Jump to content

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)
sanjeev

997.2 PDK lugging normal? - very low revs (down to 1000rpm) at light t

Recommended Posts

Hi,

I have a 2009 C2 w/PDK (non-S, therefore no Sport mode switch), and have observed that the normal shift strategy is to shift up to higher gears quickly under light throttle (such as regular in-town, in-traffic driving). Often, under these conditions, the engine will try to continue driving all the way down to ~1000 rpm in 2 and 3, resulting in a momentary lugging feel and sound on throttle tip-in.

Dealer has checked and updated PDK s/w - no fault codes, and otherwise the car checks out and drives as normal. In other words, according to Porsche programming, this is operating as designed.

Question - Has anyone else experienced this behavior, and if so, is there anything to be concerned about?

In my previous Porsches (all manuals), I generally kept the revs above ~1500 rpm, even in light-throttle use. clearly this logic could just as easily be programmed in to the current PDK ECU. Does this mean that by design, the modern Porsche engines are OK with being driven (lightly) all the way down to ~1000 rpm?

Related Question - Does anyone else feel like there is an excessive amount of engine idle vibration transmitted into the body (and felt through the seats) when sitting at a standstill in D or M?

Thanks for any info - I'm trying to determine if this is considered normal, or should I be talking to the dealer.

- Sanjeev

Share this post


Link to post
Share on other sites

The gear ratios in an automatic are such that typically they operate fine at lower engine RPMs. That being said the PDK itself could be a different beast. What you describe sounds like something you might expect from driving a high performance machine in traffic. I've read that some lambo's are horrible/nearly impossible to drive in those types of conditions. Have you tried feathering the throttle more lightly once it goes down to 2nd?

As far as the vibration it's dificult to say what is and isn't normal, you might consider taking it to the dealer and just ask the service managers opinion (who could perhaps have a technician ride along), I think for something like an opinion it would be a no charge and they sit in a lot of Porsches.

Share this post


Link to post
Share on other sites

I have PDK in my '09 C4S. I agree with you that sometimes I feel the transmission should downshift so that the car is more responsive and the engine not laboring. My solution is to use the paddle shifters to manually downshift into a lower gear,

Share this post


Link to post
Share on other sites

MWS, thanks for your note. Interesting that you note the same sympton on an S model. Is this with the transmission in Normal, or in Sport mode? Reason I ask is that I was considering upgrading to the Sport Mode (available as an add on) if this would make the transmission shift logic less prone to lugging (or alternatively, more eager to downshift).

Yes, I have somewhat adopted the manual override via the shift switches procedure too. However, i still think this should be a simple logic fix for the automatic mode.

Sanjeev

Share this post


Link to post
Share on other sites

Is it perhaps an issue with the transmission ECU adapting to your driving style? I know on the automatics they use a fuzzy logic to fine tune the shift points to match your driving style.... a light foot leads to early up-shifts.

Share this post


Link to post
Share on other sites

In "Sport Mode" I don't think it is an issue although I'm not entirely certain because when I am driving in "Sport Mode" I am probably driving a bit more aggressively and don't really allow the RPM's to drop very low.

I notice the engine laboring the most in routine slow "City" driving especially when I have to slow down considerably such as crossing an intersection where i am trying to not scape my front end and then want to accelerate quickly to keep someone from driving up my tailpipes.

MWS

Share this post


Link to post
Share on other sites

Is it perhaps an issue with the transmission ECU adapting to your driving style? I know on the automatics they use a fuzzy logic to fine tune the shift points to match your driving style.... a light foot leads to early up-shifts.

Yes, I agree that this adaptation logic is involved. I have confirmed that during driving (on open roads, with more ability to tip into the throttle) the PDK adapts its shift points to higher rpms. It is actually uncannily good at this! However, in city/slow-traffic driving, where one is invariably limited by the car right in front of you(!), I do think the shift logic adapts to shift points that are overly low.

I suspect this is a trade-off made in the interest of eke-ing out as much fuel economy as possible.

For someone who has driven for years with a habit of trying to keep the revs under driving load conditions above 1400~1500rpms, though, it is still a bit uncomfortable. I plan to drive an "S" to see how the Sport mode works under these conditions. If it avoids the "lugging" preference, I may install it anyway.

If anyone has an "S" PDK, would you mind taking note of how the shifts occur under light throttle in Sport mode, and post your observations?

Thanks all,

- Sanjeev

Share this post


Link to post
Share on other sites

2012 GTS PDK with Sport and Sport+

In Normal, the transmission shifts up at very low engine speeds, sometimes below 2000 rpm particularly if i am easy on the gas. This can lead to driving around the neighborhood in 4th or even 5th gear at 40 mph. This seems the mode to use for maximum fuel economy.

In Sport mode, using the same approach to the gas pedal, the engine shifts up at 2500 tp 3000 rpm. Nearly the same speeds at which I would shift a manual transmission. This mode mimics a manual transmission. Also in Sport mode, the throttle is much mover aggressive. For the same movement of the gas pedal in Normal, you get more throttle. On the highway at 75 mph, the transmission will run in 6th gear until the cruise control is activated. Then it shifts to 7th, dropping the revs for better highway fuel economy.

In Sport+, the transmission does not upshift until very near the redline. It holds high revs and downshifts when revs fall below about 4000. The throttle response may be a bit more aggressive than Sport, but I'm not sure. The transmission will not shift into 7th at any time, cruise control or not. This is the mode I use on the track.

In each mode, things can be a bit more or less aggressive depending upon the rate you push the accelerator. It adapts to your pedal movement and increases or decreases the shift strategies.

I hope this answers your question. It's all explained in confusing detail in the owners manual area covering the Sports Chrono package.

Share this post


Link to post
Share on other sites

And this is the issue i have with PDK, indeed any auto box with or without manual option.

In a large luxury family saloon auto simply adds to the sublime progress and compliments the luxury feeling, In a sports car auto is great if you drive in a lot of trafic but all auto boxes are a compromise and therefore manual is the only option to give the driver full control over the car.

Sometimes i drive spirited and i think just how much better it would be simply pulling a lever to change gear, likewise impressive acceleration from rest by simply flooring the pedal, never a chance of stalling or excessive wheel spin, but on those times when im just poodling about i will be in top gear at very low revs, indeed at a junction if i dont have to stop and im in third gear i can simply light throttle and continue but in an auto it will change down and that removes my choice of what gear i want to be in.

We all make choices and with every choice there is a compromise, i do like both systems but overall i preffer manual in a sports car and auto in a luxury motor.

Share this post


Link to post
Share on other sites

I have owned a 2001 C4 with Tip a little over a month and was noticing similar characteristics. At first I had a very light throttle as I was interested in knowing what I could achieve MPG wise around town. Well it is around 17.9 MPG to mid 18. After I was satisfied with that mileage info I got more interested in why it seemed in my opinion to be "Doggy" leaving traffic lights.

This is comparing it to my auto tran V8 2000 Jeep and auto tran Jeep Commander with Hemi which both can snap your neck when you accelerate from a traffic light.

So I got reading the C4 owners manual and read that if I push the throttle all the way to the floor it deselects economy mode. I tried it the next day at a traffic light and after picking myself up out of the back seat had to conclude that yes, the C4 can accelerate nicely when I want it to.

Of course spirited driving is suppose to be good for the IMS also, so I will more than likely be doing more of this. In addition I have down shifted with the paddle shifter as above posted which helps also.

Don

Share this post


Link to post
Share on other sites

Difficult to say what is normal without driving your car but I am almost sure you just own a PDK for the first time. I got my 2010 Targa 4S (first) PDK in january and I have been through the same.

Sometimes it feels a bit jerky and awkward, but I think we are just setting the bar too high.

The PDK is an extremly advanced mechanical two-clutch gearbox, the irratic throttleuse us humans sometimes are guilty of is impossible to write software that will foresee.

And with 385hp it is to much to demand a vibrationfree function in all instances.

I have experienced relatively violent jolts and "misfunctions" sometimes but I dont think it is abnormal. The box is rock solid. I laugh sometimes about myself worrying about this, after using Launch Control to kill a Corvette... The more torture I put on the car the smoother the PDK works...

Edited by Morten Astrup Steen

Share this post


Link to post
Share on other sites

Sometimes it feels a bit jerky and awkward, but I think we are just setting the bar too high.

The PDK is an extremly advanced mechanical two-clutch gearbox, the irratic throttleuse us humans sometimes are guilty of is impossible to write software that will foresee.

And with 385hp it is to much to demand a vibrationfree function in all instances.

I have experienced relatively violent jolts and "misfunctions" sometimes but I dont think it is abnormal. The box is rock solid. I laugh sometimes about myself worrying about this, after using Launch Control to kill a Corvette... The more torture I put on the car the smoother the PDK works...

I have owned a 2010 987.2 S with PDK and S-Chrono+. Right from day one, I noticed that the car wanted to idle at around 700 rpm or even less, almost stalling! I went through the same issues regarding jerkiness/lugging at idling, had three different dealers check it out, and they all declared the symptoms as normal characteristics of the PDK.

They must have been right, because I have slowly gotten used to these, and now enjoy the car in normal, sport, or sport+ mode with total abandon and without concern. It has never failed me in its 17,000 miles so far..

.

I was lucky enough to be have a Porsche factory racing instructor drive my car on the track with me as passenger, and he showed me that for most track events, leaving the PDK in Sport mode was more effective than Sport+, as it was not "constrained" by the overide of having to shift to near-redline every time in Sport+ and was thus able to respond to changing track conditions extremely effectively in just the Sport mode.

Bottom line based on personal experience: I drive most of the time in Sport mode in all situations, and reserve Sport+ for Launch Control only. In city stop-go traffic, there is perceived binding/lugging/low revs combination, regardless of whether in normal or sport mode. But I have to agree that the PDK, being such a sophisticated unit working with two gears all the time, does the best it can to deliver all that power right from idling to max rpm. I recently drove a new 991 with PDK and felt that it has been smoothed out noticeably in this regard. I was also informed by the tech that these improvements cannot be transferred to my car as they are a result of new software and redesigned control valve assembly and other hardware plumbing.

Share this post


Link to post
Share on other sites

Glad I logged on to read this. Just picked up my '09 S two days ago and had the same questions. It takes me about six months after buying a used car before I'm comfortable that every nuance isn't a mechanical problem that I overlooked pre-purchase.

Edited by Loren

Share this post


Link to post
Share on other sites

Just another observation in this matter. After trying out Sport-mode and normal mode in normal traffic I find sport mode more to lug, especially when downshifting to first gear using "Drive". I therefore prefer to use Sport mode only when I want to change manually in normal traffic.

Share this post


Link to post
Share on other sites

For info the pdk in the 997.2 has software updates that, for me solved this issue. After the update i could only say that it approaches 991 levels of smoothness even at low speeds and stop amd go traffic. No im not pulling anybodies legs i am just sharing my own experience after the update. I could only say it was the biggest upgrade to the cars performance that i have done. Check with your dealers brothers.

Share this post


Link to post
Share on other sites

I have the same issue with my 2009 C2S. The throttle dips and often I think that it's about to stall. Sport mode solves the issue but introduces jerkiness instead.

Share this post


Link to post
Share on other sites

 

I have the same issue with my 2009 C2S. The throttle dips and often I think that it's about to stall. Sport mode solves the issue but introduces jerkiness instead.

In normal mode my Turbo S wants to upshift to 7th at 30 mph which is patently STUPID. Porsche did this for MPG numbers.

So, in normal mode I shift to manual operation. Sport mode cures this barely. It still upshifts too early IMHO. Sport plus rocks. I find that once you learn the sweet spots you can actually shift smoother than the computer can. It is most certainly different than a normal manual. For instance I now downshift a lot later than I use to with a normal manual. I only let the computer shift when I am otherwise engaged say in picking a CD or in a conversation. Funny thing is that if my car had been offered with a manual I would have gotten it and that would have been a big misstake.

There is no way you can keep up with this car with a manual tranny, things just happen too fast. You brake harder, go into corners faster, accelerate faster. Porsche is right as is Ferrari.

Edited by Mijostyn

Share this post


Link to post
Share on other sites

What's the latest PDK software version for the 997-2? I've the jerkiness and have read reports of the benefit of the SW version upgrade. I've got:

 

SW Ver: 4230363720202020

HW Ver: 544332314C314432

 

 

Anyone know what the latest SW Ver is? I'm trying to work out if I've the latest or not.

Share this post


Link to post
Share on other sites

For a little over a thousand bucks you can wake up your PDK by getting the dealer to install Sport Chrono.  You get everything except for the "wart" stopwatch that very few of us use.  The shifting behavior will be much more like you are looking for in Sport Mode and the only downside is the occasional hard downshift just before you come to a stop... and this can be overcome by doing more aggressive stops or by manually engaging the last downshift when you want it.  I can't imagine not having it.

 

It's the best $1000 you can spend on your car

 

Dang! Just realized I'm responding to old posts!!!

Edited by stormrune

Share this post


Link to post
Share on other sites

Well I called up the dealer to try to find the latest SW Ver, but they won't give it out.. They just wanted to charge me $340 to 'diagnose it'.. From what I can tell it is pretty normal for PDKs to be a bit jerky and the new SW seems to smooth things out, but they don't make it easy to do the update. :-(

 

What's the latest PDK software version for the 997-2? I've the jerkiness and have read reports of the benefit of the SW version upgrade. I've got:

 

SW Ver: 4230363720202020

HW Ver: 544332314C314432

 

 

Anyone know what the latest SW Ver is? I'm trying to work out if I've the latest or not.

 

Stormrune: I have Sports Chrono already and agree it is very good with the PDK but does make the shifting harder

Share this post


Link to post
Share on other sites

My car exhibited this also. But when I had the fabspeed xpipe installed, it went away!!! No clue as to why???

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.