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Anybody try this to increase throttle response on there 2.6 M103 engines? How would this effect the EZL spark timing?

 

It would not effect the EZL timing since it is a mechanical misalignment that the EZL is not even aware of. Therefore if one has set it from 10degree BTDC to say 20degree BTDC, at higher RPM's it will be the extra 10degree earlier than designed.

But that is an interesting post. I am starting to wonder if someone has done this to my '88. I know my '89 is normally aligned because I did it myself after I removed the head for refurbishing. My '88 is a lot quicker/zippier at the low end pick-up but does lack power between 2000-2500 rpm compared to my '89. I have been assuming this has to do with the EHA adjustment but maybe it is more mechanical like this. Once I install the EHA gauge on the '88 I will know better to see if there is EHA adjustment differences between the two cars.
Currently the '89 original is perfect, meaning the EZL current barely moves throughout the rpm range. I am expecting the '88 has the adjustment so that the system has to lean it for higher rpm's but that takes up to 10 seconds to readjust back to normal. So fueling is enriched during acceleration at low end. I suspect this is a better way to gain on pick-up than the mechanical method. The specs allow for about -4mA shift in EHA currents between 750rpm to 2500rpm.

My '88 is pretty much sorted out now but of course the only way to find out if someone has advanced its timing is to remove the head and that is not happening anytime soon. One other detail is that the '88 with the better pick-up has less intake vacuum then the '89 (something like 18 inch mercury versus 15 inch mercury at idle). That might be another sign of TDC differences between the two. Both engines have very good compression around 170psi, +/-10psi between cylinders.

Anyone know if advancing the timing makes a difference in intake vacuum?

Just thinking out loud here. I have no answers.

Happy Holidays!

 

Anytime you "upset the apple cart", that can have a domino effect and may cause the ECU to respond accordingly which may cause the car to perform poorly. The MB engineers were pretty specific with what they were doing and it's why they made diy "adjustments" pretty difficult to do. I guess you won't know until you try it. There's usually a cost somewhere in the overall running of the car when straying from the factory tunning. Just my 2 cents.

 

I asked AI if advancing valve timing effects intake vacuum and here is the answer:

It will actually increase the vacuum slightly if increased a few degrees but a advancing further will decrease vacuum and will cause a choppy idle if advanced too much.

FWIW.

- Cheers!

 

BTW Dave it is my opinion that the posters on that thread are off on a tangent and just experimenting. They are misreading the FSM.
Firstly according the AI there is no difference between auto an manual transmission valve/camshaft settings. That would not make sense anyway.
I used that same schematic to set my timing. The reason the sprocket has 3 positions (-3, 0 , +3) is because each sprocket tooth represents 9 degrees.
If I recall correctly the sprocket has 39 teeth. This is about 9 degree per tooth. So to be able to align the camshaft dead on to TDC you need +/-3 degree of play.
Say if at one tooth the dots did not align and theoretically it was off by 9 degrees. You would move it by a tooth and you are dead on, and leave the sprocket alone.
But if you were off by 6 degrees, you would move it by a tooth and by -3 degrees to make it aligned.
If you were off by 3 degrees, you would leave the chain alone and just move the sprocket by -3 degrees to make it aligned.
if you were dead on already you would just not move the alternate sprocket setting and leave it as is.

In any case that sprocket setting is for getting perfect alignment, it is not for causing artificial retardation or advance.

 

Dolucasi-t You could put a timing light on to see what the timing advance at Idle and 4000-6000 rpm. There should be a timing spec in the servive manual.

Yes, I thought the timing cam gear adjustment was to adjust for chain stretch.

 

I did check the timing advance from 750rpm to 3000rpm on both cars and they seem to meet spec. In retrospect when I had the valve cover off, besides checking the cam/rockers for wear I should have checked the timing chain for stretch and make sure the alignment is still correct with the dot on the cam. I did not do that, I should have. I also did not check for the chain tensioner for wear. That requires the upper timing cover to be removed and with no oil leaks upfront I did not want to go looking for trouble. I was hoping whoever re-sealed the timing cover before I purchased this car already checked for tensioner wear. Maybe wishful thinking but with an engine at 180K miles with no oil leaks and 4 previous owners it seems to have been pretty well maintained over the past 37 years.

Still does not run as well as my 210K mile original but getting pretty close after nearly 2 years of restoration....

 

I'd be a little concerned about the timing chain on the newer to you W201 if you don't have any service records indicating that it's been changed. MB typically recommends changing the timing chain at 100,000 miles. Just my 2 cents.

 

I thinking that Mercedes had a different cam for California delivered m103 engines. If you look at EPC there are 6 or so part numbers for m103 engines. Just a wild *** guess.

 

I don't know for sure if that's the case. It might also just be superseding part numbers from over the years. Maybe the MB Classic Center online parts store can shed more light on it?

 

This is news to me as well. I know that M103 will have at least 4 different part numbers:
2.6L pre- March '89 (old camshaft build)
3.0L pre - March '89 (old camshaft build)
2.6L post-March '89 (new camshaft material build)
3.0L post-March '89 (new camshaft material build)

Not sure why there would be 2 additional varieties.

I have both 1st and 2nd varieties in my cars. I could not tell the difference when I swapped in a '90 camshaft/rockers from an automatic to my '89 camshaft/rockers.
But it is not a side by side comparison and the differences could be minor.

I do not have access to the EPC and can not check this for sure.

Happy new Year to all members here!

 

I've actually run into superseded part numbers for other things for my W201 and of course right now I can't remember which parts that wound up being the case for so it might be the case for the camshaft. Pure speculation on my part.