Emission CO

[Sens]

Hello,

I finished my engine replacement with an overhauled M130. Big success!!
New filters, new gaskets, new injectors,  …. Linkage tour done, ignition OK (123 distributor), valve clearance OK, new spark pluged, etc…
Happy!!!

One question about the emission.
At idle, I tuned the engine to 4% CO.
I measured with an old  Bosch ETT 008.00. (not calibrated)
However at 2000 RPM I read between 5 and 6 %, which is high. I think it should go down.

I did the split linkage test at 2000 RPM and it looks well tuned.
By removing shimms under the Barometric Compensator the CO went down to 4% at 2000 RPM.
But now the engine screems for fuel when accelerating. It runs bad. When I push the throttle quickly, nothing happens.

Adding the original shimms again makes the engine run really well. At idle and at full throttle.
I must add that it is an 280SL engine, but the FIP belongs to the original car: a 250 SL.

Anyone has an idea why in my case the CO % goes up to 5-6% in stead of going down?
Is it somything to worry about, since the engine runs great!

Thanks!! Halvor

[Cees Klumper]

Not hindered by the actual answer to your question as to why the co goes up towards 2,000 rpm, I would suggest not to worry about it since the engine runs so well.

[Sens]

Yes Cees,

I fully agree!

I might try to see what a little difference in the 123 distributor tuning gives: 8 or E is possible.

Thanks again!!

Halvor

[mauro12]

Is very difficult to tune these cars for a perfect co. I’ve recently overhauled the injection pump and the emission is still high. My injectors should be replaced because they are on the limit of the opening pressure . I run with 8% co and 600hc. I could bring down the co but I’m sure the car will not run well . It depends also on the compression and many other things ..

[dirkbalter]

Is very difficult to tune these cars for a perfect co. I’ve recently overhauled the injection pump and the emission is still high. My injectors should be replaced because they are on the limit of the opening pressure . I run with 8% co and 600hc. I could bring down the co but I’m sure the car will not run well . It depends also on the compression and many other things ..

Mauro,
I also have a new engine / injectors / pump / 123.... . I did the linkage adjustments based on the manual. The initial pump rich / lean adjustment based on the you-tube video from the British guy. My engine runs very good.
After reading a bit and talking about it, I bought myself one of the Gunson CO testers. As it turns out, I am at approx. 7.5% CO. As you know, Mercedes suggests 3.5-5%. I will play with it a little bit over the next few weeks to hopefully lower it to get closer to 5%. But I don't want to sacrifice "good running" for lower CO.  I'll let you know my findings.   

(My 108, also running good, is close to 8%)

[mauro12]

How about your HC values ? When I sent my injection pump last year to https://www.oldtimer-technik.eu/ , he tested my injectors and the result was a low opening pressure in 4 out of 6 . The spray pattern was acceptable . He suggested to replace anyway but I didn’t want to spend such money at that moment . I had a terrible experience the  year before , I bought 6 brand new r2 injectors , we put on the car and the car was not working at all. I sent them back and I’ve been refunded 1000€. ( brand new injectors totally defective from the factory , bought from mbclassic.de )
For this reason I preferred not to buy now . How can you bring the Co Down ? Only with the idle screw on the pump ?

[dirkbalter]

Mauro.
My little tester only does CO. I figure the other exhaust gases will be in line as well, once the CO is within range.

I was studying the you-tube videos on the concept.
https://www.youtube.com/watch?v=WzFflPK1y_E

As for my injectors, I bought a set of new ones from RM European at a reasonable price. But I tested them prior to installation. I saw guys complaining about bad new injectors and was worried like you. I still have my old injectors and after a lot of cleaning (ultrasonic) as well as mechanically opening and closing them with plastic pics, these are spraying good now too.

Yes, my first attempt will be to dial the screw on the side of the pump back a couple of clicks and see what happens. From what I understand and also from the German speaking forum, these cars like running a little rich. We will see.
Dirk

[Sens]

Hi again,

I have put the shimms back under the barometric compensator and the engine runs very well at 4% CO at idle.

I talked to the local Pagode mechanic and he said, like Cees mentioned, not to worry about CO at higher RPM’s.
In fact the engine runs without load and that gives you a useless value of CO.

So idle at 4%, engine running fine and you are good to go!!

Halvor

[mauro12]

Having an high value of CO at idle means also to have higher fuel consumption? At higher rpms the co could be within the normal values . Right ?

[dirkbalter]

Since my pump was rebuild and calibrated, I don't want to mess with the basic set up. The idle CO screw is the only one I am touching and (from what I understand) will only effect the idle CO settings and idle performance. Another good indicator on how your engine is running (lean /rich), may be to take a look at the spark plugs.
   

[Cees Klumper]

Hey Dirk, if I were you I would check with the FI pump rebuilder on one thing, which is would it be ok to tweak the idle fuel mixture adjustment screw at the back of the pump? I can't imagine that would be an issue, particularly if you keep track of the number of clicks you adjust it by. Adjustment may be necessary if the air mixture screw on the intake manifold adjustment, to get to proper CO level, produces a too high or low idle RPM. The main calibration (not even sure it can be done for idle setting away from the actual engine) I think would be for the mid- and high-range RPMs? Anyway, I would just ask the rebuilder before committing to never touching that one screw for the idle fuel setting. 

[dirkbalter]

Cees.
Agreed, but I think I wasn't clear. I did my initial set up based on the below recommendations which I found very good and adjusted the mixture screw accordingly.
https://www.youtube.com/watch?v=28uD3JVbQ-I
Car runs very good.
However, when checking CO, it shows 7.5%, which is a bit high, I think. All I want to do is lower the CO a little bit by adjusting the mixture screw on the pump, a couple of clicks in or out to get closer to 4.5-5% CO, without effecting the performance.
Does that make sense?

[mauro12]

Guys just to give you my experience . The specialist who rebuilded my pump last year ( https://www.oldtimer-technik.eu/) told me that the only thing I can touch is the idle screw on the pump . This have to be set up because every car has a different compression or condition that could lead to more or less fuel at idle . I decided to give some clicks ccw but I didn’t think too much about that . I don’t want to risk to damage something. The screw is located very deep as you know and is not very comfortable to touch . Also you would need a gas analyzer and a battery tender because you need to screw or unscrew only with the engine off . My next emission test will be in 2 years and I will not touch until than.

[Cees Klumper]

Sorry Dirk, yes makes perfect sense, I think I misunderstood your original post. All good, and I think you should be able to tweak the idle CO by adjusting air inlet screw on the inlet manifold in conjunction with the mixture 'slotted' screw at the back of the pump so the CO goes down while still maintaining a proper idle RPM.

[Cees Klumper]

@Mauro that sounds fine. I am using a basic gas analyzer from Gunson, they are still available new (bought mine used off Ebay many years ago) and don't cost that much, they seem to work well as I was able to compare my results to that of the MOT-equivalent test station in The Netherlands.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p4432023.m570.l1313&_nkw=gunson+exhaust+analyser&_sacat=0

[dirkbalter]

@Mauro, I turned the screw a couple of clicks. Got the CO down to approximately 4%. Not sure I like it. To me it feels like I have less pick up torque from stand still.

[stickandrudderman]

Mauro.
My little tester only does CO. I figure the other exhaust gases will be in line as well, once the CO is within range.

Co is a product of combustion so unburned fuel will not affect your Co. This is why HC (unburned fuel) are so helpful in diagnosis but of course, a multi-gas exhaust gas analyser is a big expense for the DIY mechanic.
Maybe I'll make a little video of this.

[mauro12]

Yes a good video would be very helpful for all of us . Especially about the clicks on the pump . The screw is located in not the most comfortable place to touch . I guess with 4% of co , the HC should be within the correct limiit  . 700 HC is too high? What is the cause according to your experience? I believe  is high but not too much . Last time I had 9%of co and 700 of HC . Probably I need to tune a bit better .