are the 720cc injectors from the rx7store low or high impedance? i have an 87 TII and i think it has low. am i correct? if so what will i have to do to use these injectors.

 

They should be low, especially if they are GReddy ones.
Check the color of your stock fuel injectors - if they are purple or tan, you're low impedence.  If they are red or pink, you've got high impedence.


-Ted

 

what's impedance?

 

Resistance to electrical flow. Impedance is measured in Ohms, usually represented by the capital greek letter omega, but in equations its represented by the letter R, such as V=IR, which is the fundamental equation governing linear, "ohm's law" devices. V = volts, I = current (amps), and R is the resistance.

 

how would i know if they are greddy? they should be but is there anything on the side that will let me know?

 

Use a multimeter... Measure Impedence. Problem solved.

 

Just to be a bit pedantic, impendance is actually represented by the letter Z in equations as its not the same as resistance (R).. (generally non linear)

(i'm sure you probably do know the distinction between the two, just thought i'd add that bit )

 

We are using Ohms to measure the injectors, so his math is fairly correct.

 

Perfectly correct, yes, but your measuring resistance not impendance...

My bad, just in an **** mood because i'm doing some circuit analysis for uni..

 

so how would i know if they were greddy or not?

 

Ask the people that are selling them?

 

im·ped·ance ( P ) Pronunciation Key (m-pdns)
n.
Symbol Z A measure of the total opposition to current flow in an alternating current circuit, made up of two components, ohmic resistance and reactance, and usually represented in complex notation as Z = R + iX, where R is the ohmic resistance and X is the reactance.
An analogous measure of resistance to an alternating effect, as the resistance to vibration of the medium in sound transmission.


re·sis·tance ( P ) Pronunciation Key (r-zstns)
n.

Electricity. The opposition of a body or substance to current passing through it, resulting in a change of electrical energy into heat or another form of energy.


Maybe we are misusing the word Impedance?

 

No right word, the fuel injector is effectily in an alternating current circuit.

What you'd be measuring with a multimeter is just resistance of the injector in a DC circuit.
This will give you an indication of its impedance in an AC circuit. (in this particular situation.)

 

You guys are right I was giving him a very beginner's def. Impedance IS technically Z, and is technically complex but I figured if he had to ask... And yes, the true impedance of an injector will change based on frequency and duty cycle (alters the harmonics present since its roughly a square wave driving the injectors) because an injector is basically an inductor (the coil actuator) plus a resistance, with probably very minimal to negligible capacitance. But for the purposes of categorizing injectors into high-z and low-z units we are using the Ohmic DC resistance as White_FC said.

Impedance with zero complex component is identical to resistance (rather, resistance is defined as the real portion of impedance, to be pedantic) as J-Rat so quoted.

And if you want to really twist some noodles, go find the tuned frequency for your injectors, plus give me the impedance at 1 khz, and I'll bet you'd find some interesting things. I'm too lazy, however. Think of how much of that "square wave" is lost in the crappy wiring harness and the filtering effect of the injector itself. What's the max frequency they see, a 5th order harmonic of 8khz (redline rpm)? That's 40khz... which would require several hundred metres of line to come close to even 1/8th wavelength, so we are safe there with a 1-2M run from the ECU. So if we can neglect the line length, we may be able to neglect its capacitance effect as well at that frequency. Hm. Any thoughts here?

 

Now where'd my signal generator go.......

 

Man, I am just a tech, not an engineer..