IDM mod. Does it work?

[clux]

Originally Posted by cookie88 It absolutely does work.....especially if you have aftermarket injectors. Almost all of the "hotrod" PSD's you see on the boards and in magazines et.al. run 140v. IDM's. It's just that in most cases they did the mod so long ago they don't even remember to list it as a mod. Way back when I got to ride in a truck with a switched 120/140 IDM, so I know it makes a difference...but I had never been willing to experiment on my own expensive part, nor had it been high enough on my mod list to pay the premium for somebody else to do it. That is about to change however....last weekend I scored a 95 F-superduty IDM. As soon as my resistors come in I'll be doing a 140 conversion on it for my truck. So I'll have more better first hand for ya'. So cookie is the idea that the injectors fire sooner or faster or both with the mod? I'm not sure I understand the theory behind this mod, but it sounds intriguing if you have a spare IDM.

[Tenn01PSD350]

Read about it here.

[mongo75]

I'm installing 175's this week too- SO, running tuners will not effect the injector timing like this mod will??

So if I'm reading everything correctly, I can do this and it will safely add HP/TQ in addition to the DP tuner and new injectors?

If the above assumption is correct, is it worth it? Maybe an IDM could be found on ebay and that could be used instead of the one in your truck....

[clux]

Yeah I've read that Tenn, but I'm still not clear if the benefit is from more fuel or simply timing advance. Seems to me that if all you are doing is turning it on sooner (faster) the same thing could be achieved through simply advancing the timing.

[cookie88]

The timing of the fuel shot is not changed, but since the injectors physically open and close faster more fuel is expelled during a given injector cycle.

[Tenn01PSD350]

I am no expert on this. I have spoken with Dave at Swamps about this as they sell modded IDMs. The general concept I walked away with was that it is basically upping the current to fully open the solenoid faster. The biggest limit of the HEUI system is the amount of time available to inject or something along those lines. Upping the current makes it upen faster and and more completely. As RPMs go up, the problem gets worse.

So in effect, it seems to me it would not change the timing of the electrical event, but might change the actual event as the solenoid would fully open against the spring pressure more quickly. That is what I think I know about it, and it could be totally out in left field.

EDIT: before posting, I see Cookie answered that. I don't think the closing is affected by the voltage as that is spring operated from what I think I know. The extra voltage makes it perform better against the poppet/poppet spring assembly.

[clux]

So on split shot injectors, that would mean a smaller pilot event and a larger main shot. Seems to me this mod may be more suitable for use with single shot injectors?

[cookie88]

The pilot shot is mechanical....it is not going to be altered at all save it will be over sooner.

All this mod really does is allow the injector a tiny bit more time to empty itself. The flow path within the injector is not really relevant as it works exactly the same way for either style.

[clux]

Sorry to keep hammering on this but I'm just trying to think it completely through, I'm learning a lot here.

So the pilot shot is mechanically metered, always the same volume of fuel. It happening quicker then would result in higher pressure and possibly better atomization, right? That and a longer duration main shot.

Sounds like all positive to me then, regardless of injectors.

[cookie88]

Yeah man....you got it. The only down side is people charge $200 for this mod when a $1.09 pack of resistors and a little practice with the soldering iron is all that's required.

[Tenn01PSD350]

Originally Posted by clux

So the pilot shot is mechanically metered, always the same volume of fuel. Yes, this is correct for the same given ICP and FP.

It happening quicker then would result in higher pressure and possibly better atomization, right? No, your ICP and fuel pressure will remain unchanged.

That and a longer duration main shot. This is where you see the benefit from what I understand. This provides more opportunity to empty the injector. Big oil addresses this by pushing harder for the shorter or marginal event.

This is about all I think I know about this if I remember correctly.

[clux]

Originally Posted by Tenn01PSD350

It happening quicker then would result in higher pressure and possibly better atomization, right? No, your ICP and fuel pressure will remain unchanged.

If you moving the same volume of fuel through the same aperature in less time, the only possible way to do that is higher pressure. So either the PI event has to have less volume or the pressure is higher.

[Tenn01PSD350]

Originally Posted by clux

If you moving the same volume of fuel through the same aperature in less time, the only possible way to do that is higher pressure. So either the PI event has to have less volume or the pressure is higher.

It is a function of how long the poppet is open and how quick it opens. Nothing else changes but the opportunity for full emptying of the injector. So if the injector is fully emptying in your truck for every event, then you will have zero benefit. Do you think it is fully emptying right now?

So we are looking to move more volume out of the injector by overcoming the poppet spring quicker and holding it fully open better with higher current. The PCM timing of this remains unchanged. I can't really say much more about this as it was several months ago that I spoke with Dave about it.

[f350rebel]

I think i just reopened a big can of worms

[mongo75]

LOL.... If I could find a better detailed explanation with better pics, I'd be willing to do this.

Thanks again for getting ideas in my head Mike!!!!