Member Since: 20 Jan 2005
Location: Wiltshire UK
Posts: 143
I'm still here lurking ever omnipresent in the underworld
Remember I used to work for LR at Gaydon and the rolling road is a very interesting piece of equipment.
Dynometers and the like are
I find it rather interesting that you are all concerned about the effects of ancillary equipment when we drive something that is as areodynamic as a brick!! I used to have collegue with a Rover 618, and when he wanted to boost his car, he would simply turn off his air-con, it's that dramatci on an underspec'd engine. Hence the reason in hot climates that everyone has engines sufficiently large enough to easily power their air-con, else they'd fry!!
5th Jun 2006 9:43 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26779
OK, while we are on the physics things, why has my fuel consumption jumped to over 26 without trying since I fitted the 17" rims to my HSE?
Could it be a small difference in rolling diameter?
5th Jun 2006 9:48 pm
Martin Site Admin and Owner
Member Since: 06 Nov 2004
Location: Hook Norton
Posts: 18573
Rolling resistance - are the 17" tyres narrower?
And hello Al 8)
5th Jun 2006 9:50 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26779
A little bit, 235 as opposed to 255 on the 19" so that could be it then
5th Jun 2006 9:51 pm
SN
Member Since: 03 Jan 2006
Location: Romiley
Posts: 13710
255 -> 235 thats nearly 10% - makes sense to me!Steve N | 21MY Defender | 08MY Discovery 3 (history) | 06MY Discovery 3 (ancient history)
Last edited by SN on 5th Jun 2006 9:56 pm. Edited 1 time in total
5th Jun 2006 9:56 pm
Big Al
Member Since: 20 Jan 2005
Location: Wiltshire UK
Posts: 143
It could be, I'd have to think about it, but it seems plausable since there would be a greater moment of inertia to get the wheel to roll if the wheel is larger, plus the fact that with larger tyres you have more (not sure here if I've got it the right way around!!) rubber in contact with the road and therefore greater frictional forces.
I've got 19" wheels and I never get above 23mpg, and this is keeping the tyres inflacted to the maximum fully laden pressures to reduce the amount of "flat" at the bottom of the tyre, ie reducing the contact area.
5th Jun 2006 9:56 pm
simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
Gareth,
Swap your mini's wheels onto the D3... see if that helps even more
5th Jun 2006 9:59 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26779
The Mini has 17's too!
5th Jun 2006 10:21 pm
SN
Member Since: 03 Jan 2006
Location: Romiley
Posts: 13710
Bet ya don't get the full 240mm wading depth with them though ..... Steve N | 21MY Defender | 08MY Discovery 3 (history) | 06MY Discovery 3 (ancient history)
5th Jun 2006 10:25 pm
Mr Bling
Member Since: 06 Mar 2006
Location: Lancashire
Posts: 259
I have to eat some humble pie. I'd forgotten the motor/dynamo effect, i.e. the increased electrical load produces a magnetic field, effectifely making the alternator harder to spin.
Does the alternator always spin when the motor is running or does it cut in and out like an airconditioning compressor?
If its always spinning, then, the load on the engine will be no different no matter what accessories are on. Isn't it the load on the alternator itself that will vary?? or dose the alternator have some kind of clutch pack that allows varying load on the engine??Have a nice day!
2010 Cayenne Diesel with PASM & Off Road Pkg
2005 HSE D3 (Sold)
6th Jun 2006 6:00 am
DSL Keeper of the wheelie bin
Member Since: 11 May 2006
Location: Off again! :-)
Posts: 73125
Just read through, now have a headache!
6th Jun 2006 8:15 am
Mr Bling
Member Since: 06 Mar 2006
Location: Lancashire
Posts: 259
There is no clutch, BUT the increased current drawn creates a magnetic "pull" acting AGAINST the direction of rotation, therefore mechanical resistance is increased2005 Disco 3 TDV6 7 seater. Leather, DVD, fully colour-coded.
1970 Triumph Spitfire Mk3
1981 Triumph TR7 FHC (16V Sprint)
2001 Porsche Boxster 2.7
MTD 12.5 hp Ride-on mower!!!
6th Jun 2006 8:23 am
Ken
Member Since: 20 Feb 2006
Location: Here
Posts: 10865
Told you TFC would deal with the oily bits
6th Jun 2006 8:26 am
DG Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50979
TFC....we are not worthy.... 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
| 08MY Discovery 3 (history) 
