One of the persistent mysteries in poor power production experienced in fuel injected engines.

Poor power - caused by mismatched injector fuel delivery.

What prevents many tuners from diagnosing the the problem of poor power production caused by variances in fuel injector fuel delivery rates, is the use of O2 sensors on dynamometers, and "tuning to an A/F Ratio" schemes, as promoted by "sellers" and "marketers" of dynamometer equipment.

When a tuner uses a dealership level dynamometer to tune, he will commonly look at an air fuel ratio that is based on the amount of O2 (oxygen) that is left in the exhaust. They will then change the injector pulse width to richen up all the cylinders so that the amount of O2 left in the exhaust gas is some "magic" so-called "A/F Ratio - commonly... 13.1:1 according to latest urban legend proclamations by common dealership level dyno manufacturers.

Let's assume that one injector flows 10% less and another 5% less than to other 2 injectors, who luckily are within 2% of each other.

They "A/F Ratio" crowd will richen up the fuel injection, and proclaim that it is as good as it can be and they don't know why the bike isn't one of the better examples of that model bike and send it out the door or out onto the track - not crisp, not smooth at part throttle / high rpm.
Watched it done all the time at AMA races..... You'd think that they would know better -

So - what happened? What is going wrong??
Let's assume that the two cylinder with the higher flow rated injectors "were" correctly fueled. The other 2 were 10% and 5% too lean.

So - instead of seeing that problem, as you could with a more sophisticated dyno, like the 5 Gas EGA EC997 chassis dyne systems, the tuner will simply richen up all cylinders until he gets some "magic" A/F Ratio (based on that exhaust residual oxygen %) and call it a day -

So - what he actually ended up with was sort of like this:
1 cylinder that is still 5% too lean (power loss), still, 1 cylinder just right (yippee!) and 2 cylinders 5% to 7% too rich (bummer - power loss).Compare that to all cylinders having the correct amount of fuel......

We did sponsored work for Arclight Racing
They had that problem of unequal fuel metering, cylinder to cylinder - Fix? Almost 2 True HP on 750 Supersport bike - That's diagnosable on the EC997 chassis dyne system, but not on common dealership level dynos that proclaim "tuning to an "A/F Ratio" as a panacea to lack of tuning knowledge and handicapped equipment -
All for the dealership level dyno's $2000 training per person and $1800 per year to learn how to not tune properly???

We had a GSXR750 that had been to multiple shops for poor power as a complaint, dynoed on "dealership level" dynos - using "a/f ratio" scheme for diagnosis.

This example is one of the worst occurrences that I've seen except for injectors from engines that have been running AMA legal race fuels - One them had a mysterious 3-4 TRUE HP loss -
With the 4 gas EC997 dyno..... that indicated..... "This is messed up!"

After 1 test, the 4Gas EGA EC997 indicated that "average" fueling was OK, but, the O2 level was very high - as was HC (hydrocarbon ppm). CO2% was sub 8%. Can't diagnose that on a dyno with an O2 sensor and the "A/F Ratio" scheme....... Another reason to NOT tune to an "A/F Ratio"........

Diagnosis, after 1 test, - Step 1 - Pull the injector rack, clean and match the injectors.

Result?  5+ TRUE HP / peak   and 2-3 TRUE HP / low and midrange rpms.

Just because an injector isn't listed, it doesn't mean that we can't do them.

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