My 318 dyno results
How come you want me to take out initial timing, but add VA? I can't see it making any difference in the end?
Also, wouldn't connecting it to my manifold vacuum just make my idle quality worse, due to my lumpy idle (making timing jump up and down?).
It's not the air gap. :)
Simple
Mattax (well said IMO) already gave an excellent argument/explanation for reduced idle timing. More VA will make that up as soon as you give it light throttle.
Most engine I have worked with like well over 42 degrees of timing at 2000, to say 46*@2400 for cruising,( and even up to high 50s with aluminum heads and lean-running). I really like the Big Vcans with 22ish degrees in 'em. That means the power timing in that zone has to be reduced to run with those. So if you take say 20 from say 44 then you need say 24@ say 2200, for power timing.
Yeah, you can run a smaller can and more centrifugal, but then you lose the Part-Throttle advantage.
Like when on the choke. At this time with a cold engine, it's almost impossible to have too much advance. So if you set the initial to say 16*, and run 1* per hundred rpm, then at a warm-up speed of 1500 rpm, the best you can have is say 16+ 7 =23* ..... but a 22* Vcan would about double that, and so smooth her right out :) . But wait! With all that advance, maybe you can reduce the warm up speed. Say to 1200. The mechanical might be 16+ 3=19, and maybe the Vcan loses signal and drops to 11, so you still have 30*!
But when you put it into gear, maybe you lose 2 mechanical,and so 28* may remain, and as you gently take off, 11* more will jump in right away for 39* now, and increasing by 1*per 100 rpm as you drive away. By 2800 most all the timing will be in, and so now it could be as much as 36+22=58*.
Iron headed engines usually don't like this much, this early, so I put a two stage curve in,to limit the curve at about 2800, and then I bring in the last 4 to 6, at some later rpm that the engine is happy with. This would drop the PT timing at 2800, to say 52*...
2800 is my chosen 1-2 shift rpm. Not every engine is happy with 52*@2800PT, so for those, there are plenty of Vcans to chose from....... or used to be,lol.