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#2
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It's always been sequential multi-port. Conventionally, "sequential multi-port" means the injectors open one by one as the intake valve under it opens. "Plain multi-port" means they all open at the same time.
now that I sound like I know what I'm talking about, can someone tell me WTH a "dual spray" injector is? does this mean it has two nozzles or 2 spray modes (oscillating and static)?
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IggDawg is cool -IggDawg 1992 Teal SVX LS-L 160k miles 4.11:1 final drive, K&B dropsprings, ART front rotors, stainless steel brake, aluminum underdrive crank pulley, Kuhmo Ecsta Supra 712's, K&N drop-in filter. Previously owned by Alacrity024. FOR SALE 1994 SVX LSi, Barcelona Red #1659, build date 11/93, 117k miles, RIP ECUtune stage 1, bead crush, smallcar shift kit, TB bypass, SS brake lines, silencer removed, alternator and grounding wires, Mobil1 @ 117k |
#3
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You can't open all your injectors at the same time, silly! How would that work! Multi-port and sequential multi-port are two ways of saying the same thing! Just like single point injection and central fuel injection. The dual spray injectors have two spray patterns. At a certain RPM (I don't remember which) the injectors use the second pattern, which sprays more fuel. Dave Last edited by red95svx; 06-02-2004 at 07:08 AM. |
#4
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phil
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~Phil Teal 1992 Subaru SVX Turbo - Sold in May 2011 to peace-frog. |
#5
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I suppose I could take out one of my injectors and hook it up to the ol' oscilloscope
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IggDawg is cool -IggDawg 1992 Teal SVX LS-L 160k miles 4.11:1 final drive, K&B dropsprings, ART front rotors, stainless steel brake, aluminum underdrive crank pulley, Kuhmo Ecsta Supra 712's, K&N drop-in filter. Previously owned by Alacrity024. FOR SALE 1994 SVX LSi, Barcelona Red #1659, build date 11/93, 117k miles, RIP ECUtune stage 1, bead crush, smallcar shift kit, TB bypass, SS brake lines, silencer removed, alternator and grounding wires, Mobil1 @ 117k |
#6
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The image caption provides somewhat of a description, and the picture there might help a bit. It still isnt a technical explination.
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#7
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Dual spray, twin spray......I was close.
Dave |
#8
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The other kind simply fires all of the injectors at the same time. This does pretty much the same thing as the old bolt-on band-aid called throttle body injection (read: they're both inefficient). |
#9
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READ IT AGAIN. IT SAYS SEQUENTIAL MUTIPORT...at least 92 does
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#10
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Good point... But it still only says "sequential" for 1992, 1996, and 1997. Take notice that I have a 1994, thus my reason for not seeing that small little detail for the 1992. |
#11
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How can you fire all the injectors at once? The intake valves don't all open at the same time! Are you telling me that the injectors fire at a closed valve? Doesn't sound right. Throttle body injection involved one injector that fired into the throttle body, not quite the same as MPI. Dave |
#12
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#13
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I would suppose that the fuel that is sent via non-sequential MPI has the same problem. Some of it makes it into the piston chamber, and some of it doesn't. What I'd like to know is whether or not all of the injectors are fired at every intake stroke of each individual piston, or at some other random interval (maybe TDC or BDC?). Now, let me ask you this... What do think was less efficient: Non-sequential MPI or throttle body injection? I'm gonna go ahead and say throttle body injection. But non-sequential also has it problems. Just makes more sense to me for the injectors to be placed as close to the intake valves as possible, sequential firing or no. Putting a single injector two feet away for several multitudes of cylinders seems like a pretty bad plan to me. Last edited by deruvian; 06-03-2004 at 09:42 AM. |
#14
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"Sequential Multi-Port" and plain old "Multi-Port" are definitely two different animals.
Sequential multi-port typically squirts fuel slightly before the intake valve opens and stops just before it closes. This is how it's supposed to operate, but in reality it doesn't always work like that. When the engine demands more fuel, the duty cycle of the injectors increases. Near full throttle, or peak demand, the injectors may be open almost continuously. This varies tremendously from car to car and ECU to ECU. Some sequential multi-port systems are only kinda sequential. Some systems may inject fuel during every engine rotation, regardless of whether it's a power stroke or an intake stroke. The plain old multi-port systems really do just squirt fuel at random. They do squirt the right amount of it, but whenever they want. I believe the old Volkswagen CIS units squirted fuel continuously but vary the flow to meet demand. Which system is best can be debated. Injecting fuel straight into the port at the exact moment the valve opens is not always optimal. The throttle-body systems have one huge advantage in that the fuel has a chance to completely atomize during its journey down the manifold. I think the biggest downside to this system is that when the engine is cold the fuel won't atomize. It also suffers problems from unequal fuel distribution to each cylinder; thus some cylinders run lean and can be damaged, while other cylinders run rich and inefficiently. The plain old multi-port and CIS systems have the same advantage of throttle-body systems in that the fuel, or at least some of it, is injected before it's needed and has a chance to atomize. The need to give fuel a chance to atomize is probably very small, and I would speculate that it's not very significant under most circumstances. Under compression, the fuel is super-heated, and this should vaporize it almost instantly, so unburned fuel is probably not an issue - at least at lower RPMs. In fact, it really doesn't matter when or where you squirt the fuel, it has nowhere to escape to so it will get used - hopefully in equal distribution to each cylinder. One thing to consider about a throttle-body system is that as the fuel atomizes it's basically evaporating, which causes the air to cool, and with cooler, denser air, you can cram a little more into the cylinders. More power. If it vaporizes inside the cylinder, it's too late to cool the air before it's inducted. I think the ideal system would be a sequential multi-port with throttle-body. I would use the port injectors when the engine is cold, when it's idling, and to enrichen the mixture during throttle advancement, i.e., the accelerator pump function. As far upstream as possible, I would have a throttle body injector, or array of injectors, to meter the exact desired air/fuel ratio at all times. The throttle-body would provide a steady supply of fuel-rich, fully atomized, and cool air. The port injectors would supplement the fuel needs as required. Modern electric fuel injection is clearly a great system, but I'm still fond of my Bernoulli fuel injectors. |
#15
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Nobody wants to type a really long reply to that? LOL...
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