Passed Thanks to Duke and Peter
 

1985 380SL Passed Emissions
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A big THANK YOU to Duke and Peter
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Test Results and Summary
NOX limit 3.00 ***final 1.88 ***prior 3.60
HC limit 2.00 ** final 0.51 *** prior **1.16
CO limit 30 *** final 4.90 *** prior **6.47
CO2 limit none *** final 326 *** prior 379
all grams per mile

The key was ignition timing the MB CD had a value of 13-19*adv at idle for the 116.962 engine. The actual tested reading was 10-12* adv Duke you were exactly right the 6* retard you advised bringing the value to 4-6* was the USA certified emissions value which not having an emissions label on the car I found a picture of buried in the MB CD.

Emissions Systems FI,AI,TWC,OS Peter thanks to you I resolved where the EGR system had gone, there isn't any.

Final Test prep was new plugs, 1/2 filled tank of premium fuel, FI cleaner, all emissions systems working and being second in line I let it idle while waiting to keep it hot. Good to know that a 20 year old MB (103k) will pass with flying colors when properly tuned.

Thanks again from a new member.

Bob,

Congrats and thanks for the follow up appreciation, but I think Duke is the hero. I will also remember his advive on the retard issue in my future dealings with the state.

Peter

I think I may have mentioned before that I have a MSME from the University of Wisconsin Engine Reseach Center where I did emission related research, so I have an indepth understanding of emissions generation and control.

The simple act of retarding initial timing is very effective at reducing emissions readings, and can often turn a marginal failure into a solid pass.
I only wish we could do this for M103 engines being as how they are often on the ragged edge of the HC limit and California has identified them as "high emitter profile". Unfortunately, the electronic timing control system built into the EZL ignition module does not allow the initial timing to be adjusted.

Duke

Just to concur, my 1994 Infiniti G20 failed the smog inspection the other day.

The tester noticed that my timing was off. It was at O degrees, but it should've been 15 degrees BTDC.

It took it home, and set the timing to 15 degrees, took it back to the smog inspection "test only" station, and it passed.

He said my timing was at 13 degrees, not 15, but he said you are allowed to be off 3 degrees + / - .

I noticed when comparing both inspection sheets that the 15 degrees made a surprising difference.

Bridges and Theory
 

I am following this (old) thread sice I have to go get my M104 smogged today and since I am new to the board. Autozen - the bridge you are referring to is the Tacoma Narrows Bridge. It was built in 1940. It fell down right after it was completed, and I mean right after. The failure mechanism was resonant vibration leading to huge displacements ("it moved too much"). The root cause of the vibration was wind blowing through the channel. The wind induced harmonic forces on the bridge structure and the forces then excited the bridge at its natural frequency. It fell down. There is a video that shows the whole event. Here is a link: http://www.civeng.carleton.ca/Exhibits/Tacoma_Narrows/

The bridge was designed using the best theory that the guys had at the time, which told them things like how thick to make the support columns and how many bolts to place in the connections. What they did not know (much) about at that time was something called flow-induced vibration, nor did they have the (computer) models necessary to estimate whether it would have been a problem for this bridge.

The point is - the theory works. If it didn't, no bridge anywhere would be standing. The designers of the Tacoma Narrows bridge used the best information and theory they had at the time. The bridge in fact stood up to the loads they designers had anticipated and that they had the tools and skills to deal with, again at that point in time. The problem was they did not have the skills or ability to deal with the vibration, and when it occured, the bridge became overloaded and failed.

As a design engineer in the fluid flow business I often am amused by plant operators, craftspeople, or other hands-on types who will immediately place blame and denigrate a system and its engineer/technician who designed it because it quit working or otherwise failed. When you get into it to see why it failed, many times it turns out that it's something that they did (improper or infrequent maintenance), didn't do (opened the suction valve too fast or didn't enable a shutdown device), or it was something that the theory behind the system does not address, for example, plugging or clogging of sensing lines. Of course this does not exclude design or engineering failures - I've been involved in plenty of those also. That is where experience must be married to theory to make a successful installed design. But to throw all theory and science out the window under the claim that art or operational experience is the only way, is indefensible. It is unfortunately true that a lot of engineers and scientists have arrogantly rammed designs down people's throats simply because they thought they knew better. The best design takes into account the experience and training of all team members: engineer, operator, and mechanic. - Pete

I grew up in Seattle and got my BSME from UW. I remember a class where we watched the film of "Galloping Gertie" in its final death throws and then the road structure began to disintegrate.

Analysis was done at UW, which determined the probable cause of failure. One of the "aesthetically pleasing" aspects of the original bridge was the "thin" road support structure that consisted of fabricated solid beams beneath the road rather than an open truss structure such as the Golden Gate Bridge. It was an aerodynamic problem caused by this solid girder road support structure that caused the road structure to begin twisting - an oscillation would set up. It's analagous to the sound that's created when you blow across the top of a bottle since sound is just a pressure wave oscillation. The name "Galloping Gertie" was applied shortly after the bridge opened as movement was quite noticeable to users, and I think it failed only about two months after it opened in a relatively modest wind that was less than 40 knots - far below what the designers believed the bridge could easily stand.

The replacement bridge upped the total lane count from two to four and an open truss road support structure was used instead of the solid girder structure, which allowed the wind to pass through without creating significant displacement forces.

One other interesting anecdote that I recall. The State of Washington bought an insurance policy on the bridge, but the insurance broker, thinking that the chances of ever having a claim were remote, pocketed the premium and never established a policy with the underwriter. I don't recall if the state was able to collect anything, but I think the insurance broker went to prison!

Duke

Well the M104 passed smog barely and I do mean barely. Allowable HC is 82 ppm and the measured amount was... 82 ppm. The other four gases were waaaay below max.

Great anecdotes Duke on the bridge. I first saw that video when I took vibrations and then again in a grad-level failure analysis class. Don't you know every engine school in the country has gotten a lot of mileage out of that old movie!

I saw in an earlier post that you did your MS at Wisconsin - did ya ever go to the Superior or Waukesha plants? I took a trip to the Waukesha plant once for a couple days to observe run-in and bench testing on a couple 1000 hp 900 rpm natural-gas engines I bought to drive gas compressors here in Kalifornia. One was a lean burn and one was a clean burn, both turbocharged. Long story there! I also used to witness emission testing of large stationary IC engines and fired equipment. We used to test for NOx (and SOx) way before they ever started doing it on cars. Makes for some interesting discussions with the smog techs when you take your car in. The principles are all the same, combustion is combustion. - Pete

That was a really interesting explanation.

wb, BSEE 1975.

Nope, just visited the GM Research Center in Warren, MI. GM sponsored by research assistant fellowship.

Duke