[W126 Coupe] Exhaust Gases -Euro 500SEC

[Jack]

Rich,

I had trouble getting my 500SEL EURO to pass emission testing. 
It has the same engine as yours.

With these higher compression engines and 92 octane being the highest
commonly available, you can lower these numbers substantially by doing these
tricks. 

This is how I got my car to pass after many repeated attempts.

*   Have at least 3/4 of a tank of gas.

*   Add 1 - 2 quarts of alcohol in the tank. 

*   Drive the car for an extended time, say 20 minutes, at high speed to get
the cats good and hot. Not WOT but, shall we say, "briskly".

*Turn off A/C and immediately go the test station and try to avoid lines. 

*You need to get the test done before the cats cool back down.

*You might need to retard the timings 5-6 degrees also. Too much advance
will also cause pre-ignition (NOX). On the 500's the timing was still
adjustable unlike the 560's which have EZL.

The theory---
The alcohol will temporarily increase the octane helping to prevent pre
ignition and thereby reduce internal cylinder temperatures and reduce the
NOX. It also, leans the mixture out slightly because it stoichiometric
efficiency is 9:1 rather than the 14.7:1 of gasoline. 
The NOX is the hardest one to get to pass. The H/C and CO are relatively
easy and should be able to be adjusted down for the purpose of the test. The
problem is, when you get HC & CO down the NOX will go up.

Keeping the temperature up on the cats enables them to further break down
exhaust gases better, giving you a cleaner tailpipe.

================================
Fuel By weight Percent fuel 
Gasoline 14.7 : 1 6.8% 
Natural Gas 17.2 : 1 5.8% 
Propane (LP) 15.5 : 1 6.45% 
Ethanol 9 : 1 11.1% 
Methanol 6.4 : 1 15.6% 
Hydrogen 34 : 1 2.9% 
Diesel 14.6 : 1 6.8%

Once you get it to pass you will want to set it up so it drives better
again.

Here's a link to more information on exhaust gas analysis.
www.autoshop101.com/forms/h56.pdf

In former life I used to sell emission test equipment and automotive
analyzers.

Jack H.

==============================================================

Hello All:

The following are the test results of the emissions test performed this
afternoon on my 85 Euro 500 SEC:

               25/25 test
50/25 test

                      reading             allowed         result
reading        allowed        result
HC ppm             212                 137              Fail
216             140             Fail
CO %               1.86                 0.87             Fail
1.85             0.79           Fail
NOx ppm          1028                 956              Fail
1036            1046           Pass
RPM                1302                 2500 max
1357            2500 max
CO+CO2 %       15.5                  6.0 min
15.5             6.0 min

The following items are new: 8 fuel injectors w/ air tubes, Beru spark
plugs, Beru ignition wires, Distributor cap and rotor button, ICM and
various vacuum hoses and vacuum connector, 1 can BG 44 intake system
cleaner.

The car now runs great. Just can't seem to satisfy the clean air nazis in
this state. Is the mixture too rich?
Any ideas how to rectify this situation? Oh yeah, the car does have
catalytic converters.

Rich Jaffe
85 Euro 500 SEC 259K
83 300 SD         192K