Fw: BJYM and my modified BJYM is now online

[Bruce Plecan]

>>>I've uploaded my BJYM code which is for a '95 Chevy 1/2 ton truck, 350
>>>(5.7L), 4L60E, AC, 3.73 rear gears.
>>>My modified code contains mods for the following "enhancements".
<Snipped list of goodies>

>Insensitive clippage<
>>
>>Sounds like you have one neat truck.  I've got a 91 454SS (C1500)  running
>>about 1 bar of boost on pump gas.  A couple of things in your summary
>caught
>>my eye................
>>2) With the airflow potential of your base motor, you might want to
>consider
>>stepping up to something like a 177 or a 174 Roots?  You could spin it
>>slower, and probably get more air, and cooler air.  Or, have you thought
>>about a Whipple style screw charger?  Way more air and way cooler!  They
>can be reached at 1-209-442-1261.
>>
>>4) Where is your MAP sensor port location?  Below the supercharger, or
>below
>>the TBI but above the supercharger?
>>
>>5)  It is fairly easy to get rid of the rising rate regulator scheme, if
>you
>>want to "trick"  the calibration somewhat.   You can either rescale the
cal
>>for a 2-bar sensor (lots of work, and I don't recommend it) or continue to
>>use the stock 1-bar, below the TBI, and model the engine as a very "large"
>>engine, with equally "large" injectors.  You will need to know a few
>>specific addresses, but I am sure that they are available through the DIY
>>page.
>>
>>Here's how it works.........................Consider your 144 as an "air
>>pump", with its own RPM dependant VE curves.  Use the 1-bar Map sensor,
>>below the TBI, together with engine RPM, to step through the normal
>software
>>VE tables. You want to make the software "think" that the base engine
>>displacement is much greater than 350 cubic inches, say 700 cubic inches
>for
>>sake of illustration.   You also want to raise the base fuel pressure at
>the
>>injectors, to a constant level at which you would have sufficient fuel
mass
>>flow to feed your engine at a VE table value of  "FF" at the highest RPM
>>breakpoint of the tables.  So as to avoid excessive base fuel pressure,
you
>>could at the same time step up to BBC injectors which are available in
>>either 80# or 90# flavours, and will drop in wherever a Rochester injector
>>previously resided.  Let's assume 30 psi, with 80# BBC injectors, which
>will
>>give you about 250#/HR maximum injection delivery.
>>
>>Now, adjust the main injector scaling variable in the software (probably
>>KNEGRCST) so as to "tell" the software that you have a 700 cubic inch
>engine
>>with 250 #/HR injection capacity, instead of the stock setting of 350
cubic
>>inches and 110#/HR.  You must also change the EGR mass table values, in a
>>similar ratiometric fashion, if you have not disabled EGR through the
>>software.  (There are ways to disable the EGR, which would also correct
>your
>>Code 32 problem.  Someone on the DIY page should be able to help).  As an
>>example, my KNEGRCST was formed as the product of  "1461.5 * (one cylinder
>>volume in litres/injector rate in gm per second)".
>>
>>Once these things are complete, you can use the software VE table values
to
>>"cut-down" the fuel delivery rates, to match your engine's fuel
>>requirements.  No codes, no problems, and very consistent control over the
>>fuel, once everything is dialed-in.
>>
>>Too bad I can't give you any more specific details, but I have no idea of
>>what BJYM consists of.  I use this method in my truck, to control about
>>700HP and about 560#/Hr of injection capacity.  But, my PCM and software
>are
>>different.  Good luck, and stay in touch!

I find that terribly clever, and was wondering what ideas you might have
about using a 2 bar MAP sensor.  What always threw me off was that I thought
there
was a huge baro correction, but that might not be the case.  So 0'ing the
baro corrections, and disabling the malfunction flag, might "work"?..
  The "worst" I'd see would be disabling everything related to baro, and
maybe
opening up the BL/INT to dial in the calibration.  Of course this is in
reference to an off highway none emission application.
Bruce

>>Walt.