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Originally Posted by 1zippo1
By the way st-ranger. I like porsches but there has been some argument conserning there policy on electronical safety systems. I've recently read an article where they compared the 911 Carrera with a Corvette and the last one was the most fun on the track. The PSM annihilates any form of provoking oversteer with braking when entering a turn. Shouldn't it have been beter to install a locking diff instead of a PSM that works on the brakes... What's your oppinion about this? I know PSM is safer but it's annoying that it autimatically re-activates when you touch the brakes.
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well, it`s their opinion when they say they had more fun in the vette, i won`t…
and that the PSM annihilates any form of oversteer when braking into a turn is kinda new to me...
as far as diff-lock is concerned all Porsches that really need a diff-lock ( e.g. GT2, GT3..) has an asymmetric differential lock that delivers 40% lock under power to improve traction, and 60% lock on overrun to stabilise the car. for those cars PSM isn`t even available.
also the "40 years" anniversary edition is equipped with an extra mechanical rear diff-lock and PSM to improve handling...
but IMO PSM is ( one of ) the best systems, even to drive fast around a track, not only for safety matters.
and when you want a track car, simply don`t order PSM, it`s only standard in the C4, C4S, TT and all 955 modells, but the following report should show you, that i´ve experienced that PSM is quite good for track use.
as i mentioned before i´ve driven a C2 as a company car during my time at weissach, and due to my work in the driveline departement i also had the chance to ride some modells on the test track at weissach, so, luckily, i´ve quite some experience with racing Porsches.
i think everyone is quite familliar with the basic principle of the PSM, so i needn`t explain all the tech. details.
so it doesn`t really depend on what you´ll do with your Porsche, just for showing off or to race around a race track, IMO when PSM is available and you can afford it, take it. don`t get me wrong, if you are looking for a street-legal race car, like a GT2 there`s even no PSM available, it needn`t need it, but this car has other handling characteristics than a C2 or something like that.
with PSM a level of safety can be provided, that´s impossible to achieve by driver skill alone, even for a professional.
tell me if you want to know how PSM is functioning in detail, i won´t explain it at that point...
as zippo mentioned you can turn the PSM off. when you "turn it off," you are taking only the outputs offline. the PSM system is still collecting data from the ABS system, the yaw sensor, the lateral acceleration sensors and the steering wheel position sensor. if you have
PSM off, and the levels of slip are exceeded, and you do not touch the brakes, the car will continue to slide. if you have not exceeded the
levels of slip allowed, and apply the brakes (no matter how hard), PSM will not active its outputs. however, if you have exceeded the levels,
AND apply the brakes (no matter how hard), PSM will activate until the car has regained control or you get off the brakes, at which point PSM stops outputting. PSM assumes that since you hit the brakes that you are not comfortable with the level of sliding and that you want it to help. so concearning PSM and racing, PSM can be a good asset, because it allows you to explore the limits of traction on the first few laps at a new track more confidently. when PSM activates you can feel it, much like you can feel ABS. it will show you where you are losing traction while keeping you on the track if the loss was unintentional. when it engages, it may slow you down where you might not want it to later, i.e., where you really do want more oversteer, but on those first few practice laps, who cares? IMO that has been the "problem" of the test driver zippo is refering. you can actually throttle steer the car quite well with PSM on as long as you are
smooth, the yaw is not excessive, and the corner is fast enough to allow smooth inputs.
so far, so good. since you can turn PSM off, why wouldn’t you want to buy it, even for a car you intend to race? it seems like the best of both worlds. however, remember above where I said that when PSM is off, it is still collecting data and if you hit the brakes when the levels of slip are exceeded, it will intervene. that could be a negative in one racing technique, trail braking, where you are obviously on the brakes and turning. there are two reasons to trail brake, one in which PSM is neutral or even a positive, and one in which it can interfere with the driver’s intention. the first is when you are trail braking to lengthen the straight or to maintain a higher speed through the first part of a turn. in this case, you want the car to stay on its directed path. if things are going as intended, PSM is very unlikely to engage even though you are on the brakes. if it does, it is probably because you lost rear traction in a pretty big way. by engaging it didn’t cost you time since your intention was to slow down anyway and it may have saved you from spinning. the second use of trail braking serves a different purpose. if you are trail braking to induce some oversteer intentionally to tighten the corner, PSM could interfere in the same way as when it is on and you lift to oversteer.
Porsche wanted the car to perform like a Porsche not a family saloon, so the PSM has been designed for minimal intrusion, its limits are really high and you can reach the same lateral g-force number with the system in or out on a steady state cornering circle. thus, if you are a good driver, you can keep the power on in a drift and even adjust the car’s attitude on power in a corner without interference. but if you lift off suddenly or brake, and the car is in danger of destabilizing, the system will reach out and save you.
but the best argument is yet to come, the difference is small around the Nurburgring for a skilled test driver. only within one second a lap in fact. this is the way the car is made. if you are smooth, there is no interference from the system. but if you are ragged, the system will be cutting in all the time to stabilize the car, so an aggressive driver will be slower with the system on.
i hope this answers some of your questions zippo...
as always, if there are any questions left, don`t hesitate to ask
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