[Diy_efi] Smog pump and emissions testing question...

[Mark Romans]

Retarding timing reduces peak combustion temps and helps emissions.
On my GM ECM, 1227165, the air is injected during open loop into the exhaust
ports just outside the head.  When the ecm goes into closed loop the air is
injected
into the 3 - way cat in the middle.  The first part of the cat does NOX
reduction and
the 2nd part does HC and CO reduction.  (And likes AIR injection).  When I
go to
WOT the air vents and no air is injected into the cat and it goes inert.
Mark

----- Original Message -----
From: "Perry Harrington" <pedward at apsoft.com>
To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
Sent: Monday, April 28, 2003 1:58 PM
Subject: Re: [Diy_efi] Smog pump and emissions testing question...


> On Mon, Apr 28, 2003 at 03:12:23PM -0400, Brian Renegar wrote:
> > I've got emissions testing coming up for my 91 Mustang.  Here in
Maryland,
> > they do the "road dyno" testing now.  I'm trying to prepare and have
> > everything tuned properly so it will pass.  The engine is fully built
with
> > twin turbos.  The thing I'm worried about the most is the cam, which is
a
> > Motorsport F303.  This particular cam is not "emissions legal", however
> > that doesn't mean it won't pass.  I've passed with another Motorpsort
cam
> > (E303), which has more overlap than the F cam does.  The F cam, however,
> > has more lift (.512 versus .498) and more duration (I forget those
specs),
> > and I don't know how that affects emissions.
>
> The emissions will rely heavily on ignition timing.  The Ford computer
runs
> closed loop at idle once warmed up.  The only thing to muck with then is
the
> timing.  Less timing reduces emissions.  I had to do this on my Mustang
when
> I got it smogged here in CA.
>
> >
> > So anyways, the other issue is that I have removed the smog pump and all
of
> > it's associated tubing and vacuum solenoids.  I was planning on just
> > installing the pump and running the hose directly to the exhaust, since
> > that's what the computer's strategy would be during warm
> > operation.  However, I just had an interesting conversation with a
> > friend.  He suggested instead of running the tube down to the exhaust
> > H-pipe, to run it to the back of the cylinder heads (which is the other
> > location the factory setup runs the smog pump to).  He said that the
longer
> > the exhaust gasses are in contact with the fresh air being pumped in,
the
> > more residual combustion (I guess you could say) will occur, and the
lower
> > the emissions.
>
> First, the banjo air injection on the heads is plugged up on most
vehicles.
> Carbon buildup impacts the tube and plugs it up, so this does nothing.  It
may
> visually pass, but past the first 3/4 of 100k, it definitely doesn't work.
>
> Okay, the strategy as I know it is this:  At startup air is injected into
the
> head.  Once the cats are sufficiently warm (probably a timer), the pump
then
> injects into the cats.  Ford used dual 2 way cats on the stock H pipe,
their
> injection didn't do much more than further the combustion.  Most
aftermarket
> dual cat pipes use 3 way cats.  This is where air injection actually does
something
> useful.  In a 3 way cat the air is injected between the intaks an exhaust
> stages and causes a further catalyzing process.  These cats will produce
> nitrogen and water, where 2 way cats do not.  This beneficial.
>
> As for the pump, if the hose routing is physically in the way, get the 93
> Cobra electric pump.  These lived down on the passenger side wheel well.
> Now route the hoses to the stock valves, but in convenient locations.
>
> Any intelligent (this is important) SMOG guy will inspect the system and
ask
> questions.  You must be able to explain how the system works and where the
parts
> are from.  I do not advocate disabling of emissions control devices.  I
want
> to have fun, but I don't want to help destroy the environment at the same
time.
>
> >
> > It sounds like a good idea to me.  But I'd love to hear what others have
to
> > say about this too.  BTW, I have a programmable chip with data logging
> > capability, so I will be able to decrease the timing, and set all fuel
> > trims to 14.7:1.  It still worries me some though, that I have forced
> > induction.  If the dyno operator decides to give it too much gas, I will
> > HAVE to add some fuel, or risk blowing the motor up.  And from what I've
>
> Again, the Ford computer runs closed loop until: WOT or "high load".  You
> can adjust the high load timer to a higher number or run the stock 2
seconds.
>
> WOT is exempt from SMOG testing.  He will test your vehicle at a given
speed
> on the dyno.  Likely to be 40-45MPH in 4th gear.  If you have the proper
gear
> ratios (not 4.10 or higher), this is about 2000RPM.  He may test your
vehicle
> at 2500RPM instead.  The Ford EGR code doesn't open EGR until 40MPH, so
that's
> a magic number.  Ford didn't add any lean-cruise until much later, so it's
> going to be closed loop for the entire test.
>
> > seen, and heard by others, the dyno operators here know absolutely
nothing
> > about how to properly run an engine on the dyno.  Things like shifting
too
> > soon, and then having to floor the gas in order to keep the rpm where
it's
> > supposed to be during the test!
>
> Well, they can only test at steady state throttle and speed.  Your turbo
motor
> shouldn't have any problems with keeping steady.
>
> >
> > Brian
> >
>
> I've got an '89 Mustang GT, 306 with TFS TW heads, E303 cam, TFS street
intake,
> forged pistons, roller rockers, 24lb injectors, and it passed smog in CA
without
> having to pay the tax (ya know, here's $200 bucks, make it pass).
>
> --Perry
>
> --
> Perry Harrington Data Acquisition & Instrumentation, Inc
> perry at dainst dot com http://www.dainst.com/
>
> Those who would give up essential liberty to purchase a little temporary
safety
> deserve neither liberty or safety. Nor, are they likely to end up with
either.
>                              -- Benjamin Franklin
>
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