Stoich value...can someone answer some questions?
09-07-2004, 12:26 PM
#1
On The Tree
Thread Starter
iTrader: (8)
Join Date: Aug 2004
Posts: 185
Likes: 0
Received 0 Likes
on
0 Posts
Stoich value...can someone answer some questions? I know whatthe number represents, but is it a resultant value, or is it a goal value? Meaning is it tuneable? If I were to change it to something richer or leaner, will the pcm try to achieve the new number?
If not, what's the story behind it?
If not, what's the story behind it?
09-07-2004, 12:55 PM
#2
FormerVendor
iTrader: (1)
Join Date: Feb 2002
Location: Waldorf, MD
Posts: 3,059
Likes: 0
Received 0 Likes
on
0 Posts
I wouldnt change it. You narrow band stock o2 sensors dont work to well outside of the 14.7:1 ratio.14.7 is there because the EPA says the least emmissions are emitted (cats are most efficient at 14.7) at that AFR. If you want richer or leaner mixture buy a WB and tune in open loop full time
09-08-2004, 01:45 PM
#3
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
14.7 is the chemical ideal (you would see a different
value in an alcohol car or multiple options in a flex-
fuel system).
This value and the fuel/air multiplier set the intended
AFR. Sensor, actuator and cal table errors cause the
deviations from this ideal.
The O2 voltage vs airflow mode table sets the feedback
"pivot" value that is supposed to match the narrowband
sensor switchpoint. If you made that (say) 300mV rather
than 550mV that would make the system learn to a
leaner center than normal. You might also want your
mode vs airflow table fixed up to give you more mode cells
between idle and highway cruise to fiddle with. If that's
what you're after.
value in an alcohol car or multiple options in a flex-
fuel system).
This value and the fuel/air multiplier set the intended
AFR. Sensor, actuator and cal table errors cause the
deviations from this ideal.
The O2 voltage vs airflow mode table sets the feedback
"pivot" value that is supposed to match the narrowband
sensor switchpoint. If you made that (say) 300mV rather
than 550mV that would make the system learn to a
leaner center than normal. You might also want your
mode vs airflow table fixed up to give you more mode cells
between idle and highway cruise to fiddle with. If that's
what you're after.
09-09-2004, 11:28 AM
#6
TECH Addict
Join Date: Sep 2003
Location: Atlanta, GA
Posts: 2,065
Likes: 0
Received 0 Likes
on
0 Posts
anyone got examples in hptuners format of making the car burn leaner when in closed loop. Dont want to muck up the open loom trims eh
just need better city mpg and under light loads with cooler thermostat i think the block can handle little leaner.
also i believe headers/ory confuse o2 sensors since heat passes faster through than with original design+cat.
Examples in hptuners table format would be great or some more logic.
how far can we push the car without knock i guess would be another question? 5%?
just need better city mpg and under light loads with cooler thermostat i think the block can handle little leaner.
also i believe headers/ory confuse o2 sensors since heat passes faster through than with original design+cat.
Examples in hptuners table format would be great or some more logic.
how far can we push the car without knock i guess would be another question? 5%?
09-09-2004, 12:23 PM
#7
TECH Regular
Join Date: Apr 2003
Location: Atlanta, GA
Posts: 413
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by samz28
anyone got examples in hptuners format of making the car burn leaner when in closed loop. Dont want to muck up the open loom trims eh
just need better city mpg and under light loads with cooler thermostat i think the block can handle little leaner.
also i believe headers/ory confuse o2 sensors since heat passes faster through than with original design+cat.
Examples in hptuners table format would be great or some more logic.
how far can we push the car without knock i guess would be another question? 5%?
just need better city mpg and under light loads with cooler thermostat i think the block can handle little leaner.
also i believe headers/ory confuse o2 sensors since heat passes faster through than with original design+cat.
Examples in hptuners table format would be great or some more logic.
how far can we push the car without knock i guess would be another question? 5%?
9.0:1 BLACK SMOKE (NO POWER)
11.5:1 RICH BEST TORQUE @ WOT
12.2:1 SAFE BEST POWER @ WOT
13.3:1 LEAN BEST TORQUE @ WOT
14.6:1 STOCHIMETRIC AFR ( CHEMICALLY CORRECT )
15.5:1 LEAN CRUISE
16.5:1 BEST FUEL ECONOMY
18.0:1 CARBURETED LEAN LIMIT
22.0:1 EFI LEAN LIMIT
