7 speed DSG lag in tiptronic mode - 118TSI

[kimiraikkonen1a]

Hi, I picked up my new 118TSI DSG last week and am extremely happy with the car. Just a great car to drive, punchy enough to get you excited every time you get behind the wheel.

The only issue I have is that i have noticed that when I switch to the manual tiptronic mode I experience some lag from the time I shift up a gear to when the DSG system actually changes up a gear. It is most prominent when shifting from 3rd to 4th. Lag time usually feels to be around 1 second. The shifts certainly do not feel anywhere near 8 milliseconds. I only mention this because there is a distinct difference when compared to the tiptronic mode in the MK5 GTI with the 6-speed DSG. I notice that in the MK5 GTI, the gear changes are extremely sharp and almost instant and I was expecting the 7-speed DSG to deliver a similar if not better response.

When in "D" mode i don't seem to experience any lag, but then again im not really pushing the car hard to feel the gear changes during normal driving patterns as the car is very smooth.

Has anyone else noticed/experienced this??

I have done 860km so far and haven't pushed it too hard. I have kept it under 4000rpm but can't imagine that this should affect the manual gear changes.

[Maverick]

You've answered your own question, the car is new and you haven't taken it above 4000rpm. The DSG still has 2nd selected because of your RPM's and when you ask for 4th it has to change from 2nd to 4th causing a delay. You can easily test this by dropping the car into 2nd under the same conditions. Nothing to worry about, the gearbox won't select the correct every single time.

[logger]

I reckon the delays you see in Tiptronic mode at lowish or stable revs are more likely because the Mechtronic is "confused" about what you are trying to do. The gear change you request is divergent from S or D schedules. For the most part, when driving very sedately there will be NO anticipated gear selected on the Idle gear train. So when you request an up change from 3rd to 4th, drive shaft 2 will be in neutral. This will be what causes the up shift delay. (2nd Gear will not be selected at all). On the other hand if you apply anything more than a whisper of torque you will find the anticipated gear will indeed pre select in advance allowing a semi instantaneous change. An exception is on a mellow start off, trying to take 3rd too soon while the DSG7 is using both 1st and 2nd to smooooothly get you going. It will be reluctant to relinquish 1st gear until 2nd gear takes all the torque and you will get a delay of several seconds after the 3rd gear change request.
Give it more of a boot ful and I expect most of the delays you see will vanish.

[cme2c]

I was showing the car off to my son on the weekend and at a constant 60 km/hr, changed 7-6-5-4-3-2-3-4-5-6-7 about as quickly as I typed this. He felt nothing, all I could see was the revs changing and the MDS display changing. It changed as quickly as I could move the lever. The car has 3000 kms on it, and the DSG is still getting better.

[logger]

DSG7 Tiptronic Changes.xls Shows how the gearbox behaves if you drive it around gingerly in Tiptronic mode. Trying to confuse it. You can clearly see how most of the time there is no gear lying in wait. It shows how it will deny or delay gear changes requests if it deems them inappropriate and also that it will initiate them without you requesting them. Sample rate ~ 1sec so some change requests may not have been recorded. 6 minute drive never much above 2000rpm. Ideally if driving like this, you would use "D"rive. But interesting to see how it behaves.

[mr gee]

ted, too many https in your link.
excellant use of VCDS to explain this..thanks

[logger]

ted, too many https in your link.
excellant use of VCDS to explain this..thanks

Thanks. Link is fixed now and should work.

[coastie]

Another great explanation about the DSG workings. I gather if you accelerate with intent then the DSG will anticipate the manual upshift and select higher gear on the idle shaft same as it does on the slow down and automatic downshift.

Nice work.

[logger]

Another great explanation about the DSG workings. I gather if you accelerate with intent then the DSG will anticipate the manual upshift and select higher gear on the idle shaft same as it does on the slow down and automatic downshift.

Yes that is pretty much how it works. With the live data stream you can readily see the Neutral idle shaft selection (NN) when driving in a steady state, apply some torque and observe the next higher gear getting selected on the IDLE shaft. In anticipation of a likely up shift. Line 420 on the XLS shows this. Accelerated from 32->39kph triggered the selection of 4th but importantly no actual gear change.
I am not sure exactly what triggers an IDLE shaft anticipatory Down Shift. Probably a combination of things like speed, requested torque and Eng RPM. I noticed in some of my earlier logs using "D" and "S" that decelerating from 7th to a stop with foot off pedal, it still works its way back down through all the gears. Because fuel economy is paramount, it keeps the engine "windmilling" just above IDLE revs using transmission torque. If you took your foot off the pedal at 100kph and it threw open both clutches with no fuel flow the engine would obviously stall. Instead it shuts off fuel flow and as road speed decreases it shuffles down through the gears to keep ENG just above idle. At a certain point Fuel Flow returns and Transmission torque is no longer required to windmill the engine.

Nice work.

Thanks Coastie.

[kimiraikkonen1a]

Thanks logger, for all the info and the spreadsheet. It all makes sense, the 118tsi performs alot better if u are accelerating and really giving it some stick. However I still notice a significant difference between my 118tsi and my gf's MK5 GTI. Ive compared the two under the same conditions and varying rev ranges and for every scenario the MK5 GTI is more responsive and sharp regardless of which gear you're in or the rev range.