I have an 87 190E 2.6 with 115K on the clock. I got the dreaded registration renewal in the mail that stated that I had to have the car smogged at a "Test Only" station. So I changed the O2 sensor last night just to be on the safe side. The car has had new plugs and ignition wires within the 3K miles. All morning I drove the car hard to really heat up the cat. Took the car into the test only station...and she passed. I have to say waiting for the results felt like I was back in college waiting for my girlfriends pregnancy test results. Now as I look at the report it looks like they made a mistake in that it says the car is a four cylinder 2.3L. Oh well, I figure the 2.3L passing limits are lower if anything. Here are the results:

15mph
RPM 2225
CO2% 14.6
O2% 0.4
HC ppm 66 (Max 118)
CO% 0.21 (Max 0.75)
NO ppm 699 (Max 799)

25mph
RPM 2769
CO2% 14.4
O2% 0.6
HC ppm 44 (Max 93)
CO% 0.07 (Max 0.63)
NO ppm 334 (Max 738)

Those are good HC numbers for a 2.6, but could be better as the O2 is fairly high, which, if consumed in the converter, would lower HC and CO. Also, your NOx is high.

Do you have the data from the last test to compare the improvement, if any?

Did you go to a drive through test only station with a short line and keep the engine revs up while waiting?

For comparison my last numbers were (HC, CO, NOx, O2):

15 MPH, 1657 revs: 113. 0.36, 261, 0.1
25 MPH, 2665 revs: 058, 0.18, 188, 0.0

If the converter was hotter during the 15 MPH test, the 0.1% O2 could be consumed to further reduce HC and CO. The 15 MPH test heats up the converter to the point where it is "100 percent efficient" during the 25 MPH test - all O2 is consumed - but the HC and CO is still higher that average for the year group. NOx is about average.

The difference in revs is because my car has a manual trans. and both tests must be run in second gear to be within the RPM limitations.

I'm due again in February, and I'm sure I will be directed to a "test only station" being as how ours cars have been tagged by the BAR as "high emitter profile", but there is a drive through test only station not far from me that is cheap and convenient, so I would probably go there anyway.

I think one of the "problems" with these engines is the semi-hemispherical combustion chamber. It has a fairly large quench area that probably increases engine out HC relative to a design with a smaller quench area.

Duke

Actually these results have to be taken with a grain of salt as the machine thinks the car was a 2.3L 4 cylinder. I watched the tach as they were running the test and there was no way that the rpms were as high as they indicate on the report. For the 15 mph test, the tach was reading about 1700 rpm. I don't know how much of the readings would be affected by this "error". I had to wait for one car to be tested and I let the car idle during this time. So the cat was warm at best for the 15mph test. But they did have to stop the test and let the car sit and idle for 180 seconds so running the idle at 2K likely wouldn't have helped much. They did run the fan infront of the car but the temp guage was sitting at 100C. For a catalytic converter with 115K....I'm happy with the NOx results. The last test run two years ago was not performed on the dyno and just an idle and high idle test. If those results will help in your data collection I can post them as well.

If they type in the wrong displacement, it would have no impact on measured emissions, but might affect the test weight and emission limit.

Most VINs are now bar coded onto the registration form, and when scanned will show correct data for the engine because there is an engine code in the VIN field.

Yes, I would like you to post the two-speed no load test numbers from two years ago.

Also, what is the "test weight" and "VLT record #" on your report from the recent test. These are in the data field at the top of the test report.

The catalyst cools off at idle, so while waiting you are best off to keep the revs at 2000 with the A/C on and widows open to keep as much load on the engine as possible. Based on my IR gun measurements, the converter inlet surface temp cools off several hundred degrees after five minutes of idling, after driving the car in normal urban traffic.

With an auto trans the engine might still be in first gear during the 15 MPH test, which has higher relative load the the 25 MPH test, which is likely in second gear. Thus, with and auto trans the revs at both speed will be close to the same.

The load is programmed into the test software based on vehicle weight and aerodynamic characteristics. Though the test is run at steady speed, the load is greater than required to maintain a the steady speed on a level road. That's why the test is called "acceleration simulation mode". It's essentiall yequivalent to going up a hill at steady speed.

Duke

I was interested to see how close your 190E 2.6 emissions were to the test limit (even with the mistaken engine type).

I had my 1991 420SEL (W126) smogged a few weeks ago, also at a test-only station (again, because CARB has labeled these cars as high-profile emitters), and my results were only a small fraction of the allowable limit in all cases. (I can't recall the results from memory, but seem to think they were all around 10% or less of the allowable limit.)

The place I had it done was pretty crowded, so the car was fully warmed up by the drive to the test station, but then was sitting off for 45 minutes. Then, when I was called, they had me drive it to the end of the street (2 blocks) and back, just prior to the test.

What really frosted me was four years ago, when the car passed all of the actual emissions tests, but the mechanic (this was at an M-B dealer) said that I had a clogged crankcase breather pipe (actually a metal tube), and so he had to mark down a failure (of the EGR system). Replacing this tube involved several hours of labor and a fair amount of money. Afterwards the emissions readings passed again, with exactly the same values. Perhaps I was taken for a ride on this one.

Bob Schleicher
1991 420SEL, 172,000 miles

Duke, here are the results from the previous smog checks (back to 97). Test weight was 3100 and the reason for the test is "High Emitter Profile". I forgot to get the VLT record #. What does the "VLT #" reflect?

2002
RPM 2461
HC (Max 140) 37
CO (Max 1.00) .08
CO2 14.5
O2 0.4

RPM 823
HC (Max 120) 68
CO (Max 1.00) .02
CO2 14.5
O2 0.5

2000
RPM 2330
HC (max 140) 44
CO (Max 1.00) .16
CO2 13.7
O2 4.1

RPM 700
HC (Max 120) 120
CO (Max 1.00) .05
CO2 13.7
O2 4.1

1999
RPM 2687
HC (Max 140) 80
CO (Max 1.00) .32

RPM 700
HC (Max 120) 52
CO (Max 1.00) .04

1997
RPM 2486
HC (Max 140) 82
CO (Max 1.00) .29

RPM 705
HC (Max 120) 57
CO (Max 1.00) .02