[Diy_efi] 305/350 Swap 10-month Progress Report...

[Mike Frels]

I fixed my lean condition and got a 10-20 reduction in my BLMs when I did something really simple. I removed the #24 Accel injectors that I had put on my car while I was having cleaned the #24 LT1 units that I had clogged up with a really stupid mistake. When I restarted with the cleaned LT1s back in my idle BLMs dropped from 160 to 140 and all other ranges dropped close to or the same amount.

I plan on going back to the same smog station and ask them to sell me just a run on their smog treadmill. The results should be more meaningful this time in my tuning from now forward.

Mike

-----Original Message-----
From: "Marcello A. Belloli" <mbelloli at speedymotorsports.com>
Sent: Mar 20, 2005 11:56 AM
To: Mike Frels <mfrels at ix.netcom.com>
Subject: Re: [Diy_efi] 305/350 Swap 10-month Progress Report...

Mike,
     You can have no change in CO (which would show in blm) by retarding
timing.  But have serious reductions in NOx.  I thought that was what
we were trying to correct.  Your Hi BLM's are a lean condition in
relation to the map in your computer for fuel trim, but not
necessarily a lean running engine.  Can you get into the chip on your
computer?  First thing I would do is move the limits for block learn
way up to something like 200 or more.  Then run it and see just how
much higher the correction goes.  Get an idea of exactly how far off
you are.  I'm guessing 160 is the rich limit on your system as is, so
you've hit that limit and so all you know is you need more fuel.  The
question is how much?  At the same time put a Wideband O2 or 4 gas
analzyer and see what the real world readings are.  Before the CAT of
course.  Clamp off any air injection so you see what is really
happening.  Lamda 1 or A/F of 14.7:1.  Most cars run in or around
.5-.6 co in close loop.  If you are in fact seeing a co reading .5
with a blm of 160.  your feedback system is working.  You will need
to make corrections to your fuel system.  If the co is much higher
(above 1%) you have either air leaks in your exhaust system, or a
problem with the o2 sensor.  We get lots of cars with air injection
management valves that are leaking and causing just a little extra
air in.  Just enough to drive the co up over 1%, and failing the
smog.
     I in no way know everything.  That is for sure.  But I spend most of
my days making cars that don't pass smog pass.  We are having to get
more creative every year to keep the older cars on the road.  As an
example - We are now seeing a lot of late 70's trucks that are
failing for CO.  These carbureted vehicles.  What we are finding is
the Power Valving system as is, is coming on too soon for the dyno
testing.  The truck would pass the two speed idle test without a
problem.  But the extra load is engaging the power enrichment systems
on these trucks, and they are failing for CO.  I honestly don't think
there is anything wrong with the trucks. It is a problem with the
smog check program as it is.  But we can't fight it.  So we are
modifying the carburetors to hold back the power enrichment, and
putting bigger jets in to compensate.  The end result is lower co
emissions in the range they are now testing.  But still plenty of
fuel enrichment.
     Have a good one.

Marcello








> After retarding the base there was no testing done. The only thing I
> looked as was subsequent scans. They showed absolutely no perceivable
> reduction in BLMs. 160s were still 160 where they were before changing the
> timing. I checked scans after a couple of days driving and still no
> change.
>
> Mike
>