Staged Injection with Same Size Pri & Sec Injectors

[hugemikeyd]

Reading over the documentation it would seem that the Secondary Extra mode is being removed and the Sec/Pri Ratio mode transitions from the Primary to Secondary only. Does that mean that if the Primary and Secondary injectors are the same size, having 0 in the Secondary Injection Table is the same as putting in any value in there? Meaning that, since the injectors are the same size, we can't achieve more fuel?

[Vaughan]

If the primary and secondary injectors are the same size and you are using Sequential Staged mode with one injector wired to each output then set the Sec/Pri Ratio to 1.000

The Secondary Extra mode adds more fuel on top of what has been calculated is required for the engine rather than simply splitting the calculated fuel requirement between the available injectors. It was left in because it existed historically but we don't recommend using it.

 

For Primary/Sec Ratio mode with a ratio value of 1.0 if you calculate that you need a 20ms pulse on the primary injectors and have set a 0% split you will get a 20ms pulse on the primaries and no pulse on the secondaries, a 25% split would give a 15ms pulse on the on the primaries and 5ms pulse on the secondaries, a 50% split would give a 10ms pulse on the on the primaries and 10ms pulse on the secondaries, a 75% split would give a 5ms pulse on the on the primaries and 15ms pulse on the secondaries and a 100% split would give no pulse on the on the primaries and 20ms pulse on the secondaries. In all cases the same amount of fuel is delivered but where it comes from is changed.

If the engine was running at an engine speed such that 20ms was longer than the time between engine cycles (over 100% injector Duty Cycle for just the primaries) then a split of 50% would deliver the correct volume of fuel as it would be 2 10ms pulses at the same time instead of a single 20ms pulse width.

[hugemikeyd]

Ah I see what you mean, thanks for explaining.

The engine is a rotary, which would require the Staged Injection to meet the fuel demand without having the primaries work too hard. The question I have for myself is if I have enough injector for the secondaries, I went 1000cc for all 4 injectors.

Thanks again

[Adamw]

Since you have a lack of cycle time, most rotaries are set up so that both the pri and sec are running the same duty cycle at WOT, so you can get the most fuel possible from all injectors.  In your case this would be 50% in the staging table.