123 Ignition Vacuum Adv, Learn me on some vacuum |
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123 Ignition Vacuum Adv, Learn me on some vacuum |
nditiz1 |
Jul 11 2018, 06:59 AM
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#1
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Senior Member Group: Members Posts: 1,182 Joined: 26-May 15 From: Mount Airy, Maryland Member No.: 18,763 Region Association: MidAtlantic Region |
Ok so I'm currently running the 123ignition dist on my 2056 with dual webers. I read the instructions and don't understand the mapping. I also don't know how it all works together. Can someone educate me on the vacuum adv and what curve would be best? As the rpm's increase it creates more vacuum thus creating more adv, but if I already have a curve setup to go from 12 degrees at idle to 28 degrees at 3000+ will the vacuum adv move the timing even higher once it is hooked up and mapped?
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Mblizzard |
Jul 11 2018, 11:14 AM
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#2
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Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
To echo what Mark said, after running the 123ignition on my 2056, the vacuum advance is not necessary.
Look at the literature that shows the vacuum advance start, vacuum end, and degrees the vacuum is effective only over a short range and it is quickly overtaken by the programed advance. As shown in the original Bosch dizzy information (note this is a representation of the curves and the values have to be doubled to read correctly) shows that at 3500 RPM you get a total of 22 degrees advance which matches the 123 numbers. Yes I know that you are thinking at 3500 rpm advance should be at 27 degree. True but the engine is not designed to fire at TDC so there are about 5 degrees to account for that fact. Looking at the dashed line for vacuum advance it shows that the vacuum is not additive meaning it will never advance above the 22 degrees due to vacuum. It only helps the change occur faster. On my 2056, I used the negative advance because as with the stock engine, with the timing set to give you 27 degrees at 3500 rpm it results in more timing at idle which will give you more RPM. The higher timing at idle gives you more RPM than the 900 you want so you can take some of that out using the negative vacuum settings if needed. Using curve B allowed me to adjust the idle into the perfect range. You may or may not need to play with the negative vacuum depending on you idle adjustment. Attached image(s) |
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