Air / fuel mixture meter

[ccsmith51]

I have an 02 sensor and the air /fuel ration gauge below:



I have an O-360 in my RV-4. I'm thinking about installing this gauge in the panel, and the sensor near the EGT probe.

Does anyone have an air / fuel indicating system installed?

Would this be a beneficial addition to my panel?

Thanks,

[airguy]

If you're burning 100LL the oxygen sensor will likely have a very short life.

[ccsmith51]

Originally Posted by airguy

If you're burning 100LL the oxygen sensor will likely have a very short life.

I burn 100LL, and I'm told the sensors last 100 hours or so on average. I'm looking into running 91/93 non-ethanol unleaded mogas if I can find it economically and conveniently. That would certainly extend the sensor life.

I have only one CHT and EGT. My question regarding the meter is, would the meter allow me to lean better, when compared to pull the knob until rough then push it back in. If so, and I got lower fuel consumption, then the savings would certainly pay for a $30 sensor every 100 hours or so....

I read an article on leaning aircraft engines and found the following:

"The fuel / air ratio for best power is around 1:13 and for best specific fuel consumption (SFC) it is 1:17. Peak EGT occurs at the chemically correct ratio of 1:14.7 and peak CHT at a slightly richer ratio."

On my meter the center two green LED's light at 1:14.7.

[Sig600]

Wide or narrow band O2 sensor?

[ccsmith51]

Originally Posted by Sig600

Wide or narrow band O2 sensor?

I don't know, and can't seem to find out with a simple Google search. It is a Bosch 11027.

[Sig600]

I suspect narrow band (wide band are pretty expensive, the sensor is bulky), in which case it's worthless to you IMO. If O2 sensors were an accurate/reliable way to meter fuel over EGT I think we would've seen it on production engines by now. The other piece of that puzzle is you don't have a MAF to tell the system how much air is going in the front end, so how is it going to give you accurate info?

[Neal@F14]

Since this is an automotive type air/fuel mixture indicator (Intellitronics ?), then I'd be worried that where it shows its green "happy" range is probably the stoichiometric ratio which might place a Lyclone aircraft engine right at peak CHT (between 25 and 50 ROP EGT) where you probably don't want to be running it continuously for very long.

[ccsmith51]

Thanks for the replies and insights. It sounds like this arrangement will not provide me with any reasonable benefit. You have saved me a bunch of time that I can apply to other improvements in my recently purchased bird!!

With that in mind, with a carbureted engine, and only one EGT and one CHT, is the best way to lean to pull mixture until roughness, then richen until smooth?

BTW, that is what I was taught when I learned to fly in Cherokee's in the 70's. The A65 powered Champ in which I got my first 50 hours in the 60's had no mixture control at all!!

Thanks!!

[L.Adamson]

Originally Posted by ccsmith51

With that in mind, with a carbureted engine, and only one EGT and one CHT, is the best way to lean to pull mixture until roughness, then richen until smooth?

It works for me. I'll go two to three turns in, with the red knob. There are a range of temps I like to see on my EGT. Usually in the ballpark of 1325-1350. If it's lower, I know that I'll end up clearing the plugs during the mag check. Note: EGT's can vary between planes, depending on the exact location of the sensors. I'm just running one on cyl. #3.

L.Adamson --- RV6A

[rv6ejguy]

The narrow band meters are not particularly useful or accurate as the sensor is really designed as a switch for ECUs to target stoichiometric mixture of around 14.7. They are not too accurate on either side of this. They output a 0-1V, non-linear signal.

Wideband types output a 0-5V linear signal and are highly accurate. They are the modern way to tune for best power and to see what the AFR is under all conditions. You can use Decalin Runup lead scavenger in your 100LL to extend sensor life.

EGTs work well too once you establish where best power is although more factors are involved there and it is somewhat indirect. EGTs work well for setting best mixture for LOP operation.