AFM Mod: Rich or Lean ??
09-15-2006, 02:12 PM
#21
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OK; what changed right before you noticed the truck running rich? Start with the most recent changes; they generally lead you to the solution. Someone suggested a possible leaking injector; that would do it. Do you have any associated driveability problems such as missing, odd idle behavior, low power, backfiring, poor mileage, etc.? When was the last time you changed the O2 sensor? Does it start OK? Run well hot/cold?
Last edited by TNRabbit; 09-15-2006 at 02:13 PM.
09-15-2006, 11:26 PM
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OK; what changed right before you noticed the truck running rich? Start with the most recent changes; they generally lead you to the solution. Someone suggested a possible leaking injector; that would do it. Do you have any associated driveability problems such as missing, odd idle behavior, low power, backfiring, poor mileage, etc.? When was the last time you changed the O2 sensor? Does it start OK? Run well hot/cold?
its not missing; just as of the last few days i have noticed a slight idle issue; low power? i dont think any lower power than it should have; never backfires; great gas mileage (25 mpg on a recent camping trip) i havent changed the o2 sensor, the bolts are rusted on there, but i want to do it even though its not throwing any CEL's; it starts fine; it does run a little cold i have noticed it takes at least 15 minutes of driving to get any hot air out of the vents, and even then the Engine Temp. Gauge has barely budged.
09-16-2006, 03:38 AM
#23
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honestly you should pull the EFI fuse when you set it back. If it has tuned to run richer in closed loop it is the ECU's doing most likely....(that is of course barring all physical ailments)
09-16-2006, 10:36 AM
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bumpin'yota: yes of course the EFI fuse will be pulled. i might actually only pull the fuse and see if that solves anything, if not, i will set it back to the original location.
09-19-2006, 12:57 AM
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Well, my truck seems to have found the sweet spot. Running at 11-12* advanced with 1 click leaner in AFM. The power is acceptable (although not as peppy as at 13-14*), almost no pinging - just a slight rare ping if going under load with low RPMs. Running on the cheap petrol.
Oh, and 3 full turns out for the idle bypass screw. By the way about this screw. I was trying to lean out idle but found that on 4 full turns the engine wasn't keeping idle when just started hot and would tend to stall. Made it richer (3) and voilla.
Also obviously new plugs/cap/rotor and clean injectors helped - it starts sooner than I can release the key
Hmm - I wonder if cleaning and actually opening up cold start injector somehow helped...
By the way, it took almost a week for ECU to adjust - so if you make any changes and reset ECU please do allow some time before making any judgments.
Will continue monitoring but so far so good.
Oh, and 3 full turns out for the idle bypass screw. By the way about this screw. I was trying to lean out idle but found that on 4 full turns the engine wasn't keeping idle when just started hot and would tend to stall. Made it richer (3) and voilla.
Also obviously new plugs/cap/rotor and clean injectors helped - it starts sooner than I can release the key
Hmm - I wonder if cleaning and actually opening up cold start injector somehow helped... By the way, it took almost a week for ECU to adjust - so if you make any changes and reset ECU please do allow some time before making any judgments.
Will continue monitoring but so far so good.
Last edited by tomasp; 09-19-2006 at 01:12 PM.
09-19-2006, 03:11 PM
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Another crazy idea...
OK - no need to attack me on this, I am just discussing theoretical stuff here.
Found this link on Yotatech http://www.autoshop101.com/forms/h34.pdf - actually,very good and informative to understand what different types of AFM are and how they work. While I was reading it (about our 2nd gen vane AFMs) one idea popped into my head.
The "dampening chamber" is used as a "shock absorber" (see above file). Well...one could drill a hole (or a few of a different size) into this chamber and use a short bolt to plug it if not needed, after tapping it, of course. By opening a small hole one could potentially decrease the dampening effect to some degree where it would result in a better throttle response.
A few potential issues:
* "Jerkyness" - caused by the vibration of the measuring vane. I am sure this can be easily dealt with by adding a capacitor to the output to filter out any short spikes. One could hook up the oscilloscope to the output and actually measure those spikes to determine the proper capacity required - maybe banging the airbox with a fist?
On the other hand OBD-1 ECU can be so slow to react (as I read) that it might not even need that.
* Effect - I am not sure how well this "dampening" thing works in the stock setup, maybe it is there to filter the "spikes"?
It shouldn't impact fuel economy as it is more controlled (as much as it can be in AFM) by the spring. This, however, potentially could improve the throttle response or "up and go" feel.
What do you guys think - now you can criticize me
Thinking even further - if the spikes could be filtered out electronically then the dampening plate could be removed whatsover, lightening up the setup and further improving response. As for the dampening chamber (which would be just an empty pocket creating turbulence) - maybe it would make sense to fabricate a new AFM - ok, this is going too far now, I better stop right here.
Found this link on Yotatech http://www.autoshop101.com/forms/h34.pdf - actually,very good and informative to understand what different types of AFM are and how they work. While I was reading it (about our 2nd gen vane AFMs) one idea popped into my head.
The "dampening chamber" is used as a "shock absorber" (see above file). Well...one could drill a hole (or a few of a different size) into this chamber and use a short bolt to plug it if not needed, after tapping it, of course. By opening a small hole one could potentially decrease the dampening effect to some degree where it would result in a better throttle response.
A few potential issues:
* "Jerkyness" - caused by the vibration of the measuring vane. I am sure this can be easily dealt with by adding a capacitor to the output to filter out any short spikes. One could hook up the oscilloscope to the output and actually measure those spikes to determine the proper capacity required - maybe banging the airbox with a fist?
On the other hand OBD-1 ECU can be so slow to react (as I read) that it might not even need that.
* Effect - I am not sure how well this "dampening" thing works in the stock setup, maybe it is there to filter the "spikes"?
It shouldn't impact fuel economy as it is more controlled (as much as it can be in AFM) by the spring. This, however, potentially could improve the throttle response or "up and go" feel.
What do you guys think - now you can criticize me
Thinking even further - if the spikes could be filtered out electronically then the dampening plate could be removed whatsover, lightening up the setup and further improving response. As for the dampening chamber (which would be just an empty pocket creating turbulence) - maybe it would make sense to fabricate a new AFM - ok, this is going too far now, I better stop right here.
10-03-2006, 10:19 PM
#29
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good thought process and yes Ithink it would work but whetheror not you'd feel a difference is highly doubtful...
I say trash the whole vafm setup and convert to a 3" MAF!
I say trash the whole vafm setup and convert to a 3" MAF!
10-03-2006, 10:43 PM
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Well, my truck seems to have found the sweet spot. Running at 11-12* advanced with 1 click leaner in AFM. The power is acceptable (although not as peppy as at 13-14*), almost no pinging - just a slight rare ping if going under load with low RPMs. Running on the cheap petrol.
Oh, and 3 full turns out for the idle bypass screw. By the way about this screw. I was trying to lean out idle but found that on 4 full turns the engine wasn't keeping idle when just started hot and would tend to stall. Made it richer (3) and voilla.
Also obviously new plugs/cap/rotor and clean injectors helped - it starts sooner than I can release the key Hmm - I wonder if cleaning and actually opening up cold start injector somehow helped...
By the way, it took almost a week for ECU to adjust - so if you make any changes and reset ECU please do allow some time before making any judgments.
Will continue monitoring but so far so good.
Oh, and 3 full turns out for the idle bypass screw. By the way about this screw. I was trying to lean out idle but found that on 4 full turns the engine wasn't keeping idle when just started hot and would tend to stall. Made it richer (3) and voilla.
Also obviously new plugs/cap/rotor and clean injectors helped - it starts sooner than I can release the key
Hmm - I wonder if cleaning and actually opening up cold start injector somehow helped... By the way, it took almost a week for ECU to adjust - so if you make any changes and reset ECU please do allow some time before making any judgments.
Will continue monitoring but so far so good.
have you been doing your timing with a timing light ?? or what??
and what do you mean by "clean injectors" ??
10-03-2006, 11:13 PM
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The only bad thing about it is that I will have to re-do my fibreglass ISR pipe that I am building now 
10-03-2006, 11:16 PM
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Clean injectors are injectors that have been cleaned with ultrasound on a special cleaning/flow testing machine. Phew - you sound harsh, have I done something bad?
10-04-2006, 10:22 AM
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haha no not at all... i was just curious on how you cleaned your injectors. i was hoping you just didnt dump some fuel injector cleaner in the gas tank and consider them clean
10-04-2006, 10:40 AM
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Instead of messing with the damping chamber, why not reduce the spring tension somehow? Wound reduction in spring tension actually improve flow (not maximum WOT CFM obviously).
Last edited by AlaskaToy; 10-04-2006 at 10:42 AM.
10-04-2006, 12:37 PM
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The dampening chamber thing is not about flow or power - it is about throttle response - however as bumpin'yota noted it might be hard to notice any difference.
10-04-2006, 12:54 PM
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Well, reducing spring tension is what AFM mod is all about - you reduce the tension to improve power and increase fuel consumption and you can also increase tension to reduce power and reduce fuel consumption.
The dampening chamber thing is not about flow or power - it is about throttle response - however as bumpin'yota noted it might be hard to notice any difference.
The dampening chamber thing is not about flow or power - it is about throttle response - however as bumpin'yota noted it might be hard to notice any difference.
Anyway *related* I just finished up my silencer and airbox removal. I used an AEM dryflow element. While I had the AFM out, I filed all the sharp edges and steps off. Can't say it helped, but it sure didn't hurt anyting. I figured since it is the most restrictive part of the whole intake, why not let the air that does squeeze thu it go thru as smoothly as possible.
Last edited by AlaskaToy; 10-04-2006 at 01:00 PM.
05-28-2007, 03:44 PM
#37
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taikowaza
I know how it feels to yank the circuit board connections by loosening those two evil little screws ...however I was able to solder the connects back to the circuit board without having to buy a whole new unit...guess you weren't so lucky! I guess I thought those two screws on it would be like the screws on the connections for computer to monitor or computer to printer...that kind of thing but I was wrong.
I know how it feels to yank the circuit board connections by loosening those two evil little screws
...however I was able to solder the connects back to the circuit board without having to buy a whole new unit...guess you weren't so lucky! I guess I thought those two screws on it would be like the screws on the connections for computer to monitor or computer to printer...that kind of thing but I was wrong.
05-28-2007, 04:56 PM
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Plain and simple, you have a Bosch closed loop fuel injection system.
The way the computer is programmed, there is not much you can do, short of having the ecu reprogrammed. Any "adjustments" you make at sensed by the O2 sensor. that tells the ecu what to do to fuel.
The AFM tells the ecu how much air is flowing into and along with the TPS, tells the ecu how much load is on the engine. All the o2 does in general, is tell the computer if what it did is right or to tweak it some more.
So, change your cam, injectors what ever, you change the parameters that the ecu is programmed for. They don't match, you get doggy performance and or poor mileage.
Same would go with the differential, tires, transfer or tranny gearing. Although this is more dependent on final gear ratio than anything. IE, bigger tires, go to taller gears.
The way the computer is programmed, there is not much you can do, short of having the ecu reprogrammed. Any "adjustments" you make at sensed by the O2 sensor. that tells the ecu what to do to fuel.
The AFM tells the ecu how much air is flowing into and along with the TPS, tells the ecu how much load is on the engine. All the o2 does in general, is tell the computer if what it did is right or to tweak it some more.
So, change your cam, injectors what ever, you change the parameters that the ecu is programmed for. They don't match, you get doggy performance and or poor mileage.
Same would go with the differential, tires, transfer or tranny gearing. Although this is more dependent on final gear ratio than anything. IE, bigger tires, go to taller gears.
05-28-2007, 06:28 PM
#40
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The amount of mis-information on the AFM mod is ASTOUNDING.
As far as I recall My AFM spring ran backwards and thus rich was lean and lean was rich when looking at the CW, CCW instructions.
Basically by "tightening" the spring, you make it harder for the flapper to open, it takes MORE air entering than previoulsy under the old spring tension, and the AFM tells the ECU that there is less air than there really is the system runs "lean"... in THEORY.
The PROBLEM is that the EFI system isnt that DUMB!!!!
It ALSO looks that the 02 sensor readings.
I know - the o2 sensor is not a wide band 02.
That doesnt matter.
Unlike you or me, Bosch / Toyota had engineers, engines, dynos and a lab available to them.
They ran the EFI connceted to BOTH the standard and a WBEGO in the lab.
Now, what you may NOT also realize, is that the EFI is designed to cycle the EFI from rich to lean about every 5-10 seconds (I forget the actual cycle time - check the FSM for the 02 reading cycle times).
Thus even though they dont have a WBEGO in the system - they have TONS of DYNO time where they can tell cycle times and rich lean response to load factors.... thus EFI has a built in MAP for a baseline of expected reading for the AFM reading/TPS reading/ Air Temp reading etc...
What this REALLY means is anyone who is fiddling with the AFM without looking at the Vf signal is just "yakkin" that they are tuning their EFI. They are just playing games - probalby no better than buying a Tornado or a TRD sticker.
What is the "Vf" signal?
Its the EFI indicating the ECU's percentage of TRIM.
(check under Jeff Moskiwitz'z site or the old Supra sites - thsi tech is OLD)
The EFI can compensate up to around 25% (measuered as a change in injector pulse width) after that it gets kinda raggedy (i.e. its guessing and its guessing in big steps rather than small steps)
So if you have a Vf meter (make one - its 0 to 5 volts) ... you can adjust the AFM to try to get the Vf signal to peg to the CENTER. This puts the baseline injector pulse width within the expected pulse width after the 02 sensor correction factors are made (i.e. the 02 sensor readouts requires ZERO correction factor from the ECU. This is what you want. After that the ECU can handle up to a 20% correction factor with out any trouble.
This is VERY handy if you do what I (and other have done) - the spring slips and whoops - did it unwind once or twice?
Im running larger LUCAS injectors - I had to adjust the AFM to get the engine to run right.
As far as I recall My AFM spring ran backwards and thus rich was lean and lean was rich when looking at the CW, CCW instructions.
Basically by "tightening" the spring, you make it harder for the flapper to open, it takes MORE air entering than previoulsy under the old spring tension, and the AFM tells the ECU that there is less air than there really is the system runs "lean"... in THEORY.
The PROBLEM is that the EFI system isnt that DUMB!!!!
It ALSO looks that the 02 sensor readings.
I know - the o2 sensor is not a wide band 02.
That doesnt matter.
Unlike you or me, Bosch / Toyota had engineers, engines, dynos and a lab available to them.
They ran the EFI connceted to BOTH the standard and a WBEGO in the lab.
Now, what you may NOT also realize, is that the EFI is designed to cycle the EFI from rich to lean about every 5-10 seconds (I forget the actual cycle time - check the FSM for the 02 reading cycle times).
Thus even though they dont have a WBEGO in the system - they have TONS of DYNO time where they can tell cycle times and rich lean response to load factors.... thus EFI has a built in MAP for a baseline of expected reading for the AFM reading/TPS reading/ Air Temp reading etc...
What this REALLY means is anyone who is fiddling with the AFM without looking at the Vf signal is just "yakkin" that they are tuning their EFI. They are just playing games - probalby no better than buying a Tornado or a TRD sticker.
What is the "Vf" signal?
Its the EFI indicating the ECU's percentage of TRIM.
(check under Jeff Moskiwitz'z site or the old Supra sites - thsi tech is OLD)
The EFI can compensate up to around 25% (measuered as a change in injector pulse width) after that it gets kinda raggedy (i.e. its guessing and its guessing in big steps rather than small steps)
So if you have a Vf meter (make one - its 0 to 5 volts) ... you can adjust the AFM to try to get the Vf signal to peg to the CENTER. This puts the baseline injector pulse width within the expected pulse width after the 02 sensor correction factors are made (i.e. the 02 sensor readouts requires ZERO correction factor from the ECU. This is what you want. After that the ECU can handle up to a 20% correction factor with out any trouble.
This is VERY handy if you do what I (and other have done) - the spring slips and whoops - did it unwind once or twice?
Im running larger LUCAS injectors - I had to adjust the AFM to get the engine to run right.
