Since Injector Dynamics showed up claiming high pressure capability for our injectors, it seems like the new buzzword in the injector market. It is now common for suppliers to claim that their injectors run at high pressures.
Some have even gone so far as to one up us! "If the ID2000 will run to 9 bar (130.5 psi) then our 2000 will run up to 10 bar (145 psi)!"
We recently ordered a set of EFI Wizard 2000cc injectors and the paperwork claimed "These injectors have been tried and tested to operate at fuel pressures in excess of 10 bar. On our larger fuel injectors such as the 2000's that translates into over 4000cc/min."
When we got them on the bench one of the first things we found was that with a 14V supply, the injectors stopped opening at about 108 psi. So much for 10 bar! Maybe they meant with a 24V electrical system?
The other thing we noticed almost immediately was that as we increased pressure, the flow decreased. That's right! At 14V supply voltage with a 5 millisecond pulsewidth the flow actually decreased as we increased pressure above about 60 psi.
Seems impossible right? Not really. There is a simple explanation, and as usual a graph to illustrate what's happening.
We've all seen the internet math for injector flow rate right? It says that as we increase the pressure, the increase in flow is equal to square root of the pressure change. So for instance, if we increase the pressure from 3 bar to 4 bar the flow should increase by 15.4% (4 divided by 3 equals 1.333, and the square root of 1.333 is 1.154 for a flow increase of 15.4%)
This rule holds true if the injector is held wide open in the static position, but once we cycle it on and off as we would on a running engine the whole picture changes. As fuel pressure is increased more force is required to open the valve, and so the dead time increases. As a result, the dynamic flow does not increase at the rate that it should.
One of the many tests that we perform here at Injector Dynamics is the pressure sensitivity test. It involves testing the injector dynamically at 3 bar, and then increasing the pressure in small increments and measuring the flow increase.
This type of testing clearly illustrates an injector's ability to deliver fuel at higher pressures, and when the data is plotted graphically it certainly separates the men from the boys.
The best part is that it doesn't require our sophisticated equipment to perform this test.
Do you question our assertions that the EFI Wizard has real issues at high pressures (well, we don't really consider 60psi 'high')? No problem, just install one in your New Age or ASNU flowbench, set the pulsewidth to 5 milliseconds, and let it rip. (These parameters are especially convenient by the way because EFI Wizard's own flow test sheet shows flow data at 5msec. Clearly only at 3 bar though!)
So what does this test show? For starters, it shows that the ID1000 has a weaker magnetic circuit than the ID2000, or the ID725 because it will not handle the higher pressures that the other two are capable of. Those of you familiar with the ID line know that we set an upper limit of 100 psi for the 1000, while we recommend pressures as high as 9 bar (130.5 psi) for the ID2000, and the ID725. The graph makes it clear why doesn't it?
Did anyone really think we were guessing when we set those limits?
It also shows that the magnetic circuit in the EFI Wizard could benefit from a dose of Viagra.
So what would you consider to be the maximum useful pressure for the EFI Wizard 2000?
And more importantly, now that we have clearly illustrated just one of the many untrue claims made about the product, will they continue to market them using the same unproven "me too" specs?
Or do we need to continue pointing out the obvious? Stay tuned...