Unusual problem with LH 2.2 system

[James Boughton]

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Hi to everyone,
	This is the first time I've responded to anything on the diy_efi list.  =
I hope my input can be of some use.  I have more of an engine background =
than electrical (or computer) so you guys have pointed me in the right =
direction on a lot of the EFI hardware that I am looking for.  Thanks.

Now a few questions for John Bertram.  Did you install the Saab APC =
knock sensitive boost pressure control system yourself?  Are the LH 2.2 =
system and the EZK 117 system OEM components?  OEM systems can run very =
rich at wide open throttle (WOT) for a number of reasons (I am assuming =
that 12-14 psi of boost is WOT?) including catalyst temperature control, =
exhaust valve durability, or possibly knock control.  This is NOT =
10%-15% rich for power improvement we are talking 25%+ here.  NOx =
control is currently not of concern to OEMs at WOT since emissions =
cycles do not include any WOT operation, yet!  US06 is the new cycle =
that the EPA is instituting to force manufacturers to operate at =
stoichiometric for approximately 2 sec. under WOT conditions.  But, back =
to the question at hand.  When you lift out of the throtlle there is =
typically a routine that reduces the pulsewidth for a short time because =
fuel vaporizes more readily at lower pressures and the puddling in the =
intake manifold will cause a short period of over rich condition if this =
routine is not implemented.  In my experience, however, I have never =
seen a car spew black smoke just because this routine was not =
functioning.  As a matter of fact this routine wasn't used by some OEMs =
until relatively recently.  It sounds to me like some portion of your =
steady state calibration is amiss.  Possibly your base fuel surface is =
wrong since it sounds like you have made some hardware changes to the =
engine.  If it is possible to drive steady state in the condition that =
is causing the black smoke you can easily find out.  I am not familiar =
with calibrating turbos (maybe you can teach me something here), but if =
it is possible to hold around 3psi of boost and some of your higher rpm =
operating points for about 5 seconds you may find your problem.  Also, =
when you lift off completely you are probably going into decel fuel =
shutoff (DFSO) and thus no black smoke.

FYI on O2 sensors.  The frequency of most systems for feedback control =
of the fuel/air mixture is around 2-3Hz on the high side.   There isn't =
anyone who knows the answers on catalysts (or if they are they aren't =
sharing it with anyone I've worked with) so closed loop fueling is full =
of opinions and question marks.

Hope this info is helpful, but it may just make things more confusing.  =
Such is the world of IC engines and control systems.

Jim Boughton
boughton at bignet.net
Owner, Boughton Engine Systems Technology

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