Re: 340 Dak

From: JT McBride (James.McBride@GDEsystems.COM)
Date: Fri Mar 06 1998 - 11:55:30 EST


>Jt writes: >>one complication is what to do about the open-loop fuel
>metering map in the computer. I am afraid those 22 extra cubic inches
>Wouldn't it relearn???? If not then get a RAM computer for a 360.
>I've been led to believe that the computer would "adapt", though.

The base map is fixed. The computer never has any reliable data to
"learn" from at startup, so the open-loop map is tied to the factory's
knowledge of how to start a particular engine, given ambient pressure,
and temperature. Once the O2 sensor output comes up, along with engine
temperature, the closed-loop map CAN be updated. That controls how the
injection timing will be changed as you romp on the throttle, let the
engine coast, etc. The O2 sensor doesn't respond quick enough to be
useful for engine control changes, but after the engine is operated
steady-state at a particular throttle setting, the map can be adjusted
by what the O2 sensor is saying about the mixture.

At least this is how the Chevy controllers work (with knock sensing
thrown in for good measure) and how I presume the less capable Chrysler
computer is designed. Ford also works this way.

I've been planning to go closer to 360 cid, so the Ram 5.9l SBEC could
be used. But I really like the magic of the 340 - spins well, makes big
horsepower. I also really want to build a distributorless ignition.
And now coil-on-plug is available from the Mopar parts bin (Concorde).
We'll see. If I engineer one, I'll sell it too.

Jim

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