The Truth About Injectors; Injector Flow Bench
Once again, an old truth re= ars its ugly head; ‘if you don’t want to know the truth, you shouldn’t ask the question!’
The fuel injector test benc= h is one of those testing devices, like the dynamometer, that will produce results t= hat make your life more difficult.
The injector test bench I&#= 8217;m familiar with is the ASNU but there are others.
This particular device has =
an
ultra-sonic bath for cleaning the business end of injectors and a pump and
fixtures to test the flow rate of the injectors at a variety of different d=
uty
cycles and pulse rates. The pulse rates are represented as RPM but I would
think that 5000 RPM would be 2500 pulses per minute. And, it is.
![3DP1010003](3D"Injectors_files/image002.jpg")
Photo 1 This is the ASNU injector test bench. The ultra-sonic cleaner is beneath the stainless steel cover on the left, the graduated cylinders are used to meas= ure the flow.
Another parameter that is c= hecked when testing fuel injectors is the spray pattern. Fuel Injectors are suppli= ed with a variety of spray patterns for different results. There are multi-hole tips that produce a wide pattern and single-hole types that produce a pencil thin stream.
![3DP1010007](3D"Injectors_files/image004.jpg")
Photo 2 This shows the spray pattern test. There are extra points for anyone who can identify the rider and bike in the photo in the background.
The quality of the spray pa= ttern is determined subjectively by visual inspection, while the flow rates can be determined objectively by measuring the flow in graduated cylinders.
The ASNU offers the ability= to test the injector flow using a test that runs through about 10 different pulse r= ates and duty cycles. This basic test takes 30 seconds, 3 seconds per cycle but it can be run at any of the cycles from 5 seconds to 30 seconds adjustable in 5 second intervals.
Here comes the important pa= rt.
The earlier versions of the= ASNU would only support the tests at different pulse rates and the several duty cycles.
The latest version supports= a ‘static flow’ or 100% duty cycle test and it has a calculator t= hat is used to determine the maximum rated flow of an injector.
Several years ago, I worked= at a shop that had the older version of the ASNU and every time I checked inject= ors there seemed to be a significant mis-match in their flow rates.
This result made me wonder = why I never saw a pair of injectors that weren’t within a few percent of one another. It also made me wonder how a manufacturer could sell a product that varied so much.
![3DP1010008](3D"Injectors_files/image006.jpg")
Photo 3 Here is what, from my experience, is typical for a test of 6 injectors test= ed at one pulse width and some frequency that relates to the operating range of our engines.
This is the result of a tes= t of 6 Weber IWP069 (yellow band) injectors at some combination of pulse width and cycles that represents the range in which they normally operate (so kill me= , I didn’t take good notes.) But, it’s typical of the kind of resul= ts I usually see.
One answer was that all of =
the bad
injectors sold to Ducati and Harley-Davidson were shipped to
I may not be a good person,= but I doubt that Ducati or Harley-Davidson know that. Maybe I‘m just not paranoid enough?
If the answer isn’t t= hat the motorcycle manufacturers have sought me out to be the recipient of their rejects, what is the answer?
In all of the flow tests th= at I performed using the older version of the ASNU I could only test with the injectors pulsing, which is the mode in which that they are expected to operate. When I finally ran a test at static flow I realized how the inject= or manufacturers could offer their injectors with anything like a quality stan= dard that I had previously not seen.
![3DP1010003](3D"Injectors_files/image008.jpg")
Photo 4 This is a ‘Full Flow’ test of 6 W= eber IWP069 injectors. This is the test that allows the injector manufacturer to offer a quality standard of plus-or-minus 1.5% at maximum rated flow.
I was testing 6- IWP162 Web= er Pico injectors from H-D Delphi systems trying to find matched pairs when I decid= ed to try the new ‘Static Flow’ test to determine the flow rates.<= /p>
I was floored, they were al= l within 1.5% of one another! They were nearly within +&- 1%!
Since then I have found the= same result with every type of injector I’ve tested. I’ve tested the side-feed injectors from Magneti-Marelli H-Ds and Ducati 748-916-996 and th= ey follow the same patterns. They have quite a bit of variation when they are cycled but they are very close when tested at full flow.
![](3D"Injectors_files/image010.gif")
Chart 1 This is a graph of 8 – IWP069 injectors at full flow.
This is the graphic represe= ntation of a full-flow test of 8 – IWP069 Weber Pico injectors. I just added = one to the left and one to the right from the test of 6 injectors from the prev= ious photo.
I decided to do a fairly co= mplete test of 8 of these IWP069 injectors, so I tried to use a combination of pul= se width, cycles-per-minute, and time that would give comparable flow volumes = (so they could be compared directly.)
Then I averaged the values = of each of the 6 tests and calculated the percent variation from that average.
With this information I can represent the results as flow volume comparisons for each test, or percenta= ge variation for the same tests.
First the test results;
|
Cycles |
Injectors |
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1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
|
Average |
|
|
Flow,
ccs |
|
|
|
|
|
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|
|
45s
- 12mS@2500 |
83.0 |
85.0 |
85.4 |
85.0 |
82.0 |
85.5 |
86.6 |
82.5 |
|
84.4 |
|
|
98.4% |
100.7% |
101.2% |
100.7% |
97.2% |
101.3% |
102.6% |
97.8% |
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|
45s
- 6mS@5000 |
85.0 |
88.0 |
90.0 |
89.0 |
85.0 |
90.0 |
91.5 |
84.2 |
|
87.8 |
|
|
96.8% |
100.2% |
102.5% |
101.3% |
96.8% |
102.5% |
104.2% |
95.9% |
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|
30s
- 12mS@5000 |
86.7 |
89.0 |
90.2 |
89.7 |
86.0 |
90.2 |
91.2 |
86.5 |
|
88.7 |
|
|
97.8% |
100.4% |
101.7% |
101.1% |
97.0% |
101.7% |
102.8% |
97.5% |
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35s
- 3mS@10,000 |
78.0 |
80.0 |
85.1 |
83.6 |
78.2 |
82.2 |
86.1 |
78.2 |
|
81.4 |
|
|
95.8% |
98.2% |
104.5% |
102.7% |
96.0% |
101.0% |
105.7% |
96.0% |
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30s
- 2.5mS@12,000 |
73.1 |
75.0 |
80.8 |
79.1 |
73.0 |
77.8 |
82.8 |
73.6 |
|
76.9 |
|
|
95.1% |
97.5% |
105.1% |
102.9% |
94.9% |
101.2% |
107.7% |
95.7% |
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|
|
Full
Flow |
72.0 |
73.0 |
72.8 |
73.0 |
71.8 |
73.1 |
73.1 |
72.1 |
|
72.6 |
|
|
99.2% |
100.5% |
100.3% |
100.5% |
98.9% |
100.7% |
100.7% |
99.3% |
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Table 1 This is the table of results from six different tests on 8 Weber injectors<= /p>
Next, the flow graphs;
![](3D"Injectors_files/image012.gif")
Chart 2 The different flow volumes resulted from different test times at different = pulse widths and cycle rates. This isn’t the best way to show the results.<= /p>
You might notice that the g= reatest variation occurs at higher cycle rates (RPMs) that would be good news for t= he H-D guys, not so good for the 999 Ducati guys.
Finally, I decided to graph= the results by the percentage variation from the average and that graph looks l= ike this;
![](3D"Injectors_files/image014.gif")
Chart 3 This chart very effectively shows the percentage of flow variation among the examples tested. They vary from plus 8% to minus 5%
This accentuates the realit= y that the variation is greater at higher cycle rates and it also shows that the variation is greater at shorter duty cycles. Compare the results between 6m= S@ 5000 and 12mS@5000.
Conclusions
The static flow results hav= e to be the type of test that allows a manufacturer to claim any product consistency whatsoever.
Since we know we’re n= ot supposed to run injectors beyond 80% duty cycle (actually you can probably = run closer to 90% on engines that operate under 6000RPM) the static flow test h= as no relevance other than determining what size injectors any application requires.
Anyone who has been involve= d with fuel injection tuning has seen case after case where some ‘cannedR= 17; map hasn’t been able to produce the good results that a custom calibration will produce.
The results of this testing= would be the answer to the question ‘why don’t ‘canned’ m= aps make every bike run right?’
Matched injectors
It has been pointed out to = me that some companies sell ‘matched injectors’ that are matched at sta= tic flow. If the results of this test are typical or even believable, matching injector flow rates at static flow doesn’t begin to address the issue= s.
Marren Fuel Injection has b= een offering matched injectors that are 0% variation at full flow and plus-and-= minus 2% at a controlled pulse rate. Clearly they ‘get it.’
The last question is; do the
vehicle manufacturers who have these things certified, and the EPA, underst=
and
this and do they realize it is a problem?
If they do, do they enter t= he certification process with matched, nominal injectors and rated fuel pressu= re regulators?
If the answer is ‘no they weren’t submitted= with matched, nominal injectors’, then, none of the vehicles produced (until the manufacturer has introduced closed loop systems) have managed to meet the certified emissions standards except the vehicle that were submitt= ed.
If the answer is ‘yes they were submitted with ma= tched, nominal injectors’, the same thing holds true except there is a slightly greater chance that some vehicles have met the standards.
I’ve been told by som= eone in the know’ that manufacturers do create their certified calibrations w= ith matched injectors.
As the EPA and CARB are cra= cking down on older vehicles that don’t meet emissions standards in place at the time of manufacture, they should be aware that these variables involved with any non-closed-loop system mean that the majority of these older vehic= les, modified or not, have never met the standards that were in place, and it is their lack of testing that has kept them un-aware of these facts.