I found them online, but I kind of need them asap.

Does it have to be exactly 16amps, or can it be like 15.xx amps?

Stephen- Let me know if you have those asap please and thanks!

 

also, can I use just regular old resistors? They dont have to have fancy aluminum housings, do they?

One last thing, what wattage do I need?

 

12-16 amps is ok. The problem is when you go over that such as drawing 19 amps with no resistors, it could burn out one or both of the injector drivers. Of course you can go too far the other direction also.

 

so what about wattage? I'm seeing 10w, 30w and such.

 

The ones I have are 25w.

 

But I mean, does the wattage matter? Or would 10w be fine?

 

If you can't find 25w resistors then use 30w ones. 10w resistors may overheat.

 

Sorry but have to disagree with the maths here.
The way the injectors are wired and the use of 2 current limiting resistors means the currents will as shown below. I've used 1 ohm resistors as an example.
However I have a problem with anyone recommending current limiting resistors, even the 'experts'.
If you put any extra resistance in the line to limit current you will drop the voltage available at the injector. Not sure exactly how this will affect the injector operation but they are designed to operate at a particular current & voltage. I know people have used resistors in the past but in theory it is not good practice.
Bosch OEM injectors are 4.6 ohm. (0280 150 803) according to Bosch data.
Porsche handbook quotes resistance check for 951 Injectors as 3.5 - 5.5 ohms. Porsche KLR Test Plan document (WDK 453 920) quotes 2 - 3 ohms as a test, so 2.8 ohm injectors would be fine here without extra resistors.
The max current capability of the driver transistor in the DME seems to be between 12-16 amps.
Who you believe for all these numbers is up to you. Basically don't use lower resistance injectors if you don't want to risk blowing the tranny (unless you believe the KLR Test Plan book) !

(BTW: all four injectors fire at once, pins 14 & 15 connected together - which I didn't know until recently)

 

uhh...

Hmm...so your saying 2.4ohm injectors without resistors won't hurt the injectors driver?

 

2.4 ohm injectors will exceed the 16amp rating of the injector driver. The DME uses batch fuel injection which means it fires 2 injectors at a time, not all 4 at once. I've cranked my car over with the intake off and saw this for myself.

Some people have gotten away with low ohm injectors and no resistors while many other have blown out thier injector drivers doing this. I have yet to see nor hear of any issues resulting from properly installed resistors with low imp injectors.

Granted either yours or my numbers could be wrong and thier are many other variables you could add in. I use that formula as a reference, not as gospel. Numbers on paper are all just thoeries. What I go by are real world results.

 

All four injectors fire at the same time, period. Pins 14 & 15 are connected together. Don't ask me the reasoning behind this injection system.
No, I'm not saying 2.4 ohm injectors are ok. I'm saying that if you put current limit resistors in series with the injectors you will reduce the voltage at the injector.
Sure you will limit the current passed by the transistor but what do the injectors need to operate correctly ?
It's just simple maths and a bit of knowledge of electronics.
Every other thread I've read about using resistors got me going on this one.
I am using 2.8 ohm #72 Siemens 3145, no resistors - will see what happens in a year or 2.

 

Been running 2.8 ohm injectors for years with no problems. Wouldn't use anything else with the stock DME.

 

This possibly makes some sense of the no firing problems I experienced running 1.5ohm resistors with delphi (2.3ohm from memory) injectors. Maybe voltage was an issue.
Switched to 1ohm and the injectors were happy again.
thanks.

 

When I stated all injectors are switched on together I was referring to the 1986 model 951.
Possibly they changed the DME later to have batch firing ?

If you must use resistors I wouldn't recommend anything higher than 0.5 ohm. It may appear to work ok but you start to limit the voltage available at the injectors, as well as reducing the current.
0.5 ohm 25W Metal Clad resistors will give you approx 14 amps draw with 2.4 ohm injectors, 8.5v at the injectors.
Using 1 ohm resistors will reduce this to approx 10 amps but only 6.5v at the injectors.
As these are Peak & Hold injectors the higher current draw is only for a very short time compared to total 'on' time.

 

Yes, in stock form they all fire at the same time twice per cycle. Sometimes I forget how unstock my "stock" DME is. I really don't see how that changes the calculation though since there is still 2 injector drivers. The wires are split at the DME and is why you would use two resistors, one on each wire. If it wasn't split you'd use one resistor or you could use 4 smaller resistor with one on each injector but that's a bad place to put them. The values would equal out to the same if using the correct resistors. Wattage has alot to do with as well. The voltage drop is minimal and should effect most injectors. Some do need to be "kicked" a little harder with can be done by the DME software and chip tuning.