Join Date: Jun 2005
Location: Westlake Village, CA
i compiled this chart comparing curves, for when i finally get a 123 Tune for myself. the stock USA 2L vacuum advance is included. the stock curves average out the factory range per dizzy, and use the factory static setting. the Jim K. and Alfaholics curves are third party info from the BB, so i cannot verify their accuracy.
if you program yours for more than stock idle speed "mechanical" advance ("initial advance"), i would use a lower max vacuum advance at idle vacuum. for example, many engines seem to like around 20* of advance at idle. so if you set your static timing at 10*, i would start with a max vacuum advance setting of 10*. 10* initial +10* vacuum gives 20* at idle. then, to optimize the settings later, you can turn up or down your vacuum curve if you do or don't hear pinging under certain loads.
one thing interesting i noticed, is that the stock Alfa vacuum advance starts pretty late, around 10 inches Hg of vacuum. the american V8s i work on usually have their vacuum advance starting between 0 and 5 in. Hg.
looking at the 123 Tune charts above, i like how they use Manifold Absolute Pressure, so it looks like you can also retard for boost pressure!
i notice only 7 points on the the 123 Tune centrifugal curve above. the instructions i downloaded say you can input up to 10 points. is that true?
Dionisio di Fiflos
73 GTV - 81 GTV-6 *R.I.P.* - 65 Mustang GT Vert - Honda Hawk GT - Yamaha FZ6
Last edited by darth dino; 05-20-2014 at 11:22 PM.
Reason: higher quality photo