The Clio III is an important car for Renault. The European small-car segment has been consistently expanding in recent years, rising from 30.8% of the European market in 1998 to 34.5% in 2004. With close to 5 million vehicles sold in 2004, the A and B segments account for more than one-third of European vehicle sales.

The B segment, in which Renault competes with the Clio and the Modus, has grown from 21% of the total market in 1998 to 27.9% in 2004. The diesel mix in the segment has also increased rapidly, climbing to 44.1% in 2004, compared to 19.8% in 1998. Almost half of all Clios sold in Western Europe are now delivered with a diesel engine.

Clio III goes on sale in September with a choice of gasoline and Euro-4-compliant diesel engines. The gasoline engine range comprises 1.2-liter, 1.4-liter, and 1.6-liter 16V units, while the 1.5-liter dCi diesel comes in three power outputs.

It is the mid-powered diesel that offers the best fuel economy.

Digging in a little deeper to the different diesel configurations can provide some insight into approaches for increasing performance and efficiency and reducing emissions.

The different configuration of the 1.5-liter diesel in the Clio offers 70 hp, 85 hp and 240hp, with maximum torque of 160 Nm, 200 Nm and 240 Nm respectively.

The three configurations are based on the same basic engine unit. All three feature a flexible flywheel with a view to filtering out the effects of acyclic movements and use a second-generation fuel injection system.

But to meet Euro 4 emission requirements, the 70-hp version is equipped with a turbo air cooler, while the 85-hp unit features a 1,600 bar injection system. For the 105-hp version, Renault engineers introduced a lower compression ratio (16:1) and a variable geometry, multi-blade turbocharger.

And speaking of comparisons, it’s also interesting to look at the new Dacia Logan.

In 1999, Renault took a majority (51%) interesting in Dacia, the Romanian carmaker. By 2004, Renault had increased that ownership to 99.3%. In the five plus years of ownership, Renault has pumped almost half a billion euros (US$604.3 million) into modernizing the group.

With its low labor costs (less expensive that robots), Dacia was to be the provider of inexpensive cars for “emerging” markets. In 2004, it introduced the Logan.

The low-cost Logan (€5,000, US$6,000) was originally to sell only in Eastern Europe and Russia. Demand proved so strong, however, that Renault this month began selling the car in France, Germany and Spain.

The Western European version carries some additional amenities and a higher price-tag (€7,500, US$9,000). Renault expects to sell 175,000 Logans this year, increasing to 1 million by 2010, supplemented by the rollout of station wagon and pickup versions.

The Logan is also built on the same Nissan-Renault B-segment platform as the Clio (and the Nissan Micra). Its gasoline engine choices are not as advanced as those of the Clio, however, and despite being a lighter car, it consumes more fuel than its cousin. (A diesel version of the Logan is underway.) The table to the right contrasts the entry level configuration of both Logan and Clio.

So, in short, the entry-level gasoline Clio, which weighs 12% more than the entry-level gasoline Logan, uses an engine that is 17% smaller, delivers equivalent power and performance, consumes 13% less fuel and emits 15% less CO₂.

That encapsulates how enhancements to engine design can allow the downsizing of engines, resulting in better fuel consumption with equivalent performance.

Given the sales expectations for the Logan, however, it also raises a bit of a warning flag. If European automakers are going to meet the 120 g/km CO₂ target, pushing out hundred of thousands to millions of inexpensive vehicles with emissions currently 35% above the target isn’t going to help.

Renault needs to do better on the efficiency and emissions attributes of the Logan engines.