Can we run without Fuel Injector resistor box ?

[Heryst78]

Hey Guy's

I was watching an old thread about all the electrical connections on our engine, and i saw a part I don't have, Miller didn't send me it with the swap.

It's the Fuel Injector Resistor box.

The engine doesn't want to start. maybe it's because of that ?
Can I delete it easier ?

Thanks a lot

 

[luv2rallye]

Some injectors (usually low impedance) use them while others (usually high impedance) don't. You'll have to check with the manufacturer's documentation. Our stock factory turbo ones use them. Run without them when you shouldn't will almost certainly burn up the ECU injector output drivers (and may damage the injectors too).

 

[Heryst78]

Thanks a lot

I have stock injectors, I’m swapping and I want to run for the first time with my new engine
I need to know if the engine can start without this regulator ?

Thanks

 

[luv2rallye]

The 2g stock turbo uses injector resistors but the 2g stock NT doesn't (and uses a different ECU). As I said, running without them when you shouldn't will almost certainly burn up the injector output drivers inside the ECU (since way too much current will flow).

 

[Heryst78]

Ok thanks so I need this parts if I want to start my Engine

Thanks a lot I will Ask Miller to buy it

 

[luv2rallye]

Of course I'm talking about USA models. In Europe the models are different so you'll have to look into it.

 

[Vegas Smith]

Or, just buy some expensive hi-impedance injectors

 

[Heryst78]

I bought an US engine from Miller so I need a US resistor
I stay with stock injector for the moment

 

[chrysler kid]

The 2g stock turbo uses injector resistors but the 2g stock NT doesn't (and uses a different ECU). As I said, running without them when you shouldn't will almost certainly burn up the injector output drivers inside the ECU (since way too much current will flow).

I've unplugged the injectors and engine harness across the motor a few hundred times and I've never seen the injector driverresistors. Where is it?

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[1990TSIAWDTALON]

They are in the ECU.

 

[bastarddsm]

OP it depends on what you are using.

The US 2g turbo dsm ecu is technically designed to run high impedance (12ohm) injectors. Mitsubishi got around this and ran low impedance injectors (~2ohm) by using a resistor pack. The resistor pack is nothing special, and I think they are 6ohm 25watt resistors. You could make your own.

So when you are looking for injectors there are 2 things to look for besides fitment. Flow rate of 450cc/min, and impedance. You can run high impedance injectors without a resistor pack, and you can run low impedance injectors with the resistor pack, as long as you have 450cc/min flow rate.

There is a rx7 injector that is 450cc/min and high impedance, some n/t 1g guys that do a turbo swap use them over here. Not sure if availible in europe.


Lastly, I think the drivers in the ecu would handle low impedance injectors without the resistor pack no problem. It's the injectors that would overheat and die.

For reference when I first started experimenting with auxiliary injectors, I just added a set of 450's and a second rail to my manifold. I made a sub harness that plugged in place of the resistor pack, and effectively ran 2 injectors in series. I ran that exact setup for years with no issues except needing huge amounts of dead-time. Now I run 2 sets of injectors, each with own resistor pack, in parallel with no issues. That's 2 times the normal current running through the drivers with no issues.

 

[steve]

1G's use a 2SD1415 Darlington transistor and the 2G's a 2SD2422 Darlington for the injector driver. Both transistors are rated for 7A continuous. The power dissipation limits are 25W and 30W respectively. That's going to be more the limit.

 

[bastarddsm]

Steve, thanks for that info. I knew it before but long forgot. As for the transistor limits, isn't that the dissapation in the transistor? In otherwords Vce * Ic, the voltage drop across the transistor * the current. If we have 7A current we would need Vce to be 3.5v to exceed the 25w limit of the 1g's 2sd2145.

That would mean with a healthy 14v charging system we would only have 11.1v on the injector, I've had a scope on it and not seen it that bad. Vce was less than 1v, or about 7W. I've never looked at Vce directly though. Am I missing something?

This is the thought process I went through when I was contemplating my dual injector stuff.

On contrast if we if we look at power dissipation in the injector with full current at 14v, and Vce of 1v through the injector (2ohm) it would be 6.5, and 84.5W!

Yes I know about inductance and rise time, just looking at steady state for now.

 

[steve]

Vce (sat) is 0.9v to 1.5v @ Ic of 3A.
Brain fart on the power limit, the number in my head was the injector power not transistor.

 

[chrysler kid]

They are in the ECU.

I looked under the hood behind the manifold on my firewall on my 96 daily driver and it has one back there

Was the fuel injector resistor pack deleted in 98?

 

[dustyboner]

no, 1998 has one. follow the harness. the resistor box plug branches off the harness at the same place as the brake fluid level sensor.

A-80 in the picture

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[chrysler kid]

ahhh I see it now

 

[Tanro]

The injector resistor box is mounted to the firewall behind the intake manifold on USDM cars.

You absolutely need it for stock, or low impedance injectors.

if you swap to high impedance injectors you can delete it but you still need to terminate the circuits. You can do it with splices. Or order a plug that does it for you. https://www.maperformance.com/produ...tor-pack-delete-plug-dsm-and-evo-8-9-plresbox

Or you can just use a crimp splice and literally just fit 3 wires in one end, 2 wires in the other. Crimp it closed. If you'd rather solder them, then make sure you get good penetration and use plenty of electrical tape in a good wrap to provide strain relief.

But I'd recommend a crimp splice, tape wrap, then heat shrink on top of the tape wrap. There is a reason OEMs use crimps and now solder joints.