TM_Corey

I have never used it. Haven't had a place I considered safe yet. Ive only had it in sports plus once and it was on accident trying to put it in sports mode. I drove a couple blocks and looked down to realize I was in sports plus.

On a side note, I asked the porsche dealer that did my PPI if they could tell how many times the launch mode had been activated and I was told no. Is that true or were they being lazy??

stevepow

Never have - never had a use for it. But I like the idea of it. Reminds me of that Mark Strand poem, The Idea

"But that it was ours by not being ours,
And should remain empty. That was the idea."

snake eyes

never used it.. never had a reason to put stress on the drivetrain like that. (yes, I'm aware they are built for it). I've tracked my car a few times but launch control isn't needed at all on a road course for any reason.

Robocop305

Use it! It's a great feeling to have your car take off like a rocket. It's also very controllable and safe. Just make sure that you have a nice empty road ahead.

voiceprint1

If the S model is making 30-40 HP over a base car, shouldn't it's peak HP and Torque numbers be much higher? 330 seems on the low side for a car nearing 400 HP?

please don't flame this

Petza914

I do not believe the Porsche DME records the # of times a PDK car has been launched. The GTR does though as you see in for sale ads "never launched" as a selling point that I think is verifiable from a scan.

StormRune

No flame, it's an excellent question. So the 330 number is the reported rear wheel horsepower number in the case of my app. First, remember that is an estimate based upon the weight numbers I gave the app and the accelerations it was observing. I think I got the weight numbers really close though. I had a nearly full gas tank so I added the published curb weight of the car and my own weight and gave that as the data entry for the car's total loaded weight. Curb weight is the weight of the car with all of its fluids just in case that wasn't clear.

Manufacturers love to report crank horsepower since that is higher. In reality, drive train losses result in less power showing up at the rear wheels. In dyno reports they tend to report just rear wheel horsepower, which is most useful in before/after comparisons for a mod or they show the number they've entered for drive train loss on the report itself. Most good reports are automatically adjusted for the current barometric pressure, temperature, and humidity and report what the horsepower would be at the SAE standard settings for those... since all of these have a profound effect on the power the engine can make at that moment.

Drive train losses include things like losses in the transmission gearing, clutch bearings, reduction gears, driveshaft joints, and even the fluid pump inside transmissions (here is an article if you are interested: http://www.superstreetonline.com/how...in-power-loss/)

The general rule for most sports cars is a drivetrain loss somewhere between 15% and 20% is used, typically higher for automatics and lower for manuals. All wheel drive cars also tend to have a higher number. Since a PDK's clutch technique is more akin to a manual, a number less than 20% is likely, but under heavy use and in Sport Plus launch it does ramp up its pump to full power (I can provide that reference if desired) so you have to assume a little higher number for a PDK in hard use. If only the optimistic 15%, then 330 RWHP would result in an equivalent crank horsepower of 388. At 17.5%, then the crank horsepower becomes precisely 400. What is for my car I don't really know... but I'll be glad to attempt to claim 400.

A bit of searching on the web seems to show that 17 or 18% is likely for our cars. It's virtually certain that Porsche knows the real numbers but doesn't report it. Some aftermarket companies use smaller loss numbers when reporting peak HPs with their products, most typically when they don't show before and after charts ("Use our product and your car will have 430HP as shown on this dyno report!"). The only way to tell for sure is to test an unmodified car in the exact SAE-approved temperature/humidity/altitude environment for determining official ratings and compare the reported RWHP number versus the manufacturer's reported crank HP number. If someone has done this I would love to know what the observed drive train loss was!

Nip are

Very good and accurate explanation. Thanks.

StormRune

Agree with Pete, I've never seen that number on a report either. Early on, the warranty for GTR drivetrains would be invalidated if launch control was ever used. After a lot of unhappy customers that used launch control and ran into this, Nissan changed its rules on that, at least in later cars (not sure about earlier models?), since they were providing that feature to its users. It certainly seemed unreasonable to build a feature into a car and then invalidate the drivetrain warranty if they used it!

This was popularly reported to be the case on earlier BMW M3s with SMG transmissions as well. I couldn't ever verify if it was true, but I had one and saw multiple reports that using it more than 15 times would invalidate the drivetrain warranty. BMW's launch control feature was never officially presented in any manual or company documentation but I can verify it was there. The steps to enable it were a bit more tricky than the GTR or Porsche feature though. Since it wasn't an official feature and just using it a few times wouldn't result in a warranty problem, I guess they had a little more standing on this. If anyone else can validate this I would love to know.

Lvt19672

Why not use the launch feature, I thought that's why you would buy a PDK.

Carmichael

PDK = "PleaseletmywifeDrivetheKarsoicanconvincehertobuyitgetriebe"

vern1

Ya I don't get this. People won't use it because they are afraid of straining the drivetrain?

Makes me a bit sad

Ducati_John

For the power number posted, in addition to drive train losses you also have aerodynamic losses (drag). I don't have a feel for how much this would be on a car like the 911, but I know on my motorcycle it's fairly high.

jennifer911

Cliff notes: Man logic = Hey guys hold my beer and ‘Watch This’!!!!

In the 3&1/2 years my boyfriend has owned his GTS he has never tried the launch control. Last fall while on holidays we found ourselves out for a day-trip on a lonely deserted back road in the Borrego desert, no other cars, just us. Using classic man logic he said, “Hey honey what a great spot to try out the launch control. “No way in hell” I said, we’re not only out in the middle of nowhere, we’re also 2000 miles from home. He gave me the speech that this is a big strong 911, the transmission etc, can take the strain with ease. I appealed to his softer side by explaining that I wouldn’t care so much if we died out here, but what about my little dog that we left in the care of an elderly couple we met back in Palm Springs. (We were staying there for 6 weeks). Because he obviously cares more for the dog than me he relented and the LC is still a virgin.

TM_Corey

This thread needs "watch this" video so I work up the nerve to use mine....