I'd have to see that to believe it Shane...40 degrees or less (for the
actual engine block) is very cold. Plus, once you start the engine, it
doesn't take long at all for the block to start heating up.
If you have any smoke coming out of the tailpipe...there's something wrong.
Black Smoke= Rich and White could be either Oil or Water (Depending on the
tint and smell of the white smoke). If you're referring to the steam from
the hot exhaust hitting the cold (40 or below) air...you can see that even
when you're engine has been running for more than 10 minutes.
On the engine temperature issue...we'll have to agree to disagree.
BTW: On the algorithms....that just saved me from some excessive research
(MAF Meter and MAP Formulas). I'll explain in detail later but the next
project, which is already in progress, requires some programmable logic for
the "conversion". It's too early to tell how the truck will respond...but
it look promising (in the lab).
Regards,
- Bernd
-----Original Message-----
From: owner-dakota-truck@buffnet.net
Subject: Re: DML: Gas mileage to crap?
I disagree with that temp range being a "requirement" for Closed-Loop
operation -
mostly because I have watched late-model Dodge vehicles go into closed-loop
(from a
cold-start) when outside as well as engine block temperature less than 40
degrees.
It is my understanding that as soon as the PCM can determine that the O2
sensor is
giving a "valid" signal - then it can close the loop and provide as close to
a 14.7
to 1 ratio as possible as required by federal emissions. This is why almost
all O2
sensors in todays production vehicles are of the self-heating variety - to
enable
the PCM to close the loop sooner and thus lower emissions. The way the PCM
determines if the O2 sensor is giving a valid reading is by monitoring the
O2 output
voltage for the first time it crosses the 0.45 V threshold. Because our O2
sensors
are heated - this ALWAYS occurs (during cold start) in less than 3 minutes.
Ever
wonder why the color/amount of smoke coming out of the tailpipe (during cold
start)
changes after about 1-2 minutes?
Temperature of an engine (or outside temp) has nothing to do with the A/F
ratio
measured at the tailpipe. Think of it from the perspective of a sensor
stuck into
the exhaust stream. It is just reading oxygen content and comparing it to
the
outside/ambient oxygen content. It will sense an A/F ratio whether or not
the truck
is running, hot, cold, under water, etc.
I agree - and that is why there is a special mode in the PCM for that -
warm-up
mode. While warming up (temp less than 140-150) there is an enrichment
value
added. Look at the formula at the following URL:
http://www.diy-efi.org/efi332/equations/algorith.htm in the section on Fuel
Enrichments.
The reason I know all this is because I am nearing completion (after 3+
years) of a
custom PCB (Motorola 68332 based) that will provide both fuel and spark
delivery to
any gasoline engine (1-8 cylinders). I hope to test it on a 3.0L Nissan V6
in the
very near future.
Latr,
Shane
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:58:50 EDT