Various Air fuel Ratio readings

[Dougster]

Hey all.

Need some input here with regards to air fuel ratio gauges

I'm sure you know there are a few types in the market...

Some analog ones which show either a needle or a light indicating a RICH, LEAN, or STOICH mixture...

Then there are some which just change from red lights to green lights....

Those i understand..

BUT, how do you read the gauges which show a numerical value... for example, the A/F reading function on the Apexi Pen Type Timer, displays a number...
How do you interpret that? Is it a number on a scale ? Or is it a value of some sort?

eg:
http://www.eautoworks.com/images/350/pic3470.jpg


Do share yea :)

Thanks in advance!

 

[speed2horizon]

A/F Ratio...

In stoichiometric combustion, 14.7 AIR : 1 FUEL. Which ever higher(bigger number) means lean, lowe number means rich...

Simple calculation:

18 AIR: 1 FUEL mean 18 portion of air and 1 portion of fuel. Anyway, the value is taken from the O2 sensor. In other words, it's not so accurate...

 

[DonaldTan]

Wait a min bro,

your turbo timer got AFR?


DonDon

 

[evo5755]

Wait a min bro,

your turbo timer got AFR?


DonDon

Only Apexi pen type have those so called "AFR" reading. hehehe..

but those rading can throw to the drain la it is useless. Accurate AFR meter would include those from Innovate or AEM Uego. Those AFR meter with sensor would cost around rm1.5k or more. So from the price, you can know the accuracy for 1.5k meter with rm250ish turbo timer with AFR function.

Speed2horizon,

since we are in AFR topic again, what from stoichiometric, what does various AFr reading represents to the horse power or combustion power? eg 12.2 AFR vs 11.3 AFR. Yes 12.2 is leaner than 11.3 but what does it represents in terms of combustion?

 

[DonaldTan]

Target Range...


Can anyone inform what range should the car be? 12? 14? or 10?


DonDon

any difference require between turbo and NA?

 

[crazykatak]

the higher the voltage ( in milivolt ) the richer the AFR mixture is.

in terms of combustion , it depends on the efficiency of the engine to combust the compressed AF mixture..as most of it is wasted as heat

 

[poosiong]

i m using autometer afr oso,but still dunno how is the mean...
sometime jumps very faster,when u kick padel then its at rich...like useless...dunno..hehe

 

[ftzone]

narrow band o2 sensor (stock o2 sensor) to read afr is basically useless for fine tuning the engine. be it from APEXi or Autometer. those are just for show!

a wideband o2 sensor from bosch would be a better bet reading afr. Innovate, Dynojet are easily available in Malaysia and they are easy to use.

the latest cars like VW Golf GTi, Toyota Camry are now equipped with wideband o2 sensors as their cost are brought down in mass production. that is what i heard at least.

as for the optimum power range, it is very subjective... but these are the basic guidelines;
Naturally Aspirated Engine - (WOT) 13.5afr
Turbo Charged Engine - (WOT) 11.8afr (Need to be richer if running higher boost)
Super Charged Engine - (WOT) 11.5afr
Bolt-On Turbo with high compression Engine - (WOT) 11afr
WOT - Wide Open Throttle.
As for cruising speeds or at below half throttle the optimum would be still 14.7afr.

Symptoms for the engine being too rich in afr.
1. Engine RPM climbs too slowly to redline or wouldn't even reach certain RPM.
2. Engine performance bogging like choking... exhaust smoke is black
3. Spark Plugs are soaked and are black in color covered with carbon (Provided the correct gap and heat range are being used)

Symptoms for the engine being too lean in afr.
1. Engine hesitates / jerking when the RPM reaches the leanest afr point.
2. Spark Plugs are white... (light brown or grey color should be the color of the spark plugs when in good afr, correct spark plug gap and heat range.)

The other method is monitoring the Exhaust Gas Temperature. Rich usually gives lower EGT reading and Lean just the opposite.

hope that helps.

 

[darkness3299]

hey guy,

im having this problem where my autometer afr is just stuck on the lean indicator. any idea why its like that? the last time when i use it, it used to jumping left and right and only when i full throttle its stays in rich.

its kinda frustrating coz when i used it on my 'ol engine i can see that its working.

thanks fer help guys!

 

[speed2horizon]

Only Apexi pen type have those so called "AFR" reading. hehehe..

but those rading can throw to the drain la it is useless. Accurate AFR meter would include those from Innovate or AEM Uego. Those AFR meter with sensor would cost around rm1.5k or more. So from the price, you can know the accuracy for 1.5k meter with rm250ish turbo timer with AFR function.

Speed2horizon,

since we are in AFR topic again, what from stoichiometric, what does various AFr reading represents to the horse power or combustion power? eg 12.2 AFR vs 11.3 AFR. Yes 12.2 is leaner than 11.3 but what does it represents in terms of combustion?

Well, stoichiometric combustion means theoretically complete combustion reaction between air and fuel where no excess fuel nor excess air that is not combusted. The fuel consumption/horse power is very dependent on the combustion efficiency, and combustion efficiency is very dependent of AFR. U dunno about that..?

Btw, the AFR reading from the Apexi extract directly from the Narrowband O2 sensor on the exhaust. It is still an indicative figure for reference. But it's less accurate compare to the wideband O2 sensor. Price difference also because the Apexi does not provide the sensor... If you gonna buy the new narrowband O2 sensor alone, it still cost hundreds...

anyway, in most cases AFR reading is more for tuning purpose. But if a very lean figure (e.g 15-16) is observe, it's not good for the engine due to the higher knock possibility. If too rich (e.g 9-10) is observed, the engine feels not responsive and burning fuel for nothing... fuel released through the exhaust unburnt.

 

[silver_le]

can we tune engine with exhaust gas temp meter
and are autogauge product reliable to used

 

[jinkl]

Only Apexi pen type have those so called "AFR" reading. hehehe..

but those rading can throw to the drain la it is useless. Accurate AFR meter would include those from Innovate or AEM Uego. Those AFR meter with sensor would cost around rm1.5k or more. So from the price, you can know the accuracy for 1.5k meter with rm250ish turbo timer with AFR function.

Speed2horizon,

since we are in AFR topic again, what from stoichiometric, what does various AFr reading represents to the horse power or combustion power? eg 12.2 AFR vs 11.3 AFR. Yes 12.2 is leaner than 11.3 but what does it represents in terms of combustion?

wht AFR means is Air to Fuel ratio , which 12.2 is leaner than 11.3 this is because
12.1 amount of air : 1 amount of fuel
11.3 amount of air : 1 amount of fuel

lets jst say la the air is a number, jst an example la , an amount of 100 is in the combustion chamber, and you are running 12.1 :1 AFR , so wht u will get is , u will need 8.2 amount of fuel

richer and leaner affects exhaust temp , that is why turbocharged or supercharged cars
are tuned to have more fuel , one reason is to cool your exhaust temp and another thing is to
prevent detonation or premature which could damage your engine, its more to a safety guideline , further more your are running boost which is compressed air , where air is more dense and it needs more fuel to burn it , lean fueling will cause high exhaust temp and detonation, might just put a hole in your piston or melt them :)

Bump:

can we tune engine with exhaust gas temp meter
and are autogauge product reliable to used

just explained above , you cant tune ur engine with those tools , yes you can , but not accurate at all and it might take more r&d and time

 

[speed2horizon]

wht AFR means is Air to Fuel ratio , which 12.2 is leaner than 11.3 this is because
12.1 amount of air : 1 amount of fuel
11.3 amount of air : 1 amount of fuel

lets jst say la the air is a number, jst an example la , an amount of 100 is in the combustion chamber, and you are running 12.1 :1 AFR , so wht u will get is , u will need 8.2 amount of fuel

richer and leaner affects exhaust temp , that is why turbocharged or supercharged cars
are tuned to have more fuel , one reason is to cool your exhaust temp and another thing is to
prevent detonation or premature which could damage your engine, its more to a safety guideline , further more your are running boost which is compressed air , where air is more dense and it needs more fuel to burn it , lean fueling will cause high exhaust temp and detonation, might just put a hole in your piston or melt them :)

Bump:

just explained above , you cant tune ur engine with those tools , yes you can , but not accurate at all and it might take more r&d and time

Anyhow, I'm not too sure why u said it's not accurate. But i tested with my stock TD04L with stock actuator, indicative scale looks quite decent...

 

[jinkl]

Anyhow, I'm not too sure why u said it's not accurate. But i tested with my stock TD04L with stock actuator, indicative scale looks quite decent...

3 nice links for good reading

http://en.wikipedia.org/wiki/AFR_sensor
http://www.iwsti.com/forums/cobb-street-tuner/36914-stock-narrow-band-o2-vs-lc-1-wideband-o2-lots-data.html

also do reasearch about the voltage output scale between both the systems, u would see the much more too

sit infront of dyno everytime :) so i alwiz do see diffrence in the readings
even if it has a small diffrence in some cars , it has the capability to blow up the engine if tuned using it.

 

[speed2horizon]

3 nice links for good reading

http://en.wikipedia.org/wiki/AFR_sensor
http://www.iwsti.com/forums/cobb-street-tuner/36914-stock-narrow-band-o2-vs-lc-1-wideband-o2-lots-data.html

also do reasearch about the voltage output scale between both the systems, u would see the much more too

sit infront of dyno everytime :) so i alwiz do see diffrence in the readings
even if it has a small diffrence in some cars , it has the capability to blow up the engine if tuned using it.

Oppss..my mistake Jin, I only have boost meter from Autogauge... I was dreaming. I thought u guys were talking about boost meter... Hehehe...