Fuel economy economical with the truth? March 27, 2009
Posted by richard in : Uncategorized , trackbackFuel economy is all nowadays. Not since the 1980s have manufacturers been so intent on producing efficient cars.
It’s all in the name of being green, you see. That’s why we’re seeing the return of the ‘eco special’.
Back in the day, car makers achieved good returns with long gear ratios, economy meters and stripped-out, lightweight equipment levels. Volkswagen Polo Formel E, anyone? Austin Metro 3+E?
25 years later, things are, of course, much more advanced. We have, err, long gear ratios, trip computers and, well, stripped down equipment levels. Audi TDIe, Ford Econetic, etc and so forth. OK… not much progress there, then. But, if something ‘aint broke and all that…
Why this post, then? Because Ford’s revealed some of the secrets behind the eco game in Automotive Engineer this month. See, nowadays there’s far more to it than simply keeping the revs low.
The fuel test cycle may be oft-criticised, but it still takes in a whole host of parameters. Which can be, for want of a better word, massaged.
Here’s 5 revealing ways the new Fiesta Econetic beats the system.
• Every kg saved benefits real-world economy – but only HUGE mass reductions affect the test cycle figures. That’s because ‘inertial weight classes’ are used, each covering around 100kg. This is basically a rolling road with a resistance against it. But… it’s only by shaving enough to move into a new band that you will improve economy.
• Fitting longer gear ratios is expensive. Volkswagen does this in Bluemotions – 1st and 2nd are standard, 3rd to 5th stretched. Far cheaper, says Ford, to simply fit a longer final drive ratio. It cuts 5g/km from CO2 emissions. But depends on having a torquey enough engine to still pull well in 1st and 2nd…
• It’s not hard to make a more aerodynamic car – but it IS costly to produce and fit the bespoke panels required. Ford reduced CO2 emissions by 2g/km, by easy measures. The maker didn’t want any more bespoke ‘workstations’ on the production line, to fit extra aerodynamic addenda.
• An easy fit, you’d think, would be aerodynamic wheel trims. Yes, says Ford – but the redevelopment work in ensuring the brakes behind them get enough cooling air is another matter. That’s why they’re not here.
• The biggest trick to improving test cycle economy is recalibrating the engine ECU. Measures here include reducing the idle speed, as it takes up a big part of the official test cycle. In the future, Ford also expects eco credits for fitting a standard trip computer.
All of this helps improve the official figures. However, only some of it will affect real world economy. Just goes to show, when judging economy cars, that it’s best to look beyond the figures, and what measures are actually employed to achieve them.
Are they test cycle cheats, or real-world benefits?
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