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Creating ignition table from engine spec.

Posted: Sun Oct 23, 2011 6:24 am
by peei
I'm trying to create a ignition table using the advance/retard from the engine specifications.
I have a NA engine (m110) in a MB280 SL which I converted to a MS2 v3 system controlling both fuel and ignition.
I'm not really sure how I should interpret the timing spec for the engine.
Does the "vacuum off" be the same as at WOT?
Could someone please enlighten me how to interpret the given values.
Using the data below should it be something like this or ???

max load(WOT) : 1500rpm/28° ... 3000rpm/34° 4500rpm /36°-40°
..
min load (idling) 850rpm/ 12°BTDC ... 3000rpm/24°(10°less than at WOT due to retard idling)

Firing order & idling speed 1‑5‑3‑6‑2‑4; 750/850 r.p.m.
601. Ignition timing –starter speed 12°BTDC <----------- This must be no load and idling
601a. (Vac. off)‑ 4500 r.p.m 34°BTDC <----------- Is this at max load (WOT)
606. Centrif. adv. at 1500 r.p.m. 28° <----------- min or max load ?
607. Centrif. adv. at 3000 r.p.m. 34° <----------- min or max load ?
608. Vacuum retard idling 10° ± 2° <----------- difference between min /max load ?
609. Vacuum advance at 4500 10° ± 2° (total 36°/40°) <----------- Is this at max load (WOT)?

Re: Creating ignition table from engine spec.

Posted: Sun Oct 23, 2011 10:00 am
by trakkies
How the vacuum advance effects the curve on a dizzy engine is likely different to how you'd set that up in MS - as a dizzy vacuum take-off is usually above the throttle so it will vary differently from the MS readings which are normally taken from the plenum.

Re: Creating ignition table from engine spec.

Posted: Sun Oct 23, 2011 11:43 am
by peei
I understand that it's hard to translate the old settings to a new map but I only need a hint from where I can start fine tune from, this is how I think it should look like (due to several examples I found on the net).
At WOT-> rich mix ->quick burn of fuel, less advance than at lower load.
At cruize -> lean mix -> slower burn -> more advance.
I've tried to keep the advance at WOT the same as the old settings, 28°/1500 rpm, 34°/3000 rpm and 36°/4500 rpm.
Please correct me if I'm totally wrong here...

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