Rover V8 Injection query - got me a thinking ..........

[Hybrid_From_Hell]

...and confused

Firing order of a V8 Rover is 1-8-4-3-6-5-7-2.

On megasquirt and Lucas the injector fire in banks, ie LHS 2 4 6 & 8 then RHS 1 3 5 7

Now, on THIS weridity (yes there are other system apparently than MS and Lucas ) the injectors are still joined to

fire 4 x injectors at a time, but they fire

1 8 4 3 & then 6 5 7 2

Now, this has got me right stumped, as it 4 x injectors at a time but not banked, the injectors are actually firing tin the same order

as the 1st 4 cylinders and then the last 4 cylinders, timing fires 1-8-4-3-6-5-7-2. as per normal

My warped little mind can't get itself round this, can somebody explain

Why and how the damn thing still works

Cat helper is no help either .............

Nige

[elbekko]

I'm probably wrong, but doesn't it work due to wasted spark? I don't know which cylinders spark together, but I guess it works out?

[Hybrid_From_Hell]

Yes its wasted spark, that means the one fires at TDC vs the other on exhaust stroke

this mixes up that order try as I might I can't get my mind around this one !

Nige

[Quagmire]

Helps keep pressure even around the fuel rail? Every time a set of 4 is fired you are firing even numbers of objectors from each side?

[zardos]

I've also thought how does bank injector firing work and not inject fuel in to the exhaust/compression and power strokes?

And the answer I think is after a google

The injectors don't need to fire in order at all because they fire at the back of the inlet valve not in to the cylinder.

Thus each time a bank is fired 3 of the injectors are just accumulating fuel behind the inlet valve and the fourth is firing against an open valve.

This means that only 1/4 of the fuel needed is injected each time a bank is fired and could thus lead to a lag in response to fuelling requirements.

So the simple answer to the question is the fuelling order is controlled by the inlet valve opening order not the injector fire order.

See http://www.auto-fact...-injection.html

[muttleyd]

I guess it comes from the fact that the duration of a 720 deg cycle is so short in terms of time, the amount of time the injector is open is relatively small. You are basically filling the port and plenum with fuel air mix and as soon as the engine is on overlap it's drawn into the engine. Timing the fuel to indivdual firing does give some advantages in performance and emissions but probably is not critical as spark timing

[TheRecklessEngineer]

There's a section in the megamanual on this.

AFAICR without looking it up, the time the injector is open is much longer than the valve opening time at any rpm much above idle. Therefore there is always a time when the injector is firing into a closed valve. It doesn't make a difference - I think one of Bowling or Grippo tested this to prove it.

Although I think MS3 will support firing injectors individually and in order.

I'm certain I've read the above in the megamanual, but I'm waaay too knackered to look it up!

[Quagmire]

To add to Mr reckless' post, carbs don't time anything and work fine.

Having the first 4 cylinders (of the total firing order) getting fuel before the second batch of four- (the last 4 in firing order) get any doesn't make any real difference.

As long as the number of squirts per cycle and duration of squirts is correct the right fuel air charge should be ready at the back of the valve for when it opens and draws it in.

Sequential fuelling only helps emissions at idle and gives negligible power increases (from what I've read).

[TSD]

From what I remember from the early days of MS (and for the real old-timers its' predecessor EFI332) ...

Muttleyd is right, when the engine is making any real power, the injection time is much longer than the valve opening period, so it makes no real difference when individual injectors are fired.

Spraying fuel on the back of the intake valve tends to aid atomisation, and also cools the intake valve. This is often said to reduce heat transfer to the intake charge, though I'm not sure if that would really add up to a measurable power increase.

The real benefit from sequential firing versus the usual MS mode of bank firing (and more so over batch firing) is reducing the number of openings and closings of the injectors, and the inaccuracy in total fuel delivery it creates. The greatest error results for the maximum number of injector firings, and the shortest pulse widths - in other words, when the engine is idling and it's harder to run closed loop to correct the tune.

Sequential injection, synchronised to each cylinder offers the highest accuracy of fuel delivery, but it doesn't necessarily mean it is fired when the valve is open (even at idle), it just means the conditions at each cylinder are as repeatable as possible at each firing.