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Z4 Roadster & Coupe Gain Efficient Dynamics

If you read this column often, you'll have noticed that the bulk of BMW's

BMW's Z4 gains a new transaxle which is responsible for shaving 1-2-percent off its fuel economy. (Photo: BMW)

product lineup has gone through changes to make the vehicles more efficient and use less fuel. The 1, 3, 5, 6 and X5 have all been modified. Now, it's time for BMW to upgrade its roadster and two-seat coupe lineup, the Z4.

Where the previous “Efficient Dynamics” treatments have revolved around giving the cars features such as regenerative braking, hybrid-like idle-stop technologies and other measures, the Z4 is the simplest of the bunch. It doesn't get any of these goodies, but rather a brand new rear transaxle that's been friction optimized in order to reduce its drag on the vehicle. The general aim of Efficient Dynamics is to make the changes as unnoticeable to the driver as possible, and to ensure that there isn't any compromise on the driving experience.

Because the M Coupe and M Roadster have the need for

Changes were made to all four- and six-cylinder Z4s, except the M Coupe and M Roadster. (Photo: BMW)

high-performance, and high-end components (plus, they're low volume vehicles by comparison), they won't be getting the new transaxle. That's alright as the M-badged cars differ from the standard Z4 in all sorts of additional ways, including the use of a hydraulic steering system instead of the electrical power unit that the normal Z4s feature.

The top of the line Z4 3.0si with its 3.0-liter straight six engine and 255 horsepower will see a decrease in CO2 from 11.8 to 11.6 oz/mi, while fuel economy increases slightly from 27.4 mpg to 27.7 mpg; the two-door Coupe version of the car with the same engine drops from 12.1 to 11.8 oz/mi of carbon dioxide, while the fuel economy rating goes from 26.4 mpg to 27.0 mpg (the biggest improvement of the two). Finally,

Little changes help to reduce CO2, keeping that blue sky blue. (Photo: BMW)

the entry-level six cylinder engine, the 2.5si (not sold in North America), sees improvements to the tune of 28.0 mpg to 28.3 mpg, while its CO2 count drops from 11.5 oz/mi to 11.3 oz/mi.

Though they aren't sold in North America, Z4s with four-cylinder engines will also feature some modifications to their engine in order to make up the difference with their fuel economy and CO2 output. The Z4 2.0i sees a drop in CO2 from 10.3 to 10.0 oz/mi, while the fuel economy increases from 31.4 mpg to 31.8 mpg.

Compared to the other vehicles to receive Efficient Dynamics, the feature found on the new Z4 isn't as grand, but it does make a (small) difference. The new transaxle will enter production on September 1st of this year. No matter the improvement, in this day and age when the environmental watchdogs are on the lookout, every ounce of CO2 and every pint of gasoline counts.

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