Pros and Cons of an EGR system - Type IV bus

[BellePlaine]

I bought a stock muffer for my fuel injected 1974 engine using 1976 heater boxes in my 1975 bus. Now, I'm contempating the pros and cons of finding and installing an EGR system. Over on TS, I found this tid-bit about the EGR system...

Here is a post from our beloved Karl re EGR before he passed on to the Light:

EGT stands for Exhaust Gas Recirculation. It is supposed to take any unburned gas from the exhaust and run it back through the engine so that it doesn't get vented out into the air and hopefully give you another mile or two.

Not quite what the EGR system does.

EGR was designed to stop the formation of Oxides of Nitrogen, NoX for short. The 3rd bad boy of smog pollution, behind CO and HC.

NoX is formed when the combustion temps exceed 2500 deg F.

The EGR valve lets in spent exhaust into the mixture to lower combustion temps.

On American made cars, the engines are borderline lean to pass smog check. If you cap off the EGR valve, the engine pings and slowly destroys itself. 99% of the old timer mechanics don't have a clue and then they create more problems.

When the bus engine has all it's smog systems working together at 100%, it runs the best it was designed.

It sounds like a working EGR system makes the engine run cooler because the engine is not using as much combustable oxygen as it does without an EGR. Cooler is better right? Plus, there is the benefit of not polluting NoX.

[Hippie]

It runs cooler with the EGR if the tune is otherwise stock (leanish), yes.
If the mixture has been enrichened for power and coolth w/o the EGR, it will need retuned when it is reconnected or it will sap power by diluting the oxygen with exhaust gasses.
That's why EGRs usually are set up to not open until the engine is partially up to temperature and they open little if any at idle. It would run rough or stall.

[BellePlaine]

That's why EGRs usually are set up to not open until the engine is partially up to temperature and they open little if any at idle. It would run rough or stall.

That must be what the temperature sender that the Bentley shows does. Isn't there also an EGR sender going up an idiot light? Does the light indicate that the EGR is open when it shouldn't be (idle/full throttle) or that the EGR is closed when it should be open? I'm very curious.

I've searched the classifieds, and I've learned that the EGR componants are expensive. I think that a working system would be nice to have but not my first priority.

[satchmo]

That's why EGRs usually are set up to not open until the engine is partially up to temperature and they open little if any at idle. It would run rough or stall.

That must be what the temperature sender that the Bentley shows does. Isn't there also an EGR sender going up an idiot light? Does the light indicate that the EGR is open when it shouldn't be (idle/full throttle) or that the EGR is closed when it should be open? I'm very curious.

I've searched the classifieds, and I've learned that the EGR componants are expensive. I think that a working system would be nice to have but not my first priority.

I thought the EGR idiot light was hooked up to the speedometer to let you know when you reached the time/mileage to replace the EGR filter. I don't think it has anything to do with EGR function.

Yes, the EGR replacement parts are very expensive, not to mention the crowding factor of the EGR piping in the engine bay. Additionally, if you have EGR you must be certain there are no air leaks at the junctions or holes in the pipes since an air leak in the system will nearly guarantee melting valves, etc.

Most folks with carbs, unless they have an intact system already in place, let the EGR go bye-bye, tightly cap off the ports, and make adjustments in the carbs for cool running and smog compliance standards. I'm not sure how the fuel injection people approach EGR.

Tim

[Amskeptic]

That's why EGRs usually are set up to not open until the engine is partially up to temperature and they open little if any at idle. It would run rough or stall.

That must be what the temperature sender that the Bentley shows does. Isn't there also an EGR sender going up an idiot light? Does the light indicate that the EGR is open when it shouldn't be (idle/full throttle) or that the EGR is closed when it should be open? I'm very curious.

I've searched the classifieds, and I've learned that the EGR componants are expensive. I think that a working system would be nice to have but not my first priority.

I thought the EGR idiot light was hooked up to the speedometer to let you know when you reached the time/mileage to replace the EGR filter. I don't think it has anything to do with EGR function.

Yes, the EGR replacement parts are very expensive, not to mention the crowding factor of the EGR piping in the engine bay. Additionally, if you have EGR you must be certain there are no air leaks at the junctions or holes in the pipes since an air leak in the system will nearly guarantee melting valves, etc.

Most folks with carbs, unless they have an intact system already in place, let the EGR go bye-bye, tightly cap off the ports, and make adjustments in the carbs for cool running and smog compliance standards. I'm not sure how the fuel injection people approach EGR.

Tim

Disconnecting is an easy way to achieve better driveability in the mid-range. Though a functional EGR reduces *peak* combustion temperatures, it does so by compromising the power in the middle of the range. The greatest issue with EGR in my mind is that it is a dangerous failure point out on the road, a cracked pipe is oxygenated lean heat when the engine is expecting cool inert.
Colin

[Hippie]

That must be what the temperature sender that the Bentley shows does. Isn't there also an EGR sender going up an idiot light? Does the light indicate that the EGR is open when it shouldn't be (idle/full throttle) or that the EGR is closed when it should be open? I'm very curious.

Like satchmo said, it is just a mileage based maintenance reminder. There is a reset button there on the little control box to kill the light after requisite cleaning of carbon and testing of function...which nobody does. They just kill the light and drive on.

[reluctantartist]

So does the EGR improve fuel economy? If you remove it, what do you have to do to the AFM to compensate for it if you have fuel injection? I have an 82 california vanagon and the 1980 did not have an EGR and the AFM is a different number. So do I need the 1980 AFM now or is there something I can do to my current AFM, or should I just replace the EGR filter?

[BellePlaine]

I'd like to know if the EGR improves fuel economy as well. Does anyone here run their ACVW with an operational EGR, if so I'd love to hear from you.

Here's the pros/cons list so far:

Pros
*The EGR system reduces pollution by stopping the formation of Oxides of Nitrogen.
*The engine runs cooler in the mid-power range. I imagine that this would be especially helpful driving up hills.
*VW designed the engine to run with EGR system in place. Although, I still don't know for which main purpose it serves; to pollute less or help the engine run cooler.

Cons
*The engine has less mid-range power, i.e. not as good drivability.
*The system is crowding
*A system failure could overheat the engine. Would a steel pipe really crack though? And doesn't this concern already exist in the form of various potential vacuum leaks?
*The EGR parts are expensive.

Unknown
*Fuel economy

[BellePlaine]

That must be what the temperature sender that the Bentley shows does. Isn't there also an EGR sender going up an idiot light? Does the light indicate that the EGR is open when it shouldn't be (idle/full throttle) or that the EGR is closed when it should be open? I'm very curious.

Like satchmo said, it is just a mileage based maintenance reminder. There is a reset button there on the little control box to kill the light after requisite cleaning of carbon and testing of function...which nobody does. They just kill the light and drive on.

It's weird to me that VW would link an EGR idiot light to a mileage based reminder, but not an oil change light. Did they have their priorities screwed up?

[Amskeptic]

That must be what the temperature sender that the Bentley shows does. Isn't there also an EGR sender going up an idiot light? Does the light indicate that the EGR is open when it shouldn't be (idle/full throttle) or that the EGR is closed when it should be open? I'm very curious.

Like satchmo said, it is just a mileage based maintenance reminder. There is a reset button there on the little control box to kill the light after requisite cleaning of carbon and testing of function...which nobody does. They just kill the light and drive on.

It's weird to me that VW would link an EGR idiot light to a mileage based reminder, but not an oil change light. Did they have their priorities screwed up?

VW had to link EGR to a mileage-based service reminder because of an exclusive-to-the-United States Environmental Protection Agency governmental mandate that all emissions systems maintain standards for at least 50,000 miles, just like all the other manufacturers had to. BMW had this silly pod on the dashboards of my BMW 2002/530i's/ and the 630CSi, with EGR/Thermal Reactor/Svc reminders, we had 55 mph highlighted speedometers that could not read above 85 mph, we had seatbelt interlocks that would not allow you to start the car without your belt being buckled . . . .
Colin

(egr does not improve fuel economy)