Changing 165 fuel delivery was "General tuning question -fuel economy"

[Bruce Plecan]

> Ok  FROM WHAT I'VE FOUND  mass air is a direct measurement of the amount
of
> air going into the engine.

Nope, it's a calculation, Just the electronics to it are self contained
rather then a MAPs where it's done in the ecm.
It references MAF to a voltage drop,  this voltage drop assumes the humidity
is a constant.  Also, assumes the O2 percentage is a constant.  Both are
errors, if it was accurate there would be no need for feedback.
Just cause something is called something don't make it so.  Look at the
knock detector, it's not a knock detector, it's a noise detector tuned for a
common freq. of knock.
  If they were as they claimed life would be a piece of cake for tuning.
If the MAF and injector calibrations were right, then you would never have
to change any of those variables.  All you'd ever need to do is pick the
right MAF for the HP level of the car, and it's matching injectors, and ecm.
Guess what don't work out like that for the gm's.

snip

> So for a maf application.. the tables theoretically should not change for
> any motor you put the maf sensor on.. as long as that engine is within the
> span of the maf..   once the signal from the maf is calibrated to a
> flowrate... it should not change on any motor....

Assuming the MAF theory was accurate, and since it's not then tinkering is
needed.  Changing Air Filter Types can effect the MAF since the turbulence
of the air going across the wire changes.

> For map since the ve represents the cd of the motor... different motors
will
> have differing cd's

MAP has to be tuned to a specific engine, yes.  cd?.

> As disscused before on this list.. the maf runs into trouble with high
perf
> engines because the engine pull more air than the ul of the maf.... Or the
> range of the maf is to narrow....if their was a maf that would measure a
> higher amount of flow it would be ideal.. cept you would then have to edit
> the tables to reflect the output of the maf to actual flow rate...
another
> option that was discussed was to somehow patch the code so the maf range
was
> 16bit instead of 8.. hence doubling the range..... I'm working on that
right
> now by adding a table like the ve on the 730...maf high and maf
low....where
> 255=255g/s and max on maf high would be 255 or 510g/sec.. so that one the
> maf sig reached 250 or so it would switch to maf high.. (there would also
> have to be compensaion for hysterisis  ie goto maf high at 250g/s  then go
> to maf low at  30g/s.. there is also some other avenues I'm looking at...

Have you hooked a scope to see if the MAFs output is capable of reading a
high gms/sec?.  If you have what did the numbers do, if you don't mind
sharing.

> Now that we have the air covered, we have to let the ecm know how
> much fuel to mix with that air.... Lets say the maf is calibrated..

Kinda a big jump to get there thou.  The MAF is always reading behind the
actual flow across it other then steady state.  The system is little better
then Alpha-N in my book.  It seems to be more like a Apha-N that fine tunes
cruise mode with the MAF.  That's why they can run so good for diagnostics
with no MAF signal.  The MAF is useless in sudden transistions.  MAP is dam
near real time the errors is in the diam lenght of the sensor line.

then it
> has to know the fuel flow  it gets this from the injector size. From the
afr
> goal  ie 14.7:1 it now knows how long to keep the injector open in order
to
> get that ratio... some people fiddle with the injector size to fool the
> ecm.. I tend to like to calibrate the maf.....so the maf tables are
> right....

as possible.   As Possible varies the second you get away from the oem
ducting.

then put the actual g/s of fuel my injectors put out  (at their
> pressure) and change the a/f ratio till it is where I want it.... Then iu
> tune the spark  back to afr... ect..  the maf tables can also be changed
if
> you fingd a lean spot in your range .. but if calibrated right this should
> no happen... also the pe functions should be looked at in order to get max
> performance out of the motor..cause diff motors have differing likings for
> the amount of fuel you need when you mash the gas....

Motors by application.  Vehicle weight gearing under hood air flow, all play
a part.
Grumpy

> Mike Rolica


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