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| Vacuum Advance Curves https://www.ausmini.com/forums/viewtopic.php?f=5&t=98980 |
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| Author: | thomas_hb [ Tue Aug 20, 2019 9:32 am ] |
| Post subject: | Vacuum Advance Curves |
Hi everyone, I recently installed a 123 Tune+ distributor in my Mini K. It is an otherwise bog stock 1098 with a 1.25" SU in very original condition. While I've found the standard curve as programmed with the distributor to be functional (indeed, it already performs better than standard points and condenser ignition), I wonder if I could see some improvement by customising the vacuum advance curve. Does anyone have any experience with custom advance curves (whether in the 123 unit, an accuspark blackbox or by other more traditional methods)? I would appreciate some suggested curves to experiment with that might better suit the A-Series engine rather than just what came out of the box in the 123 (which is designed to work with all manner of 4 cylinder engines from BMC, VW, Alfa Romeo etc). Cheers, Tom. |
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| Author: | simon k [ Fri Aug 23, 2019 11:19 am ] |
| Post subject: | Re: Vacuum Advance Curves |
Vacuum advance is an economy device - as you close the carb butterfly the amount of vacuum in the manifold increases, and the vacuum advance mechanism in the distributor advances the timing. Advancing the timing allows the engine to make the same power with less fuel but is very likely to have pre-ignition under any load... but when there is load, your foot opens the butterfly and the vacuum advance mechanism retards the timing again. So, you can't get the engine to "perform" any better by playing with the vacuum advance, but you may get a little bit of fuel economy improvement For reference, my engine runs well with 39° at full load (100kpa) from 2700rpm up, and 47° at full vacuum |
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