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Performance Plus Fuel Injectors
Cleaned - Tested - Matched
One of the last (did I really say "last"?) mysteries in poor
power production is commonly experienced in fuel injected engines.
Poor power -
caused by mismatched injector fuel delivery.
What prevents many semi-professional 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 4 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 balance
injectors.
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Percentage
imbalance |
inj. 1 |
inj. 2 |
Inj. 3 |
inj. 4 |
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| initial |
11% |
93cc |
93cc |
100cc |
89cc |
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|
|
|
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| matched set |
2% |
99cc |
100cc |
99cc |
98cc |

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