Actual Co Measured on Cars

[RichieScotland]

Hi
I am trying to adjust my fuel mixture on my 230SL. I have adjusted links, checked cold start devices etc but it still idles at around 10% CO at the tailpipe. Before I get my pump checked out what actual measured values do people have on their well adjusted cars. Maybe they all just run rich ?

Thanks
Richie

[mrfatboy]

From my notes.  I think similar for 230sl but not sure.

Correct Air Fuel Mixutures according to BBB
Make sure the engine is on the rich side of 14.7 under load and doesnt ping. You should be seeing 12-13 under load at 3/4 to full throttle.

Idle       750-800   rpm   CO  3.5 - 4.5  =  AFR  12.80 - 13.20

Lower partial   1500      CO  1.5 - 3.0  =  AFR  13.40 - 13.95

      3000+         CO  0.2 - 1.5  =  AFR  13.95 - 14.50

Full load   3000+         CO  2.0 - 4.0  =  AFR  12.85 - 13.20
         

[Benz Dr.]

They run rich at idle and WOT but should lean out at regular road speeds. I think 3 - 4% would be normal at idle but some could be a bit higher. Did you try a split linkage test?

[stickandrudderman]

At idle it should be around 4%.
If you try to unwind the adjuster too much you will go beyond it's limits and will have to remove the large plug housing the adjuster to re-set it.

[RichieScotland]

Thanks - at least it seems possible to get there. I am running rich over the whole range so everything seems to be out. How do you reset the adjuster ? It has come to me with an unknown history so who knows what they have done to the pump adjustment.

thanks

Richie

[RichieScotland]

Can you tell me what is the split linkage test ?

[Pawel66]

You disconnect the linkage so that you can add air or fuel separately to the mixture. If you add just air and the engine is revving up significantly, more than, say 100-200 rpm rather than stalls - means you are running rich.

A very broadband test, just for "more or less" orientation to give you a clue where you are. May not be able to chase 1 or 2 pp of CO.

[66andBlue]

Can you tell me what is the split linkage test ?

It is right here:
https://www.sl113.org/wiki/Restricted/Linkage-tour