Potentially hazardous "quirk!" with the dry DSG

[marcusthehat]

As above, in Coleraine this evening, parked in Lower Captain Street, quite steep, when I went to pull away there was a car very tight to my front so attempting to creep out.

three times the DSG disengaged drive ( but still reading D1 on the dash) and ran back quite freely.

I again tried on the Carthall Road, again just about moved off then without warning ran back quite freely, with the lever still in "D" & D1 still showing on the dash.

I did not attempt to plant the accelerator pedal as I do not wish to abuse the mechanism.

So how is one supposed to inch or manouver in tricky or congested/tight conditions whilst on an incline?

I shall contact the dealer tomorrow.

Edited 6 July, 2011 by dieseldogg

[mannyo]

its working as designed, this is what DSG does. When you brake the clutches disengage and you lose drive. To creep forward on s hill you apply the handbrake, release the footbrake to engage the clutches, then release the handbrake. The DSG is not a conventional auto and requires a totally different driving technique.

[marcusthehat]

Apologies Mannyo,

As I was facing uphill (i.e. "quite steep") I did not need to brake, nor did I touch the brake pedal at any time.

The drive disengaged whilst I still had my foot on the throttle,(albeit at low revs because I was "inching") quite without warning.

If I had been facing downhill it would not have been an issue since I would have been "freewheeling" anyways, whilst covering/feathering the brake.

Cheers

M

PS

I got "hill holder" function ( which I dont particularly like) & do use the handbrake as the manufacturer intended.

Edited 7 July, 2011 by dieseldogg

[jrw]

You pull off as you would with a manual except instead of releasing the clutch as you pull away you release the brake and at the same time ease off the handbrake.

[marcusthehat]

I appear to be failing to communicate what happened.

(i)I have clocked up some 500,000 miles ( & possibly nearer 600,000) in manual cars, some without a handbrake.

(ii) I can hill start with or without the handbrake, I got good "fine motor skills" & clutch control.

(iii) I can hold a car stationary on a slope using the throttle only.1:7 or 1:5 or steeper, no worries.

(iv) There appears to be a definate glitch/quirk/fault with the DSG

(v) the car is booked in for electronic diagnostics tommorow.

(vi) I will keep you informed.

Cheers all

M

Edited 7 July, 2011 by dieseldogg

[howells]

I have just bought a new 1.8 Petrol L&K with the 7-gear DSG box. My car has exactly the same 'feature' - if I am very slowly creeping up a hill on a light throttle opening, the drive will sometimes disconnect and the car will roll backwards - rather dangerous! This did not happen with my previous (wet) 6-speed DSG box.

I look forward to your answer from the dealer.

Cheers, Mike.

P.S. Your description is very good and clear!

[marcusthehat]

Cheers Howells,

I did omit to reiterate in my last post that I never at any time had my foot near the brake

PS

"Failure to communicate" was best demonstrated in the Blackadder series set in the trenches of the 1st War.

The bunch of flowers delivered during the "O" Group.

Sir! Sir! says Baldrick, holding the flowers.

Stick those flowers in a vase Baldrick, says Blackadder.

So Baldrick does, flowerheads down & in, with the stems sticking out.

Atkinson's face is a complete picture as he analyises exactly what he told Baldrick to do.

Flowers..............vase.....................stick.............ah!!..................failure to specify the correct way up.

Edited 7 July, 2011 by dieseldogg

[marcusthehat]

An another thing........................

I have in the past got the impression that the car will run back on a slope without completely "losing" or disengaging "Drive".

I was playing on a suitable incline there now and confirmed this.

That is to say it is possible to mimic the manual gearbox/dry clutch action, in that when on a slope I can get the car to sit stationary or ease back, all while in "Drive", depending on the throttle position.

I am aware that with the DSG the clutch must be modulated in some way but it was my understanding that when I took my foot of the brake the clutch pack "engaged" and stayed fully engaged until I put my foot on the brake again.

This demonstration would indicate that leastwise when in "D1" the clutch may or may not be fully engaged, depending on throttle input, a bit like a centrapedal (strimmer/chainsaw) clutch works.

ALL without touching the brake.

PS

The oddity of the complete disengagment of drive is that it happens just after one has started to move forward, at about 1100 rpm.

It totally disengages, though picks up drive again with furthur throttle input.

However if I park on the flat, pull on the parking brake, but leave her in "Drive" the car will attempt to move against the parking brake, whilst at "tickover" revs.

all a bit odd

Edited 7 July, 2011 by dieseldogg

[marcusthehat]

An another thing........................

I have in the past got the impression that the car will run back on a slope without completely "losing" or disengaging "Drive".

I was playing on a suitable incline there now and confirmed this.

That is to say it is possible to mimic the manual gearbox/dry clutch action, in that when on a slope I can get the car to sit stationary or ease back, all while in "Drive", depending on the throttle position.

I am aware that with the DSG the clutch must be modulated in some way but it was my understanding that when I took my foot of the brake the clutch pack "engaged" and stayed fully engaged until I put my foot on the brake again.

This demonstration would indicate that leastwise when in "D1" the clutch may or may not be fully engaged, depending on throttle input, a bit like a centrapedal (strimmer/chainsaw) clutch works.

ALL without touching the brake.

PS

The oddity of the complete disengagment of drive is that it happens just after one has started to move forward, at about 1100 rpm.

Perhaps because as drive is engaged and the enging gets "loaded" the revs drop back............however in the 1998 TDI the engine managment unit was able to compensate for this and supplied the fuel need to keep the revs up.

i.e. I was able to move up through the gears from 1st to 5th without ever touching the thottle (and indeed without "slipping" the clutch)

The 1.6 CR/DSG does not however appear to do this?

It totally disengages, though picks up drive again with furthur throttle input.

However if I park on the flat, pull on the parking brake, but leave her in "Drive" the car will attempt to move against the parking brake, all whilst at "tickover" revs.

all a bit odd

Ah! "quote" I wondered what had happened there, clicked the wrong "reply" apparently

sigh

technology

who needs it

Edited 7 July, 2011 by dieseldogg

[eccleshill]

My 7 speed DSG has the same "feature" that manifests itself when reversing up my quite steep drive (see my avatar!) especially when loaded up with 4 adults.

I can do it to order by just reversing up the drive with foot off the throttle. It crawls along quite nicely at just the right speed until the last extra hump where the clutch disengages and I roll down the hill.

What happens is that you are not applying enough throttle to provide the power to get up the hill. In a manual you would maintain the low speed by increasing revs and slipping the clutch but with the DSG, to prevent a stall, the clutch completely disengages. What would be nice, Mr Skoda, would be if the ESP/ABS detected this event and applied the brake for an instant to stop you rolling the wrong way down the hill!

[marcusthehat]

Gerr!

Ecceleshill

I take it there is no point in getting her "diagnosed" then if "they are all like that Sir"

I still cannot figger how the clutch "slips" per my latter posting.

M

[eccleshill]

I still cannot figger how the clutch "slips" per my latter posting.

M

It does seem inconsistent with this drive loss behaviour. I have never tried holding it stationary on a hill but I have noticed with mine on occasions that when pulling away gently in D2 from an "almost stop", the engine revs rise like a conventional auto and then drop back as the vehicle speed rises to match the revs.

Tell you what! It's never boring driving a DSG - always plenty to think about

I love mine to bits :yes:

[countryboy]

I think eccleshill, has it about right, while moving at a slow speed, if the control system thinks you are heading into a stall situation then it will pull the clutch in completely, the same type of system is used in formula 1 when the car is spinning. Maybe the trick is to apply a bit more throttle and cover the brake with your left foot to control any such eventuality.

It is quite simple to get the clutches to slip in the situation you describe. They are engaged by hydraulic pressure and by simply increasing or decreasing the pressure applied to the clutch packs then they will engage to a more or less degree so transmitting drive. If the clutch packs were fully engaged straight away when you released your foot off the brake then what what would happen if you did so with the handbrake on... the car would stall. It doesn't because the control system recognises that you want to pull away but the idle control says you are going to stall if the clutches are engaged and reduce the pressure in the system slightly to induce slippage. There must also be some input from the speed sensor so that the car knows it is travelling fast enough to either change up to 2nd or fully engage the clutch in 1st gear.

Even the centrifugal clutch on a chainsaw/strimmer can be made to slip, a very similar system was employed on the Daf cars in the 1970's The clutch is disengaged by springs and engaged by centrifugal force. If the engine revs are held at a certain speed the spring force will equal centrifugal force and the clutch will slip and partially transmit drive.

Ian