Petrol Consumption

[Thrower]

I`ve read that it increases a vehicles petrol consumption if you run it with headlights on, as in daytime driving, which has been proposed by some agency study group.

Is this true, as I can`t see that it does, but maybe I`m missing something? (apart from intelligence I mean!)

[ChuckFickens]

Yes of will increase fuel consumption having your lights on, simple rule of physics, you can't create energy from nowhere, the extra energy needed to run your headlights needs to come from somewhere and the only place it can come from on a car is your fuel tank.

Though it's a pretty small increase and probably far outweighed by the increase in safety from having your lights on

[Toureman]

Our great government is telling us we must conserve energy but is now considering something which will be wasteful, with the millions of vehicles on the road this will have a significant effect on the country's emissions and fuel supplies.

[jake-the-peg]

Where exactly did you get this from?

I really cannot believe that any study group woukld suggest this and I can't see anything after a quick flit around the net.

Sounds to me like something made up to annoy the sort of people who'd believe anything about Government think tanks.

Seems to be working eh?

Chuck's right in theory but in practice complicated systems like cars have an awful lot of power losses that are unpredictable in nature. You'd never spot the loss in fuel consumption from the headlights over the rest of the "noise".

Any Government comittee's first port of call would be air conditioning in cars.

[sigma]

The headlights are powered by the battery, the battery is charged by the alternator. Surely the alternator produces the same output regardless of the headlights being on or off.

[Thrower]

Sigma,

That`s exactly what I think, which is why I`m confused!

jake-the-peg, it came from the newspaper I read, (not apparently that they always tell the truth) but it was a large article meant to be taken seriously.

[Ethel]

Daytime running lights may become a legal requirement for vehicles manufactured after a certain date:

http://www.dailymail.co.uk/news/article-106124 5/Now-Europe-wants-headlights-ALL-day--inflati ng-fuel-costs-160-year.html

And it does increase fuel costs, although one possibility is the introduction of LED lights for daytime, which will use less fuel

[Ethel]

And in the Telegraph

http://www.telegraph.co.uk/motoring/3075189/EU -resurrects-daytime-running-lights-plan.html

[jno]

I think this is already law in Sweden, hence Volvos with their lights on all day. Whether it is necessary in countries that don't have such long winter nights is arguable but if it makes other cars more visible to dozy drivers there may be something to be said for it.

[Ethel]

It will certainly make motorcyclists less visible, if everyone has their headlights glaring.

True story - this headlight always on is a legal requirement in Estonia. A UK lorry driver had his articulated truck stopped by police in broad daylight as they needed to check he had his lights on. They couldn't tell from looking as he passed by because of the glare of the sun.

[sigma]

Having read the two articles there are many comments against using headlights in the daytime but non of the comments are quantified,
It will use more fuel but how?
Looking for lights instead of pedestrians is no different than looking for cars instead of pedestrians.
There is a small risk that some drivers will forget to switch on their headlights at night. What !!!!!
'This directive will kill a lot of motorcyclists. They use daytime lights to make them easier to see but if cars are using them as well, motorbikes will blur into the background.'
No more than a car with its headlights on will.
It appears many organisations are against this proposal but are coming up with ludicrous reasons to oppose it

[Thrower]

Yes I`ve read all the arguments for and against, but I still don`t know how it increases fuel consumption.

[Ethel]

thrower,

lights, in-car entertainment, air conditioning all use more fuel

Read Step 4 here:

http://www.ehow.com/how_2264063_fuel-efficient ly-better-gas-mileage.html

[jake-the-peg]

Right so the think tank actually wants to introduce headlights during the day to reduce accidents not to ban it to save petrol.

This makes more sense.

Presumably the Jeremy Clarkson clones are up against it simply because it comes from the EU.

The best arguments seem to be:

People will forget to switch on their head lights

There will be confusion with headlights

and apparently

It'll use more petrol

Sad really.

The electric system runs off of a combined system of the battery and alternator.

The alternator has a regulator which controls the output of the regulator so as not to overcharge and blow up your battery.

On modern regulators the field current is adjusted which means that when the alternator is charging the battery it is having to push against ever so slightly more magnetic field to do so - hence requiring the engine to supply ever so slightly more power to stay at the same rev count.

But as I said before this is almost certainly so small that it's lost in the other variables.

[sigma]

Thanks Jake, we got the answer at last.

[kempie]

Perhaps further study of the increases in fatalities to pedestrians and cyclists (both motor and pedal) recorded in Poland, Bulgaria and Austria since the introduction of DRL is a worthy exercise.

sigma - the alternator converts mechanical energy into electrical energy. Any charge drawn from the battery needs to be replaced and is "extracted" from the engine; more load on the engine means more fuel required to power it. Have you not noticed the pitch of an engine change when electrical components are activated?

Various DRL studies (including those to promote DRL) show an increase in fuel consumption of around 1% to be reasonably accurate.

http://ec.europa.eu/transport/roadsafety_libra ry/consultations/drl_20060727/drl_trl.pdf

[Panic Button]

I too am baffled by the claim that more motorcyclists will have accidents if all vehicles have their headlights on.

[jake-the-peg]

I find that difficult to believe.

This report was comiisioned as in investigation into the EU work and appears very partisan.

I'm particularly suspicious of:

a/ This was based on a computer model not experimental data - yet there is absolutely nothing to prevent someone from doing this experimentally.


b/ side lights are 4-5 watts x 4 is about 20 watts electrical

That equates to 0.026 horsepower

If you take a car engine generating some 50HP 1% would be about half a horsepower.

So they are suggesting that there is an efficiency of about 5%

Yet most alternators run at 75-80% efficiency

Put a car on a dynometer and show me a loss of half a horsepower when you turn on the lights.

No?

Funny that

[Thrower]

Ethel,

I don`t want to be argumentative, but having read step 4 of the link, I`m still not convinced.

The alternator on my car doesn`t `sense` nor is it computerised and programmed, it`s driven by a constantly turning belt. That produces electricity whether you push the accelerator lightly or not and is returned to the battery. Any excess, as I understand it, when the battery is `topped up` is returned to Earth. In other words going to waste. Therefore why should it decrease MPG to turn the lights on, which are powered by the battery? The alternator doesn`t `know` whether the lights are on or off.

[jake-the-peg]

Well I don't like to be argumentative either

But you're wrong.

Excess electricity is not returned to earth, and you do have a regulator on your alternator that "senses" the battery's requirements which is related of course to what electrical devices area in use.

I know I had a regulator fail on a car once and it blew the battery apart. (great smell of sulphur)

It was an older car with an external regulator which needed to be replaced. these days they tend to be internal.


Here's a picture and details of an alternator's workings

http://www.autoshop101.com/trainmodules/altern ator/alt109.html

[kempie]

Well, to be somewhat argumentative also, no matter how "partisan" it appears to j-t-p, I put more stock in research and analysis by TRL than opinion of any layman.

http://www.trl.co.uk/content/overview.asp?pid= 94