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Old 10-01-2013, 07:05 PM   #4 (permalink)
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Originally Posted by Sam Powell View Post
However the cooler weather has caused some pre-ignition at 3000 RPM under light load right before shifting.
You could create a true DFCO configuration and it might stop the pre-ignition, when you fully lift your foot off the throttle and RPMs are above a threshhold (maybe 1200rpms) just have them completely off, you could then learn to just fully lift your foot before shifting and pre-ignition would be minimized because there would be no fuel.

Originally Posted by Sam Powell View Post
Tell me what you mean by "loaded up". What is 40-80%. Percent of what? Thanks. Car cruises at 2000 rrm at 62 MPH. Compression is 8.5:1. It was intended to be turbo charged, but that never quite worked, so I removed it. Now economy is the game.
by loaded up i mean a percentage of max output, lean burn works best with more fuel (and more load and air), lots of turbulence and warm temperatures,
you might consider a warm intake mod and see if it affects knock.

Originally Posted by Sam Powell View Post
One of the things I have tried to figure out is if at 40 MPH it is more efficient to cruise in 5th at 1200rpm, which it will do, or in 4th at 1700 rpm. The AF ratio gets leaner in 4th, and the map reading drops. But I have not had the time or commitment to go out and drive 100 miles at 40 in 4th gear and then drive another 100 miles 5th an compare actual mileage. It would be difficult to find a place in the east coast here where one could actually do that. I suppose if I worked the math maybe I could figure it out. The computer does give me milliseconds of injector open time as one of its readouts. But it does not do the match as scan gauge does.

Can't help much on this, generally higher load trumps lean burn but only to a certain rpm which varies from engine to engine.

My guess is the lower rpm wins as the difference between 4th and 5th is too great on a relatively sizable motor.
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