Topic: 280SE correct ignition timing

[stillmatic]

Can anyone help me figure out the correct ignition timing for my 280SE? I'm getting different info from the engine manual vs Chilton's and most posts I found here are referencing timing for V8's.

[Max-NL]

Attached is the german manual for the w116. Assuming you have the 116.985 engine you'd want the super unverbleit version (super unleaded). So about 26 degrees at 3000 rpm without vacuum.

[stillmatic]

Thank you Max, this is great info! For idle, is that also 4 degrees before TDC?

[stillmatic]

Also, how much would you recommend retarding it for 95 octane?

[UTn_boy]

Michael, see pictures below out of the book.  They should answer all of your questions, including the questions about octane rating verses timing.  However, do not skip the timing checks at the 1,500, 3,000, and 4,500 RPM increments.  Setting the timing at idle only may not yield the correct timing at higher rpm's.  These timing checks at various rpm's wasn't an optional thing for convenience.  They're put in the service literature for good reason. 

[Justin280s]

Great post.  I was about to ask about this.  Love this forum.

[revilla]

Hello everyone,

Coming back to what it seems an elusive subject, hard for consensus.

According to the spec (the one posted by Aaron above) for a 110.985 engine ignt timing should be:
- 32° @3000RPMs both vacuum lines disconnected (VERY clear, no issues)
- TDC +/- 3° @ Idle speed

Question: is the TDC +/- 3° @ idle with or without vacuum lines?

I ask because on the cell it reads literally "TDC +/- 3° with" BUT in the title of that column it states "Test values ignition timing without vacuum".  Thus, confusion at least for me!  Does that "with" in the idling cell mean with vacuum despite the indication of without in the column title?

Thanks in advance for your inputs.

Robert

[revilla]

And then we have this to add even more confusion...

So?
With or without vacuum lines at Idle?
30° or 32° @3000RPMs?


Can anyone clarify please?

Gracias

Robert

[ptashek]

Idle with vacuum, 1500 and 3000rpm without.

For fuel below 98RON, retard by 1° per octane (at 3000rpm, no vacuum).

[revilla]

Perfect, thanks Lucas.

It remains the 2nd mystery...

@3000 RPMs 32° (English spec) or 30° (German spec)?

Or maybe 2° don't make a difference really ()

Thanks in advance

[ptashek]

Perfect, thanks Lucas.

It remains the 2nd mystery...

@3000 RPMs 32° (English spec) or 30° (German spec)?

Or maybe 2° don't make a difference really ()

Thanks in advance

French market engines would be high compression versions, same as for the German market, in which case 30° is the correct value.

There's some differences between federal/California engines us euro folks can happily ignore

[revilla]

VERY CLEAR !!! Thanks again.

I found a problem while doing the adjustment.  I must be doing something wrong.  When I set up the advance @3000RPMs 30° it's impossible later to get the spec value at TDC +/- 3° for idle.

I followed these steps when adjusting the timing:

Start engine
Disconnect both vacuum lines
Accelerate speed to 3000
Rotate distributor until advance reaches 30°
Back to idle
Reconnect both vacuum lines
But reading @ idle = 22°
Restart
Left both vacuum lines connected
Rotate distributor until reaching TDC = engine not happy
Stop

So I can’t get TDC at idle, not even close, after setting 30° at 3000.

I have vacuum in both lines.  There’s vacuum at idle in the hose going behind the pod.  There’s vacuum at the other hose going on front of the pod when at 3000.

I tested the pod and there’s no air leak.  The arm moves freely when vacuum is applied and it holds it long term meaning no leaks. 

What's interesting is that when I accelerate from idle to 3000RPMs and back, there's no noticeable changes in the advance figure.  It barely fluctuates around 30° no matter the RPMs.  Then when I reconnected the lines it goes down to 22° but never lower towards the aim of TDC +/- 3°

So I left it at 22° idle (30° 3000) where the engines seems stable and happy with no misfiring.

Anybody had the same problem?
Am I doing something wrong? 

[rumb]

Assuming your vac lines are connected correctly I think this indicates your mechanical advance does not work.

[revilla]

Thanks Rumb

what does that mean?
possible root cause?
where/what should I look at?

Help is appreciated
Robert

[revilla]

Thanks for your PMs
You’re the best!!!

As we say around here, Voilà Voilà !

Problem found and resolved. There was a deformed spring and broken plastic slider that was causing the advance adjustment mechanism to misbehave. I replaced them using an old distributor I had. I imagine these minuscule parts are either hard to find or NLA.  Once root cause killed I arrived at TDC idle and 30° @ 3000.  Eureka!

And what a DIFFERENCE in performance that makes!!! Wow!!! I expect also a positive impact in fuel consumption... that we’ll see....

BTW, thanks Rueda1 for your great post about overhauling the distributor. Excellent to say the least. I took advantage to clean things up while in there. Contributors like you make this forum the great resource it is. Bravo!

What I love the most is the learning process we go through when “playing” with a system first time. Knowing how it technically works is essential to fix it. Then the intellectual effort pays off when the solution is securely in place. The reward is to better know, repair, improve and preserve these wonders.

Thank you all. Have a good day.