Ok...as if my frankenstein motor wasnt bad enough, I need to know if my injectors will work...
I have a Series 5 Block, manifolds, turbo setup and fuel rails...Series 4 EFI and related electronics (includes harness, ecu maf, boost, and all the other sensors)

I got me a nice set of Universal Top-Feed Greddy 720cc Injectors, and with the Series 4 harness and electronics, I need low impedance injectors correct? Well what are these injectors that I have?

 

Grab a multimeter, and measure resistance across the terminals. If it's high (above 5 ohms), they're high. If it's low, they're low. Imagine that.

 

They're low impedance. If you have an 88 S4 your system is set up for high impedance and you need a resistor box so you don't fry your ECU.

 

Light blue / aqua tops, right?
Low impedence.


-Ted

 

those are the ones......so im gonna need a resistor box for each injector, or can i run one for all four? where can I get this resistor box?

 

Well, you dont necessarily need a resistor box... You can get the 10 ohm, 10 watt resistors from Radio Shack, and wire them into each injector output on the ECU. That will match your injectors (its a bit more involved then that, but thats the basics).

 

What do you mean it's a little more involved? If i splice in those resistors am I all done or is there more?

 

No, but you need to find the pinout to the ECU. Once you splice them in, you are impedance matched and ready to go.

I dont know what your capabilities are (hence the "its a bit more complicated"). It involves reading diagrams, soldering, etc...

 

i can take that on........does anyone have the diagram of the ecu plugs? and i put these on the wire coming from the injector or going to the injector?

 

In the S4 FSM fuel & emissions section 4B pages 32-33.
The link is in my sig below.

 

Correct - I just installed mine a few weeks back and I can verify that...

 

So will I be putting the resistors on the wire coming from the injector or the wire going to the injector?

 

I"ve got an 88 tII with the blue tops and no resister but my ecu is not fried.

 

Doesnt matter.

 

OK....to makw it more complicated...you said that these injectors (greddy blue tops) are set up for low impedance, which is for s5 correct? than why do these injectors plug directly into the s4 harness but they don't fit the s5 harness...i confused...someone please explain

 

No, the S5 is only high impedence.
Technically, these GReddy low impedence fuel injectors do not drop-in for S5 application.
The GReddy 720's only drop-in for early Zenki plugs; later Zenki plugs are high impedence with wrong "key" offset.


-Ted

 

oh ok so as long as the stock plug fits the injector for the 720's its the right impedence??

 

Basically, yes.


-Ted

 

is that "basically yes" ot "yes"?

 

Yes.


-Ted

 

if the ecu was going to fry would it do it right away or take a bit? i have an 88 hi imp motor and these injectore havent put um in yet the connector fits the injectors but i know the ecu is for hi im.

 

It takes a while.


-Ted

 

ok ted one more question if you don't mind answering it. I have an n333 ecu and the harness fits the injectors just fine and I"ve been running on 720 secondaries for about 2 years. Is this ok or does the n333 need the resistors? THanks man.

 

All the ECU's, as in ALL, need to see over 10ohms from the injector circuit prior to the ECU
(a slight generalization). That applies to ALL the ECU's whether series four or five. Each and every one of them. ALL of them. All inclusive. Each and every one of them.

Series four do that by having a Solenoid Resistor package with the resistors built in to the injector circuit.

The series five do that by the resistance being built into the injector itself.

If you have some cobbled up car from various parts and have not a clue about where this that and the other is in the car, then ohm out the injector circuit from the small plug on the ECU, ohming out each of the four injector wires with a simple 10buck meter from RadioShack or wherever. There is online, free, factory service manual online for free that shows the pinouts for each injector wire on the small plug on the ECU.

Even a HaYnes manual will show the wire colors and locations on the ECU plug.

In mid 1987 they changed the series four cars from low resistance to high resistance injectors. The high resistance injector cars do not have a solenoid resistor package located under the airfilter assy and attached to the fender structure, as shown in the free online factory service manual for series four cars.

Solenoid resistor packages are a dime a dozen on E-Bay. Sometimes they cost up to ten bucks though.humor

If the ECU does not see that resistance, sooner or later, the drivers in the ECU WILL burn out and the engine will not run anymore. A driver is a little man in the ecu who gets too hot and burns out if he gets too much current passing thru him. Sort of like beihg on death row in Huntsville, Texas and sitting in Old Sparky with toooooooo much current passing thru you. not funny

 

ahhh thanks for the explination! I'll wire in some resister packs asap.