The resulting fuel flow is now equivalent to a 10.000 ms pulse width. 920 for an actual pulse width of 10.920 ms. To double the fuel flow, our ECU will multiply the base pulse width of 5.000 ms by 2, and then add the dead time compensation value of. The resulting fuel flow is now equivalent to a 5.000 ms pulse width. 920 ms to our base pulse width of 5.000 ms for an actual pulse width of 5.920 ms. 920 ms entered as our dead time compensation, our ECU will add. Now let's consider the same injector and the same request for double the fuel flow with the correct dead time compensation applied. To quantify the results of doubling the pulse width, we divide 4.080 into 9.080 and we get 2.225 which shows that by doubling the pulse width, we have increased the fuel flow by 222.5%. 920 ms equals 9.080 ms, and so our effective fuel flow is equivalent to a 9.080 ms pulse width. 10.000 ms minus our known injector dead time of. If we take the base pulse width of 5.000 ms times 2, we get 10.000 ms. Now let's consider what happens when the manifold pressure doubles, and the ECU attempts to double the fuel flow of the injector by doubling the pulse width. 920 ms, the effective fuel flow of the injector is equivalent to a 4.080 ms pulse width. If our base pulse width is 5.000 ms, and our known injector dead time is. Let's consider a situation where we have a dead time compensation value of zero entered into our ECU. By linearizing the output of the injector, the fuel flow responds accurately to the simple multiplication performed by the The dead time compensation is added to the base pulse width to linearize the output of the injector. Injector Dead Times - What You Don't Know Can Hurt You Holley's Untimed Sequential injection (like full sequential) also has the benefit of good idle quality with large injectors and improved fuel rail pressure balance (pulses) even though it doesn't inject in sequence with each cylinder's intake valve opening. It still injects fuel in accordance to the engine's firing order (programmed into EFI software), however, without a cam sync sensor, it can't identify #1 cylinder. Holley's Untimed Sequential injection strategy still injects once per revolution, but without a cam sync sensor. Read "Injection Timing", "Injector Dead Time" & "Individual Cylinder Trim":Īn individual runner intake manifold (multiple throttle bodies) is the one application where sequential injection has the least amount of benefits (power-wise), because the individual runner design gets it's own (isolated) air & fuel supply for each cylinder. Also, since sequential EFI only injects once per cycle, the injector dead time is not doubled ( like it is with non-sequential injection, which results in decreased fuel flow and sometimes requires a larger injector to compensate). FYI: Sequential Injection always requires a cam sync sensor/unit.Īnother benefit of sequential EFI, is the capability to phase the injector timing, during the intake stroke for best efficiency. However, for racing applications, the most significant benefits to sequential injection are good idle quality with large injectors (for the reasons in my quote above), improved fuel rail pressure balance (pulses), individual cylinder fuel correction (adjustments), and Injector End Angle tuning ( LINK). Also, according to page 152 of "How to Tune and Modify Engine Management Systems" (book by Jeff Hartman), sequential injection always gains power at peak torque and at peak horsepower. Sequential injection will always get slightly better fuel economy and cleaner exhaust emissions. Different injection method, but essentially the same amount of fuel consumed. The increased injector pulse width is why large injectors can still idle good under sequential control but not under Bank-to-Bank control (or Paired). The total injector duty cycle remains the same (two injector events per cycle with Bank-To-Bank, Paired), but with double the amount of pulse width from sequential injection. So even though the net amount of fuel injected is the same, sequential EFI does it with half as many injector events, by injecting double the amount of lb/hr - pulse width fuel. Sequential EFI injects the total amount of fuel (lb/hr - PW), once for each combustion cycle (4-stroke engine). Bank-to-Bank or Paired EFI injects half the amount of fuel (lb/hr - PW), twice for each combustion cycle (4-stroke engine).
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