Auto Park Brake Confusion

[R36 Dreamer]

Good Morning,

I have now had the R36 for about 7 weeks, and am enjoying driving every chance I get.

Fuel consumption after 2000 kms has settled down to an average of 13.1L/100kms, which isn't bad considering the car has yet to see a motorway - basically only been driving to and from work and around the City..... Hoping to get out on the highway later on this week.

Anyhow, I am still somewhat confused about the operation of the electric park brake.

I almost always turn on the auto hold function as soon as I start the car.

Sometimes when I put it in reverse, as soon as I touch the accelerator, the park brake releases, and sometimes it does not. More often it does, but I cannot work out why it is inconsistent. It is definately not related to when I press the auto hold button, as I have tested that theory.

Then when I park the car, put it in Park, sometimes the Park Brake is applied automattically, and sometimes it isn't.

Does anyone know how it works?

It is obviously not a big deal but trying to understand and work it out has really bugged me, and I hope someone can tell me what the go is.

Otherwise I hope me pointing this out bugs everybody else too!! Just sharing the love!

Look forward to anyones response!!

[Man In Black (MIB)]

I have generally found the Park Bark comes on (when in autohold mode) when you undo your seatbelt or take the key out of the ignition. It also really affects the rolling takeoff.

[Cro]

I've noticed the same thing..

[R36 Dreamer]

I have generally found the Park Bark comes on (when in autohold mode) when you undo your seatbelt or take the key out of the ignition. It also really affects the rolling takeoff.

I think you are right ! it is linked to the saftety belt.

What do you mean it affects the rolling takeoff?

[Man In Black (MIB)]

I think you are right ! it is linked to the saftety belt.

What do you mean it affects the rolling takeoff?

At times when I have come to a busy intersection and almost stoped but then pushed the pedal to the metal, the change down pause makes the auto hold think its time to put on the brake on. It then takes a second or two to work out power has been called for and then comes off. Had that happen too many times. Thus, I don't use the auto hold anymore unless I’m coming to a complete stop i.e. traffic lights. I still get a bit of rolling takeoff lag but can usually counter this by putting it into 'Sport mode'.

My GTI also displays this lag in D mode (not as bad) but the way around it is use the flappy paddles to force it down into first.

I think the whole problem is the fact the car wants to stay in 2nd gear and is expecting to go to third. When you slam your foot down it thinks it can get away with it until the torque sensor tells it otherwise. It then goes through a somewhat lengthy process to get to first and then take off.

I imagine the R36 would not suffer from this as its S mode would be more aggressive plus the bigger engine can probably handle it better.

[Lance B]

At times when I have come to a busy intersection and almost stoped but then pushed the pedal to the metal, the change down pause makes the auto hold think its time to put on the brake on. It then takes a second or two to work out power has been called for and then comes off. Had that happen too many times. Thus, I don't use the auto hold anymore unless I’m coming to a complete stop i.e. traffic lights. I still get a bit of rolling takeoff lag but can usually counter this by putting it into 'Sport mode'.

My GTI also displays this lag in D mode (not as bad) but the way around it is use the flappy paddles to force it down into first.

I think the whole problem is the fact the car wants to stay in 2nd gear and is expecting to go to third. When you slam your foot down it thinks it can get away with it until the torque sensor tells it otherwise. It then goes through a somewhat lengthy process to get to first and then take off.

I imagine the R36 would not suffer from this as its S mode would be more aggressive plus the bigger engine can probably handle it better.

The DSG gearbox is essentially 2 x 3 speed gearsets with a clutch driving each gearset. The "odd"(1,3,5)gears in one set of gears driving one clutch and the "even"(2,4,6) gears in another gearset driving the other clutch. Once a gear has been preselected whilst the "other" gearset/clutch combo is in use, it is just a matter of disengaging one gearset/clutch combo and selecting the other gearset/clutch combo. This is why the DSG system is generally very quick and smooth to change gears.

When accalerating or decelerating, the DSG gearbox preselects the next gear in the other gear set that it *thinks* is what will be selected next, so, if you are in 1st and accelerating, the DSG *believes* that the next gear will be 2nd and pre selects it in the other gearset. Once it(or you if you are in tiptronic mode) decides to change up to second, all that has to be then accomplished is to disengage the "odd" gearset/clutch combo and then engage the other clutch where 2nd gear has already been selected. This gives for seamless and very quick changes that DSG is renowned for.

The problem arrises when you want to use a gear that the DSG didn't *think* you were going to use, like the scenario outlined by Man in Black, above. What happens here is that you may have been accelerating in 1st in the "odd" gearset/clutch combo and then moves to 2nd gear in the "even" gearset/clutch combo, and is in the process of preselecting or has selected 3rd in the "odd" gearset/clutch combo.

In this particular example, the problem arises if you quickly apply the brakes and the car slows to a speed inappropriate for the selected 3rd gear and definitely for the next preselected gear which is 4th, and then want to quickly accelerate again.

In this scenario, the car *thought* that you would keep accelerating and therefore 4th gear would have been the next logically selected gear in the "even" gearset/clutch combo and will have already preselected 4th waiting for the clutch to disengage the "odd" gearset/clutch combo and engage the "even" gearset/clutch combo. The problem is, the appropriate gear may now be 2nd instead of the preselected 4th in the "even" gearset and here is where the problem arrises. In the "even" gearset, the DSG now has to now unselect 4th, then select 2nd and then unlclutch the odd gearset where 3rd gear is already in use, then engage the "even" gearset clutch and the "even" gearset is now trying to unselect 4th and engage 2nd. This is what causes the confusing(apart from the confusion of my possibly poor attemp at explanation) and therefore the delay.

This is possibly exacerbated by the DSG's propensity to want to go to the next highest gear all the time in the incessant desire to get best fuel economy when in "D" for drive. Having it in "S" or tiptronic does seem to alleviate much of this angst as "S" is more likely to change down quickly once the brakes are applied and in tiptronic *you* select the gear anyway. Having said that, even in tiptronic or "S", the DSG is attempting to preselect a gear it *thinks* you want to use next depending on whether you are accelerating or decelerating.

The solution? Maybe we need 3 gearsets of 3 gears each and clutch combo's!! This would mean that the preselected gear, either up *or* down is selected and then it is just a matter of the DSG selecting the correct clutch to engage. I think this would alleviate all delays, but it would probably make the gearbox too big, too heavy and too costly.

As a side note, for general tottering about town, I would like to have a mode in between "D" and "S" as it seems to me that in "D" the car always seems to be in too high a gear and in "S" it seems to be in too low a gear as there seems to be a two gear gap whichever mode you're in. So, if you are in "D" which has selected 5th(too high for reasonable acceleration), then you can be reasonably sure that if you were in "S", the selected gear would be 3rd(too low for cruise for the given road speed), where the best selected gear would be more likely 4th where you could accelerate gently without the DSG having to think about changing down.

What I find with "D" mode is that in order to accelerate at a reasonable(but not necessarily fast) clip you need to push down at least 2 gears which requires a big stab on the accelerator in order to get it to kick down. The trouble with this is that the car lurches forward due to the fact that an abnormally big stab on the accelerator is required in order to get it to drop 2 or more gears down. If there was an intermediate level of gear selection between "D" and "S", then only a small dab on the accelerator would be required to get it to change down one gear and due to that smaller dab on the accelerator there would be little if any lurch in the car accelerating.

The problem of having it in "S" in the above scenario is that it is in too low a gear as you dodder about town and therefore revving too high. I find that when in "S" it sits in 3rd when going 60kmh, when 4th would be fine. When in "D" it will select 5th or even 6th which is way too high a gear.

The solution? We need a dial set up or a 3 position selection for driving where we select the following modes:
"E" for economy - now called "D" for drive
"D" for drive - not currently an option. This would be the extra mode in between the current "D" and "S" modes
"S" for sport - the current sport mode.
And of course, we would still have Tiptronic mode for the "manual" option as it is now.

With the 3 gearset/clutch combo(instead of the current 2 gearset clutch combo as outlined above) *and* the 3 mode gear selection we would have the best operating gearbox in any car, regardless of price, even though I believe that the VW DSG, as implemented, is the best anyway. This proposed set up would make it lightyears ahead of the other manufacturers and almost flawless, IMO.