Of vacuum and timing

[Papalangi]

A while back there was a thread about vacuum, how much you had and were it was measured.  Or maybe it was on mercedesshop.com?

Anyhow, it got me to wondering why mine was so low at 13.5"Hg measured by pulling the climate control line at the firewall.

Since my mileage is kinda low and it goes poot for the first minute or so when cold and seems to be a bit sluggish, I decided to go old school when setting the timing.

Usually, I follow the sticker which in this case is TDC with vacuum lines connected.  This time I used the vacuum gauge method which is to increase timing until you get around 17"Hg.

What a huge improvement!

My climate control would not bring the fan on very often as it needs to see vacuum from the temp switch on the servo, now it runs most of the time.  The poot is gone.  Better throttle response and it settles into gear nice and smooth.  It also seems to have cured the run-on, AKA dieseling.

Thing is though, the timing is now at 10BDTC and it pings lightly on WOT up a rather steep hill.  I'm not too worried about that, I can always back off a bit.

Still waiting to see if mileage improves.

Michael

[WGB]

Be a little careful and watch your temperature gauge.

The detonation is one thing but an advanced ignition can make them overheat as well.

Bill

[Papalangi]

Be a little careful and watch your temperature gauge.

The detonation is one thing but an advanced ignition can make them overheat as well.

Bill

Thanks for the tip, it's been running at 180F with a new T-stat, fan clutch and IIRC a water pump, but I will keep an eye on it.

Michael

[pez]

I run about 10 degrees on my '76 euro spec 450se with no problems. I do have a 4 core radiator, which dumps more heat than the standard 3 core, and my car is lower miles and well tuned. I also live at altitude [denver], where one can be more aggressive on the timing, too [due to lower air density, and hence lower internal combustion chamber pressures].

Overall, it works pretty good. I would suggest adjusting timing to some degree away from spec for anyone that has their car in a known good state of tune, and also knows that their valve clearances & timing are correct, too.

[Papalangi]

If anything, it runs a few degrees cooler.  Right about 180F instead of 180F and an occasional drift up to 200F

Cold idle is pretty fast but not scary.

It's going to take most of two weeks to check mileage.

Michael

[Papalangi]

Finally had to fill up on the 12th.

Still runs great, mileage went up to 13.5MPG.  Not bad for a short mixed drive commute.

Michael