123Ignition Advance/retard Curves

[westoz3.0csa]

I bit the bullet and bought a 123Ignition Distributor for my CS. A 1974 Euro spec RHD auto - Totally Stock.

It is the USB tune version and I can set up and enter curves from the Blue Books but from Stevehose' excellent post from 2014 - https://www.e9coupe.com/forum/threads/123ignition-distribu-install.16396/- It would appear these are quite conservative.
Steve posted some curves but unfortunately I am unable to see them. Maybe a victim of the Photobucket fiasco?

So hopefully rather than me trying to re-invent the wheel, I was wondering if anyone who has already gone through the process is able to send me a set of Curves that are suitable.

Carl

 

[Stevehose]

Are you going to use vacuum advance? Retard should be eliminated.

 

[westoz3.0csa]

Yes, I will be using vacuum advance taken off the Zenith ports.
My reference to retard was purely due to my Distributor having (I assume) vac advance & retard, ie 2 ports.

Once I thought more I realised that the retard would go - 123 only has one port.

 

[Ohmess]

Here is a curve I used on my prior carb setup. I currently am tuning my new carbs and don't have a picture of the current curve.

You don't want any advance to kick in until the car is running -- this makes for harder starting -- so I started my advance at 500 rpm. I have used vacuum advance with this curve as well, beginning at 26 Kp I added 10 degrees, dropping out at 60 Kp with my prior carb setup. This is not shown in the pictures. As Steve has probably mentioned, setting this is very car-specific given the condition of each individual engine and the variation in vacuum take off points. You want the additional advance in the middle of the demand, so it needs to be set so you don't add more advance when vacuum is low (hard acceleration) and the additional advance drops out when vacuum is high (over run).

If you haven't discovered this yet, you can view the vacuum that the 123 distributor is seeing my tapping into the display in the 123 tune software. I plug into my distributor with the supplied cable, leave the hood slightly ajar and use a USB extension cord to route the cable through the passenger side window. This allows me to drive around with the laptop in my passenger seat and read the vacuum and advance relative to rpm in real time. I haven't figured out how to log this data, but would like to do so. Nirvana would be to combine this data with afr data and a throttle position sensor.

 

[Stevehose]

It is possible to add retard with the 123 but that doesn't mean you should. Tonight i will post an example of a curve with vacuum advance that you can start with.

 

[westoz3.0csa]

It is possible to add retard with the 123 but that doesn't mean you should. Tonight i will post an example of a curve with vacuum advance that you can start with.

G'Day Steve,
Have you been able to find the vacuum advance curve ??

Rgds Carl

 

[Stevehose]

Sorry, traveling, will do asap!

G'Day Steve,
Have you been able to find the vacuum advance curve ??

Rgds Carl

 

[Stevehose]

Here is an example of one that includes a vacuum advance curve, the settings will have to be tweaked to account for the behavior of your engine based on cruise vacuum and when it drops out under acceleration.

 

[Ohmess]

Hey Steve - I notice you do not have a MAP starting point for vacuum advance. Why is this? I am using 1800 b/c I want to ensure I don't have additional advance at idle.

Carl -- anything to report?

 

[Stevehose]

It's because i am using advance at idle, it idles smoother, cooler (theoretically), and accelerates well from that setting. I manually advanced the advance at idle till rpms no longer increased then backed off about 5 degrees or so. That's an old curve i think my idle advance is 15 now.

Hey Steve - I notice you do not have a MAP starting point for vacuum advance. Why is this? I am using 1800 b/c I want to ensure I don't have additional advance at idle.

Carl -- anything to report?

 

[Ohmess]

It's because i am using advance at idle, it idles smoother, cooler (theoretically), and accelerates well from that setting. I manually advanced the advance at idle till rpms no longer increased then backed off about 5 degrees or so. That's an old curve i think my idle advance is 15 now.

That is very helpful Steve. My car is in pieces right now, but when I put it back together I plan to run a vacuum advance curve that looks more like yours. I did not post the curve, but if you read the description above I was running a similarly shaped vacuum advance curve that began and ended further to the left on the Manifold Advance Pressure scale. I didn't get a chance to test this at cruise, but nonetheless suspected this needed to change.

 

[Stevehose]

I am actually not using vacuum advance anymore, the curve I posted is from an old one so Carl could see an example. I couldn't detect any improvements in fuel economy etc with the vac advance so instead of constantly tweaking it I just eliminated it and just use the mechanical curve. I have managed to free myself from obsessing over the perfect afr range and vac advance under different conditions. Took a long time, but free at last.

 

[Ohmess]

I seem to recall the last time we shared a bottle of wine that you recommended I consider also limiting my obsessions about these things.

 

[TodB]

ob·ses·sion
əbˈseSHən/
noun

1. the state of being obsessed with someone or something.
   "he was consumed with getting the vacuum advance juuuust right with a devotion bordering on obsession"
   • an idea or thought that continually preoccupies or intrudes on a person's mind.
     plural noun: obsessions
     "he was in the grip of an vacuum advance obsession he was powerless to resist"
     synonyms: fixation, ruling/consuming passion, passion, mania, idée fixe, compulsion, preoccupation, infatuation, addiction, fetish, craze, hobbyhorse