Injector Resistor Wiring Question..Please Help..

[chinkyeyed69]

hi everyone...

I bought some MKIII 7mgte injectors for my NA-T and trying to wire up the resisters but not sure which wire I have to use.

I didnt buy a resistor box, I bought some resistors and plan on just soldering them inline.

my car is 94 and the wires on the injector clips are black/orange and Red/with all different colors.

I believe it should be the red/? wires but I could be wrong that is why I would like to check with you guys first before I do something stupid.


thank you.

[DrNick]

The black and orange wires are the positive ones, those are the ones you need to cut and put the resistor in.

Which resistors did you buy? They need to be at least 25W so you will find that there is nowhere to put them unless you have a box too.

[Jostar]

More info on the Resistor box installed please, or a link to it thanks..

[chinkyeyed69]

thanks DrNick...good thing I asked first before I start cutting wires..I thought it would be the red wires. thank you for saving me the trouble.

I have only 10w 10ohm 10% resistors...I dont remember where I saw it but Mark said 5w or 10w. Should I go out and buy some 25w resistors?

and I will get a project box for the installation..I see theres no room to put those resistors.

thanks alot for your help...

[DrNick]

Use this to calculate the wattage you need

http://ourworld.compuserve.com/homepages/Bill_Bowden/ohmslaw.htm

Injector powering is a bit unnusual in that they operate by switched ground. The injectors always have power to them (as soon as you put the ignition on) and they are operated by switching the ground to them. The colour coded wires are the 6 ground wires that the ecu controls.

Remember that wattage of a resistor is basically its ability to dissipate heat. A 10W resistor will be rated 10W only at a specific temperature, as temperature goes up then the effective wattage will drop dramatically. Get the data sheets for the resistor you are buying and compare this with the kind of temperatures you expect the unit to be subjected to.

I used 50W resistors and built them into a metal case which acts as a heatsink. But I overengineered mine a bit since I was making some similar things for work at the time :)

http://medusa.murdoch.edu.au/~20042484/resistor/resistor%20001.jpg
http://medusa.murdoch.edu.au/~20042484/resistor/resistor%20012.jpg

[Mr Ree NZ]

Looking good DrNIck :)

Very tidy indeed.

[DrNick]

Looking good DrNIck :)

Very tidy indeed.

Aww fanx... Heres another to show the mounting then :)

All mounted using bolts to aid heat dissipation, air can flow between individual units and the bottom most resistor had thermal tape under it to ensure the casing absorbed a lot of heat.

Totally over engineered... Total cost for parts was quite a bit over $100 so I'd generally advise people to buy one ready-made and save some cash :)


http://medusa.murdoch.edu.au/~20042484/resistor/resistor%20008.jpg

[chinkyeyed69]

wow...that looks awesome..thanks for expaining this to me...now I finally get it. Ima start this project later today...I will let you know how it goes...thanks again!!

[chinkyeyed69]

I got everything hooked up and the car is running good. is there any way I can check and see if the resistors are working?

[DrNick]

Just use a multimeter (with the car off) and make sure the total series resistance is about what it was for the stock injectors.

[chinkyeyed69]

I checked with the multimeter and everything looks pretty good...very close to stock.

I went for a test drive today and it ran fine but having some problems boosting tho. I had the same hesitation problem (feels like I just hit a wall) around 4k when I was using stock injectors @ 8psi but problem went away after I did the 12v mod.
Now I have the MKIII 440s boosting 15psi...and the problem is back. do you know what would cause this? it doesnt matter what psi I hit when I get upto 4k, it does it all the time.

[DrNick]

Sounds more likely to be ignition this time, although at 15psi you are pushing the 440cc injectors.

[chinkyeyed69]

I will see what I can do with this problem....thanks for everything DrNick

[8052JZ]

i know this thread is pretty old but got a question about resistoring injectors. I am planning on using PTE 1000cc low imped injectors ( http://www.precisionturbo.net/fuelsystems.php ) iam just wondering what resistor is needed to run these? whats the easiest way of wiring them up? inline or use a box?

ive found this diagram and was going to go off if that ( its attached )

thanks for the help

[DrNick]

But all those questions are already answered in this same thread dude. Did you read it?

Anyway PTE are 2ohm, if stock is 14ish then you need 12 ohm.

[8052JZ]

Sure did read it but was still confused on what resistor to use as Ive read mixed results in different threads, and wanted to make sure I am doing this right.

thanks dr.nick

[DrNick]

No worries man.
The reason why different threads have different info is that there is a bit of margin for error so its possible to use (slightly) wrong resistors and it will appear to run ok.

The best option by far is to measure your stock injectors and then work out what resistance you need so that its really close to that with the new injectors, that way your ECU will be sure to have no troubles :)

[8052JZ]

ok thanks I am still unsure of how to really measure out what resistor to injector to use, you know? and like you said sense the PTE 1000cc are 2ohm I would use a 12ohm resistor? based on what you said that's what I would be using if that's correct and using that chart I attached. plus I'm using the AEM standalone, don't know if that makes any difference.

so what would be the exact spec for the resistor

Found some info searching google:

http://www.tomco-inc.com/Tech_Tips/ttt38.pdf

one part of the doc that I found that was needed I believe.

If the injector is 2 ohms and we apply 12 volts to the
injector, our formula looks like this:
I = 12(volts) ÷ 2(ohms), or
I=6apms
This would be quite a lot of current for an injector
winding to handle for long periods of time.

so what would be the exact spec for the resitore

[DrNick]

Yes 2 ohms would give a series current of 6 amps which would burn out your ECU in no time. This is the whole point of using a resistor inline.

If you have a 2 ohm injector and a 12 ohm resistor then you have a series resistance of 14 ohms.

This brings the current down to 0.857 A

[8052JZ]

ok I see how this works now lol thanks again. does it matter what wattage and tolerance percentage the resistor is?

[DrNick]

Tolerance percent isn't that important as most of them are 5% which is fine.

The wattage is very important, basically the wattage is the ability of the resistor to dissipate heat. This is really important in a car engine bay which is hot to begin with. I would get 25W resistors at a minimum but if its the same price then get bigger. I got 50W resistors cuz they were only a couple of bucks extra.

[8052JZ]

AWESOME!! got all the info i need thanks to DR.nick :) ill brake it down for those that read this thread and don't have to ask nor read to much lol

Stock 2jZGE injector are High Imped that are about 14ohms. ( to be exact 13.5ohms ) supplied with 12v

Low Imped Injectors are usually 2ohms ( PTE1000cc are 2ohms )

So add a 12ohm 50w or 25w resistor to each Low imped Injector to get 14ohms of resistance. now you can either make a resistor box or solder them inline at the Black/orange wires coming from the ECU harness to the Injector clip.

Use the diagram that is attached on the lower post.

Dr.nick check out the attached pic correct it if needed, thanks

[8052JZ]

here are some pics of the resistor box i made. Cost was about 35
paid 27 for 12ohm resistors and 6 for the 9wire lead clip. the box is from a Mega squirt unit that i wasnt gunna use + 16g wire I had.


http://www.facebook.com/album.php?aid=2034389&id=1330700375&l=a1da8a7ff8

[DrNick]

Great work buddy :)