Hi guys,

At 7:08 PM last night the last person that agreed to buy 50 resistors (25 of each) got in on the deal. To make things easy for me, I found seven members (eight including myself) to split the 400 resistors with. Each of these folks have kindly agreed to then supply all others who want to buy one or two at their cost (about 10 cents each) or just give them away.

So, if you want one or two you should contact, by PM, the member who is closest to you:

TchTchr - Indiana

DieselCamper01 - Minnesota

Ron's Power Stroke - New Hampshire

leekingen - Minnesota

twtcad - Florida

Cookie88 - Arkansas

Rampage_F350 - Alabama

nlemerise - Nevada

I would expect to have the resistors by the end of the week and each of these folks should have them next week sometime.

Thanks to you guys this will work out for everyone! I apologize to those who offered to join in after the initial "seed" group was finalized...but you WILL get the resistor of your choice for cheap or free!

 

I'm not trying to be an alarmist here, but a conservative approach to mods is to try and understand exactly how they work, and what possible negative ramifications they might have before doing them. I clicked on the link provided in post #1, and there I found the following...

"WARNING WARNING WARNING WARNING
DO NOT MODIFY YOUR IDM UNLESS YOU *REALLY* KNOW WHAT YOUR DOING!!!!"

This warning is apparently referring to the mechanics of soldering a new resister in place of the old one without damaging your expensive IDM. I recommend using an alligator clip to clamp a wad of damp tissue to the new resister so that it doesn't get over heated when soldering it into place. Also be careful not to overheat any other nearby components or disrupt any other connections. Overheated components can have their values changed, and this can lead to early failure or other unintended consequences.

Be sure and re-establish a perfect water tight seal when the IDM is re-assembled, as it gets splashed every time you drive through a puddle. I also recommend loading the connector with dielectric grease.

BTW, I think the IDM mounting location was chosen to provide RFI isolation, and to enhance heat dissipation. The IDM contains a 12 VDC to 120 VDC converter which is identical to the 12 VDC to 120 VAC converter in my RV, except in the IDM version the AC is rectified to DC.

Assuming the maximum IDM output current remains unchanged due to its onboard limiter, the IDM MOD increases its average output power (and therefore its required heat dissipation) by about 40%. This is because the voltage is increased by about 17% and the duty cycle is increased by about 22% due to the faster turn on of the injector. If a 110 VDC IDM is increased to 140 VDC, its average output power is increased by about 50%!

The link provided in post #1 also states that...

"By changing some parameters on the IDM, i turn on the injectors faster and therefore keep them on longer since the PCM does not know it has happened. With a stock IDM, the injectors take 560 us to fully turn on, with the IDM mod injectors turn on in 440 us."

A turn on time of 440 us with the IDM mod versus 560 us for a stock IDM is 120 us faster, and thus fuel is injected 120 us sooner. At 3000 RPM this translates to a (120/55.55)=2.16 crankshaft degree advance in injection timing! If an aggressive tune is already pushing the timing advance to the limit, might another 2 degrees added to that eventually lead to disaster? Well, I guess only time will tell as I see that this mod is now going to be widely done by many, and combined with aggressive tunes to boot, in hopes of getting even more HP.

See my post #3 in the reference link I gave in my post #49 here for my improved cable mod. Based on the measurements reported by mustang_gt_350, the voltage at the injector is reduced to 55% of its value at the IDM output, and this could be due to the stock cable which is clearly not designed for optimized rise time and other pulse propagation characteristics, which require a proper transmission line and connectors like I suggested.

 

Which is the exact reason why there has been such a stigma surrounding this mod for years, and is also the reason people get away with charging $200 for changing one resistor.
When you buy a "performance" IDM from any of several vendors, you are not getting a new IDM. You're getting the one out of the last guys truck....and the next guy that buys one is getting your old one. It's just rediculous to pay that much for a $.21 part.

I don't think you are an alarmist Gene, but you definitely are conservative. That's a good thing...somebody has to be the voice of reason. Your advice is solid. The old axiom "you gotta pay if you wanna play" applies to every single mod that we do to these trucks.

Great soldering tips. Thanks for posting them.

 

Cookie, I could not have said it better myself! As was said, Gene your thoughts on this are a good thing and great soldering tips too. This is not micro soldering and I can not see paying someone $200 for this......and Gene since I have a Superchips programmer and their shop is in my backyard (figuratively) I'm going to talk with them about their tunes and what this does before I actually mod mine. Thank you for your words of caution!

 

Great post Gene...I was going to use a heat sink each side of the resistor when soldering it in. Drop a line when the opportunity avails itself...you get my earlier email?

 

Ernest,

Any chance that negative pulse is the voltage created by the solenoid coil collapsing and not a close "command"? Just curious is all.

I'm pretty amazed that the engineers did not better engineer the wiring harness to the injectors. Makes you wonder if the injectors only need around 50 volts and it was cheaper to bump the voltage on the IDM than to engineer another harness with better wires?

 

Anyone ever get a hold of Jody and see if this effects the DP tuner any??

 

wont be able to till after next week unless some one ask him at smoking and gets back to us....

 

I'm not sure exactly what's going on here! I was speculating based on mustang_gt_350's report of... "From the way it looks the PCM is sending 2 signals per injection event to the IDM.", and that "My stock 120 IDM was only putting out 66 volts to the injector."

The 2 signals from the PCM to the IDM could be "on & off times", or for a split shot injector with a mechanical pilot injection, the two signals could be "on time & pulse duration", but the first case is the easiest to implement. Also, I've read that newer engines use multiple injections where the injector is commanded on & off several times for each combustion event, and this requires separate on & off times for each injection.

However, you're correct in that just like is the case for an old time coil ignition system, a "fly back voltage" across an inductor is generated when the current is switched off, and it's equal to L(di/dt), and depends on the rate of change of current as the solenoid is switched off.

 

Hey Ernest -

Did you ever come up with a better wiring harness solution that you mentioned earlier? The soldering doesn't seem too hard, but if I can build a better harness for the injector pulse, well, I'm more comfortable with that.

 

It would make more sense to see that due to the inductive kickback from the solenoid. To use a negative signal to "shut off" the IDM, you would need to latch the IDM on. This I believe would be against design. I would be curious to see the duration of both signals. I would guess the first would be a short burst to add fuel to get the burn started, then as the flame front spread, the second would be the PW to add power. Just my $.02 worth..

 

Since this post is "thinking outside the box", I've added a link to another man's ideas.
The 8 Phase Motor

 

I saved your link for future reference. That guy clearly knows his stuff! His statement about torque...

"TORQUE: The word "torque" is often used incorrectly to describe low RPM horsepower. In the real world, horsepower is all that matters, because torque involves no motion whatsoever. Torque is simply the static measurement of twisting force. When torque (static force) is combined with RPM (motion), the result is horsepower (Work / Acceleration)."

agrees with my own statement concerning TQ & HP that many on FTE have claimed to be wrong...

Some interesting facts about HP...
https://www.ford-trucks.com/forums/669256-some-interesting-facts-about-hp.html#post5290668

"Torque doesn't have to be considered when calculating how well your truck accelerates or tows a load up a grade. All you need to know is your HP vs RPM curve, and then for each gear you can convert that curve into a HP vs MPH curve, and then at each MPH as your speed increases you want to stay in the gear that applies the most HP to the ground without exceeding the RPM redline. The driver who applies the most HP to the ground at each MPH will win the race, given equal weight and drag coefficient! You won't believe how many incorrect shifting strategies involving the RPM for peak torque and peak HP I've seen in drag racing forums, and only once was the correct answer that I just gave cited."

Well after reading your link, I'll make that last sentence read "twice" from now on!

 

No, I never got around to designing an "optimum" cable system between the IDM & injectors, I didn't want to become known as "the cable man"! Some sort of matching network might be needed to optimize the pulse transmission characteristics, but my basic idea is to run individual coax cables, which could possibly just be soldered at the IDM output, and then use 4 pass through connectors at each valve cover with disconnects there.

 

Ok guys you talked me into it.

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