P plate training ...not

I didn't say I didn't get it.

Here are a few blank lines where you can explain how it figures out an
hourly fuel flow rate without taking the time and the flowrate of fuel
into account.

The monkey powers the lights?

Just because it doesn't, doesn't mean that it can't. Now you're just
making shit up. And it is repeatable, to the extent that every time I
start the car and let it idle, it gives the same result, give or take a
poofteenth. I'm happy to accept that environmental changes would
influence the result, so it's probably unlikely to get identical results
under differing conditions.

Nev..
'04 CBR1100XX

 

So for all intents and purposes, the amount of additional fuel consumed
when the headlights are turned on is immeasurable, so this "lights on =
more fuel" business exists in theory only.

Nev..
'04 CBR1100XX

 

When you pop over, feel free to show me that is what I have....

Hammo

I'll provide the magicians hat!

 

Nev.. wrote:

Well, in theory, theory and practice ought to be the same, but, in
practice, they aren't.

regards,
CrazyCam

 

GB wrote:

This is, of course, a trick question.

Everyone knows that a fridge is simply a heat pump, gathering heat from
inside, and moving it outside, but... with the fridge door open, the wee
light will be on, thus heating up the insides of the room.

regards,
CrazyCam

N.B. the fridge will not use more petrol because the light is on, except
if it is a petrol fired fridge.

 

I have. Rented a Budget Ford Fiesta in England to get from Manchester to
Heathrow to catch the plane home. At 5 in the morning on the M1 (I think)
engine died. Coasted to an emergency phone. Can't call budget from them.
Looked under the bonnet, took top off distributor. No contact there, as in
missing altogether. Got the RAC out. Some genius had adjusted the points by
bending the moving arm, and it had snapped off. He had another set in his
van. Made it to the airport on time. Budget refused to give me any discount
as I 'had not given them the opportunity to fix the problem'. They did
reimburse me the 3 quid I had to pay the RAC man for the points.
Fuckers!

Theo

 

Guzzi went to brushless, permanent magnet alternator with the Cali 1100 in
1994. Used the Ducati branded regulator. After two of those I replaced mine
with an aftermarket Japanese one. Never had another problem. (Obviously it
wasn't from Honda).

Theo

 

It's all about you, isn't it?

 

Buy a Mercedes. The doors lock when you reach 15 km/h to 'improve the
structural strength of the vehicle'. Some magical thing unlocks them after
you crash, apparently.

Theo

 

It's not the torque that matters, it's the power. If your headlights
draw an extra 120W then the motor needs to put out an extra 120W - if
you factor in inefficiencyin the alternator (which is unlikey to be any
better that 80%) its going to be more like 150W. Add in the running
lights and you might get as high as an extra 200W needed from the engine.

That's not going to make much of a dent on Nev's 5.7L V8, but it's over
10% of the total max output of a Deux Chevaux.

Most cars will come somewhere in between - I'm not surprised Nev doesn't
notice the extra power consumed by his headlights, in a much smaller
engined car it'd be more obvious, on a tiny engined and/or extremely
efficient car (a Prius maybe) I'm sure it'd show up.

Nope, as I explained upthread, any modern car (unlike, I suspect, the
2cv) has an active rotor and can adjust it's output (and hence input) to
match the current electrical power requirements .

Yup, you're right there. It's true that lights require power, but it's
not _much_ power...

big

 

Excellent, and I'll bring the oscilloscope!

-----sharks

 

Oh,boo hoo, did you want to wear the pretty hat too? You'll have to nice to
Sharkey, he is the guest!

Hammo

 

Without arguing the authority of wikipedia...

http://en.wikipedia.org/wiki/Alternator#Automotive_alternators says
automotive alternators achieve between 50 and 60% efficiency.

http://en.wikipedia.org/wiki/Megajoule says 3.6MJ=1kWh, so 1kWh~=0.28MJ
or 1Wh=0.00028MJ

http://en.wikipedia.org/wiki/Internal_combustion#Engine_Efficiency says
piston engines get ~ 20% efficiency

http://en.wikipedia.org/wiki/Gasoline#Energy_content says you get
~32MJ/l from petrol.

So, 120W headlights will need 120/0.50 =~ 240W of input power to the
alternator.

To run them for an hour will require 240*0.00028 =~ 0.067 MJ.

At 20% efficiency the engine will consume 0.067/0.20 =~ 0.34MJ

Which is (near enough) 100mL of petrol.

If you're driving along at 100kmh, you should expect to consume an extra
0.1L of fuel an hour, which is an extra 0.1L/100km (or around and extra
1.5mpg). If you're only averaging 50kmh, you'll still consume 0.1L/h to
drive the headlights, but you'll be driving them for twice as long which
will bump your fuel economy up by 0.2L/100km.

(I think I got all my orders of magnitude right there)

It's a more than a thimbleful, but small enough to disappear into the
noise for most people I suspect... My little bike gets around
4.75L/100km so I _might_ notice a 0.1L increase, but it's only got 60W
of headlight. I suspect Nev's lucky to get less than 20L/100km out of
his car, and he'd be unlikely to notice a 0.1L/100km increase - it'd
almost certainly be overshadowed by head/tail winds, traffic delays,
imperceptible inclines, etc...

bored-at-work-big

 

What?

Oh, I see...

Carry on...

big (no-arse-cancer)

 

See my other post - wikipedia and the back-of-the-envelop suggests 1
decilitre per hour is pretty close to what your 120W headlights
require...

Can I get you to do another experiment? I'm wondering if 800rpm is too
slow for the alternator to be developing all the required output, and
what you're seeing is the headlights drawing the battery charge down
rather then being powered by the engine. I'd be interested to know if
you see any fuel flow difference in the diagnostics if you hold the
engine at a slightly higher speed when you switch the lights on and off
- maybe up at 2500 or 3000 rpm?

curious-big

 

And that's the best you could come up with?

 

Oh yes?

I'd like to see your calculations! Please consider diameter of the pulleys
of both crank and alternator, torque required and current and volatge flow,
also for switched and non-switched systems.

10 per cent?

One is a measurement of the conversion from mechanical to electrical with
the outcome being power, and the conversion from electrical to mechanical
would be power dependant. AFAIK, Torque is the proper term when describing
this rotational force.

If it is so small you cannot measure it, how can be called a waste? Also as
there are more than one type of alternator/dynamo/magic box it is the joy of
discussion and the pointing out that there are circumstances that "waste of
fuel for no purposes" becomes a good laugh.

Hammo
[1] ..some bits of this you've missed from other posts that may be useful
re: assumptions and the like. See above.

 

Oh...... You really are being sooky. It'd be like kicking a puppy.

Hammo

 

That'd be great.
Plans still the same?
How strong is your arm/shoulder now?

Hammo

 

My 5.7 litre HSV gets an average of about 16.5L/100km in the city and
10.0L/100km on the highway.

Boxer