[Diy_efi] Emissions Numbers...

[Mike Frels]

O2 gound is good to the exhaust manifold. A couple of weeks back I removed it, emery
clothed the bung surface and sensor surfaces, and retorqued it. I'v got gaskets 
between the manifold and heads to seal off a non-flat manifold seal surface and 
earlier O2 leak so I don't know if I am getting an optimum ground to the block. 
I was planning for this coming weekend to install an LT1 O2 sensor so I could wire
ground directly to the back of the head. Anyway...my scans show 160(lean) at idle/slow
and the sniffer HCs are low, so to my smog test unexperienced mind the results seem
to back up the lean condition. 

Also, my AIR system is functoning 100% and completely seals off flow from the exhaust
manifolds on closed loop. I have verified this more than twice.

Where can I do more reading on what the smog readings indicate?

Mike


-----Original Message-----
From: Adam Wade <espresso_doppio at yahoo.com>
Sent: Feb 15, 2005 8:50 PM
To: Mike Frels <mfrels at ix.netcom.com>, 
	A list for Do-It-Yourself EFI <diy_efi at diy-efi.org>
Subject: Re: [Diy_efi] Emissions Numbers...

--- Mike Frels <mfrels at ix.netcom.com> wrote:

> 15mph:
> HC(ppm) std-152 reading-108
> CO(%) std-.86 reading-.37
> CO2(%) 13.3
> O2(%) 2.3
> NOx(ppm) std-1146 reading-1635(*FAIL*)
> Dilution(%) std->6 reading-13.7

That looks frighteningly lean to me.  I know on
motorcycles, at "best power" you generally get
something in the ballpark of less than 1% O2, about
10-11% CO2, under 1000 ppm HC, and 5-7% CO.

The only way to get HC numbers that low, I would
think, would be at or near stoich with a three-way
cat, unless you run drastically lean.  Your other
readings sure look super-lean to me.

> If I remember right high NOx numbers are usually a
> result of high combustion temperatures due to lean
> conditions.

Well, conditions right around stoich, although you can
lower the NOx with spark timing.  I doubt you will be
able to make the numbers without a cat, but if you
can, it'll definitely improve things in the NOx
department to retard the timing, thus lowering peak
pressure, and thus combustion temperature.

> I am thinking that I may have an injector or two on
> the O2 sensor side of the engine that are either
> somewhat clogged or not opening properly at low
> speeds.

I think you probably have it backwards.  If it is in
closed-loop mode, which I am assuming it would be (it
would have to be to use the O2 sensor to adjust
fueling in real-time), then you are probably RICH on
the O2 sensor side, if anything, thus causing the
sensor to lean the mixture.

Have you checked your sensor to make sure that it is
well-grounded, and that there are no spurious signals
on the O2 sensor lead to the ECU?  Is there maybe an
air injection system that wasn't properly disabled?

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