boqueron

Sorry I could not search the forum for previous discussions on this topic: not enough letters (only three:4 W D).

I always have been driving 2wd cars . I have always been happy with this type of transmission. I have even drove Rallyes in my youth. Having owned lately two Porsches with 4wd, a C4 and my present car is a 996TT. Also very happy with this in the few occasions that I have track driven it as well as in my daily use and travel. Its true that I have not seriously driven a 2wd Porsche so it's impossible for me to compare.

I have read that a 4wd Porsche does not oversteer as pleasantly as a 2wd. The fact is that I trottle steer my TT and the back - when needed - moves in what I feel is a nice manner. In a track, with my previous C4, I did it so well that I succeeded, without really wanting to , to find my self in a 360º spin.

I have also read that the problem with a 4wd is that, when you loose the rear, the front has a tendency to exagerate the traction in order to compensate all which creates more understeer. Funny enough I felt this problem with my C4 and do not feel it in my present TT ! THis surprises me as the rear tyres section and the total back width is wider in the TT that in the C4 . Shouldn't this create more oversteer ?!! ( keeping the front equal )

What is the forum opinion on 4wd vs 2wd: Weight handicap, handling , ..a question of principles ? Any "scientific" data : track times,etc,, avalaible ?

AdamB

I'd suggest looking through the search page. This topic has been discussed again and again and again.

:-P

Juan

Can you actually "lose" the rear before PSM steps in and saves your "rear"?

Palting

Boqueron, the topic has been beaten to death, and then some. Just do a search as suggested by AdamB. He and I have had a lot of fun exchanging opinions, and others have as well, so you can search Adam's and my old posts just by clicking on his or my name and then clicking on "search all posts by user". If you read all the posts regarding AWD vs 2WD, or C2 vs C4 vs C4S, you'll be reading all weekend .

If you exceed the laws of physics, you can!! Not even PSM can save you if you exceed ythe capabilities of the car.

Juan

Main complaint with PSM/VSC.

Doesn't provide for a "learning experience.

With just brief drive wheel(s) slippage (plastic crosswalk striping) the Trac system on my 92 LS400 would simultaneously apply rear braking and dethrottling of the engine, oftentimes leaving me in the midst of on-coming traffic with NO throttle control for the few seconds it took for the system to give control back to me.

I noticed that the 2000 GS300 would apply braking and then wait a few hundred milliseconds to allow me to react by lifting the throttle myself. If I didn't then the system would then dethrottle just as my 92 did.

My 01 AWD RX300 has VSC and I'm very sure it has intervened a few times but the aural and visual indications do not sustain long enough that I can change my attention from driving to instrumenation.

In so far a I know the PSM on my 01 C4 has never intervened. The only real opportunity was with a professional driver and he immediately turned PSM off upon starting the car.

But.

Why not have a method of advising the driver of the inappropreate activity at the same time as intervening?

Something like a "stick-shaker" on a commercial airliner?

The idea being that the steering wheel would have a vibratory torquing in the corrective direction simultaneous with PSM taking the corrective action.

A LEARNING EXPERIENCE!

Absent something of that ilk the PSM may "silently" again and again, save my butt, and that eventually leads me to become more over-confident in the car's ability and therefore I will end up exceeding the laws of physics without ever knowing how many times I was "close".

Which leads me to the next question, does the PSM have an aural and/or visual activation indication that lasts long enough for the driver to have the time to recognize?

Remembering that if PSM is activating the driver's attention is very likely focussed, very tightly, elsewhere. And if not, it certainly should have been!

Palting

Juan, there is a light in the dashboard that flashes.

Juan

I don't doubt it.

But does it flash long enough for me to see it after the "event" has passed and I can focus my attention on it.

boqueron

Paltinh and Adam: Thanks. I will search your topics ( easier ).

Juan, Yes I can loose the rear BEFORE having the PSM starting. THe point is... how much ! The funny thing is that, following the different situations, it starts before or after. Very difficult to sense in advance.I have not been able yet to anticipate it's entrance.

I also would appreciate a "register" where I could see that my PSM entered and when.

THe other day, raining, at a speed of 100 mph aprox I suffered from aquaplaning in a corner. I only know that I concentrated in ...doing nothing, keeping the same line and...waiting to see if it recovered or not ( not funny at all I must admit ). The last thing I did was looking for the PSM light ! Of course I am unable to tell you if it entered or not I personally thing that it didn't as I did not feel anything ( no noises, no bracking, no changes in line ). But I agree with you, it would be nice to KNOW if it did or didn't work.

3 months ago tracking with a 996C4 , I tried the PSM on and off...to the limit. I succeeded to loose my back and ..spin in both modes !!! Again, very difficult to anticipate the PSM entrance.

Fortunately, I have NEVER seen my PSM entering during my daily trips( I do not know if it proves that I don't take the car to the limit or that I am a great driver ). Only when I forced ( on purpose ) the situation could I see it.

Next time in the track I intend to work on it.

Palting

When PSM kicks in, there is that flashing light that you can see, the stuttering of the brakes at the different corners of the car that you may hear and definitely feel, and you will notice that the gas pedal goes dead on you. When PSM kicks in, you WILL notice. What I will suggest is that you take your car to an autocross. Leave PSM on, and whip that car around the cones. Try it on the brakes, then off the brakes, then on the gas. Then you'll see what I mean about definitely knowing when PSM kicks in.

As far as the learning experience, the way I take it is that if PSM kicks in while on a road course, then I was doing something wrong. As I stated above, you'll definitely know when PSM does intrude. There will come a point where you think you are doing everything right, and PSM STILL intervenes. If indeed you are doing everything right, then you simply have exceeded what PSM THINKS you should do, and is now intruding on your fun. On certain corners at certain tracks, I like the back end of the C4S to step out. Not that it's faster, it's just more fun !! PSM doesn't like it, and spoils my fun. So, I turn PSM off. FUN!!! Autocross is different. In autocross, I'm usually going sideways most of the time anyway, so I definitely turn PSM off.

On the road, PSM should NEVER go on, unless you encounter something unexpected. If it goes on when the road is clear, then the driver is just being reckless.

Juan

"flashing light"....

I don't expect, and I doubt if Porsche really does either (if they actually thought about the matter) that in a situation wherein PSM has activated the driver wishes to be distracted by a flashing light, certainly not to the point of intentionally focussing on the light long enough to comprehend it's "meaning", as in which alarm is that?

It seems to me that PSM would have its greatest value to us in environments where we encounter the unexpected. Track time is all well and good but if PSM activates at those times and I don't understand why then I'm in the wrong car, and place.

It's when it activates unexpectedly that I really need to have a "learning experience". IMMHO that' the only way I will know what I did wrong, if any, and what the corrective measures were/are.

I have had the stall warning go off many times in my personal air travels, some appropreate, some not. But each and every one got my undivided attention until the situation was resolved to my satisfaction.

I suppose we all already know what happens in an aircraft when the designers decide that the flight computer will put limits on the pilots inputs.

That initial Airbus crash years ago now was the result of the flight computer not allowing the pilot to call for as much nose up command as he needed. Had he been allowed to do so the airframe might have been scrapped but all those people would still be alive.

Now I see that BMW has a design that allows the "PSM" computer to countersteer against the driver's steering inputs if it deems it necessary to avoid loss of control.

Personally I'd much rather have the steering wheel become much harder to turn (vibratory torquing against my input) in MY direction than have it take this kind of control.

There are times that it's better to hit an unavoidable object rear end first.

Worrisome.

Palting

PSM or not, usually the steering wheel IS harder to turn if you get to the point where you are forcing the car to go beyond the limits. You'll figure out just where this point is as you drive the car it's limits in a safe environment.

Although I would think that a yellow flashing light at the periphery of your visual field would register without you actually looking at it, there are other sensory signs of PSM intervening that have been stated. It's actually very easy to tell when it intervenes. Try the autocross exercise I told you about so you'll know what it feels like, then apply that to your daily driving.

Porsche has such high performance limits, that it is very hard to challenge these limits on public roads. If PSM goes on unexpectedly on public roads and you don't know why, then you are simply driving recklessly. Just my .02c.

wwest

Recklessly, Hmmmmm....

Left turn through a puddle of water, accelerating lightly, VSC on my RX300 jumps in and applied braking, sorta of a low moan is all I "heard". Didn't have time to look down and see the indicator, and/or which indicator was on, before it went out.

I realize that Porsche PSM has higher limits for activation but in virtually the same circumstance on packed snow I would expect the PSM to activate. I don't know about you but while I try to "expect the unexpected" the wording speaks for itself.

teflon_jones

most of the time the PSM on my C4 doesn't activate, even on snow. the traction control usually steps in first. but if i go to a parking lot and do a deliberate sideways slide, the PSM will definitely go off. i find that it has a pretty high limit, but my biggest complaint is that if you really drop the clutch hard and take an abrupt left turn across traffic, it will kick in and suck away engine power. this can leave you in oncoming traffic. i turn my PSM off when i drive in the city unless it's snowing. on the highway i like it since it's pretty hard to even get the traction control to kick in at highway speeds, so i figure if the PSM is going to go off i'm in a pretty extreme situation and then i'll probably want it there!

wwest

Teflon,

That seems strange.

That's the way my 92 LS400 would act. But when I got a new 2000 GS300 the Trac was clearly different in that it would apply the brakes first and then give me ("just") enough time to react and lift the throttle before dethrottling the engine itself.

I know it's a difficult thing to unlearn in a Porsche but in this instance if you are quick with throttle lift the Trac will not dethrottle the engine and now you can recover quickly, but more gingerly, on the throttle.