Thread: MSD 72lb injector help. -- Injectors bad or tune?

What's ur fuel psi set at?

44psi w/vac hose closed.

I got the car running and driving great. It was mainly an issue with the tune. Injector latency was way off. I'm fine tuning it now.

That's to high for msd's since they like no more then 3bar or factory psi. I had the exact same problem...dropped the psi to stock and all my issues were gone. Give that a try...may run better. I also shot u a text

3 bar = 44psi

Well, 43.5 to be more exact heh.

-G

I confused that with 4bar....fail. that's supposed to be the setting with the hose off

Ya I did it with the hose pinched which gives me the same readings as taking it off.

@ebinkerd: Your PM box is full, but the tune is in the Calum section:

http://www.sr20-forum.com/rom-ecu-tuning-file-exchange/43138-ecu-bins-tunes-2.html#post905964

I've since modified the timing/fuel maps using a different base tune, but the injector latency is the key to getting the car to idle and cruise perfectly.

I'm super confused. I'm about to install this resistor box and it seems I originally installed the resistors incorrectly.

I quoted above that the resistors were installed on the individual pins going back to the ECU, *NOT* the 1 pin.

In case anyone reads this and knows the answer -- where do I splice my resistor box into? I'd assume it's the 1-wire power signal, not the 4-wire ground signal. If I were to splice and aggregate the resistor into the 4-wire ground signals, then all 4 injectors would be firing during each stroke, essentially throwing fuel into 2 cylinders which are not firing. Am I thinking about this wrong?? Super confused right now!

@ebinkerd

-G

OK so I'm pretty much certain that I originally had installed the individual resistors on the wrong wire. The car recently had an issue where it completely lost injector signal and stalled on the road. It re-started after about 5 minutes.

I'm surprised my ECU has lasted this long w/no resistors at all. I've had the 72lb injectors wired in for over a year! The car did stall once before last year, but started right up. I wasn't sure what to make of that at the time. I was assuming a loose ECU connection or chips on my Calum ECU.

I don't think the ECU is fried as the car started back up after about 5 minutes. I think the ECU just overheated. Going to correct all this mess w/the resistor box.

I found the GTI-R injector wiring diagram in the FSM to prove I'm not crazy here. It seems a lot of people are wiring this *WRONG* Which is interesting because we are all told your ECU will fry if you don't put in resistors. Well, it seems a lot of people are running their MSD's without any resistors and either never have issues or have intermittent issues like I'm having recently.



As you see, there are 4 wires going back to the ECU harness and 1 wire which is supplying the power. The resistor box is connected to the power wire, not all 4 of the grounds going back to the ECU.

Hey buddy, sorry its taken me so long to reply. What the resistors do is create voltage division. Low imdepance injectors are just a coil with a very low resistance, think less than one. This is bad for and electrical circuit because it create too much amp, V/R=I, or 12v/.01= 1200amps. very bad. So what the resistors do is create a voltage division. In this case it is 2ohms + 1ohm. I am using 1ohm for the injector cause I do not know the ohms off the top of my head. R1=1ohm, R2=2ohm. Using voltage division, R1/Rtx12v=4v at the resistor. Now one would think that resistors are in parallel, but that is not the case. Inside the ecu is a driver. The drivers job is to ground the circuit, so at any given point in the cycle, only one resistor has voltage. Even though they share a common 12v, they are grounded separately. So, it does not matter what so ever to have it wired before or after the injectors, just as long as you have 1 resistor per wire, either ground or power, but not both.
@gomba