autoevolution
 

How Renault Increased 1.5L Diesel Engines' Efficiency

Although not too popular in the US of A, diesel engines still represent the people’s choice in Europe when coming to fuel consumption. And Renault just announced to improve its smallest Satan’s-fuel burner unit, which is also very popular among Dacia buyers - the 1.5-liter dCi four-pot.
Renault 1.5 dCi 1 photo
Photo: Renault
Trying to keep up with fuel consumption and emission regulations, the French automaker is now introducing a new steel piston type for its mass-production 1.5-liter diesel unit, also used by Nissan in many of its small cars.

You might think this sounds a bit awful, as you though aluminum pistons are much better due to their small weight. Well, you are partially right, but steel pistons come with their own advantages.

First of all, they are much more solid than aluminum ones, thus better resisting to wear and tear. Another advantage is that they tent to expand and contract at about the same rate as the cast-iron engine block. Which means that the combustion chambers will be tightly sealed almost every time.

Drawbacks? Yeah, they have some, like higher mass, low thermal conductivity and their predisposition to oxidation, but Renault said they dealt with these aspects.

Due to the higher strength of steel, the automaker reduced the piston’s wall thickness and land height by 58 percent as well as compression height by 22%, compensating for the part's higher density. As a result, the piston-pin assembly’s mass is equal or even lower that those of the aluminum counterpart.

The heating problem has been dealt with by adopting a more efficient piston gallery for oil to flow better around and cool the part. Renault says that the steel pistons’ temperature now matches that of the aluminum one.

Piston oxidation has been solved by coating the surfaces with special anti-oxidation compounds, while a DLC (Diamond Like Carbon) pin coating along with a molybdenum one on the piston skirt help reduce friction.

Despite all these changes, power at 4,000 rpm has increased by 2 percent. Torque and BSFC (Brake Specific Fuel Consumption) have been also improved by 1.7 percent.

While the overall result is not that impressive, we consider it a step forward and Renault said they will continue to upgrade the new steel technology for future diesel engines to provide people a cheap choice in opposition to hybrids.
If you liked the article, please follow us:  Google News icon Google News Youtube Instagram X (Twitter)
 

Would you like AUTOEVOLUTION to send you notifications?

You will only receive our top stories