Modificare diagrama functionare EGR, la alh.

[sebica79]

cum as putea verifica daca egr functioneaza corect?

sa aiba legatura cu creterea consumului si mers neregulat la ralanti la cald

incearca sa scoti furtunul ce intra in el, cel mare gros ... si poti sa vezi vizual daca este sau nu depunere de funingine si nu numai. Iar mabrana o poti verifica incercand sa creezi tu vaacum-ul cu gura pe egr. Daca e sparta membrana, atunci nu o sa resuesti sa creezi vaacumul.

[ender]

1. Ideea este ca la viteaza mica, valva sa fie "inchisa" pt ca cantitatea de NOx este redusa, iar in momentul in care turatia este crescuta, atunci se va deschide tot mai mult pt a reduce temperatura in camera de ardere, implicit si cantitatea de NOx.

2. Acuma, in cazul in care valva EGR ar ramane tot timpul deshisa, motorul poate sa ajunga sa mearga f rau, chiar sa se opreasca - nu e o regula. Daca valva ramane inchisa atunci temperatura din camera de ardere nu mai poate fi controlata ceea ce duce la cantitati mari de NOx iar motorul poate sa ajunga sa aibe un sunet putin neanormal, chiar sa bata - nu este o regula.

3. Pentru a putea proteja chiar si uleiul, este indicat ca valava egr sa functioneze in parametrii normali.

~Sebica

1. Temperatura in cilindru creste fara aportul EGR-ului in admisie, dar nu necontrolat. La viteze mici (incarcare mica, load) valva este deschisa foarte mult (dc 80-95%). La load mare si in special la WOT, EGR-ul este oprit (dc 4-5%). Paradoxal, la WOT temperatura in cilindru (in jurul TDC) este echivalenta cu temperatura la sarcina mica, datorita faptului ca boost-ul este mare si IQ-ul este maxim.

2. Nimic mai fals. Motorul nu se opreste cu EGR-ul deschis la maxim; el functioneaza la putere mult mai redusa (IQ-ul rezuta din diferenta dintre flowrate-ul motorului, la o anumita turatie, si semnalul dat de MAF, semnal care scade odata cu cresterea EGR-ului).

Daca EGR-ul ramine inchis in permanenta, se aplica punctul 1. Pentru motoarele off-road se poate scoate EGR-ul pentru maximizarea eficientei si a performantelor; motorul nu "bate" si nici nu se aude intr-un fel mai aparte.

3. Uleiul se uzeaza mult mai repede daca EGR-ul este pornit, in primul rind prin acumularea de soot si de apa. Cu EGR-ul pornit motorul ajunge mai greu la temperatura de lucru si acumuleaza mai multi produsi de combustie, in special la drumuri scurte si in anotimpul rece.

EGR-ul a fost introdus numai din motive de poluare. El scade randamentul si scurteaza viata motorului.

[sebica79]

1. Temperatura in cilindru creste fara aportul EGR-ului in admisie, dar nu necontrolat. La viteze mici (incarcare mica, load) valva este deschisa foarte mult (dc 80-95%). La load mare si in special la WOT, EGR-ul este oprit (dc 4-5%). Paradoxal, la WOT temperatura in cilindru (in jurul TDC) este echivalenta cu temperatura la sarcina mica, datorita faptului ca boost-ul este mare si IQ-ul este maxim.

2. Nimic mai fals. Motorul nu se opreste cu EGR-ul deschis la maxim; el functioneaza la putere mult mai redusa (IQ-ul rezuta din diferenta dintre flowrate-ul motorului, la o anumita turatie, si semnalul dat de MAF, semnal care scade odata cu cresterea EGR-ului).

Daca EGR-ul ramine inchis in permanenta, se aplica punctul 1. Pentru motoarele off-road se poate scoate EGR-ul pentru maximizarea eficientei si a performantelor; motorul nu "bate" si nici nu se aude intr-un fel mai aparte.

3. Uleiul se uzeaza mult mai repede daca EGR-ul este pornit, in primul rind prin acumularea de soot si de apa. Cu EGR-ul pornit motorul ajunge mai greu la temperatura de lucru si acumuleaza mai multi produsi de combustie, in special la drumuri scurte si in anotimpul rece.

EGR-ul a fost introdus numai din motive de poluare. El scade randamentul si scurteaza viata motorului.

Nimic mai adevarat la toate 3 puncte ... am exemplificat exact invers.

[sebica79]

Ca si completare la cele scrise mai sus ... insa nu am avut rabdare sa traduc atata ... consider ca poate fi util :D

Fuel efficiency mode

EGR has been used to increase fuel efficiency on many cars since the mid-1980s. During steady throttle cruise conditions, EGR is used to reduce throttling losses. Throttling losses are energy that is used to create intake manifold vacuum and overcome the intake restriction of the throttle. It takes significant horsepower to create the intake manifold vacuum that occurs under cruise conditions.

During light-load cruise conditions, the EGR valve is gradually opened much more than is necessary for N[O.sub.X] emission control. The open EGR valve reduces intake vacuum and replaces some intake airflow with EGR flow. The reduced intake airflow reduces engine power, but the throttle is gradually opened to replace the lost airflow. Either the cruise control or the driver does the throttle opening.

Because the EGR valve is opened very gradually, the driver doesn't even notice that he is opening the throttle to maintain speed. The end result is intake airflow and, therefore, the fuel flow are both slightly reduced, but intake manifold vacuum and throttle losses are significantly reduced. The benefit is reduced fuel consumption under freeway conditions. This EGR based fuel efficiency mode is common on EGR equipped vehicles built during and after the mid-1980s.

Ignition advance

EGR flow can be used to allow increased ignition timing advance. That means the computer strategies used to control ignition timing are heavily influenced by EGR.

As EGR flow increases, ignition timing is automatically advanced. Anytime EGR is reduced, ignition timing is automatically retarded. This response seems to be especially strong and quick on OBD II vehicles. It is so effective that disabling EGR will rarely result in a N[O.sub.X] emission failure in loaded mode emission tests. But, disabled EGR valves will usually result in increased fuel consumption and reduced power because of the impact on ignition advance.

Combustion chamber temperatures

EGR reduces N[O.sub.X] formation by reducing combustion temperatures. The exhaust gases that are recirculated slow the combustion process and reduce peak temperatures. Modern engines that use EGR systems are designed to perform very well with the slower combustion that EGR causes.

When the EGR system on one of these engines is disabled, combustion chamber temperatures can rise dramatically and actually melt components. The advanced computer-controlled systems on newer cars prevent this from happening, but it still occurs on many older cars.

Idle overrides

The EGR system has a number of overrides that prevent or reduce the computer EGR commands. Some of them are well-known, but others are overlooked by most technicians.

Engines do not tolerate EGR well at idle, so the throttle position sensor (TPS) input causes the computer to eliminate EGR commands at closed throttle. The vehicle speed sensor (VSS) and brake on-off switch (BOO) also can prevent EGR operation until the vehicle and engine are operating under conditions that tolerate EGR flow. Applied brakes, closed throttle and slow vehicle speeds can all prevent EGR commands.

WOT overrides

Most EGR commands are designed to reduce N[O.sub.X] emissions. So when N[O.sub.X] emissions are not a concern, EGR commands may be overridden.

Cars are not designed to have the lowest N[O.sub.X] emissions possible. They are designed to pass federal and state emission standards. The certification process does not include testing emissions under full-throttle acceleration, so PCM strategies often eliminate EGR commands when the TPS indicates a wide-open throttle (WOT).

ECT overrides

N[O.sub.X] emissions are formed at extremely high temperatures. When an engine is cold, N[O.sub.X] emissions are not a problem. In addition, engines do not tolerate EGR when cold.

EGR is not needed for emission control on cold engines, and it would tend to cause driveability problems on cold engines. Thus, EGR is reduced or eliminated when the engine coolant temperature (ECT) sensor indicates cooler engine temperatures. The ECT sensor has little or no influence on EGR commands when the engine is warmed up to normal operating temperatures.

IAT overrides

EGR tends to increase the chance of surge symptoms. The recycled exhaust gases inhibit combustion and increase sporadic partial misfires when the engine is operating under a variety of compromising circumstances.

When the air/fuel mixture is too lean or unstable, EGR operation can cause surge complaints. The injection nozzles on most new engines are placed in the intake manifold very close to the combustion chamber. This subjects the nozzle to very high temperatures that can cause vapor locking in the nozzle, which is prevented by the cooling effect of the intake air.

But when the IAT is very high, the nozzles can partially vapor lock and increase the chance of engine surge symptoms. Under these conditions, EGR commands are reduced or eliminated. Most port fuel-injected engines will start reducing EGR flow when the IAT sensor indicates temperatures of 130[degrees]F to 150[degrees]F. This override strategy does not apply to throttle body injection.

BARO overrides

At high altitudes, low BARO reduces maximum engine power. In order to increase engine power, EGR commands often are reduced at higher engine loads when operating at low barometric pressures. This override usually has no effect at low to moderate loads.

EGR control strategy

Under normal engine operating conditions, EGR commands are influenced primarily by engine speed and calculated engine load. The load is calculated from MAF, engine speed and BARO.

In engines that do not have a MAF sensor, MAF is calculated from engine speed, IAT and MAP. Load and engine speed have a direct impact on EGR commands, but MAP, MAF and IAT only have indirect impacts.

Speed density systems use air temperature, air pressure and air volume to calculate MAF. The MAP and IAT sensors provide pressure and temperature. The engine speed and the PCM's programmed knowledge of the engine displacement provide the air volume.

Thus, MAF is calculated from the pressure, volume and temperature information provided by the MAP, rpm and IAT sensors. Any fault that affects intake manifold vacuum will skew the MAF calculation on a speed density system. EGR leaks and incorrect base ignition timing frequently skew the speed density calculation of MAF. Increased EGR flow due to leaks or sticking valves will generally increase fuel and EGR flow, but decrease ignition advance.

Calculated load is really MAF expressed as a percentage of the maximum theoretical MAF at any given engine speed and BARO. Load increases with MAF; load decreases as IAT increases. It generally increases with MAP. However MAP is affected by EGR, but load is not. Load is similar to volumetric efficiency.

EGR commands usually are increased as engine speed increases. Load is a little more complicated. As load increases, combustion temperatures increase. EGR commands also must increase to limit those temperatures. Federal and state emission certification does not include testing under extremely heavy acceleration or high engine load conditions. So, EGR commands are usually increased as engine load increases up to a critical point. After that critical point, EGR commands are reduced as load continues to increase.

The critical point at which EGR commands are decreased with increasing LOAD is about 50 percent on a typical car. It may be lower than 40 percent on high-performance cars and more than 60 percent on lower-powered cars. This is because a high-performance car can meet the maximum acceleration required by state and federal emission tests at much lower engine loads. Engine conditions that are not reached during certification testing can produce higher emissions without penalties, so EGR is not necessary under those conditions.

Fault finding

All this information about how EGR is controlled may be interesting, but does it help us diagnose EGR faults? Yes, it does.

Basic EGR commands are based on the same sensors that the PCM uses for fuel control and ignition timing. Both fuel control and calculated load are based heavily on MAF. When MAF is undercalculated, both fuel and EGR delivery will be reduced at light to moderate loads. When a MAP, MAF or IAT sensor causes MAF and load to shift fuel metering, EGR and ignition advance will all shift. The shift in fuel delivery will be sensed by the oxygen sensor and corrected by the PCM, and the fuel trim records will reflect the fuel correction.

Under light to moderate loads, positive fuel trim numbers (or high block learn numbers) indicate that EGR has been reduced and ignition advance has been increased. Negative fuel trim numbers (or low block learn numbers) indicate that EGR has been increased and ignition advance has been reduced.

Fuel trim also is affected by fuel pressure and injector restrictions. Whenever fuel trim records are higher than about 10, it is a good idea to check fuel pressure and verify the accuracy of IAT, MAP and MAF.

Comparing scan tool values to a vacuum gauge can validate the MAP sensor, but IAT and MAF are a little more difficult to validate. The easiest way to validate an IAT sensor is to check the scan tool value before starting an engine in the morning when IAT should equal ambient temperature.

The BARO value also provides clues about EGR commands. The MAP sensor is usually used to record a BARO value during engine start-up. Before the engine cranks, manifold pressure and barometric pressure are equal. If the MAP sensor has drifted, the BARO value that is stored at start-up also will be off. Cars that do not have a MAP sensor will calculate BARO from MAF, IAT and engine speed during low speed, WOT operation. This is actually a reverse of the speed density calculation. The calculation actually provides a MAP value, but under low engine speed WOT conditions, BARO equals MAP.

If a car's BARO value is wrong, the MAP, MAF and IAT sensors should be checked for accuracy. Technicians should understand that restricted air filters, restricted exhaust and certain valve timing and camshaft problems also can cause the stored BARO value to be incorrect. When evaluating the datastream BARO value, compare it to other cars in your shop or the BARO value that is available from a state-certified emissions test analyzer. The BARO used by television and newspaper weather reports is a corrected value that should not be used for automotive diagnosis.

When troubleshooting EGR systems, most people are more comfortable checking the mechanical bits first, and fortunately that's where most problems lie. But when passages are clear and the valve opens and closes properly, the task is to determine if the valve is operating as commanded and if the commands are based on good sensor data.

Sursa:

COPYRIGHT 2004 Advanstar Communications, Inc.

COPYRIGHT 2004 Gale Group

[andREI]

Nu e chiar foarte aplicabil la TDI prima parte. La TDI nu ai 'Throttling losses' adica pierderi de eficienta datorate obturarii clapetei de acceleratie pentru ca NU ai clapeta de acceleratie. Articolul pare a fi scris pentru benzinare.

[razdan]

Google mi-a aratat ca sursa postului lui Sebica79 este articolul lui Kevin McCartney "Decoding EGR strategies: when the mechanical components check out, it's time to look closely at the commands being issued. It begins with an understanding of how the PCM uses the EGR valve"

Kevin McCartney, citez din articol, "is a five-time Ford Motor Co. Certified Training Program award winner. His experience in automotive computer diagnostics spans 28 years as a master technician, manager, instructor, master trainer, consultant and technical writer/editor."

[sebica79]

Google mi-a aratat ca sursa postului lui Sebica79 este articolul lui Kevin McCartney "Decoding EGR strategies: when the mechanical components check out, it's time to look closely at the commands being issued. It begins with an understanding of how the PCM uses the EGR valve"

Kevin McCartney, citez din articol, "is a five-time Ford Motor Co. Certified Training Program award winner. His experience in automotive computer diagnostics spans 28 years as a master technician, manager, instructor, master trainer, consultant and technical writer/editor."

Da, asa si este, am atasat doar copyright-ul pentru ca ala este cel mai important :D , insa ca sa zic asa ... ai accentuat faptul ca, ce este scris aici, sau mai bine zis, acest articol nu a fost scris de o persoana neacreditata.

@andrei: stiu ca am fost putin off topic, pt ca aceasta sectiune este dedicata in totalitate TDI-lor, dar am considerat ca nu strica - eventual trebuia sa delimitez citatul.

Ce a facut @ender mai sus, ar fi un rezumat sau concluziile ce le-ai putea trage dupa citirea unui astfel de articol.

Modificat 23 Martie, 2006 de sebica79

[MIGUEL]

Google mi-a aratat ca sursa postului lui Sebica79 este articolul lui Kevin McCartney "Decoding EGR strategies: when the mechanical components check out, it's time to look closely at the commands being issued. It begins with an understanding of how the PCM uses the EGR valve"

;) nu google ti-a aratat ci MIGUEL in postul nr. 5 ;)

on-topic: de cand mi-am redus EGR la maxim nu am mai avut probleme cu turbina, am verificat de curand si cursa actuatorului merge f usor.

Am inteles ca inchiderea totala a EGR la motorul meu ar produce limp-mode ?

[sebica79]

Prin reduicerea EGR-lui la maxim, nu este afectat si catalizator-ul?! Daca da, in ce masura?

[ender]

Tot ce este scris acolo, sau in mare parte, este abureala ecologica.

Putem dezbate pas cu pas tot ce este scris, multe lucruri se contrazic intre ele ( pistoane topite la incarcare partiala, fara EGR, dar care rezista la WOT ;) ) dar nu are sens pentru ca n-avem de-a face cu benzinarele pe acest forum.

Nu mai luati de buna tot ce gasiti pe net!

[andrein]

Exact cum zice Ender ! Am ajuns la concluzia ca unele "sugestii" legate de setarile masini sunt facute pentru a proteja mediul si nu pentru binele masini/motorului. Deci trebuie sa reusim sa facem o distinctie riguraoasa intre 2 sfaturi.(sa le vedem si implicatiile)

Modificat 24 Martie, 2006 de andrein

[Bogdan_G]

Am redus azi EGRul dar nu am sesizat nici o modificare in functionarea motorului ....trebuia sa simt ceva ???

@Ender se poate "dezactiva" EGRul hardware ? Adica sa opturez cumva traseul din evacuare spre EGR ...sau intra in Limp Mode ?

[MIGUEL]

Eu am simtit ca-i mai vioaie, la partea cu limp-modeul astept si eu raspuns.

[andREI]

La TDI-urile mai recente puteti sa va captusiti cu o eroare stocata in memorie, nu limp mode. La al meu (TDI mai vechi) nu se seteaza eroare daca blochezi hardware EGR-ul. Uitati-va in semnatura mea si vedeti ca am facut deja asta.

[Bogdan_G]

Pai poate o sa ne schimbam si noi semnaturile in curind ;) trebuie doar o zi cu soare si manecile suflecate .

[Northman]

Am scazut si eu EGR-ul, se simte ca masina e mai vioaie in turati medii.

[misu tdi]

Avand in vedere ca 70% din parcurs rulez in oras, trasee scurte, sinuase in vitezele inferioare,drumuri de munte, m-am gindit sa modific diagrama de functionare a ciclului EGR, in sensul ca sa reduc cantitatea de gaze, "injectata", in admisie.

Acum intrebarea este, afecteaza in mod negativ aceasta, functionarea motorului, a turbosuflantei ?

Este un nivel, precis, pina la care e bine sa fie reduse gazele ?

Daca a mai facut cineva asta rog sa scrie aici, si ce imbunatatiri ati observat la motorul vostru.

[FABIAn RuSu]

http://vwforum.ro/index.php?showto...34029&st=20

http://vwforum.ro/index.php?showtopic=22244

[marius1982.11]

La mine sunt reduse de tot(din soft) si mai merge, in rest, motorina si ulei sa bagi si piciorul, ...la podea.

Turbo merge cam din turatii mici ceea ce e mai ok, dpdv la puterii [nu si al noxelor], dar na,la mine poate nu se pune ca nu e softul stock.

[MasinaPoporului]

Inainte de a face orice modificare notati-va valoarea existenta.

Folosirea gresita a adaptarilor poate conduce la nefunctionalitatea motorului, asa ca orice modificare o faceti pe propriul risc !

Pentru realizarea acestei adaptari trebuie sa folositi un cod pentru a va loga.

Codul este 12233.

[select]

[01 - Engine]

[Login - 11]

introduceti codul 12233 pentru a activa adaptarile speciale

[Do It!]

[Adaptation - 10]

introduceti valoarea numarului canalului ales:

canalul 3 : ciclul de lucru EGR

Pentru a scadea cantitatea de gaze recirculate trebuie sa cresteti valoarea presetata (32768) pana spre valoarea maxima (de obicei 33768 - valoare la care MAF raporteaza la ralanti 370mg/h, ceea ce este inca in limitele prevazute de fabricant)

Aceasta modificare creste cantitatea de Nox din gazele de esapament.

P.S: nu stiu cat este de corecta si buna aceasta operatiune :)

[misu tdi]

@masinapoporului, dar ce pot strica oare, in afara de faptul ca polueaza mai mult ?

[MasinaPoporului]

Nu stiu... :cool:

[Swat Cat]

nu stici nimic... o sa se incalzeasca putin mai greu....

un mic avantaj care il simt cu egr off este turbo lag scazut

[FABIAn RuSu]

pe topicul celalalt http://vwforum.ro/index.php?showtopic=34029&hl= discutam ca se incalzeste mai usor si infuleca mai mult cu rata mica sau EGR taiat :icon_thumright:

la ASZ mai mult de 33638 nu te lasa ECU sa setezi - asta insemnand undeva peste 50% rata EGR la ralanti

Modificat 29 Martie, 2009 de FABIAn RuSu

[WNT89]

Pana la urma in afara ca polueaza mai mult modificarea lucrului EGR ARE CEVA CONTRAINDICATII ??

eu am modificat ieri la 1.9 tdi AXR de la 32768 la 33400 ... nu am facut cine stie ce km de atunci insa parca e mai vioaie un pic