Secondary Multiplier

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ciphermonk
Posts: 23
Joined: Fri Nov 04, 2016 8:47 pm

Secondary Multiplier

Post by ciphermonk »

When you're running a second set of injectors the Secondary Multiplier parameter under Run Mode Fueling / Corrections / Secondary Multiplier is set to the primary injector flow rate divided by the secondary flow rate. Here's my concern.

If I'm currently running a setting of 1.2 with 550cc injectors and I'm planning to switch to 1000cc injectors I realize that a setting of .55 - .72 is probably what would be after in order to keep the current fuel tables the same. Isn't doing this going to essentially limit my secondary injectors though?

If the Secondary Multiplier is what's used to modify the pulse width sent the secondary injectors, by lowering it from the current 1.2 to .55 - .72, aren't I essentially making the 1000s behave like 550s based on the pulse width? Guess why I wouldn't just leave the Secondary Multiplier where it currently is (or slightly lower it to say 1) and then retune the portions of the fuel table where the secondary injectors are active.

This would allow the larger injectors to flow more fuel given the same pulse width which is what I'm after by switching to them in the first place no?
stevieturbo
Posts: 1321
Joined: Sun Dec 07, 2008 2:04 pm

Re: Secondary Multiplier

Post by stevieturbo »

How much fuel goes through the secondary ( and indeed primary ) will depend on the fuel blend table too.

0% is all primary, 100% is all secondary.

So there is more at play than just those scalings, but keeping them correct should make it work easier if changes are made.
ciphermonk
Posts: 23
Joined: Fri Nov 04, 2016 8:47 pm

Re: Secondary Multiplier

Post by ciphermonk »

Thanks Stevie.

Realize that 0 is all primary and 100% is all secondary but doesn't the multiplier influence the pulse width sent to the secondary injectors? So say in a given cell in the fuel injection table there's a injector pulse request of 10ms and the split table in the same cell is set to 40. So 40% of the fueling is handled by the secondaries and 60 by the primary.

Assuming that the Secondary multiplier is 1, I'm assuming that would mean that a 6ms pulse would be sent to the primary and a 4ms to the secondary. Now if the Secondary Multiplier is .5 then would that end up halving the pulse sent to the secondary injector? So the same 6ms to primary but only 2ms to the secondary injector?

If that's the case and your goal is to try to increase fueling by adding a second set of injectors, is there any reason why decrease the value to less than 1 since it's causing you to decrease the fueling by the secondaries?

I might be misunderstanding how it work the tables interact in which case sorry for wasting your time. :-)

My point for bring this is up is I question why when switching from 550s to 1000c injectors I wouldn't simply leave the multiplier at the same value but then re-tune the areas of the table where the secondary injectors are active. this allows me to take advantage of the extra flow of the larger injectors if I wanted.

Does that make sense?
stevieturbo
Posts: 1321
Joined: Sun Dec 07, 2008 2:04 pm

Re: Secondary Multiplier

Post by stevieturbo »

I think you're over complicating it.

If you know injector flow rates, and the scalings are correct. Then a change from 500cc to 1000cc with the correct scaling should hopefully have a very small effect on actual tuning required for the change.

As to how the overall duties end up and what load is placed on each injector, log both pw and duty for both and see if you're happy with the split as to how much work each set is doing.

But if all the numbers are correct, scalings correct etc....then 50% in the blend should be literally that load applied to each injector. ie both of them operating around 50% duty.
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