Download Powerstroke Diesel IDM mod Doc

Powerstroke Diesel IDM mod
I thought I might put this on a seperate page for eveyone to read. First lets start with
som FAQs
What is an IDM?
IDM stands for Injector Driver Module. It acts sort of like an amplifier for a stereo.
You couldn't hook up 18" house speakers to a walkman right? The IDM and injectors
work similar, injectors require a lot voltage to start up quickly enough and 12V from
the battery doesn't cut it.
Where is it located?
The IDM is located on the driver's side fender wall below the hood hinge on 94-97
trucks. 8mm bolts hold the IDM in place and a 10mm bolt holds the connector on. On
the newer style trucks, they are hidden in the drivers side wheel fender just inside of
the F-#50 decal. You need to remove the plastic fender wall to reach the IDM. 10mm
bolts hold the bracket and a 10mm bolt holds down the connector.
How does it work?
Injectors are very inductiove loads, similar to light bulbs. When you trun on a light
bulb, it does not turn on right away. it takes time for current to flow through the bulb.
Time here is in millionths of a second (us). By changeing 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 (see below), with the IDM mod, injectors turn on in 440us (see below).
What sort of improvements will I see?
A while ago some friends of mine dynoed this mod and got improvements of
20hp/60ft-lbs. I will eventually post them, but for now email me and i will send them
to you. I finally got around to placing my truck on the dyno. Peaks did not change
much but the graph shows areas of improvemnt of over 100 ft-lbs. See the dyno
graphs below.
What negative side effects will this create?
I spent 3 months with an oscilloscope and temperature sensors on my truck to find out
if componets get over stressed with this mod. I did not find a single component that
would warm up and hotter thatn stock. Also, I found that the IDM has electronics on it
to limit the current to the injectors to about 7.5 amps rush in, 3.5-4 amps holding
current.
Swamp's Hi-Voltage / Hi-Frequency IDMs
Notes & Comments on Swamp's High-Voltage High-Frequency Injector Driver Modules.
This modification was developed more as a repair technique than as a performance
modification, although it has given some very noticeable gains on most trucks. Stock trucks
show the most gains, highly modified ones the least.
Any gains are also very dependant on what condition the original IDM is in: If the
original IDM is already modified, and the pulse gap is shorter than .36-.38 milliseconds,
little to no gains will be seen. If the original IDM is a stock EDU-100A model (used in 19941995.5 PSD's), the greatest gains will be seen. (Every EDU-100A I have seen was a weak,
sick puppy.) Trucks with higher mileages on their injectors will also see more gains.
The only way to tell whether a truck will benefit from the HV-HF mod is to view the injector
voltage waveforms on an oscilloscope. If the pulse gap is longer than .40 ms, if there is a
double gap, or a ragged and uneven hold-pulse, then this mod can help.
The HF mod is not nearly as simple as the HV mod; whereas the latter involves replacing a
single resistor with another one of a fixed, known value, the HF mod is more of a balancing
act akin to changing the rate at which a playground see-saw pivots: the weight of the kids,
how far they sit from the center, and how hard they push, all have an effect. The
characteristics of the injector waveforms dictate which component(s) need to be changed or
replaced, and since no two units respond identically, I often have to solder and desolder
components multiple times to get satisfactory results.
It takes a minimum of 1-1/2 hours from the time I crack the IDM case open until I can seal
it back on. After opening the case, I hook it up to my test bench / engine simulator which
consists of a complete engine wiring harness modified with two PCM connectors (one for
1994-1997 PCM's and the other for 1999-2003 units), an IDM connector, 8 injectors and a
cam trigger wheel with a CPS mounted to a variable speed motor which allows testing up to
6000 RPM. A control box allows simulating any sensor input to the PCM--EOT, EBP, IAT,
MAT, BARO, MAP, TPS, etc and a custom circuit provides an ICP "feedback" signal to
the PCM proportional to the IPR duty cycle. A cutout box allows disabling any injector, and
a breakout box allows instant access to any signal into or out of the PCM or IDM, and the
wiring harness also has the ODB-II plug for connecting a diagnostic scan tool, so I can
monitor the PCM Data Stream, etc, and also run Injector Buzz Tests.
After I get it up and running, I scope the waveforms on all 8 injectors. Then I start making
notes on a form: customer data, IDM model & serial number, PCB revision number, and a
dozen or so voltage, frequency and duty-cycle readings. The voltage and frequency readings
are re-recorded after any change is made. Once I deem the waveforms to be satisfactory, I
do what I call a "Heat Stress-Test". A stock IDM draws 10-12 amps at full load, a HV one
12-14 and a HV-HF 18-20 amps, causing a substantial increase in temperature. For this test
I put a thermocouple probe into the heat sink for the low-side switching transistors (the
hottest components), wrap the IDM in a heavy bath towel, and run it at 2 ms of injector
pulse width and 3,000 RPM, recording the temperature at 5 minute intervals while
monitoring the injector waveforms. If the unit is still running normally after 25-30 minutes,
I call it good.
If it fails, usually evidenced by injectors dropping out and not firing, but sometimes a
complete shut-down with it recovering after it cools, or occasionally something something
going up in smoke, then I fix the problem and then repeat the test until it passes.
The 2 ms / 3000 RPM is based on an engine running WFO under a sustained, heavy load
mile after mile, and the engine will probably melt down before the IDM overheats.
However, I currently do not want people who do heavy towing to order the HV-HF IDM's; we
still need to do more testing in this area.
All IDM's that we sell will now have both the Hi-Voltage and the Hi-Frequency mods done to
them. Price is $275.00 with a $200 core charge if we don't get your old IDM back, and it
includes return shipping to send your core back. (We don't want your $$$, we just want our
cores back. :) )
Warranty is one year.
If anyone has an extra IDM, we will mod one of them in trade for the other one. If you
have non-working IDM's, 2-3 of them will get your good one modded.
IDM’s
DPS110 94.5-98 models
Replaces the following IDMs:
F5TF-12B599-AA
F5TZ-12B599-AA
F5TF-12B599-AB
F5TZ-12B599-AB
F6TF-12B599-AA
F6TZ-12B599-AA
F7TF-12B599-AA
F7TZ-12B599-AA
F7TF-12B599-AB
F7TZ-12B599-AB
F7TF-12B599-AC
F7TZ-12B599-AC
F7TF-12B599-AD
F7TZ-12B599-AD
F7TF-12B599-AE
F7TZ-12B599-AE
F7TF-12B599-AF
F7TZ-12B599-AF
F7TF-12B599-AG
F7TZ-12B599-AG
DPS120 99-03 models
Replaces the following IDMs:
2C24-12B599-AA
2C24-12B599-AB
XC3F-12B599-AA
XC3Z-12B599-AA
XC3F-12B599-AB
XC3Z-12B599-AB
XC3F-12B599-AC
XC3Z-12B599-AC
XC3F-12B599-AD
XC3Z-12B599-AD
Last edited by mech2161 : 09-05-2006 at 07:50 PM.
IDM mod
Well the brown truck arrived at 8PM tonite and I got resistors to do the IDM mod myself. I
just took the IDM out of my 96 stroker and it was a 5 minute job. I am going to let it sit
inside tonite to warm up to a workable temperature.
For those who dont know what the mod does, here it is in a nutshell.
There are 3 kinds of IDM's for the 7.3- a 100, 110, and 120. That number represents the
voltage supplied to the injectors. OBS PSD's have 100's and maybe 110 and most SD's use
the 120. The mod changes the output to 140 volts which makes the injectors act more
quickly and accurately resulting in a smoother idle, better response, and a few extra HP and
TQ. I am going to do it in the morning, maybe after I go ski for a few and I will report the
results when I get it installed and run the truck.
Well I did the mod last night and it went really well. One thing is for sure is that you need a
really steady hand. Just a small slip and you fried some circuitry. I sealed up the IDM and
let it cure over night so the seal would set.
The difference is night and day with the modded IDM. At first it idled really high, but once
the PCM learned what the IDM was doing, it settled down to normal in a few miles. Throttle
response is far quicker now and boost builds faster. I was just cruising in 3rd gear behindd
someone and they turned off the road so I floored it. Boost went from 2-3PSI to 25PSI in
about 1 second. Quite impressive... The sound of the truck is a bit smoother and quiter
which is a good thing. Power is seemless and it pulls harder to redline than it did before.
This mod did far more than I thought it would. I am very impressed. And Karl.. I will do
yours if you want. no problem...
__________________
I'm glad to hear that it worked so well for you!
I have an extra 110v IDM sitting here.......hmmm.......I wonder what I should do with
it???
Are these values correct for the metal film resistors?
IDM-100 uses a 75.0k Ohm (75,000 ohm) 1/2 watt 1% tolerance Metal Film resistor
IDM-110 uses a 75.0k Ohm (75,000) 1/2 watt 1% tolerance Metal Film resistor
IDM-120 uses a 73.2k Ohm (73,200) 1/2 watt 1% tolerance Metal Film resistor
Also, what sealant did you use?
Those are the ones you can use. I actually used the 1/4W ones that a lot of people have had
good luck with. The 1/2W ones give a little more leadway but there have been users that
have run the 1/4W for years. I used a GE electrical component sealant. It is made for hot
and cold conoditions and I have had good luck with it in the past. I might find out how much
the Ford sealant is when I am at a dealer, but for now I will use what I have. From the butt
dyno, it feels like a solid 25HP. The truck accelerates so much harder.
One theing that I will do is try a 15W soldering iron. I used a 30W and I think it was a bit
too hot. Also I cut off about 1/8 inch from both ends and stood the resistor up on end. This
made it a bit easier to hold while soldering. After I got it all in, I hot glued it to the
components that are next to it to aid in stability. If you try it, good luck. I bet with your set
up, it will be even more impressive.
I have a couple of questions about this mod:
Do all the IDM's interchange? Single/Split shot, S.D./OBS the same?
TO my knowledge or lack there of, they all do.
The instructions show a switched model - is that what you did? Or did you just add the one
resister and the two wires...
I used a resistor and did not make it switchable.
Where the two wires solder onto the board - is that where the surface mount resister was
located that was replaced?
That is the location.
I also have a Cali AB Split shot truck - do you recommend this upgrade to the IDM now that
you have had some time to get used to it?
I will tell others to have it done. It really works well. Better than I thought it would.
Is this a mod anyone with basic soldering skills can do, or is there too much chance of
destroying an IDM if not done properly (I like my truck and don't want to be without it!)
With any mod, there is risk. I have a experience with electronics and I like to tinker. If you
feel confident in your skills and can afford a new IDM, then go ahead and give it a try. If
you dont, have it done by someone who has done it with success.
Thanks for playing 20 questions. This looks like a good low budget mod that I would like a
bit more info on before I destroy my IDM!
It is not low buck... It is low cent.
The IDM is a voltage amplifyer that takes the injector signal from the PCM and cranks the
voltage up to over 100 volts DC to fire the electrical part of the injectors.
OK just did my IDM mod on my 99. I used the 75.0k OHM resistor, and the install went
great! Like I had said, the most difficult part of the entire Mod was getting the darn IDM out
of my fender well. The resistor soldered in very nicely and I sealed the IDM up with RTV and
re-installed it in my rig. I noticed the improvement immedietly, as soon as the truck started
and I touched the "go" pedal the response was MUCH better, very noticible. The whole
project took me about 2 hours because it was a Son of a B to get it out of my fender and reinstall it ( just very tight quarters). I would definetly reccommend it for anyone who was
wondering "Is it worth it", yes its worth it in my opinion. All in all, the mod cost me less
than one dollar to do, and is VERY noticable. I'm glad I did it and would do it again.
The mod is easy, about 30 minutes including removing the IDM
You only need the 75k resistor BUT it has to be a HIGH quality resistor.
NO RatShak stuff here.
I did see a bit of improvement but my truck has almost 400k miles.
he IDM mod jacks up the driver voltage from 100vdc to 140 vdc and thus giving a faster
injector opening ( a couple of degreese and a slightly longer pulsewidth duration)
I got both resistors from Digikey for 34 cents.
The part numbers are as follows.
75.0 K Ohm CMF75.0KHFCT-ND
73.2 K Ohm CMF73.2KHFCT-ND
About 17 cents per resistor without tax. and about 7 bucks shipping to me. So its a good 10
dollar mod.
Injector Driver Module
The solenoid-operated poppet valve requires 115 volts at up to 8 amps to operate, which
is more power than the PCM can supply. Therefore, a high power device, the Injector
Driver Module, is used to supply power to the solenoid on command from the PCM.
The sticker on the IDM will identify it. IDM-100, 110 or 120.
It's an IDM-120 on my '01
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.
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?
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.
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.
The hardest part of this mod is getting the lid off the IDM. Takes about 15-20 strokes
through the sealant with an exacto knife to get the sealant loose enough to get a tool pried
under the lid. The layout of the module is exactly as pictured in the Forgotten link and it is a
simple matter of desoldering the stock resistor and soldering in the 75, or 73.2k resistor.
The whole deal took maybe 30-40 minutes start to finish.
Pulled the fender liner and installed the IDM-140. Initial impressions are it starts much
faster, I was not expecting this but it makes sense. And it revs like a gasser. Snap throttle
engine acceleration is much quicker....doesn't even seem like a diesel it revs so quick.
They say this mod is worth about 20hp. I say it is worth at least that....probably more like
40. This is how I expected this truck to run when I put the injectors in it.
You guys running big sticks and stock IDM's....you're cheating yourselves. Do the mod.
E-series = IDM 110. 94-97 F-series = IDM 100. 99-03 F-series = IDM 120
To convert IDM 120 to 140 you need a 73.2k ohm resistor. .5w 1%.
Digi-Key - PPC73.2KXCT-ND (Vishay/BC Components - 5033ED73K20F12AF5)
If you come up with an old IDM 100 or 110, they both take a 75k.
Digi-Key - PPC75.0KXCT-ND (Vishay/BC Components - 5033ED75K00F12AF5)
99-03 IDM removal instructions
On the fender liner there are 3 8mm mount bolts, one straight up, one front side, and one
rear. Then 3 or 4 tiny little bolts, 7/32" fits, along the fender lip. After that three plastic
push pins, one in the very front and two at the bottom rear below the outside edge of the
fender line.
Once all the mout hardware is removed start at the rear and gently pry the liner around the
fender well lip. Once it's started it pulls down pretty easily. There is no need to disconnect
all the wire harness on the topside that attached to the liner. There is enough room for the
liner to lay down on the tire with them connected.
When the liner is down, look inside the fender all the way to the rear. It's a 10mm bolt
holding the IDM connector on, and two (2) 10mm bolts holding the IDM bracket in place.
Once those two bolts are out, pull straight down to disengage the IDM/bracket from the
fender.
There are three (3) 8mm bolts securing the IDM to the mount bracket. Once The IDM is off
the bracket use whatever means are at your disposal to get the sealant off the lid and
remove the lid of the IDM. After that, follow the pictures in the link in post #1 and solder in
the appropriate resistor.
Reseal the lid and reinstall in reverse order of removal.
That's it.....done deal.
thanks for the info Scott..let me get this strait..you de soder the resister that is built into
the board shown in pic where the green and yellow wire is..and them 2 wires are added in
with a new resister correct?? if so..i see the resister has a brown stipe on one end..if i did
this just like the pic...witch way does the brown stipe on the resister go??? or does it do its
job ether way?? i know diods only work one way..im not great with electronics so please
excuse so many questions...
ron.....adding the wires are only for a switch to turn the mod on/off. It is not necessary and
is not recommended on the site with the pics from what I read. As far as resistor direction,
I'm not sure......if you do not get an answer here, I would ask the supplier if it goes both
ways........LOL
All you need to do, is remove the original resistor, and solder in the correct resistor as
listed
above for your model IDM. (Should be a sticker that lists the model near the connector).
In the pics I have, you would solder to the same place on the board that the green and
yellow
wires are soldered. You shouldnt use wires or switches.
It doesn't matter which direction you solder the resister. Current through them flows the
same. The stripes on them indicate how much resistance they provide.
pulse width and pcm/idm signals
http://www.ford-trucks.com:80/forums...m-signals.html
Quote:
Originally Posted by mustang_gt_350
...Ok, I spent some time with some help of a friend playing with the IDM and a scope today.
From the way it looks the PCM is sending 2 signals per injection event to the IDM.
I also Measured the output voltage while runing and was very shocked on how low the
actaul output to the injectors are compared to what i have read the working voltage is. My
stock 120 IDM was only putting out 66 volts to the injector Noting near the often qouted
120 volts...
Quote:
Originally Posted by ernesteugene
...I read that the IDM has it's own little onboard computer/microprocessor, and that the
PCM sends the IDM digital words which instruct the on and off time for each injector pulse. I
think the two signals you see are the one word for on and the other word for off. Also, the
off pulse is reverse polarity to drive the solenoid in the off direction.
Quote:
Originally Posted by ernesteugene
...The PCM programming controls the Injection Time IT*=crank degrees, and the injection
Pulse Width, PW*=crank degrees. These parameters control the timing and the amount of
fuel injected, and this in turn tailors the peak combustion pressures in the vicinity of TDC,
and this is what determines the cylinder MEP and resulting HP.
To program for maximum HP, you want to control the IT* and PW* to maximize MEP at
each RPM. Of course the Ford PCM programming has to worry about other things as well,
including emissions, MPG, and reliability.
At 3000 RPM, for example, each crank deg is 55.55 usec. At 3000 RPM, an impulse (zero
time width) injection at 30* BTDC, is followed by a 20* ignition delay, then a 5* delay as
pressure rises to a maximum, so maximum occurs at 5* BTDC. The actual pulse width, PW,
is about 555.5 usec, so that fuel is injected over a 10 deg interval of crank degs. Therefore,
fuel injection occurs from 30* to 20* BTDC, then 10* to 0* BTDC for initiation of burn, and
maximum pressure at 5* BTDC to 5* ATDC, and this gives maximum cylinder MEP and thus
HP.
It's clear to me from the above, that the IDM mod will advance the "effective" timing some,
and therefore the use of this mod should be accounted for in the overall tuning, as in with a
DP program.
whats this Gene is talking about??
Injector pulse width. It's the amount of time the PCM commands the injectors to stay open.
By doing this mod you increasing the IPW a tiny amount, thereby effectively advancing the
timing an equally tiny amount. His contention would seem to be that your chips tunes
should be adjusted to compensate for this.
IMO, seeing that we are likely talking about less than a millisecond difference, I don't know
that it would be necessary to bother with it.....but your best bet would be to ask jody if he
compensates for it or not.
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.
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?
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.
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..
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...
http://www.ford-trucks.com/forums/669256-some-interesting-facts-abouthp.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!
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.
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.
he 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 qtip 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 ?
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.
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.
When I did my IDM mod (bought a low mileage used one to modify), back in April, I used
the low melting temperature rosin core solder the was included in an inexpensive 25 watt
pencil type soldering iron kit. I used the smallest tip that was included in the kit. I scraped
the sealant from the old resistor with a pick before melting it loose. I tinned the connections
with a little more solder and held the resistor (bent in a "U" shape) with a small screwdriver
onto the connections. I applied heat with the iron and let it 'melt in'. It took very little heat
and the solder melted pretty quick, I cleaned the area with alcohol on a Q tip and they
applied some clear RTV silicone over the resistor and connections as a sealant. I used some
polyurethane roofing sealant to reseal the case and let it cure for a few days, since I still
had my original IDM in the truck . Pictures, that might help, of this in the first mods album
in my gallery. No problems with the soldering, sealing, or installation. It's been working
great ever since.
The only place you might have gone wrong was the use of the RTV on the resistor as
"sealant". Everything else was perfect.
Most commercially available RTV contains acidic acid. It's outgassing is what causes the RTV
to cure. This acid isn't good around copper, either. If it has the familiar "vinegar-like " smell,
it's got acid.
If you're going to use RTV, a much better kind is that which cures by the absorption of
moisture from the atmosphere. Unfortunately, it's not readily available. Dow-Corning 3140
and 3145 are good examples. Cheap, they ain't.
A clear lacquer-like material called "conformal coating" would have been the optimum
material to seal the board itself against moisture. These are usually acrylic or urethane
based.
I know this doesn't help much, now that it's done, but there's always a next time.
BTW, I wouldn't use the "low-temp" (usually eutectic) solder on the resistors used to fix the
overhead displays in our trucks , as it is the high heat from the resistors that causes these
joints to fail. But that's another discussion, for another problem, on another day.....
So Pop - what is the best sealant to use on the new resistor and circuit board that is readily
available?
I'm hoping to do this by the weekend and what to do it as right as possible the first time!
That I don't know. I just keep some of the right stuff around. 3145.
Keeping it as completely away from moisture is a real trick. In a baggie with desiccant in
the fridge will prolong its life, but every couple of years I have to replace it.
I suspect any that doesn't have that distinctive "vinegar" smell would be "close enough".
Did some checking today and the closest I can get the DC 3140 or 45 stuff is from SLC,
Utah. I want to get this done this weekend so don't have time to wait for stuff to be
shipped. I'm going to go looking around town tonight and tomorrow for something that's
close enough.
How about some good old 3M 5200 marine adhesive? It's a polyurethane adhesive, and it
dries by absobing moisture in the air. The only problem with using that is you would
basically be sealing the IDM for life. They do make 5200 remover, but that stuff is very
strong no matter what you use to get it off...
__________________
I just thought I would post this to save some people a little trouble.
I just did the IDM Mod on my 1995 PSD which has the 100a IDM. Once I looked at the
circuit board I realized that the factory resistor would be a pain to remove. I cringe at some
of the blogs I've read where some guy scrapes the factory resistor off with a screw driver,
there are about 150 different ways to ruin your board doing that. I happen to work for the
world's largest micro-chip manufacturer so I took the board into one of our labs and had a
tech look at it. He brought it to me an hour later with the new resistor soldered on....Here's
the time saver part.... He didn't remove the old resistor, he just soldered the new one on
over it so the new one is effectively a bridge across the original resistor.
So if you're bound and determined to do this yourself don't risk messing your IDM up with
a screw driver. Either get the right tools and de-solder the old resistor or just solder the
new resistor right over the old one.
errr....this only works if he cut through the old resistor, taking it out of the circuit.
Otherwise, you'd be putting two resistors in parallel, meaning the net resistance would wind
up considerably less. (for non-ngineers, google "parallel resistors" for the formula and
explanation )
Good catch, I did forget to mention that he scribed through the old resistor taking it out of
the circuit.
Maybe a dumb question, but how did he do that (scribed through)
I'll ask how he did it, but I stand corrected here. The stock resistor pops off pretty easily
with a fine screw driver or knife. I got excited because people on several different sites
make this mod sound easy, my intent was to discourage someone who has never soldered
before or worked with small electronics from grabbing a screw driver and messing up their
board.
I read that the IDM mod will raise the injector voltage from 110V to 140V. Will this hurt
the injectors in any way?
No, have ran one for 150k miles
Some where there is a write up on this mod. Graphs and all. If memory serves me right,
Joe servo developed it. He was in contact with one of the engineers who designed the
injectors we use. After all the testing they found no problem running them at the higher
voltage. The IDM showed no degridation either. Also I have not read a bad claim that I can
remember. The issue is what will you gain. Joe servo found that the mod would shorten the
rise time of the signal to the injector. Read that as turning on quicker. As some one sited
earlier the older units will show the most improvement. Apparently the showed the slowest
turn on time. Any way if the pulse width is the same but the rising edge can be made a bit
quicker you could get a tad bit more fuel. I am sorry. The injectors are driven by a pulse.
The longer the pulse the longer fuel is delivered. More fuel more power. Think of it this way
an airplane flying at 1000 feet then accends to 2000 feet then down to 1000 again. It takes
time to accend. takes lots of power. to accend the pilot trottles up gaining speed and lift.
But still takes time to reach altituce. If we install the big motor in the same plane. We can
fly almost straight up. and be at altitude longer. No problem getting down can be there in a
heart beat. Same with the current required to open the injectors. More current means
quicker rise time and opening time. The injector still turns off at the same time. I don't
recall the benifits completely. Some say snappier responce. Some say couldn't break the
tires loose before.
Here is a link to learn more about this mod. Be informed, go slow and if it works let us all
know about. IDM Mod
ok so bout to do the IDM mod and I Went to the ford dealer to get the grey RTV sealant
stuff and He told me he didn't have it and that it would take 2 weeks to get in..
Is there any alternative ? such as from napa or something?
thanks in advance..
permatex ultra grey 599BR
Or contact your local International dealer, they carry the same stuff that Ford has.
I used clear RTV sealant with a 400* rating. It was just what I had at home. My father in
law is an electrcian and it is for electrical boxes rated for automotive/industrial to make a
waterproof seal available at electrical wholesale stores not home depot. So far so good.
Dottie brand #RTV 8 self dispensing can