Bench racing ecms

[Bruce Plecan]

-----Original Message-----
From: Scot Sealander <Sealand at clarityconnect.com>
Subject: Re: Bench racing ecms


Oh, TPS accleration is not in the fuel "equation".

>No.  It is a transient condition.  It is just an add.

Not being smart here <g>, but a+b=c, is that not an equation?.

>> What equation do you speak of here?.
>Well, the ECM's job is fairly simple.  Determine the amount of air (mass)
in the cylinder, multiply by inverse AFR, and then multiply by an >injector
constant to get the amount of fuel.
>So fuel PW = air in cyl/AFR * Inj const
>The trouble is getting the "air in cylinder" term.  Some like a MAF, so
>you have a airflow rate in g/sec.  Just divide MAF by RPM (adjust terms to
fit) and you will have the air in the cylinder.

>MAP method is a little harder.  You have to know how much the cylinder
volume is, and what the VE is under the operating conditions.  The air temp
and MAP determines how dense this air is.

>> What kind of time intervals?.
>Depends on injection type and operating conditions.  The higher the
>RPM and/or load, the faster the engine will respond to fuel rate
>changes.  TBI will take longer.

Sec.s/milliseconds, just an WAG.
>> You say you've run ecms, care to share any of the results!!..
>
>Yes, it makes a lot more sense to run them on a real engine.... ;-)

Running two ecms under identical conditions using something
like diacom pluses or a dual trace scope would be rather difficult.
>
>My personal opinion is that you get the code out, then figure out
>how the code works.  Then make the tuning changes to make the engine run
the way you want.  You can use bench time to confirm the changes that you
have made in tuning.
>
>To make it easier to use ECMs on the bench:  I got a 17x5x4 inch Budd box.

OK what's a Budd box?. Something trick or just a AL experimenters
box?.

 Used this box to mount, hmmm, 16+12 red and 16+12 black binding posts from
rat shack in four rows.  These correspond to the two connectors in the '747
ECM. Hack out the portion of the harness for the ECM connectors.  Wire then
into the Budd box connectors.  Makes connections to the ECM real easy.
>
>The box also has a connector for the wall wart with a loose black and red
>wire for power, and an ALDL connector (the car dash end) mounted, to
>allow easy connection to a scan tool.
>Works for me!
>Scot Sealander   Sealand at clarityconnect.com
>
>
Cheers
Bruce