Exhaust analyzer

Hello - I am a new member here from CanadaI have owned my 1972 350SL Djet for over 25 year, and I am active on the Benzworls and Peachparts forums in North America. Please excuse me using English.

On my own car, I installed a full time AEM wide band Air-Fuel ratio meter (pictures below) This makes setting mixture (%CO) easy. But many owners do not have such a meter. I read on this forum about a low cost infrared CO meter. Could anyone provide details of manufacturer and where such a meter can be purchased. This would help many D-Jet owners.

Hi Graham,

welcome to this website. English is absolutely okay, that is why I have translated my whole compendium to English. Mentioning benzworld: The only thing we do not appreciate is if someone copies drawings, pictures or tables from here and publishes them e.g. on benzworld as happened in the past with Norbert's measuring gauge for trigger contacts. Linking to this website is of course welcome. I know it wasn't you, so please forgive my statement.

Now when it comes to your qeustion regarding the AU tester. Yes I do use two infrared based ones. One is Gunson's professional gas tester. Thats i ssimiliar to this tester . Mine can additionally measure dwell and rpm. I bouht it second hand for 100€. And I own a Bosch ETT 08.14 gas tester as well. Both have an accuracy of roughly 0,5% which is good enough for not catalytic cars. Tomorrow I will buy a Bosch 4 gas tester ETT8.41. That has the big disadvantage that you need to recalibrate it allthe time with a verification gas. Let us see whether it will run at all. And it is only needed for catalytic combstion diagnosis.

There should be old Sun exhaust testers available in the US, similiar to the Bosch one. Intersting enough you can pay more for Bosch infrared testers than for a 4-gas tester. The infrared ones need no real maintenance other than maybe a filter.

Hi Graham,
I'm very glad I can Welcome you in this forum, too.
I know you're an active member in North-American forums

You wrote: "On my own car, I installed a full time AEM wide band Air-Fuel ratio meter (pictures below) This makes setting mixture (%CO) easy."
Never saw such an instrument before

Does this mean you adjust the mixture when driving, or just the mixture at idle?

Regards
Norbert

Hi Norbert,

no this is just a broadband sensor plus a meter. Americans like to work with air/fuel ratio and not with lambda. So 14 would be equivalent to lambda 1. Such devices are rather popular in American classic cars. A friend of mine uses it on his Adenauer and that made him find out that his fuel injection pump was too lean in high revs.

nordfisch wrote: Hi Graham,
I'm very glad I can Welcome you in this forum, too.
I know you're an active member in North-American forums

You wrote: "On my own car, I installed a full time AEM wide band Air-Fuel ratio meter (pictures below) This makes setting mixture (%CO) easy."
Never saw such an instrument before

Does this mean you adjust the mixture when driving, or just the mixture at idle?

Regards
Norbert

Hi Norbert,
As Volker said, on my car, I installed the AEM wide-band O2 sensor kit that comes with an AFR gauge. The sensor actually outputs lambda, I believe, but display is in AFR because that is what many understand better. I paid about $200 for the complete kit, but I have seen others for even less. But AEM and Innovate were the leaders at time I did install. I looked at Gunson and others, but really, I don't they are good enough and they would have even cost us more! I also found that measuring at tailpipe was inaccurate - I had back mixing of outside air. Measuring near engine is best.

Regarding adjustment. Idle, I did in garage by giving engine short burst and turning ECU knob from centre position until I got a suitable AFR (easy to convert from %CO to AFR and vice versa). I chose a high %CO (rich mixture) for idle - seems to help with hot starts. For load mixture, we adjust the MPS. Take car and run it at various loads. Check vs MB original specs (available in Technical data Manual) and decide on a suitable setting. So trial and error method, not adjusted while driving.

Innovate have a 2 sensor unit that would be good for our V-8s! They also have portable meters.

www.innovatemotorsports.com/

Hi Graham,

we are just doing an experiment here in Germany. Rennstrich8 (Tobias with his racing 280CE) with an M110 with increased bore has tried to adapt his car. While this is principally possible by tuning the ECU on a test stand, I have advised him a - as I believe - better solution. He will install a lambda sensor and an old lambda control unit to adapt. There are actually two different versions available. One that changes the water temperatur sensor resistance and one that acts similiar to the idle-run potentiometer to influence the basic injection pulse.

Unfortunately we have no results yet. I am also eagerly wating. But I consider such solution better than an A/F ratio meter as it is self-adaptive. Tuning the MAP sensor is easy to access on type 3 MAP sensors, but you are very limited as you can only parallel-shift its load-curve. And it can well be that such a sensor will not fit the car next door anymore as tolerances of sensors, ECU and MAP sensor just add up to be too lean or too rich.