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Grega
03-12-02, 11:46 AM
What exactly is the difference? From what I understand (little) non sequential is known as "batched" injection?

How exactly does sequential injection work? At what stage is the piston at when the injector(s) is/are pulsed?

On a batched system/non sequential I take it for example, on a V6, 1 & 6 are pulsed, 2 & 4 are pulsed, then 3 & 5 are pulsed (not in that order not combination)

Ideas/Thoughts/Comments?

Forg
03-12-02, 12:19 PM
Batch-fire injectors go off all at once, or in one or two groups. The ECU doesn't know which cylinder as firing (because a dizzy is taking care of that bit), so it opens all injectors in one go. So on a 6 cylinder engine, the injectors open 6 times per cycle.

Now, a sequential injection system knows which cylinder is firing, so it opens the injectors in the same sequence as the cylinders are fired. I don't know exactly when in the cycle the injectors open optimally; it's probably just a bit before the valve opens. Anyway, with this system each injector fires once per engine cycle.

Note that injetors take some time to open & close. So you get more accurate fuel metering if the injector is opening once, rather than 6 times, per engine cycle. Also, because there's less of that "dead time", the injectors can handle more fuel. Thinking about it, they probably last longer too.

In the example you gave, a non-sequential system would probably pulse every injector at once; in other words, 1 & 2 & 3 & 4 & 5 & 6 would be pulsed when the first cylinder fired, then the same again when the second cylinder fires, etc. Obviously each injector is only open for a 6th of the time of a fully sequential system.
Actually, you ask about V6's ... were you wondering about VR vs. VS (ie. GM3800 vs GM3800-II engines)? 'Cos sequential injection was introduced for the VS, and probably accounts for some of the 20kW power increase.

Rota_Motor
03-12-02, 12:42 PM
uhh yeah, pretty good explanation

although to add a couple things ;)
on the early falcon syastems up to EA I think, the ECU recieves a pip signal from the distibutor, and every 3rd pip it fires injectors 1,5 and 3, every sixth pip it fires 2,4 and 6. so every combustion cycle every injector is still only fired once each, but the ECU has no idea when it happens, just that it does happen.

and then the later models have reference so it knows exactly whats goin on and pulses the injectors just before the inlet valve opens I believe. I believe it gives a little extra power, and better fuel economy, but mainly helps in reduced emissions as the fuel is drawn straight into the cylinder whereas the batchfire sits behind the valve until it opens.

Forg
03-12-02, 01:49 PM
When you think about it, it wouldn't make any difference (in terms of precise timing) at higher injector duty-cycles, because the fuel would still be spraying while the valve closes, and be sitting there in the runner until the valve opened again. In other words, the same as happens with the batch-fire system. :)

Norbie
03-12-02, 02:46 PM
Yup, sequential injection is only beneficial in part-throttle conditions... improves fuel efficiency and emissions, but that's about it.

Forg
03-12-02, 04:08 PM
... and also gives you 1/(#cyls) of the injector dead-time? I would've thought that would have the effect of markedly improving an injector's duty-cycle percentage; especially on something like a Cizeta Moroder V16T? :)

Beavis
03-12-02, 05:35 PM
An extremely (can't state this enough) helpful MoTeC engineer told me that full-sequential injection also improves throttle response a bit.

The MoTeC M48 series can drive a V12 in full sequential mode, with the right upgrade (couple hundred bucks)..

Forg
03-12-02, 09:26 PM
Originally posted by Chris
An extremely (can't state this enough) helpful MoTeC engineer
Hmm ... I've noticed the same thing. Never bought a thing off them; they keep convincing me that what I've got will do the trick, and telling me how to do it. It really helps to give the impression that they know what they're doing ...

Grega
05-12-02, 06:24 AM
grouse, thanks guys for the explanations.

forg, yes i was comparing the earlier vn/vp/vr v6 with the vs v6 (ecotec) and onwards.

i wonder if the earlier non sequential inejction system ie: the 1227808 series of ECU could run a ecotec motor?

the vs ecotec gained a cam angle sensor which probably helps tell it when to open the injector for said cylinder.

Forg
05-12-02, 08:06 AM
Originally posted by Grega
i wonder if the earlier non sequential inejction system ie: the 1227808 series of ECU could run a ecotec motor?
It probably could, but my guess would be that it'd be a bit of a bodge unless you could retune it a bit.

dk
05-12-02, 05:54 PM
Norbie,

Does the 1JZ-GTE run batched injection?

dk

Norbie
05-12-02, 09:40 PM
That's a good question, but I'm not sure what the answer is. I'm sure the later versions would be sequential, but the earlier ones may not. The 7M was definitely batch-fire.