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post #17 of (permalink) Old 08-11-2017, 03:49 AM
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Join Date: Jun 2011
Location: Avalon Beach, Australia
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Originally Posted by Gubi View Post
Man, that's crazy retarded at idle. But you can't fix that with the base 123. That's why the tune version is a better option.

Tom Sahines posted the below on the 750/101 forum. Note that the octane values he states are PON and are about 5 less than Australian RON.

I guess if it idles okay you're sorta fine, but -12 at idle is definitely suboptimal.

"I have evaluated the early 123 distributors and come to the conclusion that there are no good usable curves. The early 123 distributors simply copied many of the original Alfa curves which are no longer appropriate. Remeber that when those curves were designed pump gas was more like 95 octane vs the 91 octane we can get today. My dyno work has shown that with today's gas 36 to 38 degrees of total advance is optimum. Most all of the motors I build want to have 6 to 8 degrees of initial advance for a good idle and off idle performance. As noted when you add the 37 degrees of advance from the 123 built in curves you end up with about 44 degrees of total advance. At that level you will have engine knock and damage will occur. The only option is to use a high octane race fuel or set the maximum advance to 38 degrees and live with a crappy idle."
Hi Gubi,

The idle is perfect, at around 800-900rpm steady and the car starts with a half turn of the key without choke in the mornings (preceded by four or five pumps of the throttle). My friend who has a tarmac rally 1750 can't believe how well it drives.


"horsepower sells cars - torque wins races".
1969 MK1 1750 GTV
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