Injector Dead Time Calculator (Injector Characteristics)
Source: https://commons.wikimedia.org/w/index.php?title=User:David_DeGrace&action=edit&redlink=1
You can measure the fuel flow of the injectors. But you need to find the injector dead time/injector offset. This injector dead time calculator can calculate the dead time with data you can get from your injector cleaning/flow checking machine.
This is the calculator, enter the data, get the dead time. Detailed instructions on how to use the calculator are included below
This is a new calculator, if you see anything obviously wrong with the calculations, leave a comment below!
Fuel Injector Dead Time Calculator – Required Data
We need to carry out three tests with
The same voltage and same fuel pressure over each test and
For each test, we must alter the pulse width/injector on time (and know the pulse width for each test) and
We need to measure the total fuel flow of the injector over one minute.
In Short
We need:
–Pulse Width for each test (should be different between each test)
–Pulse frequency for each test (can be the same between tests)
-Total fuel flow volume (cc) per injector over one minute (the test is one minute long, or run test for 30 seconds and multiply flow volume by two etc)
-And fuel pressure and injector voltage should be the same across all the 3 tests.
Write down the data for each test and enter the numbers into the StrikeEngine fuel injector characteristic calculator to get the injector dead time.
Varying Voltages
To calculate injector characteristics for different voltages, we need to repeat the whole process with the new voltage but same fuel pressure as before.
How to Find Pulse Width and Frequency?
If the device/fuel injector cleaner/tester you are using to test the fuel injectors does not tell you the frequency and/or pulse width of the mode/program you are using, then you’ll need a multimeter than has an oscilloscope function. The scope function will tell you the frequency of the pulse and you can visually see the pulse width on the table. If you don’t have an oscilloscope and you want something cheap and reliable, I recommend this model , KKMOON KKM828. Its reliable, sturdy and has the oscilloscope function and is low cost for what you get.
About Injector Dead Time
I think the most important thing to remember is not to ask the injectors to operate close to their injector dead time. If for example the injector dead time is 1 millisecond, don’t ask for pulse widths of one millisecond or less. Injector pulse width requests less than the dead time leads to unpredictable fuel flow.
And also, not to run our injectors close to where their “off time” is close or less than the injector dead time/injector offset time. For example if the injector duty cycle we are asking for is 90% and this leaves only 2 millis when the injector is not being ask to flow, and the injector dead time is 3 millis, we are not going to get consistent fuel flow when we need it most.
Why Do We Need Injector Dead Time?
Some examples.
-We want to know what condition of our injectors. Are they behaving consistently, is the dead time similar for different pulse widths and frequencies (the correlation number in the calculator)?
-We have a stand alone ECU which is asking for this data, but the injector supplier does not supply the dead time.
-We want to precisely time the injection of fuel into the engine. Not so critical at low RPM but it maybe at higher RPM. At 6000RPM, 1 millis equals 36 degrees of crankshaft rotation. Note: The injection dead time includes the time it takes to open and close the injector. For fuel timing, ideally we would know the injector opening time specifically. Given that it usually takes longer for the injector to open than to close, using an open time that is 50% to 70% of the total dead time would probably get us in the ball park.
Injector Dead Time Videos
Here is a quick vid highlighting the issues of tuning when we don’t have the injector latency/injector offset/injector dead time data.
And Haltech touch on injector offset in this video (Timestamp 13:30). Injector dead time is most important at idle and light loads.
Shane T has some interesting video showing the importance of knowing the injector offset and an alternative method (much more complicated than the one on this page!). Idle effect. Alternative measuring method.
Equipment
What equipment should we use to gather the data for the calculator. Ultimately, I think a proper injector cleaning/testing system is by far the cleanest, easiest and most reliable way to go. Fortunately these setups are not too expensive these days, for example this one looks like it will do the job. We run the tests on the system, log down the data and enter the data into this calculator.
