Injector sizing for sequential, semi sequential and batch fire

[Sprocket]

I am getting my self confused with this a little so if some one can point out where im going wrong.

Required fuel value is the value of fuel required at 100%VE for the engine in question, this is the amount of fuel required per cylinder at peak power.

Depending on how the injectors are fired, sequential is one squirt of the required fuel amount at 100%VE, semi sequential is two equal sqirts of half the Required fuel amount at 100% VE, and batch fire is four equal squirts of a quarter of the Required fuel amount at 100%VE.

Surely if the injector size was to remain the same, and the injector is sized correctly for sequential, when changing to semi sequential the required fuel value is till the same, but the injector is now twice as big as it needs to be?? Does this mean you can half the size of the injector and still supply the same required fuel??

Running 460cc injectors on an engine of 180bhp in sequential is %70 duty. If i changed to semi sequential but kept the same injectors, duty would fall to 35%? and the injector in practice is too big??

Is this correct?

[rob@vems.co.uk]

Its per injector per cylinder.  The number of times it fires depends on how the divider is setup when on batch.

[Sprocket]

I understand that

ok let me set it out another way. Now i have buggered the secondary VR (for now) i want to run semi sequential where there are pairs of injectors fired alternately similar to the wasted spark ignition. I have two sets of injectors that came from two Rover 820 T series engine with 180bhp, first set of injectors are 460cc and the second set are 230cc.

I have estimated my engines HP to be 184, so assumption would say these injectors are ideal. The fuel flow rate for this at %70 duty estimated at 332cc with a BSFC of 0.5 and AFR 12.5. Bost to achieve the 184 is 15 psi, but i only intened to use that on track days and running 8 psi pretty much all other times with 140hp estimated

This is where im a little concerned that i am going to make the right choice. If i use the 460cc injector in sequential, it will be fine, i dont have equential, but if i were to use it in semi sequential it will be twice as big as it needs to be? In saying that, it would imply that the 230cc injectors will be big enough and with a little 'duty' room for the fuel rail pulsing phenomenon i have read about. the 460 would be well too big when running at 8 psi???


Would i configure, 'alternate banks' to 1..0 and 'divider' to 2?? with h[0] table entries 0-1 and 1-2 where the injectors are wired in pairs

The 'divider' tells the firmware to traverse through the h[0] table twice if set to 2??

[rob@vems.co.uk]

Keep firing them sequentially, just make sure that you're injecting on the cylinders that are firing as you are assured of a closed valve when injecting.
using the divider the way you suggest will work but you'll have terrible transient fueling because it takes two engine revolutions.  I have lots of 36-1 triggered engines running sequential fueling.

[Sprocket]

Ok Cool so i could still use the 460cc injectors sequentialy and they will fire once every cycle, just not timed to phase of the engine.

Just trying to get my head round the different ways of configuring the h[0]table and how it runs through the entries.

If i were to wire the injecters in pairs, and set the h[0] enteries to h[0]=01 02, and the divider to 1. this will alternate the pairs of injectors thus firing them every 360 degrees, thus twice every cycle. Is this correct? This way i can use the 230cc injectors and still achieve the same required fuel??? Same could be achieved by using four injector outputs and using the binary mask to fire pairs of injectors.

The injector fires at the missing tooth (36-1), or 60 degrees BTDC (same thing)?? so you could play around with the trigger wheel position and 'adjust' the injection start point??

I think its right as i have the SPi set for h[0]=01, divider set to 1, and that fires every 360. or at least i assume it does?

LOL so many questions

[rob@vems.co.uk]

No need to wire them in pairs, you can add the channel numbers together:
01 + 08 = 09 and 02 + 04 = 06  would have 1&4 paired, and 2&3 paired.

You dont need to move the trigger wheel, just the trigger tooth, alas the 60deg BTDC gives you little scope to play with.

[Sprocket]

Thank, im starting to understand this now