Air to Fuel Ratio - What's the Point?

[Vlad Soare]

Hello,

One of the things that can be displayed on the instrument cluster is the air to fuel ratio. What's the point of that?
If I had a carburettor and wanted to experiment with its tuning, then I guess the air to fuel ratio would be a good indicator of what I was doing. However, in a fuel injected engine this ratio is automatically set by the ECU and cannot be changed or influenced by external means in any way. So, what's it to me whether the air/fuel mixture is lean or rich, considering that I can't do anything about it anyway? What am I supposed to do with this information?

Is it just a beautiful but useless gimmick, or does it really serve some practical purpose that I'm missing?

Thank you.

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[EFI]

AFR is a critical thing to keep an eye on when driving hard, you don't want that to go too lean. For a stock car yeah it's pretty useless, but for others that are modding the cars it's a very useful feature. Salut.

 

[1Slow5PointOh]

It's actually helped me. I have long tube headers on my car and have been tuned by lund. I have had zero problems with my car, no hesitations, no codes, nothing. Recently though, my built in AFR gauge has been a static 14. Not moving in the slightest. I believe it's either an exhaust leak or a bad O2 sensor. I wouldn't have even known given the car still runs perfectly.

 

[Johnnybee]

I keep mine up as one of the three gauges I can display in the centre of the digital display. Keeps a look out for me for the low pressure sensor in the fuel rail going bad.

 

[The_Phantom]

I work with AFR's on modern engines every day. On a stock car, really it's just a cool gadget as was said above. However, if adding forced induction, long tube headers, certain CAI's.....you need to remap the ECU to recognize your changes. Otherwise, you can lean out the motor which results in a wonderful noise followed by many expletives.

 

[Kong76]

I pay attention to it quite frequently especially during WOT and after release to check the snap back. Idle as well. It will help in trouble shooting certain issues with performance.

 

[Shifting_Gears]

Yep, useful tool.. stock or modded.

 

[Vlad Soare]

I see. I hadn't thought about modifications. It makes sense now.
Thank you.

 

[tom_sprecher]

Or the vacuum gauge.

 

[dg556]

It's actually helped me. I have long tube headers on my car and have been tuned by lund. I have had zero problems with my car, no hesitations, no codes, nothing. Recently though, my built in AFR gauge has been a static 14. Not moving in the slightest. I believe it's either an exhaust leak or a bad O2 sensor. I wouldn't have even known given the car still runs perfectly.

Can i ask what it was before it being pinned to 14.0? I have just straight pipe after the cats and a cold air and my AFR will fluctuate between 13.8-14.1 all the time (except for closed throttle) IS this normal? Also very weird to me is when i get on the throttle i get the smell of exhaust filling the cabin and i also have cold air pouring in from under the steering wheel, i can not figure out why its happening and i am wondering if these issues are related or coincidental.

 

[W.O.T. Stang]

Or the vacuum gauge.

I always wondered that myself on the PP cars. It seems much more useful to have oil temp there! Like the gt500s. I wonder if it’s possible to swap one in somehow.

 

[SheepDog]

I always wondered that myself on the PP cars. It seems much more useful to have oil temp there! Like the gt500s. I wonder if it’s possible to swap one in somehow.

I wish oil temp was displayed as a real temperature, instead of Low, Normal, High. What the hell is "Normal". Useless

 

[tom_sprecher]

IIRC you can swap in the oil temp gauge from the GT350, but the dial color can not be changed. Not that that would stop me.

I would much more prefer an oil temp gauge, but not enough to go tearing into the dash. As it stands now I have boxes of parts for mods sitting around. It's so bad that the Stage 2 PP kit I bought 2 years ago has yet to be installed.

 

[Nickel]

One of the most important things to pay attention to with modifications and tuning. I leave my display on gauge mode. 14.7 is the perfect ideal ratio. You want it to be under that under load, but if I saw it over that under load, I would be pretty worried and probably have it checked out. Rich is safe, lean blows engines.

 

[Cory S]

14.7 is the perfect ideal ratio. .

Actually, with E10 fuels, 14.1-14.2:1 is the ideal lambda target. Ford has been calibrating for 14.1-14.2:1 AFR since late 2010.

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