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Ignition timing - who's advanced it on their V8?

Started by 13B, 11 September 2007, 06:31 AM

13B

Always in search of greater efficiency (whether thats better fuel economy or power or both) I'm going to check the timing on my beast this weekend and see if I can't improve on it :-)

Soooooo..... how far is the most you guys have advanced your timing and what is typically the result?

And while we're at it, can someone tell me what the factory setting for an Aus 6.9 with the 8.0:1 / 198kW engine should be?  I'll use that as my yardstick.

Oscar?  You going the be the first to respond this time?
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

oscar

Quote from: 13B on 11 September 2007, 06:31 AM
Oscar?  You going the be the first to respond this time?

Your'e unbelievable.  How did you know  ;D

Since I fixed that running issue and did the timing to TDC, I've noticed a much more sedate quieter ride, no smoke that I can see.  Though my 0-100km/h is way off. Rough count at 11-12secs. :-[  I think the dizzy slipped a little. ::)
I get pinging at hard acceleration if I get near 10degBTDC.  I try and sit around 5-8deg BTDC.  The extra power is noticable and so is the smoke.  But only when accelerating hard.  I'll see how it goes over the next few days and advance it on the weekend and hopefully do an economy run.

No idea about the 6.9 figures. I've usually set my timing by ear and listen for pinging when its warm and under load then back it off a bit.  Then I use the timing light to see where I've landed.  It'd be interesting if you did the same on a 6.9 and see what you end up on.
1973 350SE, my first & fave

CraigS

[url="http://s109.photobucket.com/albums/n77/Aegeanfoods/My%20Cars/"]http://s109.photobucket.com/albums/n77/Aegeanfoods/My%20Cars/[/url]

Bandolero

As CraigS says.
HOWEVER, you Must make sure your vaccum retard is working and check the timing with the A/C off.
If your vac retard is NOT working, that is a different story.
You will probably have to set the timing at about 8'BTDC.
Russell Bond - (Adelaide, South Australia)
1978 450SEL 6.9 .... #5166 .... 12/78 (Sold.) [url="//www.ezycoat.com.au"]www.ezycoat.com.au[/url]

Mercules

If I can give some advice on changing the ignition timing...

I was able to make a repeatable 15kw gain (at the wheels) out of my VL Commodore RB30 by running premium unleaded fuel and altering the ignition map... I got to 31 degrees of advance before the rattling began! The car had a noticeable gain in performance and fuel economy increased from avg. 460km per tank to avg. 480 per tank (kinda helped to offset the price difference of Optimax). And yes, I am embarassed to admit I have been logging my fuel consuption (and many other things) into a spreadsheet for several years  :-[  Excel is pure evil for number crunchers.

First, get a base figure of your current timing settings... then, using your timing light, watch the timing mark changes as you load/rev the engine. If you are brave enough to rev the engine hard whilst leaning right over the front of it, you should be able to see the maximum mechanical advance pre-set into the dizzy. Manifold vacuum connected/disconnected will give you a rough idea of your vac advance figure but if you want to be anal about it, get a vac pump and suck it up till the diaphram is maxed. Note these then add/subtract the figures from your base timing to attain your total advance on changes.

Be mindful of the fact that vacuum advance affects the ignition pickup position whereas mechanical advance affects the centre shasft position, meaning that the two will COMBINE under certain circumstances.... just because it runs OK on cruise does not mean it will run OK on full-throttle!!!

If you are planning to tinker with the timing, then it is ideal to use the best grade of fuel available - this will buffer pre-igniton to a certain degree - but listen carefully for pinging and make your test runs in 2nd gear @ cruise - then full throttle. One lttle ping means wind it back buddy!

Also note that ambient air temps can become a contributing factor here, as a hotter intake charge is more likely to pre-ignite than a cold one. Make note of the air temps on the day you play, especially if it is a cold one, then be mindful of it should a hot day appear.

Best of luck - let us know what gains/losses you find as I'm sure everyone here would love hear that more power is only a tune-up away!

koan

Quote from: 13B on 11 September 2007, 06:31 AM

And while we're at it, can someone tell me what the factory setting for an Aus 6.9 with the 8.0:1 / 198kW engine should be?  I'll use that as my yardstick.


Don't you have the red label on the radiator support?

0 degrees BTDC, idle at 500 RPM, vacuum connected.

At that setting my engine runs well on standard unleaded (Caltex 2000) with no pinging (pinking?). By going to Caltex 6000 I can run to 5-6 degrees BTDC, I think I get better economy this way but that's just guess.

koan
Boogity, Boogity, Boogity, Amen!

WGB

These V8 Mercedes engines do not like a lot of advance over standard settings.

If you have an 8.0:1 Oz engine there may be more leeway but my 8.8:1 Euro 450 motor will detonate very easily on 98 unleaded if the ignition is advanced over the standard setting and the temp gauge will run hotter - particularly in the hills on a hot day.

Be careful.

Bill

oscar

Mercules, that's a very informative post. 
I have to ask you about this bit though.
Quote from: Mercules on 11 September 2007, 08:54 AM
I got to 31 degrees of advance before the rattling began!

Is this 31 at idle, vac disconnected?  How can you go that far without pinging?

I was wondering about compression differences between engines and WGB confirms that lower compression engines can be wound back more, what's so different about that Holden motor that you could achieve that much advance over a w116 V8?
1973 350SE, my first & fave

s class

Bill my 450SL is also a euro, and I have found exactly the same as you. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

Mercules

Quote from: oscar on 12 September 2007, 07:47 AM
Mercules, that's a very informative post. 
I have to ask you about this bit though.
Quote from: Mercules on 11 September 2007, 08:54 AM
I got to 31 degrees of advance before the rattling began!

Is this 31 at idle, vac disconnected?  How can you go that far without pinging?

I was wondering about compression differences between engines and WGB confirms that lower compression engines can be wound back more, what's so different about that Holden motor that you could achieve that much advance over a w116 V8?

My VL had an aftermarket EFI system on it which allows you to program your entire ignition & fuel map under any intersecting manifold pressure/rpm point - 31 degrees advance was seen from about 4500 rpm to redline on full throttle - no vacuum advance when the igition is fully electronic!

Differences between the Holden 6 and the Merc V8... 2 cylinders, different cam profile, electronic EFI adn about 15 years of engine development... everything else is the same i guess! Both have similar comp ratio, both have 2 valves per cylinder, overhead cams, crossflow head, etc...

We will see how multi-point EFI goes on a 6.9 when I have finished the yellow abonination.

Cam

oscar

Quote from: Mercules on 13 September 2007, 07:09 AM
- 31 degrees advance was seen from about 4500 rpm to redline on full throttle -

Thanks Mercules, I suppose my concern was that you were getting away with 31 deg advance at idle.  FWIW, my 350 gets up to 30deg too at high revs but I'm yet to measure it accurately and find what the maximum mechanical advance can achieve and at what revs.  Will try that tomorrow.  I'm sure it'll max out before the rev limiter kicks in but I've yet to hear that work too.  Call me chicken! ;D I haven't ever considered letting my baby go anywhere near 6000+ rpm's
1973 350SE, my first & fave

OldMercs3

One my U.S. spec, '73 D-Jet 450sel I tried the stock timing spec once I got it running (bought it with a failed timing chain).  I could not accept that anyone would've paid for a Mercedes and have it run like that (even in '73) so I cranked it up.  Pleased with the results and not yet experiencing any detonation (running w/premium fuel) I cranked it up more and ultimately settled on 13 degress BTDC at idle.  I like the response and vaguely remember only once hearing a slight ping or two on hard acceleration on an extremely hot day.