Wholesale Auto Body Parts

HOME

AUTO PARTS

TRUCK PARTS

SEARCH

QUALITY PARTS

SHIPPING

ABOUT US

QUOTES

CONTACT US

TRACKING

SITES

Auto Body Parts Online - Offering Aftermarket/Replacement Car & Truck Body Parts at Wholesale Price
Pay Your Your Parts Here!CHECKOUT / VIEW CART HERE
Auto Articles
Auto Parts
Air Filters
Alternator
Battery
Brake
Bumpers
CamShaft
Carburetor
Clutch
Connecting Rod
Crank Shaft
Cylindrical Head
Differential
Distrubutor
Door
Drive Shaft
Electronics Fuel Injection
Exhaust Gas Reciculation
Exhaust Pipe
Fuel Pump
Fuse
Gearbox
Headlights
Oilpump
Piston Ring
Piston
Rank and Pinion
Radiator
Rocketarm
Seat
Self Starter
Spark Plug
Speedmeter
Universal Join
Water Pump
 
Car Parts
Air Filters
Alternator
Battery
Brake
Bumpers
CamShaft
Carburetor
Clutch
Connecting Rod
Crank Shaft
Cylindrical Head
Differential
Distrubutor
Door
Drive Shaft
Electronics Fuel Injection
Exhaust Gas Reciculation
Exhaust Pipe
Fuel Pump
Fuse
Gearbox
Headlights
Oilpump
Piston Ring
Piston
Rank and Pinion
Radiator
Rocketarm
Seat
Self Starter
Spark Plug
Speedmeter
Universal Join
Water Pump
 
Truck Parts
Air Filters
Alternator
Battery
Brake
Bumpers
CamShaft
Carburetor
Clutch
Connecting Rod
Crank Shaft
Cylindrical Head
Differential
Distrubutor
Door
Drive Shaft
Electronics Fuel Injection
Exhaust Gas Reciculation
Exhaust Pipe
Fuel Pump
Fuse
Gearbox
Headlights
Oilpump
Piston Ring
Piston
Rank and Pinion
Radiator
Rocketarm
Seat
Self Starter
Spark Plug
Speedmeter
Universal Join
Water Pump
 
Body Parts
 
Headlights
Acura
Alfaromeo
Audi
BMW
Cadillac
Chevy
Chrysler
Dodge
Eagle
Ford
Geo
GMC
Honda
Hyndai
Infiniti
Isuzu
Jaguar
Jeep
Kai
Landrover
Lexus
Lincoln
Mazda
Mercedes
Mercury
Merkur
Mitsubishi
Nissan
Oldmobile
Plymouth
Pontiac
Saab
Subaru
Suzuki
Toyota
Volkswagen
Volvo
 
Taillights
Acura
Audi
BMW
Buick
Cadillac
Chevy
Chrysler
Geo
GMC
Honda
Infiniti
Isuzu
Jeep
Kai
Landrover
Lexus
Mazda
Mercedes
Mercury
Mitsubishi
Nissan
Oldmobile
Plymouth
Pontiac
Porsche
Saab
Saturn
Subaru
Suzuki
Toyota
Volkswagen
Volvo
 
Bumpers
Acura
Audi
BMW
Buick
Cadillac
Chevy
Chrysler
Dodge
Eagle
Ford
Geo
GMC
Honda
Hyndai
Infiniti
Isuzu
Jeep
Kai
Lexus
Lincoln
Mazda
Mercedes
Mercury
Mitsubishi
Nissan
Oldmobile
Plymouth
Pontiac
Renault
Saturn
Subaru
Suzuki
Toyota
Volkswagen
Volvo

 

EGR in spark-ignited engines

In a typical automotive spark-ignited (SI) engine, 5% to 15% of the exhaust gas is direceted back to the intake as EGR. The higest quantity is limited by the requirement of the mixture to sustain a contiguous flame front during the combustion event; excessive EGR in an SI engine can affect misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing. The impact of EGR on engine efficiency mainly depends on the specific engine design, and sometimes leaads to a compromise between efficiency and NOx emissions. A functionaly operating EGR can theoretically increase the efficiency of gasoline engines through several mechanisms:

1) Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be open further, resulting in increase inlet manifold pressure and reduced throttling losses.

2) Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC, rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This causes the relatively smaller  compared to the first two.

3) Reduced specific heat ratio. A lean intake charge has a higher specific heat ratio than an EGR mixture. A reduction of specific heat ratio reduces the amount of energy that can be gained by the piston.

EGR is typically not employed at high loads because it would reduce high power output. This is because it reduces the intake charge density. EGR is also omitted at primary (low-speed, zero load) because it would affect unstable combustion, resulting in rough idle.

EGR in diesel engines

In modern diesel engines, the EGR gas is cooled through a heat exchanger to allow the introduction of a greater mass of recirculated gas. Unlike SI engines, diesels are not limited by the need for a contiguous flamefront; furthermore, since diesels always operate with excess air, they benefit from EGR rates as high as 50% (at idle, where there is otherwise a very large amount of excess air) in controlling NOx emissions.

Since diesel engines are unthrottled, EGR does not lower throttling losses in the way that it does for SI engines (look above).However, exhaust gas (largely carbon dioxide and water vapor) has a higher specific heat than air, and so it still serves to lower peak combustion temperatures; this aids the diesel engine's efficiency by reduced heat rejection and dissociation. There are trade offs however. Adding EGR to a diesel decrease the specific heat ratio of the combustion gases in the power stroke. This reduces the amount of power that can be extracted by the piston. EGR also tends to reduce the amount of fuel burned in the power stroke. Particulate matter (only carbon) that is not burned in the power stroke is wasted energy. Stricter regulations on particulate matter(PM) call for further emission controls to be introduced to compensate for the PM emissions introduced by EGR. The most basic is particulate filters in the exhaust system that result in reduced fuel efficiency. Since EGR increases the amount of PM that must be dealt with and reduces the exhaust gas temperatures and available oxygen,filters need to function properly to burn off soot, automakers had to consider injecting fuel and air directly into the exhaust system to keep these filters from plugging up.

EGR implementations

Different circulation is usually achieved by piping a route from the exhaust manifold to the inlet manifold, which is called external EGR. A control valve (EGR Valve) within the circuit regulates and perodic the gas flow. Some engine designs perform EGR by trapping exhaust gas within the cylinder by not fully expelling it during the exhaust stroke, which is called internal EGR. A form of internal EGR is used in the rotary "Atkinson cycle engine".

EGR can also be used by using a variable geometrical turbocharger (VGT) which uses variable inlet guide vanes to construct sufficient backpressure in the exhaust manifold. For EGR to flow, a pressure difference is required between  intake and exhaust manifold and this is created by the VGT.

Methods that have been experimented with are using a throttle in a turbocharged diesel engine to decrease the intake pressure to initiate EGR flow.

EGR systems were relatively unsophisticated, utilizing manifold vacuum as the only input to an start/end EGR valve; reduced performance and/or drivability were same side effects. Slightly later (mid 1970s to carbureted 1980s) systems included a coolant temperature sensor which diable the EGR system until the engine had achieved normal operating temperature. Many added systems like "EGR timers" to disable EGR for a few seconds after a full-throttle acceleration. Vacuum reservoirs and "vacuum amplifiers" were few used, adding to the maze of vacuum hoses under the hood. All vacuum-operated systems, especially the EGR due to vacuum lines necessarily in close proximity to the heat exhaust manifold, were highly prone to vacuum leaks caused by cracked hoses; a condition that plagued early 1970s EGR-equipped autos with bizarre reliability problems. Hoses in these automobile should be checked by passing an unlit blowtorch over them: when the engine speeds up, the vacuum leak has been found. Modern systems utilizing electronic engine control computers, multiple control inputs, and servo-driven EGR valves typically improve performance/efficiency with no impact on drivability.
 

Exhaust gas recirculation
 

Exhaust gas which is auto parts, recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in most gasoline and diesel engines.

EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. Intermixing the incoming air with recirculated exhaust gas dilutes the mix with inert gas, lowering the adiabatic flame temperature and (in diesel engines) reducing the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mix, lowering the peak combustion temperature. Because NOx formation progresses much faster at high temperatures, EGR serves to limit the generation of NOx. NOx is primarily formed when a mix of nitrogen and oxygen is subjected to high temperatures.

In the past, a fair number of car owners disconnected their EGR systems in an attempt for better performance and some still do. The belief is either EGR reduces power output, causes a build-up in the intake manifold, or believe that the environmental impact of EGR outweighs the NOx emission reductions. Disconnecting an EGR system is usually as simple as unplugging an electrically operated valve or inserting a ball bearing into the vacuum line in a vacuum-operated EGR valve. In almost all cases, a disabled EGR system will cause the car to fail an emissions test, and may affect the EGR flow in the cylinder head and intake manifold to become blocked with carbon deposits, necessitating extensive engine disassembly for cleaning.

 

 

© Copyright: All database of auto parts, car parts, truck parts and pictures belong to Auto Body Parts Online. Terms & Conditions
Technical questions? Contact the
Webmaster
Powered by Auto Body Parts Online