Twincharger 7DSG - Selects higher gear than it should. Thoughts?

[tinto]

^ on flat ground that is true.
Take it up a slight hill and the lack of down-shifting isn't fuel efficient.
Try it yourself

[VeedubTSI]

It all comes down to how you are driving. With all automatic transmissions, they go through a weekly cycle or however how often of re-programming themselves. Or possible from the moment you start driving.

The car learns your driving style through a 'fuzzy logic' (I know someone in this field of engineering who can confirm the existence of fuzzy logic) and adapts to your driving style. E.g. if you drive like a grandma the car will not inject as much fuel and will shift earlier, or if you drive harder the car will dump more fuel and downshift more eagerly, I found this evident and could be rectified in my primary car with taking the terminals off the battery to re-program it however do not do this on any VW as I have only verified this fix with Hondas to this date and I will not take any responsibility if you do it. However, it also depends on everything else such as flat ground, tyre pressure.

The 118TSI does sell on the merits of fuel efficiency and power as I've found with the 3 day old 118TSI it does have a 1 gear: 10kph shift point as I found myself cruising at 70kph in D7. Also upon coming off the line the DSG like any manual gearbox does take time to hook up the clutch as i find it dipping into the 900rpm range upon slight depression of the accelerator and the engine gets to the point where it wants to stall evidently in semi-auto and manual transmissions.

As for the rumbling I find it is like popular belief when driving any car, not feeding enough revs into the engine will cause it to stall and under load it will rumble as there is too much load. It may well be a combination of problems such as too high a gear and all, but this is what I think.

[Corey_R]

Welcome to the forums VeedubTSI.

This thread is a full 1 year old.
The OP, logger, has one of the most extensive DSG knowledges of people on these forums. His name is logger, because he has the abiltiy to log all the stats coming from the DSG. In fact he can prove via logs that the DSG mechatronics does not necessarily adapt to YOUR driving habbits, but rather adapts to the tolerances and wear of the gearbox itself. He can also tell you how to reset the DSG without having to take the battery terminals off.

And really, the purpose of this thread was to state that there, there is actually no problem... logger took a discussion out of another thread to show there was no problem, and when people had nothing more to add, it died a year ago...

[idaho]

Welcome to the forums VeedubTSI.

This thread is a full 1 year old.
...

I was thinking of replying as this was the first time I had seen the thread, but perhaps not. People are often berated for starting new threads without searching for and adding to existing threads, but it seems that searching and continuing on is also frowned upon. If a new group of posters wish to discuss this subject isn't it reasonable to continue this thread rather than start a new one?

[hooba]

I was thinking of replying as this was the first time I had seen the thread, but perhaps not. People are often berated for starting new threads without searching for and adding to existing threads, but it seems that searching and continuing on is also frowned upon. If a new group of posters wish to discuss this subject isn't it reasonable to continue this thread rather than start a new one?

To me it's obvious, nobody likes a smartie who can master the #$@%@! search function on this forum.

[VeedubTSI]

This thread is a full 1 year old.

*Facepalm*

[prise]

It is true that an engine under load at lower revs will normally feel and sound rougher than one at higher revs and less load but this perceived roughness at lower revs is as much a function of the tuning of the engine mounts as it is the engine itself. I have worked as a vibration engineer in the past, hence my interest in this topic.

Engine mounts are carefully tuned by the manufacturer such that the engine on the mounts has a natural frequency of vibration that is below the idle speed of the engine. As the engine speed increases, so does the frquency of the mechanical vibration of the engine. The higher the frequency of the engine vibration (higher RPM) the smaller % is transmitted through the mounts into the car body so higher revs often feel smoother as less vibration is making its way into the car body. This is the vibration we feel, not the vibration of the engine itself.

Another factor making the the engine feel less smooth at lower revs is something called torque ripple. This is the variation in output torque of the engine that results from the cylinder firings. Engine manufacturers fit special harmonic balancers, but at lower RPM and higher engine loads these become less effective in smoothing out the torque ripple which also increases the amount of transmitted vibration.

My theory is that this is often why people perceive lower revs as somehow being worse for the engine. I have a 118TSI with DSG and do agree that it doesn't sound and feel as smooth when its lugging at 1500 RPM compared to 2000 RPM in a lower gear, however provided the engine isn't pinging (which it's not) I have no concern for its longevity. 80% torque at 1500 RPM is not hard on the engine as thermal loads are low and loads from cylinder pressures are modest compared to loads from reciprocating parts it would experience at higher RPM's. I reckon the fact it rarely needs to get above 2000 RPM driving around town should extend engine life.

[idaho]

To me it's obvious, nobody likes a smartie who can master the #$@%@! search function on this forum.

I only used the New Posts function so I feel safe to continue.

It's all about fuel efficiency, chasing the poofteenth of a litre per 100km savings that consumers seem to love. Remember VW detuned the TSI from the MkV GT (120 something kw?) back down to 118kw. No doubt they've programmed the shift points as efficiently as possible.

I think the "detune" is more of a market positioning move as both engines have the same torque over the same RPM range. The only difference is that the 125kw Mk V GT Sport has the power specified 100 rpm higher (6000rpm) than the 118kw Mk VI (5900rpm).

Very Clever ...but seriously:
There is no Problem to solve in the first place. People are trying to make it one and I would like to clear things up, so a myth does not perpetuate.

So far no one has come up with a good reason not to let this powerplant and transmission operate within the manufacturers design envelope.

As various people say the shifts have obviously been calibrated to maximise economy. But you need to think about how an engine works to decide if you want it to operate that way.

Torque is directly related to cylinder pressure. The higher the cylinder pressure the higher the torque that is produced for that power stroke. The TSI engine uses the supercharger to increase the cylinder pressure at low speeds that a 2.5L naturally aspirated engine would not be able to achieve. But the price of the higher cylinder pressure is more side thrust on the cylinder walls (because the conrod is angled during the power stroke and more pressure is being applied over a smaller bore area) and more blowby of combustion gases into the crankcase.

Also, 4 cylinder 4 stroke engines have big torque peaks and troughs during an engine cycle as there is no overlap of powerstrokes from one cylinder to another. The individual strokes cause more vibration at lower speeds (because the rotating mass has lower moments of inertia at lower speeds) which gets transmitted to the dual mass flywheel (also in the DSG). So, while I generally drive our car a gear higher at low engine speeds than my wife does, I don't accelerate hard (full torque) at those same speeds.

In the end it probably is a moot point as the original owner is probably unlikely to keep the vehicle long enough to experience any change in longevity. So it comes to personal preference.

[idaho]

... 80% torque at 1500 RPM is not hard on the engine as thermal loads are low and loads from cylinder pressures are modest compared to loads from reciprocating parts it would experience at higher RPM's...

But aren't the high rpm loads hard on bearings while the cylinder pressure loads are hard on pistons / bores and essentially independent of rpm?

[prise]

Torque is directly related to cylinder pressure. The higher the cylinder pressure the higher the torque that is produced for that power stroke. The TSI engine uses the supercharger to increase the cylinder pressure at low speeds that a 2.5L naturally aspirated engine would not be able to achieve. But the price of the higher cylinder pressure is more side thrust on the cylinder walls (because the conrod is angled during the power stroke and more pressure is being applied over a smaller bore area) and more blowby of combustion gases into the crankcase.

All this is true but you don/t mention that this is happening over fewer piston strokes. Also the mass of the piston and connecting rod being accelerated up and down creates loads that increase with RPM. Golf diesel engines have a good reputation for longevity and they have been lugging at low revs and high cylinder pressures for years. It comes down to what the engines been designed to do.