Mercedes W114 250 Coupe - help!

[alabbasi]

They all thought she looked fantastic but were denied any drive as there had been gritters out the night before

Careful, even if you're just talking about grit on the road, a /8 might start rusting

 

[Charles Morgan]

It's as though they are a bit Italian.

Just to complete the circle, Dad and I popped over to see Tony and Jill. Several cheese scones, mince pies and slices of wonderful Christmas cake later (all home-made) we had a good look at the garage where Brunnhilde had been sleeping and Tony described his plans to extend his model railway to cover it in its entirety. Some photos for Druk. (all handbuilt from kits or scratch, except for one loco. Scale 7mm to 1ft, entirely authentic stations copied exactly.)

Some locals have been on the scrumpy at this station.

 

[grober]

This reminded me of another famous W114 Owner- one George Harrison.
Any developments in 2017 Charles?

 

[Charles Morgan]

Been horribly busy getting other cars sorted, practising for my concert and now that is out of the way, suffering from a hideous cold. So nothing this year yet!

 

[brucemillar]

Been horribly busy getting other cars sorted, practising for my concert and now that is out of the way, suffering from a hideous cold. So nothing this year yet!

I do believe (and have heard it said). Some women think, natural child birth without pain management, is on a par with a man's cold!!

What do they know?

 

[Charles Morgan]

As I was getting the SM out for some fettling I thought I'd see if I could get the coupe to start in this really very bitter weather. Plugging in the MS the coolant temperature was showing -5C (I suspect a small degree of sensor calibration error) but it fired up first time and then ran without stalling. I slightly retarded the timing and also let a degree more air in, in the end it still runs very rich and I think the next thing to fiddle with slightly is the desired AFR at low coolant temperatures.

However, as my colds manifest themselves in a bronchitic way 3 minutes in the garage with low temperature and lots of exhaust fumes was enough for the day.

 

[grober]

As I was getting the SM out for some fettling I thought I'd see if I could get the coupe to start in this really very bitter weather. Plugging in the MS the coolant temperature was showing -5C (I suspect a small degree of sensor calibration error) but it fired up first time and then ran without stalling. I slightly retarded the timing and also let a degree more air in, in the end it still runs very rich and I think the next thing to fiddle with slightly is the desired AFR at low coolant temperatures.

However, as my colds manifest themselves in a bronchitic way 3 minutes in the garage with low temperature and lots of exhaust fumes was enough for the day.

Chesty cold- not good- best action - bit of mollycoddling for a few days - cars can wait!

 

[C43AMG]

Sorry to hear about your latest issue with bureaucracy Charles.

On a positive note I had to renew my driving licence which I did online. The new one arrived, complete with a photograph used for my recent passport, 3 days after my application. Some things do work exceedingly well.

Thanks for reminding me. Very impressed with the ease of application and I love the photo being used from your passport. Fortunately I had the Gateway information for something else

 

[zohar.melamed]

One a bit of a bureaucratic tangent, I'm having to register my W114 newly imported form South Africa in HK. My lord the rules here are crazy. The fuel filler nozzle diameter has to be changed. All seat belts have to be replaced as they are missing the little tag stitched that conforms standard compliance. The windows have to be tested and etched with the standard number they conform to, light lenses with even a hair line fracture ( both rear ones ) have or be replaced. Any sign of an oil leak of any magnitude is a straight fail. This car would fly through an MOT in the UK.

 

[Charles Morgan]

Old Benzes normally leak oil. I'd fail them if they didn't!

 

[woody m3evo]

Wow this build is truly inspiring, credit to you mate.

 

[Charles Morgan]

On the beautifullest day of the year today out came Brunnhilde, blinking from a long winter layup. She started on the button, new seatbelts fit perfectly so I took her for a few mile run. Let's just say the main task is going to be to get her tuned perfectly as in current set up she is a huge distance away from that at present. I took the trouble to download all the data from the SM's Megasquirt and the comparison is fascinating. I know the base map set up is absurdly rich, so that's where to start. Now the distraction of selling that car is gone I can begin seriously to get to grips with Brunnhilde. I want to get her much more tuned before I do another rolling road session.

Good things - she is exceptionally comfortable, rides well, gearbox is very easy to us and she brakes well when the initial travel is out of the way. The cabin fans send a lot of ventilation through peacefully, even unassisted by the windows. She has presence and beauty even without a full clean yet, so I can see I am going to love driving her.

 

[grober]

Did you ever fit an air fuel ratio meter Charles?
280SL "K-Jet and Ignition conversion to Megasquirt" write up - Mercedes-Benz Forum
this guy used the Innovate one.

If you're handy with a soldering iron??
DIY Air / Fuel Ratio Meter

 

[Charles Morgan]

It's on the MS gauge panel. I'm going to borrow someone more computer literate than me and we'll do a long drive with all the info being captured. I don't have a rev-counter either so meaningful information assimilation is quite difficult. He can also fiddle with ignition timing on the move.

 

[Charles Morgan]

Having tried to take screenshots in Windows and given up, some photos of the SM Fuelling and AFR tables vs the W114's. You can see instantly why Brunnhilde is out of tune with a monstrous big flat spot.

W114 AFR table

SM AFR table

W114 VE table

SM VE Table

 

[grober]

The AFR table from that 2.8 M110 article?

and there's this archive material.
http://www.msextra.com/doc/ms2extra/MS2-Extra_Tuning_Manual.html#afr

interesting tweak for an uneven idle caused by long duration camshafts but might just be applicable to your idle problem? a restrictor to dampen the vacuum pulses the MAP sensor sees???
Tuning Issues
If you have a very long duration cam in your motor, and it idles poorly, you might be able to get it to idle better through careful tuning with MegaSquirt. Often a rough idle may be caused by lean air/fuel ratios. This is really is more of a cam issue than a fueling issue. The exhaust valve is held open later into the intake stroke and the intake opens earlier near the end of the exhaust stroke. At low speeds and relatively high intake vacuum you get more exhaust contamination of the fresh air/fuel charge. As you get more contamination of the air/fuel charge you typically need a richer mixture to get it to ignite and burn properly.
This means you probably cannot run a stoichiometric [chemically correct] mixture of 14.7:1 with your long duration cam. You need to run richer. So you tune your idle by ear rather than with a narrow band EGO [oxygen] sensor. And make sure you are not allowing EGO correction at idle if you have a rowdy cam! It will be trying to “correct” your mixture back to a lousy idle. If your engine will not idle well at stoichiometric mixtures, set the EGO Active Above RPM to a few hundred RPM above your idle speed. This will ensure that MegaSquirt does not try to lean the mixture back to stoichiometric to compensate for your adjustments.Remember that O2 sensors give wrong readings on a missfiring engine, big cams drive O2's nuts at idle too, so dont rely on their readings at idle.
Another tip you can try if you have a large overlap cam is to pinch off the MAP hose slightly while the engine is idling, and see if the idle quality improves. If so, then try a restriction in the MAP vacuum line. This has the effect of damping the vacuum pulses that the MAP sensor sees. Start with a ~0.040" (1.0mm) hole in the line. You may have to experiment with restrictor sizes to see what works best for your system.

 

[Charles Morgan]

I think before dealing with wrinkles, (I don't have an idle issue) I need to get the basic settings right. I am very familiar with the SM map and how it performs, the W114 on the other hand has notable weaknesses in basic mapping - an engine of this age shouldn't be running lean at any point.

Timing is the next thing - it's definitely got to be adjusted.

Only when I feel performance is close to acceptable will I start looking at other things.

 

[Charles Morgan]

Even adjusting only the lower half of the AFR settings to more sensible ones the car is driving considerably better. The battery on the cheap laptop I bought to run MS is fubar though, preventing me from working offline easily without a charger, so that must be sorted before more meaningful work.

By the time the VE table and the AFR table are adjusted (and higher coolant temperature idle - you just can't do this in the middle of the winter and get all the settings right), this will be a considerably better car.

I really could do with a rev counter though!

 

[zohar.melamed]

Do MS do Bluetooth so you can see the revs on your phone ?

 

[Charles Morgan]

I don't think so, I do have a feed from the ECU for a rev counter but I have yet to apply myself to getting one fitted (the logical position is where the clock is but that actually works).

It is just so odd after 35 years of driving cars with a rev counter not to have one!