Do you put the heater on in the car?

Gloomendoom

Strider590 wrote: »

I wrote a huge reply, the forum went tits up and now I really can't be arsed.....

Alternator runs at the same speed as the engine, for example it produces a potential 30A @ 12v @ 2000rpm and maybe 70A @ 12v @ 8000rpm... The faster the engine speed the greater that potential (up to it's maximum output), the only time you'd have a problem is if you overload the alternator at any given RPM, in which case there may be a magnetic flux produced that could place a small load on the engine.... However!!! the auxileries belt and the cam belt are not meant to withstand additional or abnormal mechanical loads to the sort of extent to which you (and im not sure who has the opinion V who's jumping on the band wagon) seem to infer. If this was the case, we would have auxiliaries chains and not belts.

As soon as you increase RPM the alternator is capable of more current and any overload problem disappears. So moving back to topic, under normal driving conditions you won't increase fuel consumption by switching on your lights, your heater, or pretty much anything for that matter and EVEN if you did, the battery would compensate for that additional electrical load before any problem was encountered.
The very reason (or one of) that manufacturer's are moving over to electrically driven PAS and Aircon etc etc is because doing so removes the additional mechanical load these used to place on the engine.

As for people talking about ECU's compensating for this that and the other, it's just not a valid point..... Nothing has changed since way before anyone had ever heard of ECU's. You have always had that slight judder from the engine when turning on electrical elements of the car. The reason being "inrush current" where electrical devices briefly draw abnormal amounts of current when first turned on.

thescouselander

Strider - your explanations are getting further and further off the mark.

Lest say an alternator is spinning at 2000 rpm - if there is as 10A load the alternator will support this by generating electrical power using a mechanical input of energy from the engine - this means an amount of torque (mechanical load) is input to the alternator.


Now lets say the load increases to 30A and the engine speed stays the same speed. Where does the additional power come from - the torque on the alternator shaft increases because there is more current running through the coils of the alternator. Its that simple.

nearlyrich

Mine is well and truly on when it's cold, no way I'm driving and shivering...

Strider590

This is what amuses me, forum sheep who follow popular opinion without question...... I'll start a thread on global warming, that'll be fun, hearing all the crap ya'll read in the papers or got fed down via the govt.

Mechanical load of an alternator does not increase to such a degree as you seem to be suggesting under normal conditions. Hence I eliminated that from the equation. I also state that an auxiliaries belt would not be capable of holding a massive load against the rotational force of an automotive engine. But quite seriously, think what you like because it really makes no odds at all to me?

There's a very famous scientist, there are in fact many who had they given in to "popular opinion" just to "fit in", we'd not have half the technology we have today.

I don't claim to know everything, but I will not be swayed by the opinions of the majority unless there's far more proof than a simple technically incomplete webpage written by an unknown source. If you want to play that game, take a look at the bottom of this page.

Now then...... Where's that witch we need to burn? must be a witch, every drunkard in the pub says so.

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Oh and something else to chew on...... I've done the math.

1 horse power (hp) is equal to 745.699872 watts.

So assuming a 90A alternator and assuming you do draw the full 90A, the maximum fuse size in most cars is 30A, so no single device is going to draw 90A.

Voltage 12v x 90A = 1080 watts.

So the maximum load is 1.45 hp, but alternators are only 60% efficient, so we can double that figure to 3hp, which quite frankly is nothing!

3hp from even a 60hp engine is less than 5%. In truth under normal conditions, were talking less than 1% increase in fuel consumption with all your lights, wipers, fans and god knows what else running. So instead of your 30 mpg, you'd get 29.7mpg.

In the case of the video that was posted of a lawnmower engine, that produces what? 5hp?
So a 3hp load onto a 5hp engine is going more or less kill it.

Now let's put this thread to bed, yes?

Poly,put_the_kettle_on

Strider590 wrote: »

In women-land, thermostat is just a rotary on-off
switch with silly numbers written on it.

Perhaps you should spend your time with more intellegent women. :cool:

lozzaman

Strider - what you've said above is what I've been trying to say above all along. That there is a load from the alternator which increases with a given load, you have previously said.

under normal driving conditions you won't increase fuel consumption by switching on your lights, your heater, or pretty much anything for that matter and EVEN if you did, the battery would compensate for that additional electrical load before any problem was encountered.
The very reason (or one of) that manufacturer's are moving over to electrically driven PAS and Aircon etc etc is because doing so removes the additional mechanical load these used to place on the engine.

Now, while the alternator load is very low as a percentage on a car engine (hence full output being possible so close to idle speed) and also that it can be delivered through a belt. Your calculations show this, other than the fact alternators will put out around 14.4v and are a little bit more efficient than the 60% you suggest.

Back to the OP, the fan load (assuming it is on to assist the heater) is so tiny you will not notice it. The major energy comes from the waste heat from the engine.

adouglasmhor

Nobody said as far as I can see there was a massive load, but any load is still a load. If you had said from the start it was negligible no one would have taken issue with you, instead you launched a massive look at me I am right flurry of drivel to show us there was zero load (an impossibility in any moving system). Well done, take any prize from the bottom shelf.

esmerobbo

How do the 160A and 200A increase fuel economy?
A: The 160A and 200A are much more efficient than the alternator they
replace. Efficiency is the percent of mechanical energy supplied by the engine
that is converted to electricity. The alternator requires less mechanical energy
from the engine to produce the same electrical output, resulting in less power from the engine,
hence less fuel consumption.
Depending on driving conditions, fuel cost, electrical usage, this could mean a fuel savings of
up to $400/100,000 miles. Under certain conditions like idle, low rpm and low to average
electrical load, the influence of the efficiency and therefore the fuel saving impact is the highest.

It is American but then again it is Bosch!

Strider590

Well excuse me, but when someone comes in asking a question, the answer they'll find easiest to understand is "yes" or "no". Complicating issues with negligible loads (to the point of non-existence) is entirely pointless. I didn't want to go to such extents (all the technobable) to answer such a simple question.

The last thing we need is more idiots driving about with no lights on because they read on some forum that electrical loads massively affect their fuel consumption. Or even some clown ploughing into the back of my car because he forgot to turn his wipers back on after going under a bridge.....

I always find that those who know their stuff will always "kiss" or "keep it simple stupid" (as per my first post), where as those out to impress usually bring out language and big words that nobody understands.

thescouselander

Strider590 wrote: »

Well excuse me, but when someone comes in asking a question, the answer they'll find easiest to understand is "yes" or "no". Complicating issues with negligible loads (to the point of non-existence) is entirely pointless. I didn't want to go to such extents (all the technobable) to answer such a simple question.

The last thing we need is more idiots driving about with no lights on because they read on some forum that electrical loads massively affect their fuel consumption. Or even some clown ploughing into the back of my car because he forgot to turn his wipers back on after going under a bridge.....

I always find that those who know their stuff will always "kiss" or "keep it simple stupid" (as per my first post), where as those out to impress usually bring out language and big words that nobody understands.

Unfortunatly most of your posts have been incorrect. Call me a sheep if you like - I admit I do like to follow the rest of the engineering profession in basing my knowlege on accepted principals and the laws of physics. At least this was enough be be awarded CEng status by the IET though.