Rovergauge injector duty cycle and pulse width interpretion
Discussion
According to RoverGauge at high rpm I seem to be getting a surprisingly low IDC.
e.g. RPM 4685 and Pulse width 8.91ms. Using an online calculator that equates to 34.79% IDC
While driving I obviously wasn't watching the IDC % as shown by RG so am relying (For the moment) on the logging and the online calculator
The engine is the equivalent of a Chim 500 with twin throttle carbon fibre plenum (ACT), original MAF and injectors and Lucas 14CUX
According to RG help
Injector duty cycle: The percentage of the time available between spark interrupts that represents the amount of time the fuel injector will be open. Once this reaches 100%, the injectors cannot flow any more fuel and any additional load on the engine may result in a lean condition. Computing this value requires that the engine speed (RPM) is also being read. Note that the injector duty cycle is read from a single memory location that is used for both the odd and even banks, so it may display unpredictable behavior during closed-loop operation (when the banks are being fueled based on different lambda feedback.)
Pulse width: Fuel injector pulse width in milliseconds. Like the injector duty cycle, this is read from a single memory location that is used for both the odd and even banks. Note that it may be possible for this value to exceed the available time between spark interrupts, which would mean that the engine is being under-fueled.
Can anyone shed a light on this?
Thanks
e.g. RPM 4685 and Pulse width 8.91ms. Using an online calculator that equates to 34.79% IDC
While driving I obviously wasn't watching the IDC % as shown by RG so am relying (For the moment) on the logging and the online calculator
The engine is the equivalent of a Chim 500 with twin throttle carbon fibre plenum (ACT), original MAF and injectors and Lucas 14CUX
According to RG help
Injector duty cycle: The percentage of the time available between spark interrupts that represents the amount of time the fuel injector will be open. Once this reaches 100%, the injectors cannot flow any more fuel and any additional load on the engine may result in a lean condition. Computing this value requires that the engine speed (RPM) is also being read. Note that the injector duty cycle is read from a single memory location that is used for both the odd and even banks, so it may display unpredictable behavior during closed-loop operation (when the banks are being fueled based on different lambda feedback.)
Pulse width: Fuel injector pulse width in milliseconds. Like the injector duty cycle, this is read from a single memory location that is used for both the odd and even banks. Note that it may be possible for this value to exceed the available time between spark interrupts, which would mean that the engine is being under-fueled.
Can anyone shed a light on this?
Thanks
May be worth asking here as its where the clever people hang out!
https://www.pistonheads.com/gassing/topic.asp?h=0&...
https://www.pistonheads.com/gassing/topic.asp?h=0&...
At 4185 rpm and 70% TPS the 14CUX code goes into 'hi-speed' mode, wherein a whole raft of processes are short cut to speed up the calculation of pulse width and the rate of injector firing is doubled.
Given that at 4800 rpm the total period for each revolution is approx 12 mS, I would take two lots of pulse width at 9 mS as acceptable. If you're not experiencing underfuelling or pinking I wouldn't worry about it.
Since you have an ACT twin throttle body/plenum set up, perhaps give Tim at ACT a call to verify if a specific 14CUX tune/remap is required or not.
Given that at 4800 rpm the total period for each revolution is approx 12 mS, I would take two lots of pulse width at 9 mS as acceptable. If you're not experiencing underfuelling or pinking I wouldn't worry about it.
Since you have an ACT twin throttle body/plenum set up, perhaps give Tim at ACT a call to verify if a specific 14CUX tune/remap is required or not.
davep said:
At 4185 rpm and 70% TPS the 14CUX code goes into 'hi-speed' mode, wherein a whole raft of processes are short cut to speed up the calculation of pulse width and the rate of injector firing is doubled.
Given that at 4800 rpm the total period for each revolution is approx 12 mS, I would take two lots of pulse width at 9 mS as acceptable. If you're not experiencing underfuelling or pinking I wouldn't worry about it.
Since you have an ACT twin throttle body/plenum set up, perhaps give Tim at ACT a call to verify if a specific 14CUX tune/remap is required or not.
Thanks for the info. Doesn't seem to be causing any issues at the moment so will wait until I Megasquirt it early next year to get more into it.Given that at 4800 rpm the total period for each revolution is approx 12 mS, I would take two lots of pulse width at 9 mS as acceptable. If you're not experiencing underfuelling or pinking I wouldn't worry about it.
Since you have an ACT twin throttle body/plenum set up, perhaps give Tim at ACT a call to verify if a specific 14CUX tune/remap is required or not.
Also bear in mind the online IDC calculator you used probably assumed a 'one injector firing per engine cycle'. The 14CUX/RV8 is designed to fire each injector bank once per revolution, twice per engine cycle as shown below. So multiplying your 35% by 2 gives a more credible IDC figure of 70%.
Edited by davep on Sunday 26th November 01:45
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