straight 6 - going back to basics

[Mos]

Does that mean no two cylinders ever fire at the same time (making ignition and injection a sequential process?)

Generally engines are designed to be smooth, so spreading the ignition events amongst the entire engine cycle makes the most sense.
If you were to fire two cylinders at the same time you would get a double dose of torque down the crank followed by a dose of nothing (or a load on the crank due to a compression stroke that's not balanced by a combustion stroke) - which generally is inferior to two single doses at different times.

Firing order is generally also chosen to provide the most optimal solution, by minimising harmonics and any inherent engine imbalances. On a 4 cylinder there aren't that many combinations, but on a V8 there's plenty to choose from. Different manufacturers can have different firing orders.
The cam grind sets the firing order - on pushrod V8s (apparently) there are off the shelf cams that change the firing order.

Does this mean you could swap two injector plugs (off a batched pair) over to the other and still have the engine run perfectly fine?

You could swap any injector to any other injector and the engine will run "fine" - you probably wouldn't be able to tell the difference.

It also means that changing paired leads on a wasted spark setup results in no change to the operation of the engine. Ignition events are critical, injection events are not, because effectively they are "stored" in the port/runner until they are needed.

There is also the factor of opening frequency, but it's been a while so exact details will be hazy. Some ECUs will open the injectors twice in one 720 degree cycle up until a certain rpm, after which they will only open the injector once in the 720 degree cycle.

Some (all?) aftermarket ECUs give you the ability to tune the injector opening and closing times in relation to other engine events. This parameter will be less relevant on batch fired setups.

(This question pretty much is the reason for all the other questions as im doing some wiring on my 1JZ and noticed the injection loom looks like a batch fire setup... and then that got me to wondering how it all works hehe.)

also is it true 1JZ's batch fire the injectors and 2JZ's are sequential?

Yes - early 1JZs are batch - 3 injection outputs, 2JZs are sequential - 6 injection outputs.
Without checking (cbf), from memory VVTi 1JZs are sequential as well.
Early 1UZ is batch, VVTi 1UZ is sequential.
At least some 1G-GTEs only have two injection outputs (for 6 injectors).
Early 4A-GEs only have one injection output (for 4 injectors).

ok cool, the swapping batch pair injector plugs still has be concerned because although the signal is common among the pair, they have their own individual earths (as far as i can see)

that makes me wonder if they are still being fired sequentially via a switched/controlled earth?

Injectors are supplied power from the IG2 circuit in the ignition switch - generally black-orange, or black-yellow. The split from a single wire to 6 wires can be anywhere, so if each of your injectors has a BO wire on it - that's the supply wire.
The other wire on the injector gets earthed by the ECU, either sequentially (individual ECU output per injector) or batch (multiple injector per ECU ouput). If the second wire on your injectors is paired, and a different colour between the pairs, this is the wire needing to go to the ECU.

Mos.

[JZA70 R]

You could swap any injector to any other injector and the engine will run "fine" - you probably wouldn't be able to tell the difference.

Thanks for the replies Mos, however this comment throws me way off! lol ...hard to get my head around that. Something to try one day haha.

Mos im running a powerfc and in its injection menu you have the ability to specify each individual injectors size and latency. What are the odds of this actually being functional? ie, Even though one of two wires on each injectors is wired together, can they still be controlled individually by the earths in turn making it possible to tune each injector specificly?

As for injector wire colours, this is what i noted.

first column is plug colour, second is signal wire colour... all earths are black

inj 1 - grey plug - blue/white
inj 2 - brown plug - white wire
inj 3 - grey plug - red/white wire
inj 4 - brown plug - blue/white wire
inj 5 - brown plug - white wire
inj 6 - grey plug - red/white wire

1 & 4 = paired
2 & 5 = paired
3 & 6 = paired



Also as for the 2 cam position sensors, i checked a spare intake cam last night and you can see there are two pickups 180 degrees apart from each other. So the second CPS is definately not for redundancy.

[big_zop]

I belive what Mos is saying is that the injectors themselves are interchangable (like spark plugs), no matter how they are controlled.

Also, would there be any reason on earth for someone to install single set of injectors of different sizes? While i dont know enough about injectors and thier specifics if you are able to program it in (their behaviour if you will), you are going to find that electronics may seem quite complex but in most cases isnt. You are not going to be able to fire a single injector of a pair by different earths.

[oldcorollas]

no, he is saying, that you can swap the injector plugs onto different cylinders, and you probably won't notice any difference at all.

it depends how the powerFC is supposed to affect the injector. can it actually change the pulse width at all? if so, it would need to know the couple of previous ones, plus forecast the next one or two, to be able to add or subtract the difference it wants...

or is the powerfc a full standalone?

[JZA70 R]

I belive what Mos is saying is that the injectors themselves are interchangable (like spark plugs), no matter how they are controlled.

Obviously. However if you start swappng coilpack plugs (from the loom) around its a different story? this is what i was thinking.

Also, would there be any reason on earth for someone to install single set of injectors of different sizes? While i dont know enough about injectors and thier specifics if you are able to program it in (their behaviour if you will), you are going to find that electronics may seem quite complex but in most cases isnt.

the individual injector settings come into play when you have 6 injectors of a kind that are not spraying evenly, weather they are dirty and clogged or just out of spec from the manufacturer. This is when it would be useful, however you would need an o2 sensor on each exhaust port to pickup on this...

You are not going to be able to fire a single injector of a pair by different earths.

what if you dont earth one of the two injectors in the batch, (the earths dont look like they are in batches) its not going to fire is it? this is all i was thinking.

[JZA70 R]

powerfc is standalone but retains the factory loom.

[big_zop]

no, he is saying, that you can swap the injector plugs onto different cylinders, and you probably won't notice any difference at all.

That does make sense too, and from what others have said it should still run smoothly - but i wouldnt want ot test it out.

the individual injector settings come into play when you have 6 injectors of a kind that are not spraying evenly, weather they are dirty and clogged or just out of spec from the manufacturer. This is when it would be useful, however you would need an o2 sensor on each exhaust port to pickup on this.

But if two injecters are paired to the same signal, isnt altering one going to affect the other? How does this work on the Power FC since it only uses the stock sensors and IIRC cant add too many more (i know it definitely cant take 5 more o2 sensors)?

what if you dont earth one of the two injectors in the batch, (the earths dont look like they are in batches) its not going to fire is it? this is all i was thinking.

That would require earths to be controlled by the computer, and for that amount of outputs you would be able to have sequential injection (not counting and complexity differences).

[LeeRoy]

Thanks for the replies Mos, however this comment throws me way off! lol ...hard to get my head around that. Something to try one day haha.

Because the 'other' injector is injecting fuel into a closed valve, the window for this to happen is almost 540* as the intake valve is only opening on the intake stroke. The timing of this is crucial to the cylinder drawing in the fuel with the valve open. The cylinder with the valve shut is irrelevant as the fuel is not being used until 540* later in the engines cycle.

Mos im running a powerfc and in its injection menu you have the ability to specify each individual injectors size and latency. What are the odds of this actually being functional? ie, Even though one of two wires on each injectors is wired together, can they still be controlled individually by the earths in turn making it possible to tune each injector specificly?

When you set injector times etc your only concerned with the cylinder that 'needs' the fuel - and consequently, your controlling that individually (although injecting fuel into into another port also). The other cylinder is merely storing the fuel in the runner for when it does need it, 540* later.

Timing of injectors is done to give optimal burn, and is much like ignition in that it will vary between engines and conditions. An example is how ignition happens on the compression upstroke due to the time delay of the burn. Injection time will take into account air speed, distance, amount of fuel to be injected, and so on.

[oldcorollas]

if it is standalone, and it runs 1 wire to earth each injector (and doesn't pair the earths together... power doesn't matter) then it can probably do individual injector trim.

if the stock wiring only pairs then up for batch fire in the ECU itself, then the PFC can probably do injector trim, but if the wires pair together before the ECU, then it can't.

bigzop, why not? you have say.. 2 sets of 3 injectors firing at same times.. none of them are at a particular point in their engine cycle during firing, and even if 1 was, the other 2 aren't... if it was properly timed sequential injection, it might make 5-10% difference for low throttle (when you are making buggerall power anyway), but for batch, it will make almost no difference at all...
there is no problem with testing it out.. it won't harm the engine.

if 2 injectors have their earths paired (batch injection), then you can only adjust those two the same amount.
you can set the trim by say.. getting the injectors flow tested, and pairing them up and adjusting the trim of the pairs to get even flow (can do that on spray bench to check), or you could use exhaust temp sensors for each cylinder to check trim.. or you could fit an O2 bung for each primary tube (but that is unlikely to happen)
anyway, there was ways to set trim per cylinder.

it is possible to have batch injection with individual injector trim, but it does require a transistor to earth each injector. firing them in batch makes electronics and programming a little (very little) bit easier, but still easy to have the trim.

[JZA70 R]

interesting.

like i said, its only the coloured wires on each injector that are obviously paired. each injector looks to have its own individual earth travelling back to the ecu. however i havent opened the whole loom up so i dont know if the earths are collaborating later on (hidden) down the loom somewhere. also the earth on each injector is significantly thicker gauge than the other coloured wire.

is there an easy way to test if adjusting injectors independantly is actually working, without installing six o2 / temp sensors?

[JZA70 R]

ecu pinout would probably be useful here

[LeeRoy]

like i said, its only the coloured wires on each injector that are obviously paired. each injector looks to have its own individual earth travelling back to the ecu. however i havent opened the whole loom up so i dont know if the earths are collaborating later on (hidden) down the loom somewhere. also the earth on each injector is significantly thicker gauge than the other coloured wire.

Bigger wire will be power not ground. See below.

inj 1 - grey plug - blue/white
inj 2 - brown plug - white wire
inj 3 - grey plug - red/white wire
inj 4 - brown plug - blue/white wire
inj 5 - brown plug - white wire
inj 6 - grey plug - red/white wire

1 & 4 = paired
2 & 5 = paired
3 & 6 = paired

You'll probably find all 6 share a power feed, but they are grounded in pairs through the ecu - equating to batch.

[EldarO]

its all right there dude.

as said before, the ECU fires the injectors by GROUNDING them, not giving them power.

[Mos]

Mos im running a powerfc and in its injection menu you have the ability to specify each individual injectors size and latency. What are the odds of this actually being functional? ie, Even though one of two wires on each injectors is wired together, can they still be controlled individually by the earths in turn making it possible to tune each injector specificly?

You can only adjust each injector individually if it has an individual output from the ECU. In your case, the ECU only has three outputs, so you can only trim the batched injectors.
I don't know specifically how the PowerFc trims injectors, but as it only has three outputs (ie as per factory) it won't be able to each injector individually.

As for injector wire colours, this is what i noted.
first column is plug colour, second is signal wire colour... all earths are black
inj 1 - grey plug - blue/white
inj 2 - brown plug - white wire
inj 3 - grey plug - red/white wire
inj 4 - brown plug - blue/white wire
inj 5 - brown plug - white wire
inj 6 - grey plug - red/white wire
1 & 4 = paired
2 & 5 = paired
3 & 6 = paired

As LeeRoy and Elmo have said - you have got this WRONG!!!!
The black wire is power, and the earth is supplied by the ECU through the paired wires.

Please have a look at any toyota wiring diagram - you *NEED* to understand this in order to understand it .. At the moment it seems like you are ignoring how it's wired up (In toyota looms black is almost never a ground).

Also as for the 2 cam position sensors, i checked a spare intake cam last night and you can see there are two pickups 180 degrees apart from each other. So the second CPS is definately not for redundancy.

CPS? Crank or Cam (I can infer from context, but you shouldn't use C..)
The second CamPS *IS* there for redundancy - the electronics of the ECU only need one of them to synchronise the crank position to the cams. IE the logic that determines when to fire the ignitors and injectors only requires one piece of information, not both pieces - the second piece is to allow for faster startup (as the engine has to, at most, make one crank revolution to synchronise) and for redundancy in case the other sensor doesn't work.

no, he is saying, that you can swap the injector plugs onto different cylinders, and you probably won't notice any difference at all.

That does make sense too, and from what others have said it should still run smoothly - but i wouldnt want ot test it out.

Yep, that's exactly what I was saying. Plenty of engines with only 1 injector output run more than smoothly.

bigzop, why not? you have say.. 2 sets of 3 injectors firing at same times.. none of them are at a particular point in their engine cycle during firing, and even if 1 was, the other 2 aren't... if it was properly timed sequential injection, it might make 5-10% difference for low throttle (when you are making buggerall power anyway), but for batch, it will make almost no difference at all...
there is no problem with testing it out.. it won't harm the engine.

Yeah, me too - why not?
There's no harm, you're just not getting the full potential out of it.
I don't know exactly how much power difference it makes, but I doubt it's anywhere near that high - I'd say 1% maybe, and only at low fueling requirements.
At high loads/rpm, you simply don't have enough injector flow rate to inject into an open valve, so the bulk of the fuel gets "stored" in the port.
It really is a law of diminishing returns (power and emissions) - if it made a big difference, it would get adopted earlier (electronics to handle it were available 20 years ago).

But if two injecters are paired to the same signal, isnt altering one going to affect the other? How does this work on the Power FC since it only uses the stock sensors and IIRC cant add too many more (i know it definitely cant take 5 more o2 sensors)?

Yes - if injectors are batched then any trimming you do affects all injectors in that batch.
The PowerFc is a direct replacement, so only has the same sensors and outputs as a stock unit (afaik).
The injector trim is usually done differently - not by 6 O2 sensors - but by flow testing each injector and recording the flow characteristics. These characteristics can then be used (if the ECU tuning permits it) to trim the individual variances. It's likely that the factory has close tolerances on new injectors, as well as some compensation/learning capability to allow for future injector replacements due to service issues/etc.
In any case, I'd be willing to bet the manifolding will have larger variances than the injectors.

Timing of injectors is done to give optimal burn, and is much like ignition in that it will vary between engines and conditions. An example is how ignition happens on the compression upstroke due to the time delay of the burn. Injection time will take into account air speed, distance, amount of fuel to be injected, and so on.

I would make the distinction, though, that timing of ignition is something that's critical, but timing of injection is not. A slight difference in injection timing won't have a large effect, but a slight difference in ignition timing can have catastrophic effects. Just for interest's sake, 1 degree of ignition timing at 6000rpm is worth about 3rwkw on my engine. I don't know what 1 degree of injector phasing will do, but I'd bet that it's nowhere near that.

If too much of the fuel doesn't make it into the combustion chamber you have a lean-even and possibility of engine damage.

My only comment there would be that if your phasing isn't right, then you will have fuel left over from the previous injection?

Thoughts?

Mos.

[oldcorollas]

thoughts? 6000rpm = 10ms/rev..
1deg = 0.028ms

ECU's rock