A/F/R gauge for tuning
- Thread starter gtxdude
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Exactly.
I’ve been using mine along with other tools/methods for over 5 years of progressively going faster at the strip, cleaning up gas stench, better response and transitions from idle up to wot. With any upgrades/changes to my engine I have to tweak the tuning. I don’t fixate on any specific reading or adhere to absolutes with tuning each circuit. More focused on a range. So I get in the range then fine tune further sometimes using the above additional methods and the final numbers are what they are. I know some prefer reading plugs and are quite sharp at it, it’s a lost art I’d say but it is possible to do the same with the afr gauge “along with incorporating some of/even all the other methods” to get it done much quicker.
This is where I believe you could be fooled maybe. Depends on how your o2's or o2 if you only have one are positioned.
In theory if have an o2 placed in the collector of a header you are reading the average of 4 cylinders. 2 could be lean 2 could be rich or any combination. Where you put the sensor could also bias toward 1 or 2 cylinders more than the others. And if it's just on one side you only have data for one side of the motor.
I have o2 sensors on each side of the motor on the dyno and sometimes they vary from side to side. Fuel distribution not usually even for every cylinder. There are many reasons for this. All that said usually when a motor is rich and misfiring my o2's show that the motor rich.
However poor fuel distribution can cause a rich or lean misfire on a single cylinder when the o2 average looks normal. I can usually pick this out by looking at individual cylinder exhaust temperatures.
In theory if have an o2 placed in the collector of a header you are reading the average of 4 cylinders. 2 could be lean 2 could be rich or any combination. Where you put the sensor could also bias toward 1 or 2 cylinders more than the others. And if it's just on one side you only have data for one side of the motor.
I have o2 sensors on each side of the motor on the dyno and sometimes they vary from side to side. Fuel distribution not usually even for every cylinder. There are many reasons for this. All that said usually when a motor is rich and misfiring my o2's show that the motor rich.
However poor fuel distribution can cause a rich or lean misfire on a single cylinder when the o2 average looks normal. I can usually pick this out by looking at individual cylinder exhaust temperatures.
They are a huge time-saver.
Please don't think I was discounting them. I am passing information on that I was told by tuners I trust....be careful of the information until you know how to read what it is actually telling you. And, my statements were actually questions.
ir3333
Well-Known Member
They read averages and i think it's a few hundred readings per minute but i'm not sure. The better ones read all 5 gases and when used on modern engines they can record and provide many tuning options and curves. I have twice been saved by mine which exhibited a flooded condition once and a fuel starving issue another time.They show exactly why it's hard to clean up the idle with a long duration cam. Without one you have a calculated guess at best but guys with a lot of experience can get pretty close without one...but not me. I have mine jetted and tuned to 12.0 - 12.5 at WOT, 13.5 - 14.5 at idle and 14.0 - 14.7 at cruz. Again these are averages. On our carbureted classics they only provide A/F ratio.
Rat Bastid
Dunamis Metron
ive got an AEM uego in summary useful as hell...like it.. been in ten years, still like it.
bung in exhaust/ mine is at the junction of the headers, needs to be in the right position
i.e 10* or more north of a horizonatal diameter-line of the pipe cross section. i.e at 10, 11 12, 1, 2 o'clock not 9 not 3 and not anywhere else.
so the thing can't fill up with condensation and burn out.
In some cases the sender and its plug are a calibrated part you can't just stick another sender into the plug the plug had a resistor etched away by a laser as they tuned the sensor during manufacture... this is a feature of some 3 and 4 wire wide band sensors and not a feature of some others. if it looks like 2 plugs, it is.... one of them stays with the sender. AEM will say in the intructions what you got... probably Bosch 4 wire.
They will die quick if you use AVGAS or leaded race fuel.
i agree with what has been said if your tune is miles out the thing will confuse the hell out of you.
sender too close to the head will read rich on overlap at some rpm or other and you risk over heating it or drownng it in fuel.
too far away leads to signal delay and if you have no muffler at all, air can be drawn in and it will read lean at some rpm or other
somewhere between the front foot well and the rear footwell on a car with mufflers works ok. its a compromise its not ideal.
OEMs put them up front closer to the head... but they know what they are doing... its an ecu controlled car and the chances of flames lapping at the sensor due to seroiusly wrong timeing or serious over fueling are low.
misfire/flat spot what caused it? wet plugs too rich the thing reads rich
misfire/flat spot what caused it? too lean, or marginal ignition system/plugs well the thing will read rich bceause you didn't burn any of the charge and it will continue to read rich until you drive through the flat spot. it may or may not go lean after that . It depends on if your mixture is now correct for your current RPM and igntion advance. but you will think its rich and lean it out even though it was a lean flat spot and it will then pig pong between rich and lean like you would not believe over a much wider rpm...
you just have to get your ears in tune...... and you nose.....
the wrong heat range of plugs will have you chasing your tail.
the car needs to run and drive for it to be of use
The AEM has an inteface on the back the can outpout a voltage that can be used in place of a lambda sensor output into an ECU of any type that has a user defined or lambda table provided you can customise range. or you can connect it to a data logger thats plumbed into igntion
if you tune to 14.7
your car won't run well at all it might if it was a heart shaped, pent roof 4 valve combsution chamber in an ally headed four pot withn VVT but not a chunky old v8
aim for 12.5 to 13.5 with foot down
no probs if it goes north of 14.7 up to 15-16 or so on cruise or when you lift off. your advance curve or ideally vacuum advance or MAP should cater for that.
a wheel nut off a vintage rover makes a good bung for the exhaustrobust weldable and same thread but most gauges come with one.
set idle then check guage, should be 13.5 13.7 14 or some such
move onto progression WOT then check cruise
any issues you have will probably stem from plugs or ingition curve. an Igntion system that just can't cut it, once the car's tune gets into the good place is often a problem. previously you were running around rich all over putting out the flame slightly as it were
i.e better mixture = more power = faster exhaust gas speed= more extraction effect= bigger inlet charge= higher combustion chamber pressure at some rpm just as it gets on cam = intermittent failure of igntion system in some way, that maybe you can feel or hear or maybe not. but your lambda guage is going suddenly rich for 200-500 rpm
resulting in
Daft lambda gauge readings = doing the wrong thing to fix the problem= having to stop and have a beer and try again tomorrow
I found i suddenly had more valuble information and i was easily lead by the erroneous crap that is also shown..becasue i never knew about it before.
they are a great and a useful tool once you know about the stumbling blocks
and of course the output when used by an ECU is sampled and filtered and processed to cater for anomolous results when everything is badly out of bounds....
your eyes can't do that,
So you tune it as you always did and use this to check results, not the other way around. this is for the last 20% the tweaking. and a useful warning system on track or at dyno.. if the gauge is all red half way through a pull.........ssssssstttttttop before you melt a piston
Dave
The position the sensor is mounted in has nothing to do with how it reads. You have to keep it up out of moisture.
Leaded fuel will not kill the sensors real fast. They go quite a while.
The rest of it I’m not addressing.
Rat Bastid
Dunamis Metron
A lean miss makes the O2 sensor read rich. there isn’t much left over oxygen but a ton of left over fuel.
So the O2 sensor says it rich and you pull fuel out and it gets richer until you kill parts.
Thats why the plugs and the O2 sensor have to match. So do the exhaust port.
Ironically, the exhaust port can lie to you too. The plug should be the ultimate arbiter of what the O2 sensor is telling you.
Rat Bastid
Dunamis Metron
The o2 sensors I have sense oxygen not excess fuel. If there was excess fuel my o2 sensors wouldn't know it. They only know how much oxygen is left over. Are you saying that a lean misfire on a cylinder causes there to be less oxygen to be left over? Where did the oxygen go if it wasn’t burned? An HC meter will measure unburned hydrocarbons. Is this what you are using?
Yes and no. What I have seen is that when an o2 sensor is placed in a collector it will read a rough average of four cylinders.
I say rough average because it can change the reading you see based on where the sensor is placed. Place it where it is biased to a lean cylinder and it will bias the reading more toward lean. Place the o2 sensor closer to a rich cylinder and it will bias the reading as richer than the true average of the four cylinders.
In one collector you could have three very rich cylinders and one very lean cylinder. The o2 sensor doesn't know it is four seperate cylinders it sees the rough average of the four cylinders as being rich. Even if one of the cylinders is lean. In this way a lean misfire on a cylinder could be seen as rich.
I haven't done this yet but i think if you were to put a o2 sensor in the primary tube of the lean misfiring cylinder it would show it as being lean not rich.
What have you seen when testing that has shown a lean individual cylinder misfiring and causing the o2 sensor to read rich on that individual cylinder?
Dave999
Well-Known Member
sensor read rich on a lean mis fire, you asked me to explain way back but i'm in a different timezone.
I can't becasue i don't know why.....
my senser is at the end of the collectors so i can't see individual cylinders just the average of the lot therfore 1 or more with a problemn can skew the reading.
i had presumed it was either to do with the temperature of the sensor or ratio of unburned fuel to air in the exhaust gas being so wildly out of normal that the sensor wasn't doing its job anymore. the thing is heated, but i have no idea what a blast of unburned mixture does to that.. i.e does it work properly when its operating in an adverse situation. they were designed for FI cars that would in theory, never be so badly wrong as you can go with a carb
Or
as you drive through the misfire the sudden pickup of all cylinders again or backfire through exhaust starts a flow profile through the carb that causes an instantaneous rich condition. its a carb a big dumb thing that reacts to a pressure difference.
tuning on the street gives less oportunity to hold rpm and analyse. so what you see is
scattered lean rich for a split second followed by rich.
and this is what i see.
i'm working with weber DCOEs that meter on vacuum pulses in a similar way to a holley...But its port on port induction so there is no plenum to smooth out the pressure waves seen at the venturi in the carb, and no plenum of volume to act as a reserve supply of pre mixed fuel and air.
i basically have 6 carburetors on 6 tuned length inlets to worry about
i've never owned a holley-like carb so can only speak from what ive done and what ive seen with what i have .
and i will get rich readings in some cases, where the only fix for the problem was bigger jets implying it was lean. That invariably leads to some air jet work, bigger, so that its then not rich higher in the rpm range, but that bigger air corrector causes the mains to come in earlier making it rich in transition..... and on and on and on....
on a dyno you will have greater control over the situation and more time to work out whats going on, what you can see may well differ from what i am thinking i see becasue you have a better view.
the OP is more than likley doing what i do...i.e its a hobby and its being done in the driveway
hence probably won't see what you see on a dyno but might see what i see...
Averages are key as you say.
looking at trend before and after the issue, and ignoring the gauge during the issue, would lead you to Lean quicker, than the BS you see on the gauge at the point of the issue. When the sensor is trying to cope with a situation that is off the scale one way or the other.
As i said, these are put to their best use, when the car already runs and drives.
Dave
I can't becasue i don't know why.....
my senser is at the end of the collectors so i can't see individual cylinders just the average of the lot therfore 1 or more with a problemn can skew the reading.
i had presumed it was either to do with the temperature of the sensor or ratio of unburned fuel to air in the exhaust gas being so wildly out of normal that the sensor wasn't doing its job anymore. the thing is heated, but i have no idea what a blast of unburned mixture does to that.. i.e does it work properly when its operating in an adverse situation. they were designed for FI cars that would in theory, never be so badly wrong as you can go with a carb
Or
as you drive through the misfire the sudden pickup of all cylinders again or backfire through exhaust starts a flow profile through the carb that causes an instantaneous rich condition. its a carb a big dumb thing that reacts to a pressure difference.
tuning on the street gives less oportunity to hold rpm and analyse. so what you see is
scattered lean rich for a split second followed by rich.
and this is what i see.
i'm working with weber DCOEs that meter on vacuum pulses in a similar way to a holley...But its port on port induction so there is no plenum to smooth out the pressure waves seen at the venturi in the carb, and no plenum of volume to act as a reserve supply of pre mixed fuel and air.
i basically have 6 carburetors on 6 tuned length inlets to worry about
i've never owned a holley-like carb so can only speak from what ive done and what ive seen with what i have .
and i will get rich readings in some cases, where the only fix for the problem was bigger jets implying it was lean. That invariably leads to some air jet work, bigger, so that its then not rich higher in the rpm range, but that bigger air corrector causes the mains to come in earlier making it rich in transition..... and on and on and on....
on a dyno you will have greater control over the situation and more time to work out whats going on, what you can see may well differ from what i am thinking i see becasue you have a better view.
the OP is more than likley doing what i do...i.e its a hobby and its being done in the driveway
hence probably won't see what you see on a dyno but might see what i see...
Averages are key as you say.
looking at trend before and after the issue, and ignoring the gauge during the issue, would lead you to Lean quicker, than the BS you see on the gauge at the point of the issue. When the sensor is trying to cope with a situation that is off the scale one way or the other.
As i said, these are put to their best use, when the car already runs and drives.
Dave
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ir3333
Well-Known Member
I don't think you could see that on an average of 4 cylinders? I jetted mine to read an average of 15 - 15.5 A/F while cruising an my car ran great..no bog or hesitation at all. It is a stock build with a small cam. Because the reading is an average of 4 cylinders my thought was that i could have a lean cylinder and wouldn't know it so i jetted back to a cruise A/F of 14 - 14.5. My gauge changes numerous times per second and i don't see anything that isn't occuring full time on average.
My experience is with a dyno. I have been on the edge of putting o2 sensors in one of my cars that I drive on the road just for the learning experience for some time now. This thread has put me one step closer to pulling the trigger on a set of sensors.
Pretty sure I'll end up in a ditch watching sensors instead of the road.
Pretty sure I'll end up in a ditch watching sensors instead of the road.
Dave999
Well-Known Member
the basic one of these has served me well enough
https://www.aemelectronics.com/prod...ego-afr-gauge/digital-wideband-uego-afr-gauge
and if you can put it in eye line when doing the work
and pop it under the dash visible but not in yer face when work is complete
less change of hitting something
use your phone to record a commentary 2500 13.5 2600 13.8 etc etc
https://www.aemelectronics.com/prod...ego-afr-gauge/digital-wideband-uego-afr-gauge
and if you can put it in eye line when doing the work
and pop it under the dash visible but not in yer face when work is complete
less change of hitting something
use your phone to record a commentary 2500 13.5 2600 13.8 etc etc
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Rat Bastid
Dunamis Metron
Rat Bastid
Dunamis Metron
Hope the op doesn't mind. I have two o2 related experiences to share. Both on fuel injection systems.
1. Had a friend who brought a big block chevy to the dyno. We broke in and baselined on a known good carb and dyno headers. Then we switched to fuel injection and customers headers so no egts. I had had the dyno o2's set up one on each side just behind the collector and a set of bungs next to those for the fuel injection (FI). The FI used a single sensor we placed on the pass side.
The motor wasn't happy and didn’t run as well as with the carb. It was a dual plane manifold and it had some split between the o2 readings side to side. Long story short we ended up moving the o2 to the driver side and the motor ran great.
Customer took the motor home and installed sometime later. Motor wouldn't run right and discovered he had a leak at the collector upstream of the sensor. Fixed that and it ran better but still not great. Then discovered he put the o2 sensor in the wrong side. Moved the o2 sensor and it ran great.
I'll post the other story later.
1. Had a friend who brought a big block chevy to the dyno. We broke in and baselined on a known good carb and dyno headers. Then we switched to fuel injection and customers headers so no egts. I had had the dyno o2's set up one on each side just behind the collector and a set of bungs next to those for the fuel injection (FI). The FI used a single sensor we placed on the pass side.
The motor wasn't happy and didn’t run as well as with the carb. It was a dual plane manifold and it had some split between the o2 readings side to side. Long story short we ended up moving the o2 to the driver side and the motor ran great.
Customer took the motor home and installed sometime later. Motor wouldn't run right and discovered he had a leak at the collector upstream of the sensor. Fixed that and it ran better but still not great. Then discovered he put the o2 sensor in the wrong side. Moved the o2 sensor and it ran great.
I'll post the other story later.
Dave999
Well-Known Member
on one side maybe the data from the 02 senser was within the bounds of the self learning in the ECU
it could trim fuel and timing appropriately for the conditions and the car ran great
on the other side the signals might have been just outside the bounds of what self learning could deal with hence trimming of fuel and timeing varied between bad and slightly less bad.
it could trim fuel and timing appropriately for the conditions and the car ran great
on the other side the signals might have been just outside the bounds of what self learning could deal with hence trimming of fuel and timeing varied between bad and slightly less bad.
Yes possible.
Something I see with the help of Egt's for each cylinder is somtimes there is a wide spread between cylinders. These motors can be hard to tune. Lean the richest cylinder and now the leanest cylinder is unhappy and vice versa. Moving the o2 sensor could have just made the fussy cylinder or cylinders happy. With only one sensor sampling an average of 4 cylinders the fuel injection has no way of knowing how those cylinders are running individually let alone the four on the other side that aren't even being sampled.
Something I see with the help of Egt's for each cylinder is somtimes there is a wide spread between cylinders. These motors can be hard to tune. Lean the richest cylinder and now the leanest cylinder is unhappy and vice versa. Moving the o2 sensor could have just made the fussy cylinder or cylinders happy. With only one sensor sampling an average of 4 cylinders the fuel injection has no way of knowing how those cylinders are running individually let alone the four on the other side that aren't even being sampled.
TT5.9mag
Two atmospheres are better than one
I have an innovate dual wideband on my boat and an aem wideband in my truck. Both turbocharged and both would be a nightmare to tune without the wideband o2s. One thing I will mention that hasn’t been said yet is to verify results of ANY tool and learn to trust or discount those results. I KNOW for a fact my o2s are accurate because I verify what they say by checking the plugs. Once you learn to trust the sensor you’ll know when it’s lying to you and when it’s not. If you don’t verify the afr readings by reading the plugs then all you have is numbers on a gauge.
Rat Bastid
Dunamis Metron
Yep, experience with them is a big deal.
Dale Davies
Well-Known Member
Years ago Popular Hotrodding magazine went through a 1982? Chev Malibu wagon. Came with the limp wrist 305 that leaked oil, TH200 trans and 2.56 gears.
They pulled the engine and trans. The engine was rebuilt with a stroker 3.75" crank and 0.030" overbore to give 334CID. They installed a Comp 268H cam, a fair cam for street. I forget the intake they used. The car had the feedback Rochester carb. They replaced the 200 trans with a 700R4.
When they went to the strip it would lay over like it was lean. They did all kinds of tricks to tune the lean condition out. Finally a reader following the build called or wrote to inform them the cam had too much intake timing and overlap. The O2 sensor read the exhaust gases as rich and leaned the carb. They installed an Engle cam with slightly less duration but more lift. By then the carb was messed up so they got a replacement Holley feedback carb. End result was 15 something in the 1/4 with the 2.56 gears and 26MPG on the highway.
An AFR guage should read real close to what is in the exhaust. Placement of the wideband O2 sensor is important and should be a heated sensor. Any exhaust leaks will provide a lean reading. Once that sensor is supplying its output to a controller, the controller will try to bring the AFR into its fuel map range.
Not exactly ABA testing going on there. Might be hard to sort out what caused what. Are you saying that overlap caused the o2 sensor th read rich?
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