running lean
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Joined: May 2003
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From: jacksonville, FL
yep im tuning mine to stay at a 12.9 all across the board, or whatever around there makes the most power. ill let you know how it works out. i think the vq likes to run a little rich but ill see once i start tinkering on the dyno.
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Joined: Oct 2003
Posts: 118
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From: Chesapeake, VA
Originally posted by PoWeRtRiP
yep im tuning mine to stay at a 12.9 all across the board, or whatever around there makes the most power. ill let you know how it works out. i think the vq likes to run a little rich but ill see once i start tinkering on the dyno.
yep im tuning mine to stay at a 12.9 all across the board, or whatever around there makes the most power. ill let you know how it works out. i think the vq likes to run a little rich but ill see once i start tinkering on the dyno.
Isn't ECU there for? ECU is suppose to ajust A/F to the optimum?
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Joined: Jun 2002
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From: Frisco, TX
Originally posted by 350ZRB
Isn't ECU there for? ECU is suppose to ajust A/F to the optimum?
Isn't ECU there for? ECU is suppose to ajust A/F to the optimum?
More info from the FSM:
SYSTEM DESCRIPTION
The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of time the valve remains open (injection pulse duration). The amount of fuel injected is a program value in the ECM memory. The program value is preset by engine operating conditions. These conditions are determined by input signals (for engine speed and intake air) from both the crankshaft position sensor and the mass air flow sensor.
VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION
In addition, the amount of fuel injected is compensated to improve engine performance under various operating conditions as listed below.
<Fuel increase>
During warm-up
When starting the engine
During acceleration
Hot-engine operation
When selector lever is changed from “N” to “D” (A/T models)
High-load, high-speed operation
<Fuel decrease>
During deceleration
During high engine speed operation
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control.
The three way catalyst 1 can then better reduce CO, HC and NOx emissions. This system uses heated oxygen sensor 1 in the exhaust manifold to monitor if the engine operation is rich or lean. The ECM adjusts the injection pulse width according to the sensor voltage signal. For more information about heated oxygen sensor 1, refer to EC-207 . This maintains the mixture ratio within the range of stoichiometric (ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the three way catalyst 1. Even if the switching characteristics of heated oxygen sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal from heated oxygen sensor 2.
Open Loop Control
The open loop system condition refers to when the ECM detects any of the following conditions. Feedback control stops in order to maintain stabilized fuel combustion.
Deceleration and acceleration
High-load, high-speed operation
Malfunction of heated oxygen sensor 1 or its circuit
Insufficient activation of heated oxygen sensor 1 at low engine coolant temperature
High engine coolant temperature
During warm-up
After shifting from “N” to “D” (A/T models)
When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL
The mixture ratio feedback control system monitors the mixture ratio signal transmitted from heated oxygen sensor 1. This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to the theoretical mixture ratio as possible. However, the basic mixture ratio is not necessarily controlled as originally designed. Both manufacturing differences (i.e., mass air flow sensor hot film) and characteristic changes during operation (i.e., injector clogging) directly affect mixture ratio.
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This is then computed in terms of “injection pulse duration” to automatically compensate for the difference between the two ratios.
“Fuel trim” refers to the feedback compensation value compared against the basic injection duration. Fuel trim includes short term fuel trim and long term fuel trim.
“Short term fuel trim” is the short-term fuel compensation used to maintain the mixture ratio at its theoretical value. The signal from heated oxygen sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the theoretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is rich, and an increase in fuel volume if it is lean.
“Long term fuel trim” is overall fuel compensation carried out long-term to compensate for continual deviation of the short term fuel trim from the central value. Such deviation will occur due to individual engine differences, wear over time and changes in the usage environment.
The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of time the valve remains open (injection pulse duration). The amount of fuel injected is a program value in the ECM memory. The program value is preset by engine operating conditions. These conditions are determined by input signals (for engine speed and intake air) from both the crankshaft position sensor and the mass air flow sensor.
VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION
In addition, the amount of fuel injected is compensated to improve engine performance under various operating conditions as listed below.
<Fuel increase>
During warm-up
When starting the engine
During acceleration
Hot-engine operation
When selector lever is changed from “N” to “D” (A/T models)
High-load, high-speed operation
<Fuel decrease>
During deceleration
During high engine speed operation
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control.
The three way catalyst 1 can then better reduce CO, HC and NOx emissions. This system uses heated oxygen sensor 1 in the exhaust manifold to monitor if the engine operation is rich or lean. The ECM adjusts the injection pulse width according to the sensor voltage signal. For more information about heated oxygen sensor 1, refer to EC-207 . This maintains the mixture ratio within the range of stoichiometric (ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the three way catalyst 1. Even if the switching characteristics of heated oxygen sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal from heated oxygen sensor 2.
Open Loop Control
The open loop system condition refers to when the ECM detects any of the following conditions. Feedback control stops in order to maintain stabilized fuel combustion.
Deceleration and acceleration
High-load, high-speed operation
Malfunction of heated oxygen sensor 1 or its circuit
Insufficient activation of heated oxygen sensor 1 at low engine coolant temperature
High engine coolant temperature
During warm-up
After shifting from “N” to “D” (A/T models)
When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL
The mixture ratio feedback control system monitors the mixture ratio signal transmitted from heated oxygen sensor 1. This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to the theoretical mixture ratio as possible. However, the basic mixture ratio is not necessarily controlled as originally designed. Both manufacturing differences (i.e., mass air flow sensor hot film) and characteristic changes during operation (i.e., injector clogging) directly affect mixture ratio.
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This is then computed in terms of “injection pulse duration” to automatically compensate for the difference between the two ratios.
“Fuel trim” refers to the feedback compensation value compared against the basic injection duration. Fuel trim includes short term fuel trim and long term fuel trim.
“Short term fuel trim” is the short-term fuel compensation used to maintain the mixture ratio at its theoretical value. The signal from heated oxygen sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the theoretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is rich, and an increase in fuel volume if it is lean.
“Long term fuel trim” is overall fuel compensation carried out long-term to compensate for continual deviation of the short term fuel trim from the central value. Such deviation will occur due to individual engine differences, wear over time and changes in the usage environment.
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Joined: Sep 2002
Posts: 575
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From: Atlanta
http://autoweb.autospeed.com/cms/A_1595/article.html
Here is some decent information for those who are not familiar with what is really lean on a N/A engine.
"Bosch state that most spark ignition engines develop their maximum power at air/fuel ratios of 12.5:1 - 14:1, maximum fuel economy at 16.2:1 - 17.6:1, and good load transitions from about 11:1 - 12.5:1. However, in practical applications, engine air/fuel ratios at maximum power are often richer than the quoted 12.5:1, especially in forced induction engines where the excess fuel is used to cool combustion and so prevent detonation."
For a N/A engine, 13 to 14 A/F ratio's is really not that lean, or more specifically depending on how you gauge the word lean, it is not dangerous to your engine.
Here is some decent information for those who are not familiar with what is really lean on a N/A engine.
"Bosch state that most spark ignition engines develop their maximum power at air/fuel ratios of 12.5:1 - 14:1, maximum fuel economy at 16.2:1 - 17.6:1, and good load transitions from about 11:1 - 12.5:1. However, in practical applications, engine air/fuel ratios at maximum power are often richer than the quoted 12.5:1, especially in forced induction engines where the excess fuel is used to cool combustion and so prevent detonation."
For a N/A engine, 13 to 14 A/F ratio's is really not that lean, or more specifically depending on how you gauge the word lean, it is not dangerous to your engine.
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Joined: Nov 2002
Posts: 4,686
Likes: 0
From: NOR - CAL
i noticed when i dynoed that my a/f was at a 13.7-14.0 under 4k rpms then suddenly dropped very rapidly till bottoming out at 12.2 at redline.
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Joined: Mar 2004
Posts: 28
Likes: 0
From: long island,NASSAU
Originally posted by alex30327
http://autoweb.autospeed.com/cms/A_1595/article.html
You seem to know alot about this. The place that installed my pro charger never tuned it and let me drive out at under 10% I finaly had it tuned it nose dived at 3500rpm under 10% after 19 pulls on the dyno its at a flat 12.9% I think I might have fouled the plugs running so rich Is 12.9%ok or should it be leaner?
Here is some decent information for those who are not familiar with what is really lean on a N/A engine.
"Bosch state that most spark ignition engines develop their maximum power at air/fuel ratios of 12.5:1 - 14:1, maximum fuel economy at 16.2:1 - 17.6:1, and good load transitions from about 11:1 - 12.5:1. However, in practical applications, engine air/fuel ratios at maximum power are often richer than the quoted 12.5:1, especially in forced induction engines where the excess fuel is used to cool combustion and so prevent detonation."
For a N/A engine, 13 to 14 A/F ratio's is really not that lean, or more specifically depending on how you gauge the word lean, it is not dangerous to your engine.
http://autoweb.autospeed.com/cms/A_1595/article.html
You seem to know alot about this. The place that installed my pro charger never tuned it and let me drive out at under 10% I finaly had it tuned it nose dived at 3500rpm under 10% after 19 pulls on the dyno its at a flat 12.9% I think I might have fouled the plugs running so rich Is 12.9%ok or should it be leaner?
Here is some decent information for those who are not familiar with what is really lean on a N/A engine.
"Bosch state that most spark ignition engines develop their maximum power at air/fuel ratios of 12.5:1 - 14:1, maximum fuel economy at 16.2:1 - 17.6:1, and good load transitions from about 11:1 - 12.5:1. However, in practical applications, engine air/fuel ratios at maximum power are often richer than the quoted 12.5:1, especially in forced induction engines where the excess fuel is used to cool combustion and so prevent detonation."
For a N/A engine, 13 to 14 A/F ratio's is really not that lean, or more specifically depending on how you gauge the word lean, it is not dangerous to your engine.
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Joined: Sep 2002
Posts: 575
Likes: 0
From: Atlanta
Originally posted by ATI 350z
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Joined: Nov 2002
Posts: 4,686
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From: NOR - CAL
Not if you add enough fuel to compensate.
N/A is about 10hp rich from factory on the 2003's if you are talking N/A. You could get an Apexi SAFC or Emanage or reflash if you were lean though. You won't know until you run the setup it isn't really black and white on all cars.
N/A is about 10hp rich from factory on the 2003's if you are talking N/A. You could get an Apexi SAFC or Emanage or reflash if you were lean though. You won't know until you run the setup it isn't really black and white on all cars.
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Joined: Feb 2003
Posts: 2,788
Likes: 0
From: brooklyn ny(rutgers college)
this is a good thread so i bumped it up
is it true to assume that you should only get a reflash after you put in ALL of the mods that you think you will do
will you have to keep sending it back every time you put something in?
i only have injen exhuast xerd pipes and putting in UR pulleys so i think ill be fine as far as lean goes
but if i put on intake...then i want to put on plenum it might be a judgement call...
so like i said...should i wait till i do everything before i plan to reflash....and what exactly do they do for a reflash..how exactly does it work (im assuming they accomodate to each persons specific mods but how)
and lastly..how long do they take to do it
is it true to assume that you should only get a reflash after you put in ALL of the mods that you think you will do
will you have to keep sending it back every time you put something in?
i only have injen exhuast xerd pipes and putting in UR pulleys so i think ill be fine as far as lean goes
but if i put on intake...then i want to put on plenum it might be a judgement call...
so like i said...should i wait till i do everything before i plan to reflash....and what exactly do they do for a reflash..how exactly does it work (im assuming they accomodate to each persons specific mods but how)
and lastly..how long do they take to do it
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Joined: Jun 2003
Posts: 20
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From: Long Island
i have kinetix cats and plenum, stillen intake, with a z tube on my g35 and u/r crank pulley and my a/f was around 14:1 untill very late in the rpm band, it is not dangerous but it is a bit lean, technosquare hopefully will fix this.... well see im sending a copy of my af curve too so hopefully they fix it, there site says 12.5:1 i would like to get it around 13:1 though, i need to talk to them but everyone with just exhuast and cats i wouldnt be too worried.....
ok from what i have read so far, if you dont have headers and a plenum u wont be running really lean, well i have Crawford headers, plenum and the Injen SES and CAI but i have the stock cats still. do you guys think im running really lean? i get honestly about 300-320 miles on a tank max. ave. mpg is 19+ and is rarely over 20mpg.
could new spark plugs help? if so what kind?
thanks
john
could new spark plugs help? if so what kind?
thanks
john
Originally posted by 12SecZ
Not if you add enough fuel to compensate.
N/A is about 10hp rich from factory on the 2003's if you are talking N/A. You could get an Apexi SAFC or Emanage or reflash if you were lean though. You won't know until you run the setup it isn't really black and white on all cars.
Not if you add enough fuel to compensate.
N/A is about 10hp rich from factory on the 2003's if you are talking N/A. You could get an Apexi SAFC or Emanage or reflash if you were lean though. You won't know until you run the setup it isn't really black and white on all cars.
this is kim at saipan?
let me ask you some ...
A/F Gauge easy to read ( lean or rich )
but in EGT how can i detect lean & rich ?????
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Joined: Mar 2003
Posts: 568
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From: Minneapolis
Originally posted by nitrous350
Hi Max
this is kim at saipan?
let me ask you some ...
A/F Gauge easy to read ( lean or rich )
but in EGT how can i detect lean & rich ?????
Hi Max
this is kim at saipan?
let me ask you some ...
A/F Gauge easy to read ( lean or rich )
but in EGT how can i detect lean & rich ?????
With that said, I'm not sure what the max temperature is that you want to stay beneath. Overall, if the engine is running too lean, then the exhaust temps will be running hot, and you want to stay below that temp threshhold to prevent a burn-down.
I'm not sure if this method is better, worse or the same as the A/F measurement for lean conditions.