Economy driving tip: drive faster!

[robdf2]

Sorry, been away for a week or so and just catching up on stuff..

Anyway, who learnt something?? Me? I'm not trying to start an argument here, but it is true, the 56mph figure used is purely a standard set by the EU govt as a benchmark for fuel consumption averages so the manufacturers can print figures. Do you really think that all cars somehow miraculously reach their sweet spot at this speed???

So, accounting for drag coefficient, gearing, weight, etc, isn't it amazing that they all come out most efficient at 56...... Think about it..

The generally accepted "most efficient point" is the lowest speed your car can cruise at smoothly in top gear, whatever that may be.

As you said, have a look on the web, you might learn something...

im sorry i didnt relaise you were an expert on these matters , next time i will think twice about posting a comment or suggestion , you are correct in everything you say.
As you are such an expert and you know all the data for calculations whats my sweet spot then?

 

[bonehead2]

I'm not an expert, but I do know that many people believe 56mph to be a magic number for economy.

Your sweetspot is probably just after dinner, with a couple of glasses of wine in you, when you're nice and relaxed. As for the car, it's probably somewhere you don't want it to be as you drive a Cupra (as do I). In fact, in mine, it makes a huge amount of difference if you drive at a gear speed where the turbo hasn't cut in. So, boring, but economical. Once the turbo's spooling, the fuel consumption goes up fast.

I don't actually get that excited about it, don't do that many miles and use my KTM RC8 for the daily commute, but I was just trying to dispel the 56mph myth.

 

[GainfulShrimp]

I'm not trying to start an argument here

You say that, but then the overall tone of your posts is very sarcastic and frankly they read precisely as if you *were* trying to start an argument.

Anyway, back on-topic...

but it is true, the 56mph figure used is purely a standard set by the EU govt as a benchmark for fuel consumption averages so the manufacturers can print figures

If that's true, it's in the manufacturer's interest to make the sweet spot for speed vs economy 56mph - or as close to that as possible - seeing as that's the speed that will be used to determine the official consumption figures.
Consumption figures aren't just for tree huggers and hypermilers - they affect things like BIK tax for company cars meaning that efficient cars are more tempting to company/fleet buyers. So in other words, the more efficient the manufacturers can make their cars for the testers - at 56 mph you say - the more cars they'll sell.

Do you really think that all cars somehow miraculously reach their sweet spot at this speed???

Nope, I think it's by design rather than any kind of miracle.

So, accounting for drag coefficient, gearing, weight, etc, isn't it amazing that they all come out most efficient at 56...... Think about it..

Weight will be a constant as far as speed vs economy is concerned - a heavy car will take more fuel to get up to speed, but once cruising the weight really isn't all that important.
Drag does vary with speed however and gets worse the faster you go, so that would tend towards a slow optimum speed.
The gearing of top gear is one of the factors used by the car designers/engineers tweak the speed which is most efficient - it's perfectly possible that they choose 56mpg as the goal if they're going to be tested against that.
Efficiency isn't the only goal - you won't sell many boring or difficult to drive cars however efficient they are - but it's important.

The generally accepted "most efficient point" is the lowest speed your car can cruise at smoothly in top gear, whatever that may be.

Agreed, but then "whatever that may be" is likely to have been a design goal rather than an accident.

As you said, have a look on the web, you might learn something...

Isn't that why everyone uses forums? Except trolls maybe...

 

[bonehead2]

Perhaps what I wrote sounded a bit trolley, but that's only cos you don't know me and it's quite hard to disagree with something without sounding that way.. Oh, then it was embellished by the fact I was then told I was wrong.

So, what you're saying adds up, that manufacturers would have a vested interest in trying to get good figures at a point that they're measured, but as we all know, that isn't the be all and end all for them (though there is a sway towards it as time moves on). Many people don't buy their cars purely on fuel consumption, which is why we have people driving Cupras and not just ecomotives. Buying's a complicated process of which the car's economy is one component. The performance car manufacturers are only trying to bring their figures down to satisfy directives to have an average economy figure across the board for their entire range, not because they think it'll help them sell more cars. It was one (of many) reasons Porsche tried to buy VW.

Anyway, as it happens, most cars can reach their top gears and cruise comfortably in them at 50+mph so the figures probably are most efficient around this speed, but - and the important part of this repsonse is - all cars are not most efficient at 56mph.. Some may try and engineer something to match this figure, but it's an arbitrary number that simply matches 90kmh.