Year Federal California HCs CO NOx Evap HCs CO NOx Evap g/mi g/mi g/mi g/test g/mi g/mi g/mi g/test Before regs 10.6 84.0 4.1 47 10.6 84.0 4.1 47 add crankcase +4.1 +4.1 1966 6.3 51.0 6.0 1968 6.3 51.0 6.0 1970 4.1 34.0 4.1 34.0 6 1971 4.1 34.0 6(CC) 4.1 34.0 4.0 6 1972 3.0 28.0 2 2.9 34.0 3.0 2 1973 3.0 28.0 3.0 2.9 34.0 3.0 2 1974 3.0 28.0 3.0 2.9 34.0 2.0 2 1975 1.5 15.0 3.1 2 0.90 9.0 2.0 2 1977 1.5 15.0 2.0 2 0.41 9.0 1.5 2 1980 0.41 7.0 2.0 6(SHED) 0.41 9.0 1.0 2 1981 0.41 3.4 1.0 2 0.39 7.0 0.7 2 1993 0.41 3.4 1.0 2 0.25 3.4 0.4 2 1994 50,000 0.26 3.4 0.3 2 TLEV 0.13 3.4 0.4 2 1994 100,000 0.31 4.2 0.6 2 1997 LEV 0.08 3.4 0.2 1997 ULEV 0.04 1.7 0.2 1998 ZEV 0.0 0.0 0.0 0 2004 0.125 1.8 0.16 2<>It's also worth noting that exhaust catalysts also emit platinum, and the soluble platinum salts are some of the most potent sensitizers known. Early research  reported the presence of 10% water-soluble platinum in the emissions, however later work on monolithic catalysts has determined the quantities of water soluble platinum emissions are negligible . The particle size of the emissions has also been determined, and the emissions have been correlated with increasing vehicle speed. Increasing speed also increases the exhaust gas temperature and velocity, indicating the emissions are probably a consequence of physical attrition.
Estimated Fuel Median Aerodynamic Speed Consumption Emissions Particle Diameter km/h l/100km ng/m-3 um 60 7 3.3 5.1 100 8 11.9 4.2 140 10 39.0 5.6 US Cycle-75 6.4 8.5<>Using the estimated fuel consumption, and about 10m3 of exhaust gas per litre of gasoline, the emissions are 2-40 ng/km. These are 2-3 orders of magnitude lower than earlier reported work on pelletised catalysts. These emissions may be controlled directly in the future. They are currently indirectly controlled by the cost of platinum, and the new requirement for the catalyst to have an operational life of at least 100,000 miles.
The preferred technique for describing mixture strength is the fuel-air equivalence ratio ( phi ), which is the actual fuel-air mass ratio divided by the stoichiometric fuel-air mass ratio, however most enthusiasts use air-fuel ratio and lambda. Lambda is the inverse of the fuel-air equivalence ratio. The oxygen sensor effectively measures lambda around the stoichiometric mixture point. Typical stoichiometric air-fuel ratios are :
6.4 methanol 9.0 ethanol 11.7 MTBE 12.1 ETBE, TAME 14.6 gasoline without oxygenates<>The engine management system rapidly switches the stoichiometry between slightly rich and slightly lean, except under wide open throttle conditions - when the system runs open loop. The response of the oxygen sensor to composition changes is about 3 ms, and closed loop switching is typically 1-3 times a second, going between 50mV ( lambda = 1.05 (Lean)) to 900mV (lambda = 0.99 ( Rich)). The catalyst oxidises about 80% of the H2, CO, and HCs, and reduces the NOx .
Typical reactions that occur in a modern 3-way catalyst are:
The requirement that the exhaust catalysts must now endure for 10 years or 100,000 miles will also encourage automakers to push for lower levels of elements that affect exhaust catalyst performance, such as sulfur and phosphorus, in both the gasoline and lubricant. Modern catalysts are unable to reduce the relatively high levels of NOx that are produced during lean operation down to approved levels, thus preventing the application of lean-burn engine technology. Recently Mazda has announced they have developed a "lean burn" catalyst, which may enable automakers to move the fuel combustion towards the lean side, and different gasoline properties may be required to optimise the combustion and reduce pollution . Mazda claim that fuel efficiency is improved by 5-8%, while meeting all emission regulations, and some Japanese manufacturers have evaluated lean-burn catalysts in limited numbers of 1995 production models.
Catalysts also inhibit the selection of gasoline octane-improving and cleanliness additives ( such as MMT and phosphorus-containing additives ) that may result in refractory compounds known to physically coat the catalyst, reducing available catalyst and thus increasing pollution.
Reduced gasoline volatility and composition changes, along with cleanliness additives and engine management systems, can help minimise cold start emissions, but currently the most effective technique appears to be rapid, deliberate heating of the catalyst, and the new generation of low thermal inertia "fast light-up" catalysts reduce the problem, but further research is necessary [76,82].
As the evaporative emissions are also starting to be reduced, the emphasis has shifted to the refuelling emissions. These will be mainly controlled on the vehicle, and larger canisters may be used to trap the vapours emitted during refuelling.
Compound in Water Water in Compound % mass/mass @ C % mass/mass @ C normal decane 0.0000052 25 0.0072 25 iso-octane 0.00024 25 0.0055 20 normal hexane 0.00125 25 0.0111 20 cyclohexane 0.0055 25 0.010 20 1-hexene 0.00697 25 0.0477 30 toluene 0.0515 25 0.0334 25 benzene 0.1791 25 0.0635 25 methanol complete 25 complete 25 ethanol complete 25 complete 25 MTBE 4.8 20 1.4 20 TAME - 0.6 20The concentrations and ratios of benzene, toluene, ethyl benzene, and xylenes ( BTEX ) in water are often used to monitor groundwater contamination from gasoline storage tanks or pipelines. The oxygenates and other new additives may increase the extent of water and soil pollution by acting as co-solvents for HCs.
Various government bodies ( EPA, OSHA, NIOSH ) are charged with ensuring people are not exposed to unacceptable chemical hazards, and maintain ongoing research into the toxicity of liquid gasoline contact, water and soil pollution, evaporative emissions, and tailpipe emissions . As toxicity is found, the quantities in gasoline of the specific chemical ( benzene ), or family of chemicals ( alkyl leads, aromatics, olefins ) are regulated.
The recent dramatic changes caused by the need to reduce alkyl leads, halogens, olefins, and aromatics has resulted in whole new families of compounds ( ethers, alcohols ) being introduced into fuels without prior detailed toxicity studies being completed. If adverse results appear, these compounds are also likely to be regulated to protect people and the environment.
Also, as the chemistry of emissions is unravelled, the chemical precursors to toxic tailpipe emissions ( such as higher aromatics that produce benzene emissions ) are also controlled, even if they are not themselves toxic.
Unfortunately, "renewable" ethanol is not cost competitive when crude oil is $18/bbl, so a federal subsidy ( $0.54/US Gallon ) and additional state subsidies ( 11 states - from $0.08(Michigan) to $0.66(Tenn.)/US Gal.) are provided. Ethanol, and ETBE derived from ethanol, are still likely to be used in states where subsidies make them competitive with other oxygenates.
Be prepared to try several different brands of oxygenated or reformulated gasolines to identify the most suitable brand for your vehicle, and be prepared to change again with the seasons. This is because the refiners can choose the oxygenate they use to meet the regulations, and may choose to set some fuel properties, such as volatility, differently to their competitors.
Most stories of corrosion etc, are derived from anhydrous methanol corrosion of light metals (aluminum, magnesium), however the addition of either 0.5% water to pure methanol, or corrosion inhibitors to methanol-gasoline blends will prevent this. If you observe corrosion, talk to your gasoline supplier. Oxygenated fuels may either swell or shrink some elastomers on older cars, depending on the aromatic and olefin content of the fuels. Cars later than 1990 should not experience compatibility problems, and cars later than 1994 should not experience driveability problems, but they will experience increased fuel consumption, depending on the state of tune and engine management system.
Maximum Incremental Reactivities as mg Ozone / mg VOC carbon monoxide 0.054 alkanes methane 0.0148 ethane 0.25 propane 0.48 n-butane 1.02 olefins ethylene 7.29 propylene 9.40 1,3 butadiene 10.89 aromatics benzene 0.42 toluene 2.73 meta-xylene 8.15 1,3,5-trimethyl benzene 10.12 oxygenates methanol 0.56 ethanol 1.34 MTBE 0.62 ETBE 1.98<>
The most famous of these remote sensing systems is the FEAT ( Fuel Efficiency Automobile Test ) team from the University of Denver . This team is probably the world leader in remote sensing of auto emissions to identify grossly polluting vehicles. The system measures CO/CO2 ratio, and the HC/CO2 ratio in the exhaust of vehicles passing through an infra-red light beam crossing the road 25cm above the surface. The system also includes a video system that records the licence plate, date, time, calculated exhaust CO, CO2, and HC. The system is effective for traffic lanes up to 18 metres wide, however rain, snow, and water spray can cause scattering of the beam. Reference signals monitor such effects and, if possible, compensate. The system has been comprehensively validated, including using vehicles with on-board emissions monitoring instruments.
They can monitor up to 1000 vehicles an hour and, as an example,they were invited to Provo, Utah to monitor vehicles, and gross polluters would be offered free repairs . They monitored over 10,000 vehicles and mailed 114 letters to owners of vehicles newer than 1965 that had demonstrated high CO levels. They received 52 responses and repairs started in Dec. 1991, and continued to Mar 1992.
The entire monitored fleet at Provo (Utah) during Winter 1991:1992 Model year Grams CO/gallon Number of (Median value) (mean value) Vehicles 92 40 80 247 91 55 1222 90 75 1467 89 80 1512 88 85 1651 87 90 1439 86 100 300 1563 85 120 1575 84 125 1206 83 145 719 82 170 639 81 230 612 80 220 500 551 79 350 667 78 420 584 77 430 430 76 770 317 75 760 950 163 Pre 75 920 1060 878<>As observed elsewhere, over half the CO was emitted by about 10% of the vehicles. If the 47 worst polluting vehicles were removed, that achieves more than removing the 2,500 lowest emitting vehicles from the total tested fleet.
Surveys of vehicle populations have demonstrated that emissions systems had been tampered with on over 40% of the gross polluters, and an additional 20% had defective emission control equipment . No matter what changes are made to gasoline, if owners "tune" their engines for power, then the majority of such "tuned" vehicle will become gross polluters. Professional repairs to gross polluters usually improves fuel consumption, resulting in a low cost to owners ( $32/pa/Ton CO year ). The removal of CO in the Provo example above was costed at $200/Ton CO, compared to Inspection and Maintenance programs ($780/Ton CO ), and oxygenates ( $1034-$1264/Ton CO in Colorado 1991-2 ), and UNOCALs vehicle scrapping programme ( $1025/Ton of all pollutants ).
Thus, identifying and repairing or removing gross polluters can be far more cost-effective than playing around with reformulated gasolines and oxygenates. A recent study has confirmed that gross polluters are not always older vehicles, and that vehicles have been scrapped that passed the 1993 new vehicle emission standards . The study also confirmed that if estimated costs and benefits of various emission reduction strategies were applied to the tested fleet, the identification and repair techniques are the most cost-effective means of reducing HC and CO. It should be noted that some strategies ( such as the use of oxygenates to replace aromatics and alkyl lead compounds ) have other environmental benefits.
Action Vehicles Estimated % reduction % reduction Affected Cost per $billion (millions) ($billion) HC CO HC CO Reformulated Fuels 20 1.5 17 11 11 7.3 Scrap pre-1980 vehicles 3.2 2.2 33 42 15 19 Scrap pre-1988 vehicles 14.6 17 44 67 2.6 3.9 Repair worst 20% of vehicles 4 0.88 50 61 57 69 Repair worst 40% of vehicles 8 1.76 68 83 39 47