High impedance vs low impedance injectors

[red85]

I've been doing some reading lately about injectors for my turbo swap. I can't seem to find out if my Ranger (94 2.3L) ECU will fire a low impedance injector (ie 36lb/hr from a Merkur). I understand that the low impedance injector requires roughly 6A of current to fire as opposed to about 1A to fire a high impedance (12-16 ohm) unit. Will a stock ECU fire the big low impedance injectors?

 

[Yellowsplash]

To run low impedance injectors requires the use of something similar to an injector resistor pack, otherwise you'll probably end up burning up the injectors and/or possibly worse...

And since your probably going to ask, Im unaware of rbvs or even most ford vehicles using low impedance injectors. Mustang injectors (high impedance) are easily found, especially on ebay for cheap.

 

[red85]

Thanks Yellowsplash. I have an LA3 and a set of 36# Merkur injectors, but I plan on running fairly low boost initially while I "iron out the bugs" that will crop up. I also have a set of 24# Mustang injectors that I suppose I can use initially before I repin and start using the LA3.

 

[red85]

What about adding a 10 ohm resistor to each injector? Would this work?

 

[rocket5979]

Unless you really know what you are doing I would suggest that you resist the urge to build your own low impedance injector driver.

All modern stocker Ford's have high impedance injectors. Pretty much all aftermarket injectors up to 75lb/hr are high impedance and will work with your stock injector driver. There are some sets of 83 and 96 lb injectors that are made in high impedance but most have switched to low impedance by then. When you get to truly large injectors they will be low impedance and need a separate driver.

You will not have a problem here if you plan to run an injector in the mid 30# range. Plenty of high impedance choices for you there. Keep it simple and give yourself less hassle by running a high impedance injector.

 

[AllanD]

If you guys don't understand basical electrical theory I suggest you give up your electrical tools.

you cannot correct an impediance mismatch by adding a resistor.

First, Impedence is a measure of resistance in a dynamic situation.
Impedience usually refers to coils, motors or devices operated with
fluctuating current. (warning simplification in progress)

"resistance" or lack thereof is a matter of current flow.

a "Low impedience" injector is essentially an engineers way of saying "High current"

If you did something like adding a resistor in series with the injector you couldn't change the impedience, you'd change the resistance.

The fact that "impedience" and "resistance" are both measured in a
unit of measure called an "Ohm" is in this case strictly IRRELEVANT.
because of the fundemental difference between "resistance" and "Impedience"

My saying more about "impedience" would only confuse you.

Putting a resistor in series would only serve to guarantee that the injector
that "probably won't fire", will "Definatly not fire"

The only REAL technical effect of using a resistor would have is to prevent from
blowing the injector driver transistor inside the non-turbo computer.

The other real effect is the waste of time, the resistors, wire and (presumeably solder)
you'd use to make your box.

The basic fact is that you cannot make a low impedience into a high
impedience injector any more than you can make a 100w light bulb into
a 20watt lightbulb by putting a resistor in series with it.

It just doesn't work that way.

AD

 

[rocket5979]

Allan, I believe while some people mentioned modifying the injector itself (which like you said, is not a good thing) others like myself were talking about the injector driver which is obviously totally separate.

 

[Sevensecondsuv]

Just put the 35s in with the LA3. Problem solved. No need to worry about mismatched injectors. Running 35s with a stock computer is going to result in so much over fuel that it may not even start. 24's from a mustang would probably allow it to start but the truck is going to run like crap.

Just match the computer to the injectors and you won't have a problem.

 

[red85]

Holy crap AD. Do you just snap at everyone who asks a question? A little politeness goes a long way. As for how injectors work, I was unaware of the way the injector driver circuit worked. Thanks for the lesson. I think I'll just use my LA3 after all with the 35's. My oil return lines will be in next week. Can't wait to get this swap underway!

 

[krugford]

Holy crap AD. Do you just snap at everyone who asks a question? A little politeness goes a long way. As for how injectors work, I was unaware of the way the injector driver circuit worked. Thanks for the lesson. I think I'll just use my LA3 after all with the 35's. My oil return lines will be in next week. Can't wait to get this swap underway!

Well, he answered your question. There's nothing wrong with being a little harsh to break up an incorrect line of thought.

 

[shadetree]

Holy crap AD. Do you just snap at everyone who asks a question? A little politeness goes a long way.

But, he has mellowed over the years. You should have known him in the old days.shady

 

[Yellowsplash]

I never inferred that you could "build" your own resistor pack...DSMs, particularly on the 4g63 turbo engine, use an injector resistor pack that is mounted on the firewall in order to run low impedance injectors. The non-turbo 4g63 uses high impedance injectors without the resistor pack. While I know this is kinda irrelevant as we are speaking of a ford engine, there are alot of honda guys who are forced induction running low impedance dsm injectors in a car originally equipped with high impedance by simply wiring in the resistor pack. The theory exists, but its inefficient in terms of hassle...If you can just easily get the correct high impedance injectors off ebay for a steal, why mess with the thought.

 

[turbo cat]

you have alot of chices all the way up to 60#ers. lightning 42#ers are always around. You can also look into megasquirt diy ecu

 

[rocket5979]

you have alot of chices all the way up to 60#ers. lightning 42#ers are always around

Actually the choices for high impedance goes all the way up to 83 lb'ers and by now possibly 96'ers for all I know. More than enough high impedance choices for 99% of people out there.