So... injector question

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Pie + NYQuil = FTW
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I've read numerous posts and it was my understanding that our cars needed low impedence injectors in order to run correctly, otherwise you would need to get some sort of resister pack in order for the highs to work.

Well, the injectors I have in my old supra didn't say RC, but I was told they were so I finally checked what they said on them... and 4 of them say # 3172 and 2 of them say # 3162...

So I search google and I get that the 3172's are high impedence 570 injectors... But my car runs/idles completely perfect, I just get horrible gas mileage... I think this explains it.. LOL But anyways, the question is why does the car run at all with high-imp. injectors?

Now, the 3162's I can't get anything on... but they look the same as the other injectors so they must be seimen as well, but I can't find them anywhere...

So after all this time of getting 10 mpg and shiz...I always assumed I was just rich... Nope, the dude who sold me the injectors lied.. Too bad I bought them soo long ago I don't even know who it was.. NO wonder he gave me a smoking ass deal... $250 for the "rc" injectors (he gave me fake flow chart) and the lexus.

So.... Since these are high imp. injectors, why does the car run still?
 
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easy question it seems... WHo knows! guess I'll pull them and sell them on e-bay and re-install the 440's.
 
1988SupraDreams

1988SupraDreams

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MKIII Supras are supposed to have come with some sort of resistor pack, IIRC, my buddy got one for his MKIV Supra because his JDM Aristo swap was running low impedance 440's and he wanted to swap in high impedance 550's. American Supras run high impedance injectors. Someone please correct me if I'm wrong.
 
MDCmotorsports

MDCmotorsports

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Not sure Kyle. Sounds fishy. Im pretty sure the black car has all "actual" 550's.

IIRC its one of thsoe deals that you can run low/high on a low system, but not low / high on a high system.

Eh, its late I hope that made sence.
 
jetjock

jetjock

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If I'm reading correctly the OP has it backwards. High impedance injectors require no resistor pack while low impedance ones do. It all has to do with the resistance of the coil inside the injector. It's a basic Ohm's Law electrical issue that has nothing to do with the rest of the injector.

In low impedance injectors the coil is comprised of less turns of wire so it's resistance is low, so low that the current would be very high when the ECU turns it on. Remember, the injector is nothing more than a fancy solenoid. The coil is nothing more than a length of wire and the shorter the length the less resistance it'll have. If it's short enough it might as well be a short to ground. It's not far from that in low impedance injectors so the current is pretty high when the coil is energized.

This would burn out the transistors in the ECU that turn the injectors on or the injector coil itself so the resistor pack is needed to limit current to a safe value. It's why the TRSM states that when testing low impedance injectors by connecting them directly to the battery it must be done only very briefly or a resistor must be used.

High impedance injectors have more turns of wire in the coil (and thus more resistance) so the pack is not needed. If you run low without a pack you risk burning something up. If you run high with the pack the injectors will still work but not get the full current they require. As such their response time will be effected.

Add to that it goofs up the ECU's voltage correction. Since there is a delay between the time the ECU commands an injector open and when it actually does open the ECU makes a correction for it. It does this even if you have low impedance injectors. By running high impedance this correction is thrown off. In effect the ECU is "programmed" (for lack of a better word) for a specific type of injector. So even though your engine seems to be running right it's not optimum. Just another example of how you'd better understand a system before messing with it.

All that said there are other important things to worry about when choosing injectors. Nozzle style, pintle or disc, ect.
 
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I'm still considering either parting out my old supra or just selling it... I can't afford to have to projects... and the money from that one would let me buy the AEM/tuning I need in order to run the kind of HP I want.

And yes, MDC, the car i bought from you has all 550 RC injectors.
 
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