Journal of Kones. Combustion Engines, Vol 8, No 1-2,2001
Jerzy Merkisz, Pawel
Fuc
Poznan University ofTechnology
Institute ofInternal Combustion Engines and Basics ofMachine Design
Piotrowo 3 Street, 60-965 Poznan phone: (0-1033-61) 665-21-18,fax: (0-1033-61) 665-22-04 e-mail: Jerzy.Merldsz@put.poznan.pl
Pawel.Fuc@put.poznan.pl
Summary.
Introduce electronic control exhaust gas recirculation EGR system in the passenger cars and light duty vehicles was made because of fuel direct injection engines. In this engines temperature combustion process is a higher then other type engine and in this connections NO, emissions were higher to. Simultaneously was appearing problems to electronic exhaust gas recirculation control in connection with introduce on-board diagnostic system. Mainly target of this system is control exhaust aftertreatment cars equipment. In principle the exhaust gas recirculation systems are not required in vehicle fulfilling OBD II regulations but it is effective system reducing NOx emission and is applied in more and more number of models. This paper has presented regulations, technical solution and control solution exhaust gas recirculation in modem cars equipped with
OBDsystem.
Key words: OBD system, gas recirculation, steering and control
To fulfil the established gas emission values limits, which have to be held for minimum
80000 km (the required time of correct work of the catalytic converter), it is necessary to provide the appropriate technological condition of engine (the elements conditioning toxic compound emission level) and its constant control. Monitoring work of the systems enables detecting inefficiency in its initial phase when the influence on the environment is a little. The above requirements are fulfilled by OBD diagnostic system. The first phase of
OBD system (defined as OBD I) falls on the 1980 (tab.
I).
It was mainly the diagnostic of
ZI engines: ignition and injection systems and it was connected with the introduction of the first electronic admission system. The diagnosis procedures were carried out by engine control module ECM. OBD II is the following development stage of on-board diagnostic systems, which was introduced with the directive 98/69/EC and 1999/I02/EC in the European Community countries in passenger cars with the spark ignition engines since
01.01.2000 (for new official certification) and since 01.01.2001 in all the newly registered vehicles. Since 29.03.2001 according to ECE R83.05 regulation the European EOBD system version has been in force in Poland. The criteria determining limits of each monitored element error were stated according vehicles category valid legal regulations (tab. 2).
271

Table 1. On-board diagnostic system development
OBDI OBDII OBDm
On-board diagnostic of inActive diagnosis of emission Vehicle emission control by jection-ignition system eleelements and power transmisOBD II system. Automatic ments. Damages signaling.
sion subassembly.
informing the appropriate services.
Gradual development of chassis and body assembly system. Exceeded emission level signaling.
1996 2002 1984
Lack of diagnostic proceWorldwide standardization of dure standardization and diagnostic procedures and damage code. Lack of legal guarantee of diagnostic information access.
information access. Legal guarantee information accesses.
Introduction new legal guarantees connected with automatic defecting and identifying vehicles.
OBD II system distinguishes from older diagnostic procedures with being orientated mainly on toxic exhaust component emissions. The fact makes starting research necessary on the accordance of type a standard. The research are based no carrying out test on toxicity on a test bench obligatory in Europe, purpose fully introducing or electronically simulating damage and wear the elements which are supervised by diagnostic and observed the diagnostic system reaction by the reception and interpretation of information from universal diagnostic connection (fig. 1).
Diagnoskop
................................................................ 0
...............................................................
0 0 0 o
0 0 0 o
0 0 0
Exhaust analyzers
Test bench steering
OBD II universal diagnostic connection
Fig.
1.
Vehicle elements supervised by OBD 11 system
272

Table 2.
Criteria determining inefficiency according to CARB Californian regulation concerning OBD II and in European Community concerning EOBD
California - CARD USA
Device Criteria determining inefficiency catalytic reactor misfiring
NONLEVs:
0 for models 1996 the HC emission higher than 1,5 emission of a new vehicle of as much as 4000 mileage
LEVs:
0 for models produced in 1998 the HC emission is higher than 1,75 of emission in test
FrP75 (introduction in 1998 for 20% all vehicles, and in the following years
40/60/80/100% respectively)
0
TLEV, LEV, ULEV:
HC emission exceeding twice for TLEV standards 2,5 times for LEV and 3 times for
ULEV regulations, vehicle emission of 4000 mileage
0
0 discussed introduction of emission of criterion for NO since 2004 emission exceeding 1,S emission during FfP7S for models 1997 (SOnSl9O/loo%) control with maximum engine speed sonde 0" EGR secondary air, ado emission exceeding I,S indicator according to FTP7S test mission system
EVAP data protection before deleting electronic diagnostic information from
OBD system in vehicles usinz
0
0
PCV
0 thermostat
0 the possibility of
(30160/1 00%) the others elements
0 continuous control
0 coolant temperature measurement.
For models since 2000 according to SAE J 1979 in 2000 r. for 30% vehicles fleet and in next years (60/100%)
0 with equivalent leakage forming the hole of diameter 0,04" (I mm) for models since 2000-2003 (20/40nO/I00%) leakage from hole 0,02" (O,S mm) integrated control svstem. For models since 2002 (30/60/1 00%) from 2002 r.
according to SAE J 2008
Euronean Community - EOBD
ZI engines: Ml ~ 2,5 t, Nl I - introduction date: 1.01.2000 r, (new official certification of type),
MI > 2,5 t, NI II, III- introduction date: 1.01.2001 r. (new official certification) catalytic reactor
(only He), misfiring, sonde O
2, other elements increase control emission in BeE R83 test glkm PC,LDTI LDTII LDT III
HC
NO,
0,4
0,6
0,5
0,7
0,6
0,8
CO 3,2 5,8 7,3 discussed introduction of emission control for NO. rEURO IV)
EVAP
electronic control
construction of sunnlvinz svstem should be preclude emission during refuel
ZS engines: . MI 2,5 t, to 6 seats, introduction date: 1.01 2003 r. (new official certification),
M I > 2,5 r, above 6 seats, N 1 1- introduction date: 1.01.200S r. (new official certification),
Nl II, III- introduction date: 1.01.2006
r.
(new official certification) increase control emission in ECE R83 test catalytic reactor,
PM filter, others elements
(air flow, EGR etc.) glkm
HC
NO.
co
PM
PC
0.4
1.2
3.2
0.18
LOTI
0,4
1.2
3.2
0.18
LOT II
0,5
1,6
4,0
0.23
LOT III
0.6
1.9
4.8
0.28
273

zi
EGR enabling emission NO x reduction is based on supplying part of exhaust gas back to intake manifold. The method is wildly applied in ZS engine of small power and in ZI engines, classical and with gasoline direct injection (GDI). As a results it causes increasing the quantity of CO
2 and steam in a fresh load. Exhaust gas flowing with the air as results of using recirculation play the role of thermodynamic ballast, which is the gas not taking part in combustion process. Exhaust gas recirculation reducing the quantity of oxygen contained in cylinder requires proportional reducing fuel close and the same contribute to torque end power engine reduction. Independently of the kind of constructional solution it is necessary to use the cooling supplied exhaust gas. With out that the recirculation leads to the considerableworsening cylinder load.
Rule of EGR in engines ZI and ZS is different (fig. 2). In engines ZI the rest of exhaust is deliver to cylinder as additional load, enlarging in this way intake pressure and density, and in consequence also mass first load. Because, most important influence exhaust gas recirculation on combustion process and NO x emission in engines ZI is ascribe influence of capacity thermal load for the sake of increase both his masses and specific heat [1].
In the ZS engines applying EGR causes replacing part of air with the exhaust gas reducing in this way the quantity of oxygen in the load and increasing its heat capacity. The recirculation is precisely connected with controlling timing angels and forming fresh air-fuel mixture.
The advantages of recirculation are effectively used to the rate of 25% of exhaust gas in a fresh load [8].
Load massM
ZI Engine
I
I
Residue exhaust mass rn,
Load massM
Pressure PI+Ap Pressure PI
ZSEngine
Residue exhaust massm,
Pressure PI
Residue exhaust mass m,
Load mass
Mvm,
Pressure
Pl+Ap
Without recirculation With recirculation Without recirculation With recirculation
Fig. 2. Differences in principle of operation ZI and ZS exhaust gas recirculation [2]
Introduction of exhaust gas recirculation enables to reduce the quantity of NO x formed in the engine however at the cost of increasing incomplete combustion emission product (fig. 3).
The amount of exhaust gas supplied to the intake air diminishes with the increase of engine load reaching zero with the full charge in the conditions of working with cold engine and idle speed. The quantity of exhaust gas must be precisely controlled because of the danger of the increase HC and CO emissions. In typical modem EGR systems the engine programmer receives signals from: crankshaft speed sensor, temperature sensor, atmospheric pressure
274

20
18 i--
16
14
..c:
~ 12
~10
~
8
~
6
6 4
U
2 o
~.
c-
- - c o
-·-·-HC
----NOx
/
/
...
.........
-
-'-'-'-:.::.'-
.-/
-..,.--
/
/
--' -
.-'
/
/
20 40
Recirculation rate [%]
60
Fig.
3.
Influence of recirculation rate on the emission of toxic components from engine [6J sensor, flow-meter air sensor, temperature intake air sensor, load engine sensor and accelerator position sensor.
On the base of the information the controlling signal is sent to electric valve, which enables connecting EGR valve with brakes pump vacuum pressure line. On the other side the electric valve is connected with the atmosphere with the filter. EGR valve is placed in a channel connecting exhaust manifold with intake manifold. Where there is no pressure the valve is closed. Its damage is mostly related to the lack of tightness and valves lifter guide seizing as a result of carbon deposit deposition especially in engines with large exhaust gas emission.
The easiest solutions of exhaust gas recirculation systems were still used in passenger cars before introducing three-way catalyst (fig. 4). They concerned mainly little capacity engine vehicles because they let fulfil emission standards of that time. The early exhaust gas recirculation cooperated then with carburetor engine supply system. Some manufactures of engines supply systems suggested special EGR systems provided for assembling in already used cars. The systems were effective because they made NO. content in exhaust gas lower by 30-
80%, however the working pressure inequality was likely to increase, which made engine torque irregular. Additionally the danger of
He increase arose [3]. Inappropriate system selections could results in driving features worsening or fuel use increase.
....
/
................
Thr ouhng valve
mi cCl'd I i
(0000)
'-=ttb
Temperature sensor
t
Exhaust manifold
Fig.
~
;r.==-:'_=c'\):;--,
- + - + - +
ECU
4.
Scheme classical EGR [4J
EGR valve
EGR valve head
Exhaust gas recirculation valve depends on the amount of added exhaust gas.
In the easiest mechanic pneumaticsystem, dependently on engine work point determined by opening throttling valve and engine speed, vacuum pressure occurs in the intake manifold which controls EGR valve placed in exhaust line.
In modem solution the extent of the valve opening is determined by programmer on the conditions on the base of information values can be controlled only with electric signals or in a mixed way that is electric signal controls vacuum pressure value which in tum influences recirculation valve motor operator [7].
275

276
The complexity of EGR control system increases in system controlled by on-board diagnostic. Special procedures controlling EGR system efficiency and its tightness are required from controlling unit. Monitor supervising EGR system work is a conditional monitor, activated when driving system works in the conditions determined by using norm. The programmer can control whether recirculation valve opens correctly. It can cooperate with valve opening sensor informing about the extent of the opening the valve. On-board diagnostic uses different ways to check the tightness of exhaust gas recirculation valve. For example in the valve exhaust gas temperature sensor can be assembled. The exhausts gas flow around only if
EGR valve is open or tightness.
EGR system control is carried out with electronic control unit ECU by a signal from mass airflow sensor. The signal from sensor is sent to central controlling unit until EGR valve connecting and is comparable to values taking into consideration signals of valve position sensor.
The principle of function control is based on keeping the airflow level during EGR valve connection less than with the disconnected valve (fig.
5).
a)
EGRvalve steering
ECV connected withhigh sensor
I rr=~=~
/
EGR valve
Mass airflow sensor b)
EGR valve steering
ECD connected with high sensor
E!) rr===~
EGR valve p,
I
/
Massairflow sensor
Fig.
5.
Scheme of EGR engine system control ofVW engine: a) EGR valve connected, b) EGR valve disconnected. Symbol: Qlm - air flow signal, t - time, Pp vacuum pressure,
Pa atmospheric pressure [3]
4.1. System controlling EGR valve
System processes control device signal (fig. 6) with direct injection installation from electronic central unit (ECU) to the pressure making the control of EGR valve opening possible. It is supplied vacuum pressure from intake engine system, which is supplied to EGR valve if

controlling device sends the appropriate signal. The quantity of exhaust gas supplied to intake system is defined by controlling signal valve.
In the case of damage EGR valve is entirely disconnected and flow of exhaust gas to intake system channels is impossible.
Atmospheric pressure
Vacuum pressure
0 0 0 0 0
.agnostic
connection
Fig.
6.
Electronic system controlling EGR valve ofVW engine [3]
EGR valve is opened with signal from EVR regulator (EGR vacuum regulator). Exhaust gas admission cut is carried out by opening release valve in EVR regulator. Signal indicating the quantity of exhaust gas supplied to the intake manifold is sent to central control unit with
DPFE sensor (differential pressure feedback EGR), which is connected with exhaust manifold at two points (fig. 7).
In this way information about exhaust gas pressure, which is equal before EGR valve opening both in exhaust manifold and in regulation chamber, is sent to DPFE sensor. Pressure drop in regulation chamber, as s result of EGR valve opening to the stated value, causes sending information with DPFE sensor to EVR regulator, where release valve is opened.
The whole system is controlled gradually by checking the correctness the DPFE sensor functioning by electrically way. Next EGR valve tightness and the ratio of exhaust gas flowing to the intake manifold to the value of signal from EVR regulator are controlled.
Pressure lines
ECU
EGR valve
EVR valve
DPFE sensor
Regulation chamber
Pressure line.s-<:::::::::l:==:;;;;;;;;;
Intake
Exhaust manifold
Fig.
7.
Scheme offunctioning and control OBD with Ford exhaust gas recirculation system [5J
277

6.
Introduction exhaust gas recirculation enables to reduce the amount of NO x formed in engine however at the cost of increasing incomplete combustion product emission. Exhaust gas recirculation is therefore insufficient way of limiting all the toxic compounds emission. The positive effect can by achieve by applying additional elements with EGR like: catalytic reactors (oxidizing or DeNOx) constant particle filters, cooling recirculated exhaust gas, loading with turbocompressor of variable geometry.
In principle the exhaust gas recirculation systems are not required in vehicle fulfilling
OBD II regulations. However it is effective system reducing NOx emission and is applied in more and more number of models.
UKLADY RECYRKULACJI SPALIN W POKLADOWYM SYSTEMIE
DIAGNOZOWANIA OBD
Wprowadzenie elektronicznego sterowania ukladem recyrkulacji spalin w samochodach osobowych i dostawczych bylo zwiazane z zastosowaniem silnik6w ZS z bezposrednim wtryskiem paliwa. Silniki te, w odroznieniu od silnik6w z komora wirowa lub wstepna, charakteryzuja sie wyzszymi temperaturami spalania, z czyrn wiaze sie zwiekszona emisja t1enk6w azotu. Rownoczesnie pojawily sie problemy z kontrola i sterowaniem ukladu EGR (exhaust
gas recirculation) w zwiazku z wprowadzaniem pokladowego systemu diagnostycznego OBD
(on-board diagnostic). Celem tego systemu jest alarmowanie kierowcy
0 wystapieniu uszkodzenia element6w odpowiedzialnych za prawidlowa pracl( silnika, a co za tym idzie rowniez element6w odpowiedzialnych za poziom emisji spalin. W artykule przedstawiono wymagania prawne oraz rozwiazania techniczne zwiazane z kontrola ukladu recyrkulacji spalin za pornoca pokladowego systemu diagnostycznego OBD.
[I] Merkisz J.: Ekologiczne problemy silnik6w spalinowych. Tom I i 2. Wydawnictwo
Politechniki Poznanskiej, Poznan 1999.
[2] Teodorowicz A.: Analiza obliczeniowa wplywu recyrkulacji spalin na emisje NO, w silniku
0 zaplonie iskrowym. Politechnika Warszawska, materialy niepublikowane.
[3] Materialy firmy VW.
[4] Leet J., Matheaus A., Dickey D.: EGR System Integration on a Pump-Line-Nozzle
Engine. SAE Paper 980181.
[5] Birnbaum R., Truglia J.: Getting to Know OBD II. Manufactured in United States,
2001.
[6] Janiszewski T., Mavrantzas S.: Elektroniczne uklady wtryskowe silnik6w wysokopreznych. WKL, Warszawa 2001.
[7] Lundgvist U., Smedler G., Stalhrnan P.: A comparison between different EGR systems for HD Diesel engines and their effect on performance, fuel consumption and emissions. SAE Paper 2000-01-0226.
[8] Mattarelli E., Bianchi G.M., Ivaldi D.: Experimental and numerical investigation on the EGR system a new automotive diesel engine. SAE Paper 2000-01-0224.
278