1 Quiz 3 study sheet AUT 340 All questions are essay 25 worth 4 points each, the topics covered are 1. checking a PCV valve 2. emissions in the converter 3. New cylinder head technology 4. Cold start emissions 5. Diesel after-treatment 6. Emissions in genera 7. OBD 2 Monitors 8. Fuel injection, in particular Direct fuel injeIf you want to learn more check out the 99-center is a retail store where all the merchandise is priced at 99 cents. this retailer uses a _____.
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ction 9. Tier 2 and 3 emissions 10.Gasoline 11.Timing and ignition Study Guide2 1. checking a PCV valve: PCV SYSTEM PERFORMANCE CHECK A properly operating positive crankcase ventilation system should be able to draw vapors from the crankcase and into the intake manifold. If the pipes, hoses, and PCV valve itself are not restricted, vacuum is applied to the crankcase. A slight vacuum is created in the crankcase (usually less than 1 in. Hg if measured at the dipstick) and is also applied to other areas of the engine. Oil drain back holes provide a path for oil to drain back into the oil pan. These holes also allow crankcase vacuum to be applied under the rocker covers and in the valley area of most V-type engines. Several methods can be used to test a PCV system. RATTLE TEST The rattle test is performed by simply removing the PCV valve and giving it a shake: If the PCV valve does not rattle, it is definitely defective and must be replaced. If the PCV valve does rattle, it does not necessarily mean that the PCV valve is good. All PCV valves contain springs that can become weaker with age and with heating and cooling cycles. Replace any PCV valve with the exact replacement according to the vehicle manufacturer’s recommended intervals. THE 3 5 CARD TEST Remove the oil-fill cap (where oil is added to the engine) and start the engine. NOTE: Use care on some overhead camshaft engines. With the engine running, oil may be sprayed from the open oil-fill opening. Hold a 3 5 card over the opening (a dollar bill or any other piece of paper can be used for this test): If the PCV system, including the valve and hoses, is functioning correctly, the card should be held down on the oil-fill opening by the slight vacuum inside the crankcase. If the card will not stay, carefully inspect the PCV valve, hose(s), and manifold vacuum port for carbon buildup (restriction). Clean or replace as necessary. NOTE: On some 4-cylinder engines, the 3 5 card may vibrate on the oil-fill opening when the engine is running at idle speed. This is normal because of the time intervals between intake strokes on a 4-cylinder engine. SnapBack Test The proper operation of the PCV valve can be checked by placing a finger over the inlet hole in the valve when the engine is running and removing the finger rapidly. Repeat several times. The valve should “snap back.” If the valve does not snap back, replace the valve. 3 PowerPoint is about PCV PCV values should not be cleaned A rattle test is insufficient. 2 acceptable test methods: 1. Test pressure with manometer 2. On MAF vehicles calculate airflow% Testing A. Manometer: reads in Small units inches of water. B. Restrict breather side, verify quick increase in vacuum @dipstick. Emissions in the converter A catalytic converter is a aftertreatment device used to reduce exhaust emissions outside of the engine. The catalytic converter uses a catalyst: A catalyst is a chemical that helps start a chemical reaction but does not enter into the chemical reaction. The catalyst materials on the surface of the material inside the converter help create a chemical reaction. The chemical reaction changes harmful exhaust emissions into nonharmful exhaust emissions. The converter therefore converts harmful exhaust gases into water vapor (H 2 O) and carbon dioxide (CO 2). This device is installed in the exhaust system between the exhaust manifold and the muffler and usually is positioned beneath the passenger compartment. The location of the converter is important since as much of the exhaust heat as possible must be retained for effective operation. The nearer it is to the engine, the better. Powerpoint Emissions in the converter The converter must be at least 500°F to operate and normally runs 9001600°F. This presents a challenge because cold start produces the highest emissions (most challenging BAG).4 4Cold start emissions What is a way that manufacturers have used to combat cold start emissions? Other methods to improve cold start performance: 1. Install an electric heater in the CAT 2. Use secondary AIR injection 3. Retard ignition timing (1st 60-90 seconds) \ Diesel aftertreatment ∙ Nox and soot reduction 99% since 1988 with after treatment ∙ DOC Diesl Oxidation Catalyst Oxidizes (burns) HC and CO into H20 and CO2 DOC also generates the exhaust heat needed by the SCR stage Exhaust gas temperature (EGT) sensors are located upstream (EGT 1) and downstream (EGT 2) of the DOC Lightoff is confirmed by a DOC output temperature greater than its input temperature. ∙ SCR Selective catalyst reduction While diesel engines are more fuel efficient and produce less HC and CO than gasoline engines, as a rule they generate much higher levels of NOx In order to meet today’s tighter NOx limits, an SCR catalyst, along with DEF, is used to convert NOx into N2, CO2, and H2O. ∙ NOx Sensors uses two smart NOx sensors to control exhaust NOx levels The first NOx sensor is located in the turbocharger outlet and monitors the engine out NOx. 5 The second NOx sensor is located in the exhaust pipe downstream of the SCR and monitors NOx levels exiting the system. ∙ DEF Diesel Exhaust Fluid Oxidizes (burns) HC and CO into H20 and CO2 DOC also generates the exhaust heat needed by the SCR stage Exhaust gas temperature (EGT) sensors are located upstream (EGT 1) and downstream (EGT 2) of the DOC Lightoff is confirmed by a DOC output temperature greater than its input temperature. ∙ DPF Diesel Particulate Filter The DPF captures diesel exhaust gas particulates, also known as soot, forcing particulateladen exhaust through a filter substrate consisting of thousands of porous cells Half of the cells are open at the filter inlet but are capped at the filter outlet. The other half of the cells are capped at the filter inlet and open at the filter outlet The DPF is capable of removing more than 90% of particulate matter, or soot carried in the exhaust gases. ∙ DPF Diesel Particulate Filter The DPF captures diesel exhaust gas particulates, also known as soot, forcing particulateladen exhaust through a filter substrate consisting of thousands of porous cells Half of the cells are open at the filter inlet but are capped at the filter outlet. The other half of the cells are capped at the filter inlet and open at the filter outlet The DPF is capable of removing more than 90% of particulate matter, or soot carried in the exhaust gases.6 ∙ DPF Pressure connections at the DPF inlet and outlet allow the differential pressure sensor (DPS) to measure the pressure drop across the filter This pressure drop increases as trapped soot collects in the cells of the DPF during vehicle operation The rate at which soot collects varies with the power demands placed on the engine. If left unchecked, the increasing backpressure will eventually result in a drivability problem. ∙ Regeneration Aftertreatment system increases exhust temperatures by injecting diesel fuel directly into the exhaust gases entering the DOC ECMcontrolled fuel injector, called the hydrocarbon injector (HCI), in the exhaust pipe upstream of the DOC High or low temperature indicated by the EGT sensors can cancel a regeneration ∙ DPF Once soot buildup reaches a specified back pressure the ECM commands a regeneration event to burnoff the collected soot during normal vehicle operation In general, the vehicle will need to be operating continuously at speeds above 48 km/h (30 mph) for approximately 20–30 minutes for a full and effective regeneration to complete ∙ Oil and Ash Ash is a noncombustible byproduct from normal oil consumption. Low Ash content engine oil (CJ4 API) is required for vehicles with the DPF system. Ash will eventually plug the DPF and require it to be replaced7 ∙ Service Regeneration Service regeneration is one of several output control functions available on the scan tool. When service regeneration is commanded, the ECM takes control of engine operation until the service regeneration is completed in about 35 minutes May have to be performed if soot load gets to high for safe regeneration Vehicle will go into limp mode if regeneration or DEF is missing Tier 2 and 3 emissions We had three different sets of fuel economy values on Tier 2 NHTSA’s CAFE values, EPA’s unadjusted dynamometer values EPA’s adjusted onroad values ∙ Penalty for not Meeting o $5.50 per tenth of a mile per gallon for each tenth under the target value o X o The total volume of those vehicles manufactured for a given model year. ∙ Really 54.5MPG by 2025 ? o CAFE standards stem from a smorgasbord of 1970sera fuel economy ratings with various exemptions and credits. o Experts say the 54.5 mpg standard will translate to the high 30s in EPA combined city/highway gas mileage Chance to correct? o Another thing is the promise of a midterm evaluation of the program in the 2018 time frame about whether the 2022–25 aspects of this plan remain technically feasible, costeffective, and saleable.8 Why are the numbers different in the future? o However, the government’s 2016 fueleconomy numbers of 37.8 mpg and 28.8 mpg are projections o future requirements will be instead based on the size of each vehicle in a manufacturer’s fleet. Footprint 2011 The relevant dimension is called the “footprint” and is defined as the product of a vehicle’s wheelbase and track, in square feet. The idea is to apply fuelefficiency standards to individual vehicles, thus encouraging all cars and trucks to be more fuel efficient. Gas Mileage o D Driving Style o Speeding o Rapid acceleration and braking o Idling o Vehicle weight Factors that Affect MPG o Driving Behavior : o Hard Acceleration & Braking = 5% in town 30% on highway o Idling o Speed (1% drop per 1mph over 55 to 65 o Weather o Trip length o Cargo o Towing = Weight o Accessories o Terrain o ALWD or 4WD9 Timing and ignition Spark timing o When the PCM turns off the transistor the magnetic lines of flux in the primary windings collapse (this creates an about 300 volt kick) o o The many more and thinner wires of the secondary circuit are a conductor in a moving magnetic field. High voltage is induced to fire the plug. (Gap is ionized) o The PCM decides when to start dwell and turn off the coil. Too much dwell and the coil overheats. Too little and it might not be saturated. o o With multiple coils/ or low RPM, the PCM has ample time to “decide” when to turn off the coil(s) at precise instant based on CKP pattern. o “FIRE” Fast Idle Retard Exhaust control only used for 1st minute or so by some OEM’s. o o Purpose: to heat up the CAT on cold start. o o The spark is retarded: mixture still burning as exhaust valve opens. o Timing needs to be retarded at cranking. o o Engine speed is very low, advance will cause uneven jerky crank as pistons try to push the crank backwards.10 Spark timing: summary o RPM: advance as speed increases up to about 3000 o ECT: advance as temperature is colder o IAT: advance if cooler than 50, retard if greater than 90 o BARO: advance if BARO is lower than 29” Hg o TPS: retard for WOT, retard for rapid opening o MAP or MAF: retard as load increases o Knock: Retard if knock is detected Spark timing: example o Base timing= 10° BTDC o TPS= 1.1 volt o BARO= 29.2” o MAF =10 g/s o MAP: 20” hg vac o RPM= 2200 o ECT= 150° F o IAT= 80°F o Advance= 35° o o Overall timing= 45° BTDC11 What is gasoline? o Gasoline is a blend of 500+ hydrocarbons with 3 to 12 carbon atoms each o It is a flammable liquid, less dense than water and a dielectric o No exact freezing point , some portions may start to solidify at 97°F o Heat energy is about 125,000 BTU’s per gallon o Gasoline is the fuel that is oxidized to create heat and pressure o The oxygen in the atmosphere is critical o Perfect combustion results in heat, water and carbon dioxide o Hydrocarbons come from crude oil, crude oil grades vary greatly o Hydrocarbons are compounds made up of hydrogen and carbon atoms in many different structures o Saturated hydrocarbons cannot take on any more hydrogen, unsaturated hydrocarbons can o Isomers are compounds made up of the same formula but are arranged differently. Example: Octane and ISOoctane o o Alkanes are single bond hydrocarbons o Alkenes are double bond hydrocarbons o Alkynes are triple bond hydrocarbons o Arenes (aromatics) are in a ring structure Hydrogen o Most abundant element in the universe o Lightweight, flammable gas o Diatomic: H2 o Not usually found by itself on Earth o 1 proton, 1 electron o 0 neutrons12 Carbon o Chemical basis of life o 4th most abundant element in the universe o solid, stable element o 4 electrons in outer valence: can form covalent bonds Hydrocarbons o Simplest is methane CH4 o Not in gasoline Hydrocarbons: o About 15% of gasoline are o N paraffin's o Pentane: 5 carbon atoms o Can be arranged or bonded straight or ISO (branched) or bonded single, double, triple or circular arrangement o Other types of N paraffin's: o Butane (good for RVP adjust) o Hexane o Heptane o Octane About 30% of gasoline are isoparaffins:13 o Remember these are still hydrocarbons but the molecular structure is different o (ISO= branched) o Examples: o 2methypentane o 2methylbutane o 3methylpentane o 2,2,3trimethylbutane o About 12% of gasoline is Cycloparaffins o Methylcyclopentane o Cyclohexane o Methylcyclohexane o Traditionally gasoline was up to 35% aromatics but this number is dropping. o EPA RFG rules call for less aromatics o Aromatics have a ring molecular structure o These are good for octane boosters o They are also heavier HC’s that can boost miles per gallon o Some aromatics are carcinogens (cancer causing) o Aromatic examples: benzene, toluene, xylene, 1,3,5 trimethylbenzene, metaxylene 14 o Up to 8% of gasoline are olefins which are double bonded HC’s o o Olefins are heavier HC’s with high octane ratings and promote good MPG o o Biggest downside is they have a tendency to leave deposits on places like intake valves Examples: 2pentene 2methylbutene2 Dicyclopentadiene Bad stuff: Sulfur: promotes corrosion, can harm the catalyst. Expensive to remove. Capped at 10PPM Solvent washed gums: cause deposits Phosphorous: catalyst poison Part of what makes “Reformulated gasoline” or RFG is specifications that cap the limit of these items and aromatics and the addition of oxygenates Oxygenates: add oxygen by mass to the gasoline to reduce CO pollution. Most oxygenates are alcohol/ethers and alcohols.15 What is gasoline?: additives o ETBE: Ethyl tertiarybutyl ether , C6H14O o It boosts octane and adds oxygen. It does this with a lower RVP than MTBE o It costs more than MTBE, but MTBE had the water contamination liability and has been banned in several states o TAME: tertiary amyl methyl ether, C2H5C(CH3)2OCH3 o Another alternative to MTBE, it also is good for reducing RVP and it’s production from refinery stocks can remove C5 olefins to reduce ozone production. o Other additives: o Antioxidants: usually hindered phenols/diamines o Metal Deactivators: disalicylidene1,2propanediamine o Corrosion Inhibitors: oil soluble surfactants o Antiicing Additives: alcohols, glycols, surfactants o Antiwear additives: light oils, for engine protection 8. Fuel injection, in particular Direct fuel injection Fuel Injectors o Solenoids used to control fuel delivery into the engine16 o May use a pintle or ball and seat valve to control fuel flow o Typically ground side controlled by the PCM Direct Fuel Injectors o Besides the need for optimal atomization. o Why does the fuel pressure need to be so high? o Why do the seals have to be replaced when the injector is removed o Fuel is delivered directly into the combustion chamber o Uses a mechanical high pressure fuel pump o Delivers pressures up to 2200 PSI o Allows better fuel vaporization o Direct Fuel Injectors o There are two different modes of operation for DFI Homogenous Charge Fuel Injection and Homogenous Stratified charge o Injection occurs during the intake stroke o Used when fuel demands are high o Acceleration, heavy load, high engine speed