Gtr Injector Resistor Ballast Box

[Waldo]

how do i test the injectors resistance, so i can work out what resistors i need

[Driver]

shizer

i got my injector thingie from ad jap for $130 deliverd to perth

the guy isnt makn enuf profit

[GTRgeoff]

Pred, without being an expert on the subject, it appears to me the most economical means of producing higher flowing injectors is low impedance, while Nissan use an ECU that favours high impedence or lower current handling transistors.

Waldo, just use a multimeter to measure impedance (ohm symbol or the horse shoe shape) then calculate the correct resistor to bring to the correct value of between 12-14ohms.

Given the cost of the resistors is about $6 I'd say even $130 is a scam.

[Driver]

yea i agree its a rip off, i just wanted to have everything as u would get it from factory.

[Waldo]

do you measure accross the 2 pins on the injector? or the circuit?

[GTRgeoff]

Across the injectors mate, sorry I forgot to include that

[Waldo]

sweet as cheers mate

[Waldo]

ok just went and measured the resistance using a top of the line mega, the GTR injectors measured out to be 1.88ohms and the standard RB20det injectors measured to be 14ohms exactly, so i will use 12 ohm resistors to correct the resistance. Hope this helps anyone

[SteveL]

I've just measured the resistors in the resistor pack in my R32 GTR....each has a resistance of 5.5 ohms. I also measured the L-jet resistor pack that I have, which is either from an r30 or a 280ZX (I can't remember, but it doesn't matter as they use the sam injector system, more or less)...each resistor also has a resistance of 5.5 ohms. So using an R30/280ZX resistor pack is an option, although as I said the connector is different.

[Waldo]

i dont understand how this works, if each resistor is reading 5.5ohms in your resistor pack then the total resistance of the gtr circuit would be 7.5 ohms....does the rb20 have a resistor pack at all for the injectors? so its means if u stick gtr injectors with the injector pack you will still only get a reading of 7.5ohms whereas the rb20 injector resistance is 14ohms...i must be missing sumthing

[Waldo]

i think i understand it now....with injectors the computer sends a signal to them for example at 2000rpm it will send 3 volts, and at 7000rpm (full throttle) it sends 12v. by having more resistance (14ohms) the volts that are going to the injector will be significantly less, say 5 volts at full throttle instead of the required 12v, this is because more resistance you have it will lower the volts, but not having enough resistance it will fry the ecu. So therefor you would have to find a medium, say instead of making the total resistance 7.5ohms make it 10ohms, so that the injectors can still receive an adequate amount of volts and then its just a matter of the tuner to change the volt range at differant throttle points...

SteveL do you have any rb20det injectors if so what resistance do you get with those

[GTRgeoff]

Umm, this is a bit confusing from those figures for the impedences. Time for some research.

Sorry Waldo, the voltage will always be the same, just the switching frequency and timing for open/closed will differ with rpm.

[GTRgeoff]

Just having a think about this. With the GTSt's I'd suggest keeping the same impedences to suit those computers if making a pack, but enough success is had using the GTR resistor pack to warrant anywhere from 8-14ohms impedence.

Anyway, it could be an expensive error. Worth further investigation.

[SteveL]

i think i understand it now....with injectors the computer sends a signal to them for example at 2000rpm it will send 3 volts, and at 7000rpm (full throttle) it sends 12v. by having more resistance (14ohms) the volts that are going to the injector will be significantly less, say 5 volts at full throttle instead of the required 12v, this is because more resistance you have it will lower the volts, but not having enough resistance it will fry the ecu. So therefor you would have to find a medium, say instead of making the total resistance 7.5ohms make it 10ohms, so that the injectors can still receive an adequate amount of volts and then its just a matter of the tuner to change the volt range at differant throttle points...

SteveL do you have any rb20det injectors if so what resistance do you get with those

<{POST_SNAPBACK}>

I don't have any RB20DET injectors...sorry. The injectors always see the same voltage...it is the current drawn by the injectors that will be different - but I'm no electronics tech. The way I understand it is this....injectors with low resistance (2-3 ohms) are used where fine control is required because they have opening/closing times which can be tightly controlled. OTOH high resistance injectors do not have the fine control capability, but are by far the most commonly used (so might be cost issues, etc).

The crucial thing is that the injector drivers in the ECU will be 'matched' to the injectors, so if you are going to use GTR injectors (low resistance) with an RB20DET ECU designed to be used with high-resistance injectors I would have a tendency to add a sufficient resistor value in parrallel with each injector to more-or-less match what the ECU would normally expect to 'see'. I doubt that you need to get things 'exact', butmy understanding is injector current has a crucial effect on injector life as it effects injector heating.

Aftermarket ECU's (eg Motec) have more complex injector drivers which can vary injector current via software settings, so they can cope with a range of injector resistances.

[Cubes]

How do I go about measuring the resistance of a resistor pack? Does it have to be connected up to the car?

[Roy]

Its a resistor, so doent need power or connecting to anything to measure its value. The GTR one has 7 wires, with 6x 1 colour and 1 x odd colour, measure any of th e6 wires against the odd coloured wire

[Cubes]

With regards to splicing it in to the loom.

Do the GTS-T owners simply cut the plug off and begin soldering directly to the loom or???

[Roy]

With regards to splicing it in to the loom.

Do the GTS-T owners simply cut the plug off and begin soldering directly to the loom or???

<{POST_SNAPBACK}>

Nah, i kept the plug and spliced the wires into the loom.

One day when that girl next door finally confesses her deep seeded love for me, my lotto numbers get up and my RB20 makes enough power to strain GTR injectors, well with the plug then all i need do is unplug the resistor and plug in a leed that simply loops the wires back together so that the ECU will once again see low impedence...allowing me to run RB20 550cc injectrs etc etc

[Cubes]

love or lust??

[SteveL]

As Roy says there are 7 wires in the resistior pack plug. In the case of the R32 GTR resistor pack, one wire is white, the other 6 are black. The white wire is connected to the battery +ve terminal, so carries +12V. Inside the resistor pack the white is connected to one end of each of the 6 resistors, the opposite end of the resistors is connected to one each of the black wires. Each of the black wires connects to one terminal of each of the injectors. The other injector terminals are connected to the ECU. The ECU fires the injectors by intermittently earthing the injector terminal connected to it.....current flows, etc, etc.

In the case of engine control systems that don't use a resistor pack (GTSt's, etc), there would still be 6 wires connected to one terminal of each injector for +12V feed, but at some stage in the loom they would all become connected in common down to a single wire to the battery. It would probably be a case of some wire tracing to track that join, although I have seen an RB20DET (red top from memory) that had a small 'sub' loom for the injectors (sort of like the sub loom for the coil packs). Don't know about RB25's.