O2 sensor/air fuel meter with 100LL?


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Dan Thomas

Well-Known Member
Sep 17, 2008
100ll is ok for the engine. There is no issue there. The issue is O2 sensors are of a generation after leaded car gas. Catalytic converters can’t run on 100ll. There was no need to to develop an O2 sensor to use 100ll. Using an O2 sensor can be somewhat handy but it is only going to give an average of how many cylinders are tied to that pipe up wind of the sensor. Airplanes tend to run temp sensors. At work we run one in each exhaust, each cylinder head, and one on the turbo inlet. The mixture is extrapolated from that crossed with the fuel flow. If you want the efi to run on an o2 sensor like your car, you either have to run unleaded gas or be ready for the engine to run on a limp home mode when it gets fouled.
Something to know and remember: 100LL has four times the lead that 80 did, and 80 was pretty close to the old leaded Mogas. That extra lead causes much faster sparkplug fouling in aircraft engines designed to run on 80, and it doesn't do the oil much good, either. Converted auto engines could suffer the same way, especially if they're liquid-cooled.

Straight 100 (the green stuff) had eight times the lead of 80. Don't see it or 80 anymore. Once in a while I'll hear of some airport having 80, but it would be rare. What refinery is going to bother with such tiny volumes?


Well-Known Member
Log Member
Feb 19, 2012
If we weren't such a niche market someone might have adapted optical O2 sensors for ICE on 100LL. It looks like the physics would work, but probably needs $^:eek: to develop.
If blue flame is just right and yellow rich and white hot/lean it does not seem at first glance hard...probably is though.
Lots of cheap IR meters ..also seems like a good way to measure temperatures

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Nov 14, 2009
Rocky Mountains
  • EGO sensor - meaning 'Exhaust Gas Oxygen Sensor'
  • HEGO sensor - meaning 'Heated Exhaust Gas Oxygen Sensor'. This refers to the heater element included within the 3-wire and 4-wire types.
  • Oxygen sensor - referring to the fact that the Lambda Sensor measures the Oxygen present in the exhaust gas stream
  • O2 sensor - back to school for this one - O2 is the chemical symbol for an Oxygen molecule. The number 2 reminds us that atoms of Oxygen like to go around in pairs
  • Planar or 'Wideband' sensor - different to an ordinary Lambda, this is a more modern kind of sensor. It is fitted to engines that meet the latest emissions requirements.
  • You may hear the word 'probe' substituted for 'sensor' - eg. Lambda Probe
  • The word 'sonde' is common across mainland Europe - eg. Lambda Sonde