AWD man
Member Since: 03 Jul 2009
Location: In Drag
Posts: 831
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Technical question:
For over a year now (maybe longer) I've noticed an annoying "blip" in the revs at around 2k (maximum torque I'd assume).
I've had a gearbox flush, which initially masked the blip, but it has gradually returned.
Slight inclines seam to trigger it, with a 500rpm surge in revs but no increase in speed.
It seams to be getting worse, as my usual " little blast up the hill" every morning seams to be now all revs and no go unless I really toe it, and then it's mental...
The characteristics of the engine/transmission has just changed, with less low down torque and more revs needed to make it go, rather like a petrol engined car?
Cruising there are no symptoms, unless you reach a change in gradient, which is when the fluctuating retuns again.
The car is BAS tuned which my dealer says is most likely the cause, but i think it's just highlighting an issue the standard map does not (yet).
I've done some searching on the web, and found this relating to torque converters:
Lock-Up Clutch Mechanism
The Torque Converter Clutch (TCC) is hydraulically controlled by an electronic pressure regulating solenoid (EPRS4) which is controlled by the TCM. This allows the torque converter to have three states of operation as follows:
Fully engaged
Controlled slip variable engagement
Fully disengaged
The TCC is controlled by two hydraulic spool valves located in the valve block. These valves are actuated by pilot pressure supplied via a solenoid valve which is also located in the valve block. The solenoid valve is operated by PWM signals from the TCM to give full, partial or no lock-up of the torque converter.
The lock-up clutch is a hydro-mechanical device which eliminates torque converter slip, improving fuel consumption. The engagement and disengagement is controlled by the TCM to allow a certain amount of controlled 'slip'. This allows a small difference in the rotational speeds of the impeller and the turbine which results in improved shift quality. The lock-up clutch comprises a piston and a clutch friction plate.
In the unlocked condition, the oil pressure supplied to the piston chamber and the turbine chamber is equal. Pressurised fluid flows through a drilling in the turbine shaft and through the piston chamber to the turbine chamber. In this condition the clutch plate is held away from the torque converter body and torque converter slip is permitted.
In the locked condition, the TCC spool valves are actuated by the electronic pressure regulating solenoid (EPRS4). The fluid flow in the unlocked condition is reversed and the piston chamber is vented. Pressurised fluid is directed into the turbine chamber and is applied to the clutch piston. The piston moves with the pressure and pushes the clutch plate against the torque converter body. As the pressure increases, the friction between the clutch plate and the body increases, finally resulting in full lock-up of the clutch plate with the body. In this condition there is direct mechanical drive from the engine crankshaft to the transmission planetary gear train.
I'd like to ask those who know,
Is the same torque converter used for the TDV6, TDV8 and 4.2 s/c? 57 RRS TDV8
BAS Map
D3: Gone but not forgotten
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 19th Apr 2013 2:23 pm |
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AWD man
Member Since: 03 Jul 2009
Location: In Drag
Posts: 831
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I've just done a stall test on the driveway (away from the building  )
result, 2k rpms it holds firm so the locking clutch bit is working fine... it's the controlled slip/variable engagement that's the questionable fault. 57 RRS TDV8
BAS Map
D3: Gone but not forgotten
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| 19th Apr 2013 2:55 pm |
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John C
Member Since: 28 Aug 2007
Location: East Yorkshire
Posts: 3292
  
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Hi - did you solve this?
Wondering if it's related to this?
http://www.disco3.co.uk/forum/post1127677.html#1127677 2020 SDV6 D5 HSE, Carpathian Grey +
2022 Tesla Model Y LR... almost Carpathian Grey
Previously : 2005 TDV6 SE Auto, Cairns Blue (288K) - ours for 16 years
Last edited by John C on 18th Jul 2013 8:18 pm. Edited 1 time in total
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| 6th Jul 2013 4:40 pm |
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AWD man
Member Since: 03 Jul 2009
Location: In Drag
Posts: 831
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Hi John,
No not yet, I've transferred the car back onto the standard map because the dealership felt it was this that was causing the issue, but the symptoms are still present, just dulled down due to the lower torque etc.
I took it out this weekend with my twin axle caravan and it pulled it fine (no issues at all) so the extra load obviously made the TC lock in quicker?
Anyway... just driving it till it bongs up some kind of fault code, because up till then my dealership really isn't willing to fault trace without a starting point. 57 RRS TDV8
BAS Map
D3: Gone but not forgotten
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| 8th Jul 2013 7:45 am |
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race.it
Member Since: 15 Oct 2011
Location: Hopefully at a race track.
Posts: 851
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Mine had same symptoms, (but no map) dealer could not reproduce error for ages but I persisted and when the tc was changed all issues went away
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| 8th Jul 2013 8:54 am |
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