Thank you very much sir i pm you back!

Up there- from what my head gathers, this just sends more power to the injectors (40 volts vice 110 or 120 volts) which snaps them open sooner, instead of the normal "get around to it" way they do. It's only a millionth of a second faster or so, but that time in escence advances the timing allowing for a more complete fuel burn equating to more HP. It's kinda like a more aggressive cam having a more steep slope than a stocker, they both have the same duration, but one opens faster allowing more fuel/air (in a gas car) to enter.

Does that sound about right guys??

Yes. However, if the IDM you aquire is from a 97 model or older, you will need a different value resistor. Those of us holding the extras have both....so you'll be covered either way.

thats good to know ... i took a trip to the salvage yard today to see if i could find a spare turns out those guys were quick to take that out lol i guess it is worth something to them i guess ill have to try mine.

The resistor changes the voltage from either 110V or 120 volts to 140 volts that the injector sees. Voltage is a measure of electric potential. It's analogous to the pressure pushing water through a pipe, except it's pushing charges instead. In fact, some textbooks refer to voltage as "electric pressure". The higher voltage gives a charge a lot of potential energy.

The following is basically the same explanation, but more in terms of "EE speak"... The voltage pushes electrons (charge) thru the wire to produce a current, and the magnitude of this current is the time rate of charge flow through the wire. Injector solenoids are inductors, and it's the current (not the voltage directly) that produces the magnetic field in the solenoid, which in turn opens the valve to apply high pressure oil to the topside of the fuel plunger, which then pushes the plunger down and injects the fuel.

After a voltage is applied to a solenoid, the current is initially zero, and then the current in the solenoid increases with a delay time that's proportional to L/R, where L is the inductance of the solenoid and R is the series resistance of the solenoid and the wire connecting the voltage source (IDM) to the solenoid. After a sufficiently long time interval, the current in the solenoid reaches a maximum value equal to V/R, where V is the source (IDM) voltage. A larger R will allow the solenoid to reach its maximum current sooner, but this maximum current will be smaller, and thus generate a weaker magnetic field which can't open the valve as forcefully, and the opposite is true for a smaller R.

The stock IDM supplies a 7.5 Amp initial current to start the valve opening quickly, and then follows that with a 3.5 to 4 Amp holding current to keep the valve open during the rest of the injection event. Apparently, the maximum values of the initial and holding currents are controlled by current limiters in the IDM that aren't effected by the "resistor mod", however, the mod does apply a higher voltage, which initially increases the solenoid current faster, until the current limiting takes effect, and this causes the solenoid to open about 20% faster than for a stock IDM.

Thers only one thing that has been forgoten here, related to the soldering. I noticed in the pictures that the flux was not cleaned off after soldering. Some fluxes contain more or less acid than others. It should be removed with alcohol (typical ispropyl will work) and a q-tip. Do not drench the board with alcohol as it may remove the remaining coating on the board.

I've been soldering for almost 23 years to mil specs, I definitely recommend removing it . The acid left behind could damage the IDM circuit board. And its simple to remove with a q-tip and a alittle alcohol.

I just need to find a few resistors here in town, Couldn't anybody locate the surface mount resistors like what was already on the board ?

Anybody find one? /\ of those? :)

You don't *HAVE* to use an SMT resistor. I've been hacking electronics for years and have used SMT in place of axial & vice-versa many times. I'm about to do mine just to see what happens, but it'll be a while before I get to it. Quite a few more pressing projects to get done first. :)

About the flux, while I always clean my work, I've seen more often than not that it isn't done. Using acid core solder isn't a very good idea on any PC boards, so if that's what you have, head on down to Rat-Shack and get some rosin core.

Rosin core solder has acid in it too, that's how it cleans the connection as you solder. I was refering to the acid in the rosin. They do make a acid cored solder, with citrus acid in it, and it was used in military applications here at Raytheon(Hughes) in the late 90's, but they ended its use do to its reativity to components. The reason they used it was because the boards could be cleaned with hot water instead of chemicals. they were thinking green.:-jammin

So now I'm a little confused. What is the best solder to use in the IDM mod application? There's a computer and electronics shop here in town that I can probably get it from, but I want to know what to ask for. Thanks,

Rosin core is always the best for electronics.

Acid core should NEVER be used around copper. Of course, it WAS used around brass when soldering tanks on radiators, but the joints were washed carefully afterward, too.

Pop

We learned at work that the acid stuff is crap.

The acid solder isn't crap. It has it's appropriate application, and should be used thus.

Just not around electrical stuff....

Pop

Thanks Pop!

I'll round some up then.