Energy Efficient Motorsport

Engine and Powertrain Development 

The development of the internal combustion engine over the last 150 years led to the motorcar becoming widely available and therefore a well used form of transport. It is, however, a piece of technology that can be extremely damaging to the environment. From the energy and raw materials used in its production, to the oil and petrol consumed by the engine during its lifetime; its use is damaging. Development of Internal Combustion engine technology is one method of reducing the impact of Internal Combustion engines; another method is the introduction of new technologies such as electric motors and hydrogen fuel cells. 

Lean Burn refers to the use of ‘lean’ mixtures in an internal combustion engine. The mixture has considerably less fuel in comparison to the Stochiometric combustion ratio, generally as high as 65:1 (Air: Fuel ratio) as opposed to 14.7:1 for petrol.

Lean burn mode is used to, ‘reduce CO emissions efficiently use of more fuel-efficient engines, such as lean-burn engines, which potentially offer greater fuel efficiency, may gain importance. Operating an engine with lean-of-stoichiometric requires burning of fuel in an excess of oxygen and this can provide fuel consumption improvements of at least 10%, in addition to substantial reductions in CO and NOx emissions. Since a lean-burn engine operates close to the limits of combustion, its efficient functioning demands good mixture preparation, a very high energy spark to ignite the weak mixture and very good monitoring of combustion quality and mixture strength through a closed-loop control system.’  Many of these concepts are incorporated into recent Japanese designed engines, namely Honda’s VTEC-E and Toyota’s Carina-E. These engines can typically run at A/F ratios of 22:1, meet European and US emission regulations and offer fuel consumption improvements of up to 25% under cruising conditions (what-when-how.com).

The three-way catalyst is used in rich-burn or stoichiometric engines for simultaneous conversion of oxides of nitrogen (NO_x), carbon monoxide (CO), hydrocarbons (HC), formaldehyde (CH₂O) and EPA classified Hazardous Air Pollutants (HAPs). The three-way catalyst is effective in a wide variety of engine applications and fuels, including natural gas, propane and gasoline. A closed loop air-fuel ratio controller is required for the three-way catalyst to work effectively (dcl-inc.com).

image from aa1car.com 

 It can be seen that the exhaust gases coming in and out of the catalyst have Oxygen present. This creates a problem for our engine management system and is one of the shortcomings of the three-way catalyst.
It is convenient that the narrowband lambda sensor has the effect of the ECU cycling the richness of the mixture back and forth around stoichiometry - this means the exhaust gas stream will cycle between an excess of Oxygen then a deficit of Oxygen.
Although this is far from ideal, it simplified the control systems of early catalysts and makes sure that each part of the cat has favourable conditions at least part of the time, but even then only when the system is operating in closed-loop mode.
Later (OBD-II) catalysts have the element Cerium added to the reduction part of the cat - this is an element capable of 'storing' Oxygen and releasing it later - which enables us to combat the problem of when the car is running in open-loop mode. The stored Oxygen will automatically be released under open-loop conditions which keeps both halves of the cat working, even during acceleration or other open loop modes (lambdapower.co.uk).

image from gdabob.com 

HCCI—Homogeneous Charge Compression Ignition 

HCCI—Homogeneous Charge Compression Ignition—relies upon a very lean (high proportion of air to fuel) and well-mixed (Homogeneous) air-fuel mixture (Charge) that is compressed (Compression) until it autoignites (Ignition). (The HCCI approach is also called Controlled Auto-Ignition: CAI.)

The resulting spontaneous burn produces a flameless energy release in a large zone almost simultaneously—very different than the spark/gasoline burn or the compression/diesel burn.

HCCI combustion can deliver a very efficient engine, potentially providing a 20% to 30% boost in gasoline engine efficiency without the nasty NO_x or PM emissions of a diesel. Theoretically it can operate using a variety of fuels: gasoline, diesel, natural gas, biofuels, or hydrogen. Used in a hybrid application, the more efficient engine would increase the overall fuel efficiency of the powertrain (greencarcongress.com)

http://www.youtube.com/watch?v=rJ9ui0guXzA