levap
Member Since: 15 Aug 2006
Location: Breclav
Posts: 2
  
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| manual versus command shift |
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Hello all
I am new here but read a lot of already and I would like to ask if somebody compare fuel consumption in manual and in auto with command shift. 
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 15th Aug 2006 10:13 am |
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Ocsid
Member Since: 29 Nov 2005
Location: Hampshire
Posts: 255
  
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I have no in-depth experience comparing manual to automatic, however a 2 x 60 mile evaluation with two demonstrators towing my 1700kg caravan over the same course one after the other gave 19.4 mpg manual and 18.6 auto. I used mainly the true auto, not the comand shift facility
I dont think comand shift will make any real difference. The Auto's problem is the slip in its fluid coupling [torque converter]. This has to slip to transmit torque and in doing so wastes energy to heating its oil and thus worsening the fuel consupmtion.
In theory reving the engine, ie holding a gear will reduce this coupling loss however the engine's efficiency reduces at higher rpms thus tending to cancel any gains. I find that 5th gear is better than 6th re fuel consumption; thats before the "enchancement" , I have yet to get sufficient data to know the after effect. It seems to want to get into a higher gear earlier and hold it longer post upgrade.
After evaluating both manual and Auto re towing it was an easy choice for me to go for the Auto despite the use of more fuel.
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| 15th Aug 2006 11:17 am |
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steveho
Member Since: 07 Jan 2006
Location: lincoln
Posts: 74
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command shift comes into it's own when off roading-wouldn't even consider using during normal driving
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| 15th Aug 2006 8:35 pm |
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Pelyma
Member Since: 06 Jan 2005
Location: Patching, Sussex
Posts: 15496
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There's a voice from the past, where have you been? DS3 TDV6 HSE - Silver with Alpaca (old one) Gone
DS3 TDV6 HSE- Silver with Alpaca (new one) Gone
D4 HSE Lux - Montalcino Red Gone
Porsche Cayenne V8 Diesel S
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| 15th Aug 2006 8:36 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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steveho wrote:command shift comes into it's own when off roading-wouldn't even consider using during normal driving
I had a RRS for the day yesterday... and Command Shift was much fun just before overtaking 
Yes in off roading completely agree... I wish my manual box would change as fast when going up hill and needing 1st not 2nd to get up 
And to answer the MPG question... manual will be better always, Command Shift or not.
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| 15th Aug 2006 11:13 pm |
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Alfwarez
Member Since: 17 Jun 2006
Location: Gauteng
Posts: 63
 
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As Simon mentioned manual is better. I use to drive on Auto, my speed varies as its city driving and I use to get a fuel consumption of around 11.5 to 12 liters/100km. Since changing to manual under the same driving conditions my fuel consumption is between 9.8 to 10.5 liters/100km. Being optimistic I would say that a 10 to 12% improvement in fuel consumption can be achieved over driving in Auto. I also drive in manual using cruise control; the beauty of this is when you come to a steep hill and the revs start to drop all you do is drop a gear while still in cruise control and the car carries on without dropping in speed.
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| 16th Aug 2006 9:40 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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So you driv ein Command Shift mode with an auto box ??
I drive in manual mode in a manual box... better MPG again... but harder on the left leg around town
Cruise control also lowers MPG. Your right foot is better at controlling the speed and you are able to anticipate a hill(you see it) whereas the cruise control can only start to react as it detects the gradient slowing the vehicle.
Not really that important I know but driving the D3 myself seems to return better MPG than letting is loose on its own 
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| 16th Aug 2006 9:48 pm |
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Alfwarez
Member Since: 17 Jun 2006
Location: Gauteng
Posts: 63
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You are correct I drive in command shift. The only time I change to Auto is in heavy traffic.
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| 16th Aug 2006 10:05 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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lucky
Must admit. After driving a RRS for the day on Monday, an auto box with command shift was very nice.
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| 16th Aug 2006 10:12 pm |
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JMC
Member Since: 25 Feb 2006
Location: Aberdeen-Angus. Where the Bull* comes from!
Posts: 6417
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simon wrote:Cruise control also lowers MPG.
Sorry Simon.......Urban myth 
Just sit behind a car without cruise control and watch their speed fluctuate - even when they think they are at a constant speed.
Every car I have had with C.C. has peformed better in the economy stakes with it switched on. I understand your arguement, but it doesn't work in practice. Correct use of C.C. is the reason my auto can do 34MPG over a decent run. I will never profess to be as good as a computer at controling my engine.
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| 16th Aug 2006 10:46 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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mmm... tried CC along the M40 once and then without for a good stretch. My range went up after a while with CC off. Assume this relates to lower fuel consumption
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| 16th Aug 2006 10:55 pm |
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JMC
Member Since: 25 Feb 2006
Location: Aberdeen-Angus. Where the Bull* comes from!
Posts: 6417
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simon wrote:tried CC along the M40 once and then without for a good stretch. My range went up after a while with CC off.
I was expecting a man of your calibre to come up with something a little more scientific.....
Ten years of using CC on a number of cars and I can honestly say that I have seen up to a 20% improvement in MPG - particularly with an M30 series BMW engine. I reckon 10% improvement is a fair reflection across the range.
In truth, it may be something to do with changing driving habits too. If you drive to the tune of CC (Set it at 56 - 70 then leave it) you tend to become a more sedate driver. People pass you more frequently, but you pass them later while they are filling up with fuel
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| 17th Aug 2006 9:19 am |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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JMC wrote:simon wrote:tried CC along the M40 once and then without for a good stretch. My range went up after a while with CC off.
I was expecting a man of your calibre to come up with something a little more scientific.....
mmm sorry mate
I usually cruise around 65-70 as I cannot be bothered to hoon around these days on the motorway. Life's stressful enough. B roads are different - love the way the D3 lulls others into a false sense of security, only to then see it whip round corners and stay annoyingly in front of them or even pass them !
So CC... will do some more experimenting then. Just for you mate But still not convinced.
-s
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| 17th Aug 2006 9:24 am |
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steveho
Member Since: 07 Jan 2006
Location: lincoln
Posts: 74
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Hi Pelyma,
I pop by now and again to see whats going down-don't always post though
catch you later
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| 26th Aug 2006 8:02 pm |
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lee01277
Member Since: 06 May 2005
Location: Shed
Posts: 821
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JMC wrote:simon wrote:tried CC along the M40 once and then without for a good stretch. My range went up after a while with CC off.
People pass you more frequently, but you pass them later while they are filling up with fuel
a fact ... when I'm on CC and plodding down the M way at 65 / 70 ish, and get overtaken .. how many times does the car thats just gone past then slow down in front of you , almost saying .. phew .. done that bit. You then need to slow down to retain the gap, or pull out to maintain the momentum ..
(or they are looking at the car in the mirror trying to see what it is .. )
anyway, CC every time for me for better MPG. You can still give it a helping hand when the hill is there and then it just goes back to where it was .. ..............Somewhere in-between my old D3 and what's to come next .........
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| 26th Aug 2006 11:42 pm |
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