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Mechanically measured AFR vs wideband measured AFR

Understanding AFR

Discussion and questions related to the course Understand AFR


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Hi guys, I'm just getting into tuning snowmobile and ATV engines. My current set up for afr measurement is to use an air flow meter and a fuel flow meter while the dyno max software does the calculations for me. When tuning I do rpm sweeps from the lowest rpm that the dyno can hold the engine steady and then sweep at around 250 to 300 rpm per second. I am just wondering if there is a lag time when I measure this mechanically compared to using a wideband sensor in the exhaust. I have seen data when both ways of measuring afr were used on the same sweep run and was surprised at how different the results were. I basically just want to know if the wideband afr sensor is more accurate for transient tests?

Thanks in advance, I love the website.

I would say in general terms that measuring AFR with a modern wideband meter would probably be far more accurate than measuring airflow and fuel flow. Obviously in theory measuring air and fuel flow 'should' give accurate results, but the key is in the accuracy of your flow meters. Having very briefly looked into fuel flow meters myself, the price and accuracy of the available meters varies dramatically. To get to the required accuracy for what you're needing, I'd imagine you'd need to be at the pointy end of the price range - Same could be said for the airflow meter.

With the cost of quality widebands available on the market these days, I'd recommend investing in one. No tuner can really be without one and it will be handy if you ever want to do any real world testing as a portable wideband can be taken with you.

Ok I'll do that. Thank you for the reply.

No problem. Once you can compare the data I'd be interested to hear your findings. We intend to add a fuel flow meter to our new Mainline dyno at some stage for testing purposes.