Ernest,

Great diagnostics there.  Let us know how the MegaSquirt works out.

Mark

On 5/16/12, Ernest Christley <echristley@att.net> wrote:

I cleaned the plugs, but they just kept getting flooded, and despite the
modifications I made to the intake manifold, I
was still getting fuel pooled in there.

I moved on to checking the spark.  The timing light was only flashing
occasionally, and I noticed that my VR sensor was
mounted so that it was almost in front of the toothed wheel.  I have some
new tools I didn't have when I originally cast
the mount, so I cleaned it up, and trued it.  Timing light was still
sporadic.  Plugged the wire into a scrap spark plug
and sat it on the engine while I cranked.  Nice, consistent blue-white
spark.  May have been there all along, but at
least my VR sensor mount looks nicer.

I've got new fuel, good compression, and good spark.  Deep breath, back up,
and compare what I have now to what I had
when it was running back in November.  I consult TunerStudio (the user
interface I'm using to my engine controller).
The only thing significantly different is that I converted from using
Speed-Density to Alpha-N.

Background:  MegaSquirt has several, user-configurable ways to determine how
long to have the fuel injectors spray. One
way is to measure the manifold pressure and combine that with the RPM.
Another is to look at where the throttle is and
combine that with RPM.  Both are just secondary measurements of how much air
the engine is swallowing, and have a whole
slew of corrections and modifications for various conditions.  Tuning
involves filling numbers into a table.  Across the
bottom is the RPM.  Up the side is either the throttle position, or the
manifold pressure.  For each cell you specify a
volumetric efficiency as a percentage.  You've already specified how long
the injectors would spray for a 100% VE cycle,
so the cells essentially become a percentage of that value.  By switching
modes, my table no longer resembled reality.
Instead of picking up the value of 43 from the table while cranking, it was
picking up a different cell that had 93.
More than double the required fuel.

I switched the setting back, and gave it a try this morning.  It took about
30 seconds of spinning while it was
obviously trying to kick off before it caught up and ran smooth at 1500 RPM.
 It has taken two weeks since I got
everything painted and tried start taxi testing, but I'm now back in the
game.

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