Geoff, show me the evidence O2 sensors are primarily for cat performance.
If you've ever seen a fi system go into a bad full rich open loop state,
you'll see the cat is REAL efficient. Like white hot efficient.


"Geoff" wrote in message
gy.com...

"lifespeed" wrote in message
om...
"no one" wrote in message
...
Now I got a lot of flak a couple months ago about using O2 sensors in
marine
applications ( a statement was made that O2 sensors are only valuable
for
emissions and catalyst health - which I personally do not agree with
but
am
not in a position to argue)

Comments on closed loop aftermarket MPFI marine applications???

You can do aftermarket SEFI, closed loop with O2 and other cool things
too. Costs money and effort, but it does work, and work well.

What do you mean by "work well"? Is it as good as open loop or measurably
better? Are there noticeable gains in power, torque, startability,
driveability, fuel economy, and/or smoothness? I still maintain that
feedback fuel control exists only to keep a catalyst operating at peak
efficiency. Even closed loop systems go to open loop enriched conditions
under max power situations and/or for the sake of smoothness. I can see
that maybe a closed loop system might be slightly better on gas but if
it's
not controlled well then you're playing with fire. Otherwise I think
you're
adding complexity for minimal gain. If someone wants to experiment. by
all
means go for it - that someone just won't be me.

"no one" wrote in message ...
Geoff, show me the evidence O2 sensors are primarily for cat performance.

Here is a training document from Toyota. Read the first line of the
document #37- "oxygen and air/ fuel sensors"

http://smccd.net/accounts/sullivank/

If you've ever seen a fi system go into a bad full rich open loop state,
you'll see the cat is REAL efficient. Like white hot efficient.

The problem is with three way converters. Read document #64 from the
same link it will explain the need for tight fuel control on catalytic
converter equipped engines.

Hope this helps.




"Geoff" wrote in message
gy.com...

"lifespeed" wrote in message
om...
"no one" wrote in message
...
Now I got a lot of flak a couple months ago about using O2 sensors in
marine
applications ( a statement was made that O2 sensors are only valuable
for
emissions and catalyst health - which I personally do not agree with
but
am
not in a position to argue)

Comments on closed loop aftermarket MPFI marine applications???

You can do aftermarket SEFI, closed loop with O2 and other cool things
too. Costs money and effort, but it does work, and work well.

What do you mean by "work well"? Is it as good as open loop or measurably
better? Are there noticeable gains in power, torque, startability,
driveability, fuel economy, and/or smoothness? I still maintain that
feedback fuel control exists only to keep a catalyst operating at peak
efficiency. Even closed loop systems go to open loop enriched conditions
under max power situations and/or for the sake of smoothness. I can see
that maybe a closed loop system might be slightly better on gas but if
it's
not controlled well then you're playing with fire. Otherwise I think
you're
adding complexity for minimal gain. If someone wants to experiment. by
all
means go for it - that someone just won't be me.

"no one" wrote in message
...
Geoff, show me the evidence O2 sensors are primarily for cat performance.
If you've ever seen a fi system go into a bad full rich open loop state,
you'll see the cat is REAL efficient. Like white hot efficient.

Not a conventional three-way catalyst. Once it goes rich and all the stored
oxygen is gone it loads up with carbon really fast and it cools off. In
fact, excess fuel is used to for catalyst protection when it gets too hot.
I didn't read the posted link but hopefully it included little story on the
oxygen-bucket theory. Sometime in the near future (post-Super Bowl) I'll
find the catalyst efficiency vs. lambda charts online and post a link - TWC
efficiency diverges quickly from stoichiometry.

"Geoff" wrote in message
gy.com...

"no one" wrote in message
...
Not a conventional three-way catalyst. Once it goes rich and all the
stored
oxygen is gone it loads up with carbon really fast and it cools off. In
fact, excess fuel is used to for catalyst protection when it gets too hot.
I didn't read the posted link but hopefully it included little story on
the
oxygen-bucket theory. Sometime in the near future (post-Super Bowl) I'll
find the catalyst efficiency vs. lambda charts online and post a link -
TWC
efficiency diverges quickly from stoichiometry.


I found what I was looking for if anyone is still interested -
http://www.autoshop101.com/forms/h64.pdf, the top of page 4 shows the plots
of HC, CO, and NOx efficiencies versus air-fuel ratio.

"Geoff" wrote in message igy.com...
snip

I found what I was looking for if anyone is still interested -
http://www.autoshop101.com/forms/h64.pdf, the top of page 4 shows the plots
of HC, CO, and NOx efficiencies versus air-fuel ratio.

That is the same document I posted above. Thanks for the more direct
link. Here then is the direct link to the Toyota document for oxygen
sensors.

http://www.autoshop101.com/forms/h37.pdf

The first line is:

"The ECM uses an oxygen sensor to ensure the air/ratio is correct for
the catalytic converter."

I hope the "evidence" is good enough.