlanta

There are plenty of situations where "thinking ahead" is not an option, even for an excellent driver.

PSM gives you a little bit of fun factor before it kicks in. The main goal is to save your butt if you encounter a situation. You can always turn it off if you think you are better than a computer that samples slip angles at a few hundred thousand times a second... or maybe you want to do some track driving and feel like you'll have more fun with it turned off. You have that option too.

user 83838290

the problem I always experience with PSM (or DSC on a bmw) is that when I drive a little faster on windy roads it bugs the hell out of me... tight curve, accelerating out, I know a bit of oversteer will come so I countersteer right before it happens... everything is OK up until PSM/DSC kicks in - instead of going a little sideways but in the right direction, it makes you go in the direction of the countersteer which is the oncoming lane.

I know it's kinda specific, but still enough for me to turn it off.

seankrider

Wow - I think what I originally meant was, by turning off the PSM, the tiptronic waits for the mid-threes and fours before turning over to the next gear. That's what makes it feel less minivan-like to me. Feels like a sports car, er utility vehicle.

But I probably would like to keep the other functions live because I don't believe I can out think 1,000 samples per second on slip. Whatever that really means, driving down CA freeways.