Ignition timing 280SL/8

[Peter]

I would like to know the ignition timing of the 280SL/8 (130 engine) at idling speed with vacuum hose connected. “The Enthusiast Service and Maintenance Manual” on the site is not giving this information, the Haynes Repair manual however is but shows at idling speed two different values. 2 to 4ᵒ ATDC and 8ᵒ ATDC.

What is correct?
Could be that there the second asterisk is a printing error?

What is the correct ignition timing of the 280SL/8 (130 engine) at idling speed with vacuum hose connected?

[Shvegel]

It took me a while staring at your chart to figure it out.  The lower numbers are for US emissions only and the upper numbers are for the rest of the world.  I verified this in my BBB(big blue repair manual) as the specification is 3 degrees plus or minus 1 degree with vacuum connected.

[Peter]

Thanks for your help,  this means that I have to readjust  the timing, I used the Rest Of World settings on my USA car.

[Benz Dr.]

I don't think any of that is right. 2 degrees ATDC at idle sounds right for USA cars with vacuum switch over valves. All the rest of the world, or those places that didn't use that system, used the standard and earlier distributor which should be set to 8 degrees BTDC at idle with everything connected.

[Shvegel]

Dan,
My feeling is Mercedes tried to Bandaid(Tm) ther way around High NOX emissions by dropping the timing forward a bunch.  If you can tune to the ROW spec you will be better off.

[Benz Dr.]

Dan,
My feeling is Mercedes tried to Bandaid(Tm) the way around High NOX emissions by dropping the timing forward a bunch.  If you can tune to the ROW spec you will be better off.

I don't think you can with the late USA version ignition. Any attempt to increase ignition timing beyond a few degrees usually results in pinging. Only way you can tune to non USA spec is to change the whole system including the throttle body.

[TEJOLX47]

Hello everybody,

I was searching under this topic and came across your debate.
I have a copy of the BBB which says slightly different (please see the picture and its orange dot).
For engines with:
   US Exhaust Emission Control,
   Model Year 1970/71,
   Distributor 0 231 116 062,
it should read:
   @ 800 rpm (idle) - 8º ATDC
   @ 1500 rpm - 0-5º BTDC
   @ 3000 rpm - 25º-30º BTDC
Does it make sense?
Also, according to what I read, 8º ATDC is a retard ignition and all BTDC are advances.
Yet, the Emission control system says that advance is only turned on at 2400 rpm; that leaves the 0-5º @ 1500 rpm in a limbo, once retard should only be set back at 2200rpm.
Any comments?
Many thanks

[Nicolas Aristodemou]

I think the centrifugal (mechanical) advance of distributor 062 (late USA spec with emissions control) advances timing between idle and 1500 rpm (limited to about 10deg of advance). The vacuum RETARD when switched off at about 2200 rpm provides another 20 degrees of advance, a total of 30 degrees.

My advice to everybody that hasn't done so already is to get hold of an 123 distributor, as I have recently done myself on my 1970 280SL USA, read carefully the various posts relating to its installation (not exactly straight forward for USA emissions models) and get an unbelievably smooth running engine. The 123's electronics take care of the timing advance at all rpm ranges as per the specified preset programme. You can keep the original distributor should any purist want to revert to an original installation in the future.

[TEJOLX47]

Thank you Naristodemu.
Kind regards