Fuel Economy Figures and Actuals - Sale of Goods Act

londonTiger

I don't think they're cheating necessarily, the thing is there needs to be a a standard test environment so cars can be tested fairly. When testing the efficiency of the engine is it fair to also hook up the alternator which powers the electronics? Some cars will gavejust a radio others will hace heated seats rrefrigerator and what not, so in order to ping down the efficiency of the engine they'll unhook the alternator which is fair imo.

Also wind conditions and weather affects the car. Driving in cold weather produces poor furl efficiency. Likewise driving in a direction where there is constant wind blowing towards you will create lots of drag so will produce poor results so the car is probably tested with predefined ambient temp on dyno

The mpg claim should be a reference point for when comparing to other cars. Also for actual usable mpg knock off 15%

OddballJamie

londonTiger wrote: »

I don't think they're cheating necessarily, the thing is there needs to be a a standard test environment so cars can be tested fairly. When testing the efficiency of the engine is it fair to also hook up the alternator which powers the electronics? Some cars will gavejust a radio others will hace heated seats rrefrigerator and what not, so in order to ping down the efficiency of the engine they'll unhook the alternator which is fair imo.

Also wind conditions and weather affects the car. Driving in cold weather produces poor furl efficiency. Likewise driving in a direction where there is constant wind blowing towards you will create lots of drag so will produce poor results so the car is probably tested with predefined ambient temp on dyno

The mpg claim should be a reference point for when comparing to other cars. Also for actual usable mpg knock off 15%

Surely they would just switch the radio or heated seats off when testing rather than unhooking the alternator. Due to in the real world, you don't need a radio or heated seats but a functioning alternator comes in damn handy.

londonTiger

OddballJamie wrote: »

Surely they would just switch the radio or heated seats off when testing rather than unhooking the alternator. Due to in the real world, you don't need a radio or heated seats but a functioning alternator comes in damn handy.

It's not as straight forward as that. Some cars like SUVs have far bigger alternators which have bigger resistance. Small cars have smaller ones obviously.

So it doesn't provide a like for like comparison.

Also different ranges in a car will have different mod cons, which will dictate the size of the alternator used. So you can imagine if alternators were required to be included when testing that some car makers will play fast and loose and put in their smallest alternator when testing. So the fairest thing to do is just remove it altogether.

It's the best way to create a level playing field because weather, windspeed, draw from alternator etc are far too volatile and can have a significant difference to the fuel consumptions tests.

Ultrasonic

londonTiger wrote: »

It's not as straight forward as that. Some cars like SUVs have far bigger alternators which have bigger resistance. Small cars have smaller ones obviously.

So it doesn't provide a like for like comparison.

Yes it does. It is a like for like comparison of the cars (which is what consumers want), as opposed to engines (which is irrelevant to consumers).

As OddballJamie said, tests with electonics switched off are sensible since drivers can do this if they choose, and this is the data I would want. Tests with the alternator disconnected have zero real-world relevance.