Bench racing ecms

[Scot Sealander]

Bruce Plecan wrote:

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

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


> 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.

> Since the content search part of the archives
> is down, would you share dates of these preachings..

It started in gnttype.  I posted to the f-body list a time or two.
Finally quit.

> >That's what TPS is mostly used for, transients.
> 
> Last paragraph it didn't, hmm.

I don't get it.  I consider the transient portion most important, as
that is the most aggravating part if it doesn't work.  The bog when
you step on the gas can be annoying.  ;-)

 
> 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.


> 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.... ;-)

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.  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