Quote:
Originally Posted by SSLance
and this graph...
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OK... is this your boost retard graph, if so it is currently doing nothing!
This is an "example" curve to dial in 10 degrees of retard progressively with 10 PSI of boost. Your car is naturally aspirated - correct?
The 14.75 point you see on that chart where the red and blue meet is "0" boost -or- "0" vacuum. It is the 14.75" reference point of atmosphere, the same pressure as your outside air.
If you are not running boost, to get 14 degrees of "advance", do the following: From 0 to 5 PSI on that chart set the "degrees of retard" to "0" (same as it is now). Then, from 5 PSI to 14.5 PSI have the chart slope down from "0" to "14" degrees of retard. From 14.5 PSI to the right leave it at "14". After setting this curve, set your timing to your current 7 degrees initial with the vacuum unplugged from the MAP sensor. When you plug in the MAP if the vacuum is 20", it should jump to 21 degrees. If you have a hand vacuum pump you can test this through the range to make sure it does what you think. Anytime you want to disable the advance and go back to your base curve it can be as simple as unplugging the vacuum line from the MAP and capping the manifold port. This will dial in the full 14 degrees "boost retard" and effectively put you bask to your 7 degrees base timing.
I took the example they sent and superimposed the curve I described as a purple line, why MSD does not illustrate this is beyond me. If you like the outcome and want to dial in more, say, up to 20, then instead of going to 14, go down to 20 at the same point and reset your base timing.