Post Reply 
 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
50.4 MPG
NightFox
 

Posts: 352
Joined: Jun 2012
Location: Shropshire, UK
Post: #51
RE: 50.4 MPG

(05-11-2012 02:09pm)PhilSkill Wrote:  As Engery systems cannot be 100% efficient, The more load you draw from the car's system the more resistance the alternator has against turning, therefore more engine power is required to turn the alternator, therefore using power that could have been used to drive the wheels and so costing you mpg.

Thanks, I'm still not clear on this though. I thought that the alternator's output was constant (or at least linked to the engine speed), and not related to the actual demand on the battery. In the same way that a bike light dynamo works, if you've got the dynamo engaged it doesn't make any difference to how hard it is to pedal whether you've got the light turned on, turned off, or even got several lights rigged up to it. I thought the alternator was simply a dynamo, but connected to a battery rather than direct to the lights etc?

MY13 TD4 Pure Manual ~ Tech Pack ~ Mauritius Blue ~ Panoramic Roof ~ Adaptive Xenons ~ Park Assist ~ Keyless Entry ~ Reversing Camera ~ Powerfold Mirrors ~ Autodimming Mirror
Ordered 14/6/12 ~ Built 13/11/12 ~ Delivered 15/11/12 ~ Collected 20/11/12

[Image: 163643.png]
05-11-2012 02:16pm
Find all posts by this user Quote this message in a reply
PhilSkill
 

Posts: 3,880
Joined: Jun 2011
Location: Warwickshire
Post: #52
RE: 50.4 MPG

The magnetic field in the stator windings increases with the current draw in the car, this magnetic field acts as a resistance to the Magnetic field being created by the driven windings.

When you use the Heated windscreen the current draw may be a good few amps at 12V and as the Battery is also likely to be charging and drawing amps along with everything else, those amps will be coming from the altenator, and thus causing resistance to movement.

Your bike generator will likely be fairly inefficient and the effect of the lights current draw will likely hardly notice.

Draw enough current through your altenator and it will act as an electronic brake! (Or more likely burn out the windings Smile )

MY12 Fuji Dynamic SD4 Manual, Pano Roof, Electric Tailgate with own Close module
[Image: 124529.png][Image: 1004887.png]
05-11-2012 02:58pm
Find all posts by this user Quote this message in a reply
NightFox
 

Posts: 352
Joined: Jun 2012
Location: Shropshire, UK
Post: #53
RE: 50.4 MPG

(05-11-2012 02:58pm)PhilSkill Wrote:  The magnetic field in the stator windings increases with the current draw in the car, this magnetic field acts as a resistance to the Magnetic field being created by the driven windings.

When you use the Heated windscreen the current draw may be a good few amps at 12V and as the Battery is also likely to be charging and drawing amps along with everything else, those amps will be coming from the altenator, and thus causing resistance to movement.

Your bike generator will likely be fairly inefficient and the effect of the lights current draw will likely hardly notice.

Draw enough current through your altenator and it will act as an electronic brake! (Or more likely burn out the windings Smile )

Ahh, thanks for the good explanation! Idea

MY13 TD4 Pure Manual ~ Tech Pack ~ Mauritius Blue ~ Panoramic Roof ~ Adaptive Xenons ~ Park Assist ~ Keyless Entry ~ Reversing Camera ~ Powerfold Mirrors ~ Autodimming Mirror
Ordered 14/6/12 ~ Built 13/11/12 ~ Delivered 15/11/12 ~ Collected 20/11/12

[Image: 163643.png]
05-11-2012 03:14pm
Find all posts by this user Quote this message in a reply
eddkawasaki
 

Posts: 159
Joined: Apr 2012
Location: Lancashire
Post: #54
RE: 50.4 MPG

To help put this into context I've done a quick calculation based on the things that are normally used on a drive to work in the morning using 90% of fuse rating to give running current and I've only included the big consumers not all the sensors etc.

So if using the below

Power steering
Heater
Blower
Heated front screen
Heated rear screen
Heated seats
Radio
Amplifier
Heated steering wheel

This gives a total current draw for these items of 355.5 amps. Your alternator has to supply this plus enough to charge the battery after starting, glow plugs (these have a 60A fuse) etc. 355.5 Amps equates to a power consumption of 4266watts or just over 2 kettles on during your journey.

A 190bhp engine is 141kw so our 4.2 kw for our toys to keep us warm uses 3% of the engine power plus whatever it uses to charge the battery and supply the various sensors and processors that are running.

Hope this rough calculation helps and it is just that a rough calculation.

SD4 Dynamic Lux, 5 Door, Firenze Red, Ebony Interior, Black headlining, Black Contrast Panoramic Roof, Aeroflip Spoiler, Privacy glass, Heated steering wheel, Adaptive Xenons, TPMS & Spare wheel
Order Date: 14th May 2012
Build date: approx 5th Oct 2012
Delivery Date: Should be 22nd Oct
Actual delivery: 31st Oct

[Image: 151436.png]
05-11-2012 06:35pm
Find all posts by this user Quote this message in a reply
PhilSkill
 

Posts: 3,880
Joined: Jun 2011
Location: Warwickshire
Post: #55
RE: 50.4 MPG

Also Alternators are around 60% efficient so from engine power your 4.2kw loading on Alternator requires 7Kw of engine power, now hopefully the fuses are'nt that closely rated but yes 4% of 40mpg is 1.6 mpg just to run your toys...

MY12 Fuji Dynamic SD4 Manual, Pano Roof, Electric Tailgate with own Close module
[Image: 124529.png][Image: 1004887.png]
05-11-2012 07:39pm
Find all posts by this user Quote this message in a reply
NightFox
 

Posts: 352
Joined: Jun 2012
Location: Shropshire, UK
Post: #56
RE: 50.4 MPG

I didn't spec the kettle though, so will I be ok?

MY13 TD4 Pure Manual ~ Tech Pack ~ Mauritius Blue ~ Panoramic Roof ~ Adaptive Xenons ~ Park Assist ~ Keyless Entry ~ Reversing Camera ~ Powerfold Mirrors ~ Autodimming Mirror
Ordered 14/6/12 ~ Built 13/11/12 ~ Delivered 15/11/12 ~ Collected 20/11/12

[Image: 163643.png]
06-11-2012 12:14am
Find all posts by this user Quote this message in a reply
PhilSkill
 

Posts: 3,880
Joined: Jun 2011
Location: Warwickshire
Post: #57
RE: 50.4 MPG

(06-11-2012 12:14am)NightFox Wrote:  I didn't spec the kettle though, so will I be ok?

Yes, As long as you dont want Tea! Wink

MY12 Fuji Dynamic SD4 Manual, Pano Roof, Electric Tailgate with own Close module
[Image: 124529.png][Image: 1004887.png]
06-11-2012 12:22am
Find all posts by this user Quote this message in a reply
Fish
 

Posts: 20
Joined: Apr 2012
Location: CH
Post: #58
RE: 50.4 MPG

On Top of that I learned that per 100watt the fuel consumption increases by 0.1 Liter.
This will make almost 0.5liter/100km or (hopefully I am not wrong) = 1.4 mpg !

That's why I haven't ordered the heated stearing wheel. ConfusedBig Cry

TD4, tech pack, power fold mirrows, heated seat, ipanema sand, pano roof, xenon, fog,
dark window glas, rear cam, black rails, black rims, black grill & side panels, spare wheel
Date of order: 14.04.2012
Built date: 19.10.12
Date of delivery: 12.12.12 Bow down
06-11-2012 12:36am
Find all posts by this user Quote this message in a reply
Jai
 

Posts: 260
Joined: May 2012
Location: Australia
Post: #59
50.4 MPG

There's a difference between the British mpg and the USA mpg isn't there??


Sent from my iPhone using Tapatalk
06-11-2012 05:01am
Find all posts by this user Quote this message in a reply
FujiSan
 

Posts: 171
Joined: Dec 2011
Location: Hertfordshire
Post: #60
RE: 50.4 MPG

Yup. Miles are the same, but gallons are not. US gallon is 1.2009 of a UK gallon. so in the US you use more gallons per mile than we do in the UK.

TD4 Pure - Now a rare breed...

[Image: 131166.png]
06-11-2012 09:13am
Find all posts by this user Quote this message in a reply
Post Reply 


Forum Jump:


User(s) browsing this thread: 3 Guest(s)
babyRR is an independent web site and not affiliated with Land Rover