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  #31  
Old 07-20-2004, 11:25 AM
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After reviewing the emission controls for that model what you suggest makes a bit more sense. The puzzling part to the equation is the controls of that era are usually regulated through vacuum temperature switches. After a certain temperature is reached the valves are usually open, or closed depending on the circuit. Is it possible that vacuum valves of that era were designed to open at one temperature yet close at another temp? I discovered too much gray information regarding the actual operation of some/all the components in the emission control system for that era.

Thanks Duke.


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  #32  
Old 07-20-2004, 11:42 AM
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Several comments:

We may be saying the same thing with different words about fuel grades. Agreed that flame fronts and detonation are not the same. High compression engines require high octane fuel which burns slower, or lets the flame front complete its business, or whatever you want to call it. Lower octane fuel could result in quenching or detonation which can cause higher combustion temp and oxides of nitrogen or nitrogen dioxide. There really is no NOX. The x stands for an unknown just as in algebra. Cars requiring low octane do not benifit from premium, and in fact may suffer reduced performance.

Engine temps matter. All California testing station are required to have a huge fan to blow air at the engine compartment during the test to simulate road conditions. Stations are not allowed to pick their own fan. Only a state approved fan can be used. These fans cannot be used at the whim of the operator. There is an ambient temp sensor built into the testing machine that tells the operator when the fan must be on. The fan could be required to keep cars from overheating during the test, but I don't think that is the purpose. I've been told the purpose was to keep temps and nox down by simulating air flow during driving. I have seen no documention to that effect.

I was an electronics technician for 10 years before I become a Mercedes mechanic. I went through one solid year of electronics school five days a week. I was taught everything there was to know about electrons, outer rings, and co valent bonds and such. My point is that in those 10 years I ran into many situations where I said," well, so much for theory".

Peter
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  #33  
Old 07-20-2004, 12:02 PM
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James.
Thanks for posting that info about the radiator. I had a heck of a time about a month ago getting a couple of my cars to pass nox. They are an 88 and 90 300SEL. I just boughy an 87 300E that smokes big time. The PO told me that it barely passed smog. After I correct the smoking problem, I'm going to do a little research on the cooling system. I have digital pyrometers, access to radiators at wholesale prices, and of course cheap labor. I just had a 560 SEC smogged this weekend. I checked it on my machine which is only a 4 gas analizer, and the readings were very low. I can't check nox, but it passed the smog with very low nox. I replaced the radiator about a year ago, because it was running hot. I know none of this is scientific, but it has got me thinking. Today I will go into my 1979 manuals and look at the system on your SL.

Peter
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  #34  
Old 07-20-2004, 01:42 PM
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Quote:
Originally posted by MrCjames
After reviewing the emission controls for that model what you suggest makes a bit more sense. The puzzling part to the equation is the controls of that era are usually regulated through vacuum temperature switches. After a certain temperature is reached the valves are usually open, or closed depending on the circuit. Is it possible that vacuum valves of that era were designed to open at one temperature yet close at another temp? I discovered too much gray information regarding the actual operation of some/all the components in the emission control system for that era.

Thanks Duke.
I have a some familiarity with GM's TCS (transmission controlled spark) used in the seventies era. TCS denies vacuum advance except in high gear on automatics and may have allowed vacuum advance in both third and fourth on four-speeds. Most configurations included a thermo-vauum switch that allowed vacuum advance at all times above 230F coolant temperature. When the engine cooled down the thermal vacuum switch cycled back to normal mode.

The vacuum source was usually "ported" i.e. the signal port was above the throttle blades at idle, so there was no vacuum advance at idle under any circumstances, but some configurations may have allowed vacuum advance even at idle when the coolant temp was over 230F.

Vacuum advance increases thermal efficiency at idle and low load by increasing peak flame front temperature, but with no vacuum advance the timing is retarded below "optium" so flame front temperatue goes down (less NOx) and EGT goes up. Essentially more of the fuel's energy is thrown out the exhaust rather than creating useful work on the crankshaft.

The only way to understand all these "add-on" systems on vintage cars is to get all the OE service documentation and study it thoroughly. All of the control functions that these "add-on" systems performed back then are integrated into the engine control electronics on modern cars.

Autozen - I've never had a emission test station place a fan in front of my cars for ASM testing, but since the test is relatively short the car fans keep the temperature in bounds though they do get hotter than normal. In the case of my 190 I want it as hot as possible to keep the converter hot. This is an issue getting M103 engines to pass.

I've checked the converter inlet pipe temperature with an IR gun after normal driving followed by extended idling. It starts at about 500-600F and drops to as low 300 after five to ten minute of idling, which is why these cars tend to have high emissions unless you manage the test properly to keep the converter as hot as possible i.e. go to a drive through test station with no line, and keep the engine at 2000-2500 until the tech is ready to drive it into the bay.

Duke
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  #35  
Old 07-20-2004, 02:24 PM
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if you still can't figure it out, check on mr2oc.com. There are people on that board that know more about the car than Toyota.
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  #36  
Old 07-20-2004, 03:45 PM
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My experience with that board (I own a '91 MR2) is that 99 percent of the participants are clueless when it comes to automotive engineering issues - VERY different than this board. The one good guy is billwot, who is an engineer and considerably older and more experienced with things automotive than most of the participants.

I gave up on the MR2 board over a year ago.

Duke
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  #37  
Old 07-21-2004, 12:03 AM
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I got to my library today only to find that I have every new car intro manual for mercedes up to 93 except I don't have a 79. Not to worry I went to my service microfiche and pulled the one covering all the M117 engine emission systems from 72 to 80. The air pump always runs after it is picked up by a 17*C thermovalve.

EGR is activated through a 40*C thermovalve. EGR is activated during acceleration, during partial load, and during transition to decel. All this is done through a vacuum amplifier and is never shut off at higher temps.

I still think the idea of restricted coolant flow has some merit in high NOX readings. Remember theory is called theory, because it is just that. The reason that science progresses so slowly is because it always must follow scientific procedure. Tell that to Leonardo da Vinci

Peter.
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  #38  
Old 07-21-2004, 02:33 AM
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The ancient Greeks thought the Sun revolved around the earth. We didn't figure out the truth until 500 years ago, and it hasn't been that long since science though the sun's heat came from burning coal.

Even early in the 20th century science thought the universe was only as big as our own Milky Way until Hubble proved that those smudges of light were actually other galaxies BILLIONS of light-years away rather than just clouds of gas in our own galaxy.

Sometimes we don't understand how things work because we don't have enough information, and sometimes we just misinterpret what we observe.

Duke
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  #39  
Old 07-21-2004, 12:56 PM
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Duke, your experience on mr2oc was with the mark 2 crowd as you have a 91. I know nothing about that group. Mine is with the mark 1 crowd. The mk1 guys know what they are talking about. I have gotten very sound technical advice on that board. The original poster is asking about a mk1.
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  #40  
Old 07-21-2004, 09:56 PM
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Gentlemen, this turned out to be a good post after all.
Autozen has answered a question I had and that it became obvious after the retest. The tech didn't have the fan in front of the engine running the first time, he had it running the second time.
The car had new sparks, premium gas and it reduced the NOx number by 300. I work at a major oil refinery and can atest that theory is just what is written but the practical application and experience changes evberything.

I'll go back to my 300E.
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  #41  
Old 07-22-2004, 01:04 AM
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Quote:
Originally posted by Duke2.6
[
Sometimes we don't understand how things work because we don't have enough information, and sometimes we just misinterpret what we observe.

Duke [/B]
You see. There we go with science again. As an example: the medical profession which is based on science, believed for decades that ulcers were caused by stress and worry. It took an Australian medical doctor to inject himself with a bacteria to prove the whole SCIENTIFIC medical profession wrong. We now know that a bacteria called H Pylorie is the root cause of stomach ulcers. Science is so restricted by its codes and rules that it advances at a snails pace, not to mention the egos involved.

Peter
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  #42  
Old 07-22-2004, 01:18 AM
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That's a good example. Medicine is primarily an empirical science, and the profession believed for so long that ulcers were caused by stomach acid caused by stress - whatever- that they REFUSED to believe that ulcers could be caused by bacteria even when confronted by evidence derived through rigorous experimentation. That said your conclusion that coolant temperature has a major effect on NOx is not based on rigorous experimentation.

Physics, chemistry, and engineering are sciences. I'm not so sure about medicine.

Considering that this revelation about the cause of ulcers only happened only about 20 years ago, I wonder how far we have come in medicine since the middle ages, and most advances in medicine - like artificial organ, limbs, and arthroscopic surgery are due primarily to the efforts or engineers, not physicians.

Duke
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  #43  
Old 07-22-2004, 02:13 AM
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Quote:
Originally posted by Duke2.6
That's a good example. Medicine is primarily an empirical science, and the profession believed for so long that ulcers were caused by stomach acid caused by stress - whatever- that they REFUSED to believe that ulcers could be caused by bacteria even when confronted by evidence derived through rigorous experimentation. That said your conclusion that coolant temperature has a major effect on NOx is not based on rigorous experimentation.

Physics, chemistry, and engineering are sciences. I'm not so sure about medicine.

Considering that this revelation about the cause of ulcers only happened only about 20 years ago, I wonder how far we have come in medicine since the middle ages, and most advances in medicine - like artificial organ, limbs, and arthroscopic surgery are due primarily to the efforts or engineers, not physicians.

Duke
Agreed that engineering is a science which may explain why the Mulholland Dam failed and killed hundreds of people, and he was so distraught that he commited suicide. How about the scientifically built bridge in the Pacific North West that just went away. So much for science. You are trying to throw crap in the game by talking about the middle ages. As a matter of fact the middle ages occured after the crusades. The crusaders went to the holy land to teach those arabs a thing or two. What in fact really happened was that they brought back new medicines and new diets that were very beneficial to Europe.

In my opinion, if Einstein believed in scientific protocol. we'd still be using smokeless powder invented in 1894. Whether that is good or bad has nothing to do with the point.

Peter
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  #44  
Old 07-29-2004, 11:13 AM
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Timing Question on Another Failure

My 1985 380 Having failed at 3.6g/mi with a limit of 3.0 NOX I am trying to adjust timing these are my initial readings.

2 deg retarded at idle without vac adv cold
7 deg advanced with vac cold
I took these to check the temp advance

when hot
10 deg adv at idle w/vac spec range is 13-19 deg
30 deg adv w vac at 3k rpm spec range is not specified

25 deg adv without vac at 3k rpm spec is 25 deg at 3k

My question is that I had it in the shop and they were to retard the timing to make it pass the test. The idle readings are retarded but the high speed settings are not.

I realize there is centrifical advance taking place should I set it back to 20 deg advance at 3000 rpm without vacumn?

Is there a reason why the idle settings are retarded below spec range and the higher rpm are not?

Thanks for any help provided I realize I am new here, learning a lot and the ropes in where to post things.
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  #45  
Old 07-29-2004, 11:43 AM
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Bob,

Welcome aboard. You scored alot of points by posting the year and model in question. It gets real irritating when someone asks a question about something like timing on their car. Stevebfl always fires back the question. Is this a Ford or Chevy? That being said. How does your state run the smog check? Is this on a dyno and what speeds? I also notice you mentioned grams/ mile while Ca. measures parts/ million. I don't have any of my reference material here now. I will have to bring it home to help answer your questions unless someone beats me to it.

PS What are the rest of the readings?

Peter

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