123ignition system

[280zex]

When you get yours tony, would you be willing to post your timing map?? I am curious to know

 

Right now I'm running mech advance to 2krpm with no vac advance, then dropping the mech advance back and using the vac advance/boost retard curve over 2k rpm with rev limit at 5800.

 

And originally I forgot about that rpm limiter and was like wtf when it came on. I thought I fouled up my equipment!!! Doh!!

[Leon]

I plan to get one soon as well...

[z-ya]

Sorry guys, I should have made it clear that my MSD 6AL-2 solution is for is for NA applications only. There is no provision for manifold pressure.

 

For boosted applications it looks like 123 is a decent way to go especially if you want to keep the stock distributor look. All turbo builds I have done have been crank trigger direct fire using OEM individual coils. My latest build will use GM truck coils. This to me is the ultimate way to go for boosted applications.

[Leon]

Sorry guys, I should have made it clear that my MSD 6AL-2 solution is for is for NA applications only. There is no provision for manifold pressure.

 

For boosted applications it looks like 123 is a decent way to go especially if you want to keep the stock distributor look. All turbo builds I have done have been crank trigger direct fire using OEM individual coils. My latest build will use GM truck coils. This to me is the ultimate way to go for boosted applications.

 

The thing is, it's better for NA applications as well because of the load-sensing ability that MSD doesn't have without the additional MAP sensor. Plus, there's something to be said (and already has been) about getting a brand-new distributor over a 30-year-old unit.

[Tony D]

A setup of 15 BTDC initial basic timing, with advance starting off idle straight and linear to 2500 (could be 3500, depends on compression car weight, gas used, and head chamber) with around 32 degrees.

MAP drops 2 - 2.5 degrees per psi anywhere in the range, idle is 35kPa, up to 15 degrees additional advance added from 100 gradually to 35 kPa.

The range around 45-55 takes some playing as that's tip in... It will make that partial,cruise spark knock...

 

I tend to run lower mechanical (most use 37 total) and let load basing tweak it as if I get a load of bad gas I can always push my foot down and drop advance (and spark knock)

 

If any of that makes any sense...

Edited March 5, 2014 by Tony D

[280zex]

Yes it makes sense, thanks. When I get home tonite I can set up a map with that info and post a pic so that people can see what it would look like!

[Dan_Austin]

The MS mega-manual actually is quite instructive with how to develop a timing table and largely

mirrors what Tony described, but also points out that the full advance by XXXX RPM is at

100Kpa, or full throttle, then describes some basic suggestion of how much timing to add per

10Kpa below 100, or to subtract per 10Kpa above 100.  The amount to add/subtract per 10Kpa

was determined by the factors Tony lists and bore size.

 

In years of shade tree wrenching and tinkering with ASE mechanics, I had never heard the

suggestion to think of the full advance at 3000 RPM at full throttle as the starting point.  Maybe I

am the only one, but if not that simple fixed reference made the rest of the (simple) calculations

to create a base map make a whole lot more sense, and made it clear that I had sections of

my map with potentially 12~15 degrees of additional timing possible.  In practice it ended up

being an average of 8~10 more usable in the 2500-3200 RPM and 45-60Kpa range.  Looking

at your initial curve I suspect this is not new info to you, but maybe to someone else dabbling

with setting up their timing map.

[280zex]

unfortunately I am unable to post pix of my ignition map (error 500)..........

[Tony D]

Yes Dan, that's basically what I did with my Megasquirt. I knew the old Sun Bench to set mechanical, and then how you set up vacuum advance/pressure retard but reading ADVANCE in "inches Mercury" and RETARD in "PSI" would have made the setup easier for me.... I had to twist my head around the kPa conversions because I could tell you '2-2.5psi retard, generally', and buttloads of advance at 19" or above of Hg.... But kPa? Fugadebaudit!

 

Frankly the biggest thing I found was all the specialists charging $400 to recurve your distributor took the vacuum pot off and threw a bunch of advance (hence "all in by 2500" compared to the Nissan 3500...) to boost torque and drive through the lean transition in the carbs. 

 

The nice thing being MAP referenced is you can add advance if you want in ONE spot where you find it will take it... whereas before it was all linear. No possible hump or lump midway (like where you would polish out a small divot on the advance ramp portion of the weights in a conventional distributor to advance in a linear manner then hold the timing for a second as it passes over that little divot, then depending on how you contour the ramp it either jumps to a big advance number or smoothly comes out  to return to a linear advance. Basically you put a 'step' in the curve doing that. But you gotta be damn good to polish those ramps like that... and SCREW THAT! Digital is WAY easier!

[280zex]

Here is a map I will be loading in the morning. I added a good bit of start retard at about 10deg. I also changed my rpm limit to 6000

[280zex]

I found this graph on theturboforums.com

 

This should help explain some basic timing tuning using KPA as pressure measurements

[Tony D]

I seem to recall 18-24 on my low boost setting (10 or 12 psi) and 12-16 on my high boost (17-21psi)... It really depended on the gas I was running at the time.

That map looks like a very good basic rule of thumb chart.