Clarkson's top fuel saving tips

[feistl]

Yeah but the thing is all those electrical devices use such a little amount power (relatively) it wont effect fuel consumption.

I mean, even a very high end stereo would only use around 1000W, or 1KW. So when you consider most engines produce 100+kws, its not very much. I do know that you dont always use maximum power from the engine, and while coasting you probably only use 20-30kw or so depending. But a standard radio at normal level probably uses 50-100w which is next to nothing. More fuel can be saved in driving style.

[Ford Prefect]

well yeah, fuel consumption is mainly up to the driver, and a normal radio isn´t going to use a lot of power. But these small things do add up, and as you already pointed out, you´re not always around your car´s maximum power output, in fact, when you´re trying to save fuel and driving accordingly you will be in an area where 1KW actually does make a difference, especially considering the energy loss through the alternator just producing lots of heat at high output...

[otispunkmeyer]

Originally Posted by bone

that's another thing i don't understand

how does running more electrical equipment, result in less power?

how much power can an alternator drain from an engine? it gives hardly any resistance.

and what does the alternator care if you are running the lights AND the radio? it's not like they suck energy from the alternator and it has to work harder. it just does its thing, without knowing what happens with the power

yes the appliances will draw little power in comparison to what the engine can generate, but never the less, they do detract from the power the engine makes and more fuel must be used to generate that power for them... if this didnt happen then its like getting something for nothing....which cant happen.

if u think about it. with no appliances on the engine must run the car so it can move, all the pumps and ancillaries so it can continue to function, it must recharge the battery as it discharges to fire the spark plugs.

now u could assume thats a balanced cycle, i.e. the net energy is zero. now toss in a few electronic gubins and that unbalances the whole thing, there are now some components requiring energy and that energy cant be simply taken by reducing the energy given to all other parts, it must be generated in addition. i.e to balance the cycle, we need more power to cover the power consumed by the new additions.

the only way that can happen is by burning a tiny bit more fuel.

we are talking very very small amounts here though, so small you may not even notice, but it is happening.

[the Interceptor]

... and don't forget that the average alternator only has an efficiency of 50-62%. So for getting 1000 Watts of electrical power out, which shouldn't be much of a problem with stereo, lights, seat heater, rear window heater and so on, you actually need to put in 1613-2000 mechanical Watts.

[SL65]

Originally Posted by NooDle

quite useful tips really, didn't expect anything like that from the big man...

I've heard that using cruise control can reduce fuel consumption. That is, on the motorway/freeway. Something to do with the throttle linkage. Can anyone confirm this?

Obviously driving around town when you can be confronted with hills - cruise control is a bad idea as in order to keep the speed-up - it applies large amounts of throttle, often downchanging gear and revving quite hard. Harder than the you would if you were controlling the throttle.



Depending on temperature, I follow some Aussie guidelines and have the windows down below about 80km/h. Over that and the windows are up and the air-con is used instead. What do some of you do?

[Driller]

Best opening skit for a tv show ever!

[fbc]

Originally Posted by SL65

I've heard that using cruise control can reduce fuel consumption. That is, on the motorway/freeway. Something to do with the throttle linkage. Can anyone confirm this?

I've heard the opposite, because of:

Originally Posted by SL65

Obviously driving around town when you can be confronted with hills - cruise control is a bad idea as in order to keep the speed-up - it applies large amounts of throttle, often downchanging gear and revving quite hard. Harder than the you would if you were controlling the throttle.

But having said that, I'll take cruise every day rather than save a little fuel - it's benefits far outweigh $1 saved here and there.

Originally Posted by SL65

Depending on temperature, I follow some Aussie guidelines and have the windows down below about 80km/h. Over that and the windows are up and the air-con is used instead. What do some of you do?

I can't say I ever drive with fuel economy in mind - I just drive sensibly, with an occasional burst of enthusiasm.

[the Interceptor]

Originally Posted by SL65

I've heard that using cruise control can reduce fuel consumption. That is, on the motorway/freeway. Something to do with the throttle linkage. Can anyone confirm this?

I've made the experience that the cruise control always uses more fuel, even when coasting on the Autobahn behind a truck. The way I understand things, cruise control uses more fuel because it does everything to maintain the speed you set. When you're using your foot however, you'd speed up a little when going downhill and slow down a tad when you go up. So in the long run, you'll drive more economically.

[mat1h]

When leaving the lights, accelerate smartly. Not like a bat out of hell. But don't dawdle. Get the car into top gear as quickly as is reasonable. Fifth gear, remember, is no good at all.

[javamon]

Originally Posted by SL65

I've heard that using cruise control can reduce fuel consumption. That is, on the motorway/freeway. Something to do with the throttle linkage. Can anyone confirm this?

On a perfectly flat, perfectly straight highway with no wind and no other cars, running cruise control would likely return better economy than your foot...but that's about the only place.

Throttle linkage malarkey, I don't know. If it is an issue at all, it's becoming irrelevant due to the advent of drive-by-wire engines.

[NooDle]

Ive noticed too that no matter how 'smart' your CC is, you'll always use more fuel.
Doesn't matter if it's hilly or whatever, your own foot is always easier on the pedal and therefore easier on the mpg

[mclarensmps]

I've done 800 km on a 62 litre tank using techniques like this in my car, and that's marginally more fuel efficient than my friend's Toyota Corolla.

[IceBone]

A 100W lightbulb uses 0.1 kW, which is 0.13 horsepower. If you're using around 30-40 horsepower to cruise along nicely, that's 4% extra. Right now, i'm using 7.2 l / 100 km and without the lights, i'd be doing 6.9. That comes down to 37 cents per 100 kms or at my mileag, that's 92 euro a year. Just from running 1 100W light 24/7 cause of the law. Suddenly, the audi LED DRLs aren't just stylish, but save you around 80 euro a year too.

But that's peanuts..

[the Interceptor]

Originally Posted by IceBone

A 100W lightbulb uses 0.1 kW, which is 0.13 horsepower. If you're using around 30-40 horsepower to cruise along nicely, that's 4% extra.

You missed a digit there. 0.13 hp is not 4% of 30-40, but 0.4%.

[IceBone]

Oh yeah, whoops.

So... that comes down to 9 euros a year. At this rate, I'll go broke!

[phas3r]

He has an M3 e92?

[Crazy Vega]

For any who want to see the effects of the electrical components for themselves, go out to your car, start it up, and turn on as many electrical accessories as you please, then open the hood and unplug your alternator, if you can easily. My bet is that you'll hear your engine speed up. Plug it in, and you'll hear the load on it.

Driving through New Mexico with a nearly dead battery at night is no fun, let me tell ya.