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

["Bruce Plecan" <nacelp@bright.net>]

> Yes BUT those errors are fairly small.. the blm is ito make
> up for humidity and crap... what I'm saying is that if an engine's flow
> charachteristics are changed.. maf will still tell you the amount of air
> going in with the same error that it did before the mods... with map,
> eveything goes out of whach...... map is based on pressure drop... plain
and
> simple.. you said yourself that vacume or pressure changes in a modified
> engine..

Lets back up for a sec..  Going from one cam to another, means the air
consumed at any condition will be different.  The engine doesn't want or
need a perfect 14.7 AFR at all conditions.  The more cam you use the more
finicky it will be to tune since tthe pikes and vallies get higher and
deeper, since the cam gets very narrow in it's peak operating range.  So the
MAF system if all it does is try for 14.7 is just a rough calculation of
what will just run the engine (even ignoring WOT).
   Either way everything goes out the window, just the MAF calibration is so
course that with the BL stuff it will about run the engine.
>
> 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?.
> CD coefficient of discharge.
> > 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.
> Tested the maf on a flow bench hooked up to a 52mm tb and
> plenum....
> Got maf to put out fairly linear from 0 to 10v.... think 10
> volts was some where aroun 600g/s...I'll have to check.
> So yes it is capeable..

Now that is terribly interesting.
Grumpy

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