Sould s4 injectors have 12v or does the resister make around 6v?

 

Battery voltage or whatever the alternator is putting out if the engine is running.

 

if its 12v then what is the resister for on a s4 n326 ecu?

 

The resistance of the injectors and that of the resistors in the pack are to reduce the current, not the voltage.

 

The resistor reduces the current, not the voltage. Voltage equals current multiplied by resistance, or V=IR (Ohm's Law) . so with a higher resistance we need less current to maintain the same voltage. Factory injectors are somewhere around 2 ohm resistance plus the 6 ohm resistor pack, for a total of 8 ohm. The voltage stays constant, it is the current that is reduced.

V=IR ---> I=V/R . With the V staying constant, increase the "R" and the "I" (current) goes down. Here is a semi-accurate analogy: if you want 12psi of water pressure (pressure is similar in some ways to voltage) in a pipe, a lot less water volume (current) is needed in a smaller pipe (higher resistance).

Getting back to cars: the magnet (aka coil) in the injector can only handle so much current, and the injector driver transistors in the ECU can only handle so much power. Power is a function of current, P=I^2*R or Joule's Law.

 

the voltage should always be 12volts at the injector, regardless of the series of car.

 

Thank you for your teaching

guess i will look for something else to be wrong!

 

the N326 like to see HI impedance.(resistance) .so If you have LO impedance injectors they must have a resistor pack on the harness(located under the air box,a silver looking little attachment with a BIG plug on it).
You can run HI impedance injectors IF you splice the resistor pak so that the Resistors are Bypassed,or Use the harness from a Car around that year that does NOT have the Plug for the resistor pack.

 

YES i am using the resistor pack

 

What makes you think there's something wrong with your car?

 

^ +1

Judging from your recent threads, you're having some sort of fuel supply issue:

https://www.rx7club.com/search.php?searchid=7619099

Let us know what's going on overall, and we'll go from there. We need to know, for example, if 12V is even making its way past the relays, etc.

 

Cause it dosn't run!

 

I have fuel pressure, and spark, i also have 12v to the injector, but no pulse

 

fuel pressure where? are you sure you don't have your fuel lines backwards? the line from the fuel filter should go to the primary fuel rail.

and I'm pretty sure you'll always have 12V to the injector. the ECU is in charge of grounding that 12V. It might be an ECU problem/ problem between the ECU and the injectors.

 

Just double checking your checking - how did you verify fuel pressure?