Stéphane Martinot

Stéphane Martinot

Faurecia's exhaust systems business is responsible for the management and development of complete exhaust systems and components covering both the hot end of the exhaust system such as particulate and exhaust fume treatments as well as the cold end. In this interview, Matthew Beecham talked with Stéphane Martinot, Director of Marketing of Faurecia Emissions Control Technologies.

The current trend on gasoline engine, at least in Europe, is the downsizing linked with introduction of turbochargers. For example, a 1.6-litre North America gasoline becomes a 1.2-litre turbo gasoline. In what ways has this trend affected the exhaust system?

Downsizing does not affect the exhaust system sizing since it is related to engine power, not engine size. This has been maintained and even increased by the car manufacturers. However, one key consequence of the downsizing is that boosting is gaining momentum combined with direct injection (GDI).  Particulates on gasoline engines have already been considered in the emissions regulations with a mass limit for both Europe and North America.

With the future emissions legislation Euro 6.2/Euro 6.c (2017), particulate number emissions (6x1011 /Km) will also apply to GDI engines like on diesel engines for 2014. As a result, Faurecia foresees the need of gasoline particulate filters for, at least, part of its customer base. It is yet too early to evaluate if such strict particulate limits considering also the particulate numbers [that] will be also deployed in North America beyond 2020.

Another important technology related to the downsizing trend is the use of twin-scroll turbo-chargers. This configuration corrects the "turbo-lag" issue by separating the exhaust system with two parallel helical (twin scroll) channels.  In this respect, fabricated exhaust manifold technologies offer a compelling alternative to cast: they are about 20 percent lighter and have an inherent lower thermal inertia that enables about 30 to 40 percent improvement in emissions. In a twin-scroll configuration, the manifold can be directly integrated with the turbine which yields an optimal combination of low speed response and high-end power.

Finally, smaller engines demand more stringent packaging requirements. In the future, we will see more and more compact exhaust lines with integrated functions.

The economic crisis has led to a change in customer behaviour and switching to smaller and smaller vehicles. In terms of exhaust and catalytic systems, does that pose technical challenges? 

The switch to smaller cars is not always accompanied by a reduction of the engine power output. The required performance of an exhaust line, especially from an acoustic point of view, is directly linked to the engine power output. The challenge is then to design a global exhaust line in a reduced volume. To this end, Faurecia has developed a portfolio of acoustic valves, from self-actuated to electronically-actuated, which drastically reduce mufflers volume.

On the other hand, the switch to smaller cars is generally accompanied by a move towards down-sized more efficient powertrains. The combination of both phenomena, while very efficient for fuel savings, leads to a strong reduction of energy losses in the exhaust line thus making more difficult the after-treatment light-off. This increases the importance of thermal management in the exhaust system. We have developed a large portfolio of products - dealing with low thermal inertia insulation - to help our customers achieve the best global solution in terms of powertrain.

Although a lot has been said about the prospects for PEVs, the IC engine will be around for the foreseeable future. How do you see the powertrain market over the next 5 - 10 years and what will this mean for the exhaust system?

In the near future, the variety of alternative powertrains will become larger, ranging from the fuel-efficient combustion engine to mild, full and plug-in hybrids, to electric vehicles with range extenders, to purely electric vehicles.

Powertrain electrification will provide new opportunities for growth: today about two million hybrid vehicles are produced and many analysts predict that by 2020 they could represent as much as 17 percent of the market.

Faurecia is developing solutions to address the specific performance needs of these sophisticated vehicles. For example, the overall vehicle efficiency in hybrid vehicles can be improved by recovering the exhaust wasted heat.

In standard vehicles, the engine heat losses are used to warm-up the cabin. In hybrid vehicles, the electric powertrain emits very little waste heat. As a result, during electric phases there is a thermal deficit that needs to be addressed. One option is to use the thermal engine; another is to use the energy available in the exhaust gases as an additional source of heat.

Faurecia has developed an Exhaust Heat Recovery System (EHRS) which uses a gas/water heat exchanger to supplement the heating up of the engine coolant. With this technology, the exhaust heat helps to warm up the vehicle interior in 25 percent less time than with conventional systems. When the powertrain temperature increases more rapidly after start-up, fuel consumption improves.

This function can also be integrated in the exhaust manifold; in this case we speak of EHRM or Exhaust Heat Recovery Manifold.

In the next years, heat recovery technologies will evolve to transform the exhaust waste heat into useful electric power. This electricity can be used in hybrid vehicles either to recharge the battery or to run the electrical accessories.

Faurecia is currently is focusing its development effort on Rankine systems and thermoelectric generators that would be integrated in the exhaust line. In a Rankine system, the exhaust heat is used to produce pressurized steam which feeds an expander using a principle similar to the "old time" steam engines. In a thermoelectric generator, the heat is transformed into electricity via the usage of thermoelectric materials.

In the longer term, we expect that the integration of emissions controls with energy recovery into a common "all-in-one" exhaust unit will occur. This will include improved thermal insulation to keep the catalyst warm during the electric phases.

Finally, managing the acoustic transition from electric drive to hybrid drive to ICE drive will require completely muffling the sound of the exhaust in order to avoid the driver and passengers from being startled when the ICE kicks-in.

In this respect, Faurecia has developed a compact exhaust system, called "Exhaust for Range Extender" which could fit solely in the engine compartment and muffle exhaust tail pipe noise as efficiently as currently done with conventional exhaust architecture, without protruding any further out of the rear bumper. This type of compact architecture saves routing the exhaust pipe underneath the vehicle, leaving a lot of valuable packaging space free for the integration of the batteries, so as to maximize the vehicle driving autonomy in hybrid mode.

Further to this innovation, Faurecia presented for the first time during last IAA Frankfurt motor show a new innovation called Exhaust Dynamic Sound Technologies. One of the key characteristics of this active technology is that it allows electronic cancelling of unwanted noise from the tail pipe. This product can be combined with any type of passive cold end system to mute the exhaust to almost silent; hence providing the end-user with the benefit of enjoying a quiet ride, no matter what type of drive is engaged.

For some time, we seen how carmakers have paid close attention to exhaust sound in order to maintain and enhance its "brand". How do you set about supporting the carmakers achieve the right note?

As part of its standard approach, Faurecia provides its customers with best-in-class support throughout the development of the acoustic portion of the exhaust (aka cold end system), in order to deliver the specific tail pipe noise required by the customer.

As an extension to this area of expertise, Faurecia now offers its customers our Exhaust Dynamic Sound Technologies to cancel unwanted noise or generate sound that creates a distinguishable powertrain signature, different from one vehicle to another.

Acoustic performance is crucial to the commercial success of any vehicle. Car buyers have expectations of how their vehicles should sound as they travel down the road or accelerate up a hill. A premium car should have a sound that reflects its power, while a smaller car may sound less muscular but still may aspire to sound sporty.

I guess because of the increasing cost and price volatility in the precious metal markets, this is forcing manufacturers to squeeze more performance out of smaller catalysts.

There is clearly a will to reduce precious metal loading in the catalysts despite more and more stringent regulations. For this purpose, we have seen wash-coats with improved formula arriving on the market. The exhaust line, and thus Faurecia, clearly has a major role to play by limiting heat losses between the exhaust valves and the catalyst. Products like fabricated manifolds and insulation shields help in limiting the amount of precious metal required.

For some time, we've seen increasingly stringent emission legislation introduced leading to the exhaust after-treatment system becoming more complex, particularly for diesel engines. What lies ahead for diesel after-treatment systems?

There are four main categories of regulated emissions:

  • Carbon Monoxide - CO
  • Hydrocarbons - HC
  • Nitrogen Oxides - NOx
  • Particulate Matter - PM

 Due to its lean burn concept, the diesel engine is not compatible with the three-way catalyst system commonly used on gasoline engines which is able, in a single brick, to treat simultaneously CO, HC and NOx. The typical current exhaust device for a diesel engine is composed of a diesel oxidation catalyst - for CO and HC after-treatment - and of a diesel particulate filter - for PM reduction. Up to now, no specific system was used to reduce NOx in the exhaust line because cost-efficient engine measures managed to reduced NOx raw emissions under regulated levels. With the introduction of the Euro6.1 and hereafter Euro 6.2 or Euro 6c, the most sophisticated engine measures will not be sufficient to avoid NOx after-treatment. This means that we'll see more and more vehicle equipped with Lean NOx trap or SCR System - two different technologies to reduce NOx in the exhaust line.

Let's talk a bit more about the SCR system, which, from an integration point of view, will have the highest impact on the underfloor design. We have presented at the IAA two generation of exhaust line for SCR. The first generation (for Euro 6.1) consists in the addition to the current diesel exhaust line, of an SCR substrate underfloor completed with the integration of an AdBlue injector upstream of the substrate. Faurecia has developed a mixing system to optimize the distribution of the reductant at the inlet of the SCR substrate.

And we've gone further, and you could also see it at the IAA, by developing an extremely compact mixer allowing perfect reductant mixing within a very short distance even for large canning diameter. This technology, combined with SCR coated DPF, leads to a very compact system - every brick being installed close-coupled - with optimum efficiency - compatible with Euro6.2/Euro6c - at reduced cost and mass compared to the first generation.

And for even more stringent regulations or drive cycles, Faurecia has developed the ASDS (Ammonia Storage and Delivery System) product. Here, the reductant for NOx conversion (Ammonia) is directly stored under its natural gaseous form within a salt structure. It means that, compared to competitive solutions, there is no need to vaporize any intermediate vector nor to board useless water on the vehicle. All you have to do is heat up the salt structure that rapidly delivers the ammonia to the exhaust line allowing very fast activation of the SCR system. It makes reductant injection possible from 140°C which is 40°C lower than competitive solution. This is a clear advantage of the technology under cold conditions or city driving.

In terms of developing increasingly complex exhaust systems, how do you manage the delivery of those systems yet keep lead time and costs under control?

The remainder of this interview is available on just-auto's QUBE research service