Possibly, but most exhaust leaks will result in net exhaust outflow, however, depending where the leak is it might create a "venturi" effect that draws in ambient air.

Here is the California ASM emission test data for my '88 190E 2.6 five-speed with the OE spark advance map (2005) and the last two with the retarded spark advance map. Data is measured/max allowable. HC and NOx is ppm, everything else percent.


2005..........RPM...............HC............CO..........NOx.........CO2........O2
15 MPH....1657(2nd)......113/116....0.36/0.74...261/791.....15.3........0.1
25 MPH....2665(2nd)........58/91.....0.18/0.62...188/730.....15.3........0.0

2009
15 MPH...1681(2nd).........54/116...0.18/0.74.....17/791......15.4.......0.0
25 MPH...1692(3rd)......... 35/91....0.09.0.62.....32/730...... 15.4.......0.0

2011
15 MPH...2756(1st).........47/116....0.17/0.74.....41/791......15.0.......0.0
25 MPH...2631(2nd).........29/91.....0.10/0.62.....20/730......14.9.......0.0

Note that in the 2005 15 MPH test the HC barely squeaked by and there was still 0.1 percent (1000ppm) O2 available for oxidation.

Subsequent tests cut HC and CO by about half and all O2 was consumed. This is the result of the hotter catalyst bed from the retarded spark advance map.

The retarded spark advance map also reduced peak combustion temperature so much that the NOx reduction was about 90 percent, especially if the test was done in a gear to minimize RPM, which has the least spark advance. I always ask them to run the 15 MPH test in second and the 25 MPH test in third, but you can see that this year they ignored my request.

Also note that in 2011 the CO2 percent is lower. This may be because I still had "summer fuel" in the car, which has less oxygen than the winter blend. The higher the fuels' O2 content, the higher the CO2, so CO2 is not much of an indicator. The best diagnostic tool is the O2 content, and if it's zero, you have optimized emission performance.

My car has only about 82K miles. The catalyst and O2 sensor are original. The duty cycle is within spec, and the initial mechanical mixture setting has never been altered from where it was set at the factory. The "seal" is still intact.

Duke

FWIW, my dealer quoted me $2000 for the entire pipe with the two precats and the main cat back in January when I had a problem with a broken pipe. He told me he could also get a factory rebuilt pipe for $1300. This excludes installation.

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88 300e
89 300e
93 400e
93 500e
77 308 GTB

Ready for round 3 today....

I'd say the engine is running a little hotter than I would like...usually around 100C mark while idling A/C on and 95'ish while driving. Its 95F outside today FYI.

I replaced the water pump in 2009 when I rebuilt my head (Graf which uses OE Bearings and seals) so I know pump is probably good. I replaced radiator in 2006, BUT I purchased a no-name chinese one off ebay before I started really understanding things.

So I have a feeling its probably the radiator that is loading temps up a bit.

I just replaced the thermostat (87C...put it in 2009 when I replaced pump) with a 79C one, so hopefully that helps bring down temps a bit. It should help reduce combustion temps, so should reduce my NOx.

Waiting for the line to clear up....Luckily here in AZ it has station cams I can look at to see from home how long the line is. Right now 5-6 cars in line, I'd prefer less than 2....so just waiting patiently, should clear up in a few hours I would guess since its mid-week.

Also richened mixture by 1/3rd turn clockwise -- duty cycle is around 70% so should be richer now too. I have a good feeling this time

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

So much for smog today....

Half way down the road radiator hose start shooting fluid everywhere. Glad I pulled over quickly after being concerned seeing the temps creep up (AND glad i ALWAYS carry gallon of water/coolant in trunk). I guess I didn't clamp it back on tight enough after replacing tstat....

Car is still running hotter than it should though -- I believe since its running hotter than normal its probably contributing to my high NOx (running hotter so higher combustion chamber temps)....

I have some no-name chinese radiator I installed (in 2006) when I was new to cars, so I think its probably bad. Water pump is only 15k old, so its gotta be radiator. Even on the freeway it doesn't get back down to tstat point and I can feel a lot of pressure going through the hoses. Graf water pump by the way...
I mean fan clutch works, coolant is full, no leaks, holds pressure, new water pump, new tstat....gotta be the radiator, right?

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Coolant temperature has nothing to do with NOx formation. NOx is formed in the flame front and the higher the temperature, the more NOx is formed.

If spark advance is optimized for the speed/load condition, peak flame front temperature is about 4500 deg. F. Retarding the timing to the point where peak flame front temperature is no more than 4000 F significantly reduces NOx formation. That's why the retarded spark advance map reduced my NOx by 90 percent.

The retarded spark advance map also yields higher EGT, which will transfer more heat to the cooling jacket through the exhaust ports, and that's why the engine will run hotter with a retarded map.

The viscous fan clutch tightens at about 100C and the aux. electric fan(s) engage at 105C, so your coolant temperatures for you ambient conditions are well within acceptable range.

Coolant temperatures can increase with age due to deposit buildup in the OE aluminum radiator, which reduces its heat transfer efficiency, and some replacement radiators may have less heat transfer performance than a new OE radiator, but I don't think that's a problem with your car.

Like I said, when my car completes the ASM test in mere 60s ambient temperature conditions the aux. electric fans are on full, but that's okay. They rarely engage in normal driving, but if they do, temperature rapidly drops to about 100 before they disengage, and in heavy traffic in warm temperatures the cycle begins again.

Having the AC on can actually reduce coolant temperatures, because the aux. fan(s) will engage a low speed frequently based on AC demand.

Let us know your latest test data.

Duke

Don't know if it means anything but my radiator hoses always have lots of pressure even after I installed a new water pump and new hoses. Is this the norm in these cars or is something else happening?

Good news!

Only changes were the change from 50% to 70% duty cycle. Ran on freeway again in 3rd gear for about 10miles.

300TE // limit // result
HC: 0.18 // 1.60 // PASS
CO: 0.69 // 15.00 // PASS
NOx: 2.38 // 2.50 // PASS

Equipment Inspection: VISUAL PASS (still had to have the women override the fuel cap)

This time, I drove right onto the dyno, nobody was in line....watched all day for the lines to drop.

PHEW!!
Only just about made it...but who cares. Done!

Still cannot believe how low my HC and CO are!

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

All I can figure is that your aftermarket catalyst is good at promoting oxidation reactions, but not so good at reduction.

How does your 260E do on the IM147 test, and does it still have the OE cat?

Duke

Haven't had it done yet...will soon....its not driving good right now as I have some fuel system problems (rust in tank).

We'll find out in the coming months.

It still has everything original.

__________________
2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

The same change to the 260E spark advance map should result in similar emission reductions. When you get it tested, pull up this thread and post the results.

Duke

congrats! I'm going to try and smog next week when my lock cylinder comes in (finally back from a long work trip) and can seal intake leak over the valve cover.

As promised Back with my 87' 260E's Arizona Emissions Test results:

She passed first time no problems!! Original cat too! Heck, even passed the damn gas cap without any problems. I did NOT touch resistor whatoserver. Its still in stock position. I guess shes running real nice now!

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Hello,

I just wanted to add my thanks to"Duke 2.6" for his recommendations for managing your CA smog test.

My Mercedes 1989/300ce with 340Kmiles on the clock failed the smog test intially, with the original CAT. The CA DMV said my car had a[U] high Emitter profile.
I took it back for a re' test and passed with flying colors after, I retarded the ignition on the EZL by blocking the vacuum to it, and shorted out the 750 ohm resistor. The NOX went down dramatically

If anybody else has this issue, follow his recommendation.

Gavinbr

Same here,

I took my 1991 560 SEC (with Euro Cams, Tri-Y's and aftermarket catalysts) to the smog shop and it failed.

I fixed a vacuum leak, did the same tricks as mentioned below and it worked perfectly!

Thanks Duke2.6!