Changing 165 fuel delivery

[Romans, Mark]

The MAF calibration is affected by
1) cutting out the screens.
2) cutting out the heat sinks
3) modifying air filter housings

I had BL at 140-150 at idle and 115 at cruse.  So I put the injector
constant back to stock  (I had put in 19 lb injector constant on 23 lb
injectors).
I looked at BL and added the correction the ecm was making % wise to the maf
calibration.  It seemed to be off about 10% in the below 15 grams/sec range.
I raised all the settings by 10% and the BL came into line at idle.  BL was
fine at higher maf readings.
The maf will flow 750 cfm at 28" of water.  (Actually a bit more) but the
software only reads to 255 grams/sec so it is in effect an Alpha N system
once the maf maxes out. I max out the maf at about 4700 rpms with my 355.

Mike I'm thinking about converting to a 730 too.

Mark

----- Original Message -----
From: "Mike Rolica" <mrolica at meridian-mag.com>
To: <gmecm at diy-efi.org>
Sent: Thursday, June 15, 2000 10:48 AM
Subject: RE: Changing 165 fuel delivery was "General tuning question -fuel
economy"


> Ok  FROM WHAT I'VE FOUND  mass air is a direct measurement of the amount
of
> air going into the engine.  The maf vr rpm is just a calibration of the
> maf.. as you would calibrate a mass flow meter or any other process
> instrumentation.....
> Map, is using a differential pressure to come up with an amount of air..
ie
> it is similar to measuring flow by measuring the pressure drop across an
> orifice plate.. the engine is the orifice plate in the pipe.. get it??
> Now with an orifice plate, you need some constant or value that is
> particular to it to convert the pressure drop to flow rate.. for an
orifice
> plate it is the coefficient of discharge..
> The ve tables represent the coefficient of dischare of the engine ...in
> simplistic term(so don't flame me... I'm not about to go into the
theory!!!)
> From the pressure drop indicated from the map sensor the ve tables relate
> that pressure drop to a flow rate...except for an engine the cd is always
> changing....
>
> 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....
> For map since the ve represents the cd of the motor... different motors
will
> have differing cd's
>
>
> 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...
>
>
> 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.. 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....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....
>
> There is also tons of other stuff but this is getting prety long..
> Mike Rolica
> Plant A,
> Magnesium Products Division
> Strathroy
>
> (519)-245-4040  Ext. 265
>
>
> -----Original Message-----
> From: Rick Lindstedt [SMTP:rick at mafb.org]
> Sent: Thursday, June 15, 2000 12:44 PM
> To: gmecm at diy-efi.org
> Subject: Re: Changing 165 fuel delivery was "General
> tuning question -fuel economy"
>
> Marteney, Steven J. wrote:
> >I haven't got my copy of tunercat yet, but it's coming, or
> the rather the
> >check is going.  In the meantime, to increase fuel across
> the board, TC has
> >two settings for injector flow rate, single and double
> fire.  Is that what I
> >can use for this?  I remember a couple of months ago there
> was a lot of
>
> I dont know about that one..
>
> >hand-waving about single-fire and double-fire and what the
> difference was.
> >Hate to bring it up, but was there a clear answer that came
> out of that?
>
>
> No definete answer came ...I was the one that brung it up in
> the first
> place.. =/ I am still wondering if there any real
> gains/losses from
> switching from one to the other or if there are any...
>
> >Also, in the 165, is there an equivalent to the VE tables
> as in the speed
> >density stuff?  I didn't see anything in CATS function list
> other than "Mass
> >Air Flow vs. RPM, (Diag)" and the injector flow rate
> constants.
>
> That all I saw when I looked into the CATS...  I use GMEPro
> tho..
>
> Rick
>
>
>
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