CarbonRevo

As the title states, do 48# Siemens injectors need resistors?

eniac

Well are they high imp Siemens or Low imp Siemens? My guess is they do but need to know the Ohm to know for sure.

CarbonRevo

How will I be able to tell? There's numbers engraved on the sides, but I bought them used and do not know. The kits been used before, so it seems they would have included the resistors if it needed them?

Techno Duck

Use a multimeter and measure the resistance across the two leads of the injectors. If i remember right i think you want a total resistance of about 4.5 ohms, so you will need to add some resistors inline to make up for that.

You technically dont need the resistors for the car to run, but they are good to have because under constant full load situations you can burn up the injector driver in the DME.

CarbonRevo

Just the injector? The two pins on them, Hook my meter to that? What do I set my multimeter on to measure resistance?

Techno Duck

Yep, just the injector. Set the multimeter to the lowest number under the Ohm's setting. Usually its 200 or 20 ohms, or some just have one setting for ohms. Touch the each lead of the multimeter to the pins on the injector, you will probably get somewhere around 2 ohms.

CarbonRevo

And I need them to be 4.5 ohms? Do I have to put resistors on each fuel injector clip?

I've never seen a picture or heard an explanation of where these resistors actually go. Also, what resistors will I need to pick up when I go to radioshack?

Techno Duck

You only need two resistors because the injectors are fired in pairs. You splice them inline on the wires coming from pins #14 and #15 on the DME. If i remember right they are grey and grey / black (i think). Install them close to the DME.. so right under the carpet.

I needed 2-ohm resistors with the Siemens Deka injectors i bought from Vitesse. You should check the resistance of what injectors you have though.

This is what gets spliced inbetween wires #14 and #15. The aluminum plate is just a very simple heat sink, the white stuff is thermal paste for PC's.

eniac

The ECU driver is rated at 16 amps.

Without resistors:
2.3 ohm/4 = 0.575 ohm combined.
12v/0.575 = 20.9 amps.

With two 1 ohm resistors and 2.5 ohm injectors:
2.5 ohm + .5 ohm resistance(a 1 ohm resistor on each of the two injector drivers) = 3 ohms each
4 injectors would be 3 ohms/4 = 0.75 ohms
12v/0.75 = 16 amps.

With two 1 ohm resistors and 2.3 ohm injectors:
2.3 ohm + .5 ohm resistance(a 1 ohm resistor on each of the two injector drivers) = 2.8 ohms each
4 injectors would be 2.8 ohms/4 = 0.70 ohms
12v/0.70 = 17.1 amps.

With two 1.5 ohm resistors and 2.3 ohm injectors:
2.3 ohm + .75 ohm resistance(a 1.5 ohm resistor on each of the two injector drivers) = 3.05 ohms each
4 injectors would be 3.05 ohms/4 = 0.7625 ohms
12v/0.70 = 15.7 amps.


Mine are mounted as show below:

CarbonRevo

These are deka injectors as well. They all measured 2.4ohms. So do I need 2ohm resistors or 1ohm? I got confused between you both Jon and Stephen.

Ballistic-Chapman

Techo Duck - where did you purchase the resistors?

Techno Duck

Cory, i would use 2-ohm resistors. If i remember the Seimens injectors i had were about 2.4 ohm impedance also.

CarbonRevo

I'm at radio shack right now and none of these resistors look like yours Jon. Which do I get? LOL

eniac

1.5 or 2 ohm resistors will work. I use 1.5 ohm resistors on my Siemens 86lb injectors. As you can see in the formula I listed, 1 ohm resistors would still be too much amp draw.

I might have an extra pair of 1.5ohm ones. I'll have to check tonight when I get home.

Techno Duck

The resistors i have came with the injectors i bought through Vitesse. You can get similar ones at most electronics suppliers. RadioShack is kind of lacking as a electronic store and more of a cell phone place now if anything. Try to find a local supplier or order online.