BMW 330ci fuel economy - how is it possible?

CampDad's spanking new Efficent Dynamics 320D has averaged 57mpg. Lots of motorway, some town, never nailed it too much but not a slow driving either (80mph on motorway)

It also revs well, produces about 127g of CO2/Km and is refined from about 5mph, though at idle it is still lumpy like all dervs.

It's 50BHP and 10mph up on his old X-type Jag. In short, it's pretty amazing. why anyone would buy a non-derv 3 series new is beyond me

You seen the MPG for the 320i/318i? given the price difference between petrol & diesel these is now nothing in it/in the petrols favour. However its a different driving style low end thumping torque vs hanging the the engine out to dry on high revs - very nice in a I6.

Yes they have.
Remember the main difference between the old 3ltr BMW petrol vs this one is direct injection & then you have the ED.

A few owners on BMWland etc are getting exceptional MPG out of these new 330i's also the same with the new 330d's 49.6mpg combined...
Talk about competitive advantage.... Merc/VAG/GM what are you doing, still trying to catch up with BMW's last gen units lol.

The dynamometer is loaded using figures obtained by coasting the vehicle down to a stand still in Neutral. I.e. The deceleration of the vehicle is measured, and this is used to create a function of load against speed that is applied to the vehicle on the dynamometer

It's hard to separate the effect of weight and of aerodynamics on the basis of deceleration alone. A less aerodynamic car will decelerate faster but then so will a lighter one with the same aero. There must be more to it than that?

ETA: I'm not questioning whether you're right. I just think it's a stupid way to do it.

I believe that it is the only way to get figures that actually mean anything, as if you tested the same car in a Swedish winter and again during a Sicilian summer the same car would produce vastly differing results.

Laboratory conditions that all manufacturers adhere to is the only way for these figures to have any meaning from a buyer point of view, so long as buyers are aware that these figures are generated in a lab, which appears not to be the case.

How else is a buyer supposed to compare two differnet manufacturers car for fuel consumption when during testing they were driven in different temperatures on different roads with differing cross winds,etc,etc.

That's because it's a turbo, you were off boost on the motorway. What BMW are doing is achieving the mpg with a normally aspirated engine, which is a whole different ballgame.

It is on a dyno -- aerodynamics doesn't come into it as the car is stationary!

I'm surprised they produce mpg figures in the absence of any aero drag. No wonder the extra urban figures are ridiculously high.

This is true, except the 320i and 318i are I4.

Easy! Pay huge amounts of money upfront for one hugely complex engine with almost every bought-in feature under the sun and then pay huge amounts in servicing and probably never get the potential fuel economy savings back.

These fuel economy & CO2 figures are gathered from the standardised New European Drive Cycle (NEDC) test and bear almost no relation to driving in the real world, and some manufacturers have the opportunity to work these figures better than others.

The test is very benign in terms of engine speeds and loads and therefore with a number of add-on engine & ancillary features it is possible to switch off things that are "not needed". You don't need steering on the test so switch the steering pump off, you don't need much oil flow so set the oil pump to the minimum, you don't need much coolant flow so switch the water pump off, no need to charge the battery...... and so on. Another thing that BMW have done is they've put centrally mounted Gasoline Direct Injection (£££££) de-NOx cats (£££££) and to control the NOx cat regeneration cycle they fit NOx sensors (££££££). The advantage of running centrally mounted direct injection is the ability to run the engine more consistently at lean Air-to-Fuel ratios (AFR), which is great for fuel economy however this produces lots of NOx but very little CO and unburnt hydrocarbons. This means that the pollutants cannot reduce and oxidise each other in a normal three-way cat, and so the NOx has to be captured in a NOx cat. However, as with most things in engineering there is no such thing as a free lunch, the NOx cat will need to be regenerated every so often and to do this the engine will run rich, which is bad for fuel economy, to reduce the captured NOx.

Now some of these systems have debatable benefits over the more realistic engine operation cycle (vane type variable flow oil pumps tend to have quite high friction at higher speeds). The de-NOx strategy is very debatable considering the regeneration cycle (nice tool for the calibrators to use for the NEDC though) and many other manufacturers are going for Stoichiometric AFR over as much as the speed/load range that only requires a conventional 3-way cat (much cheaper and less risky in terms of warranty but will not achieve the same in the NEDC).

BMW are not doing anything that other manufacturers haven't got the engineering capability to do (yes even lowly Weatherspoon's burger/Vernon Kaye/Weak-Tasteless-Lager Ford), however BMW have got the opportunity to pass the cost onto the customer and critically the economies of scale to put this stuff into their engines. Other OEMs have to do more with less, which is sometimes harder than just chucking money at a requirement and this can involve some rather clever engineering (sometimes more expensive upfront engineering but less product cost).

As for the power rating, that it is achieved through adapting the engine to run at higher speeds and higher torque at that speed (and all the compromises & detriments to other engine speeds and loads that go with it). In the case of the BMW 3.0 litre NA it has very expensive machined inlet ports, expensive & bulky tuned length exhaust manifold and because of the direct injection & the twin VVT then the engine can run a higher torque at that engine speed charge cooling from the evaporation of the fuel to run a higher compression ratio and the VVT allows maximum entrapment of air in the cylinder. Again something that other OEMs have the ability to do, but have other factors to consider.

I actually quite admire BMW for what they do because they consistently hit the spot with their market. Also because their engines are smooth, powerful and they sound great. And as for massaging the figures, they are only getting around some rather ill-thought out legislation. However please can we not we not have this bullst that surrounds BMW about their superior engineering, because it is never that simple!