zguy36 Posted April 4, 2006 Share Posted April 4, 2006 Here is a post that I put up on the megasquirt forum... just thought the info might be useful here too. zguy36 MegaSquirt Newbie Joined: 20 Jul 2005 Posts: 10 Posted: Sat Apr 01, 2006 4:54 pm Post subject: predictor algorithms What is the difference between the ignition predictor algorithms? I couldn't really see much info on the advantages of each. Trying to diagnos a stumble at high rpm, I switched from 'last interval' to 'first derivative, second derivative'. When I made the switch, the engine has detonation problems that it didn't have before. Ie detonation at 10psi compared to 20psi. I don't have a timing light readily available, but seem to think that the timing has probably been advanced due to this switch, since detonatoin is such a problem now.Back to top zguy36 MegaSquirt Newbie Joined: 20 Jul 2005 Posts: 10 Posted: Mon Apr 03, 2006 8:26 pm Post subject: So, it seems as though this post is a lame duck. I'll answer my own question, at least for what I wanted to know. I stuck a timing light on the car and ran it up through the rpm. To make it easy, I set all entries in the table to 10 degrees advance. All the settings seemed to work pretty well, except for (1st derivative high, second derivative low). This one made the tach jump around and it ran like "crap". The others seem to retard the timing about two degrees at 6000 rpm, not really a big deal. The big deal however, is that when switching between the different predictors, the base timing changed as much as 20 degrees. I had no idea that this happened. When I first got the squirt up and running, I had it set to the default and based the timing there. It ran like "crap" so I switched it to 'last interval'. This made my timing 13 degrees retarded from the original setting. I didn't realize this, and you can imagine how happy I am not that I found it. Oh so much more power! (I had been driving it like that for a month!) Anyway, watch out for this so no one else gets burnt. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 4, 2006 Share Posted April 4, 2006 Interesting, thanks for the heads up. Quote Link to comment Share on other sites More sharing options...
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