greenwing

Does a box that uses the tapped wire setup on a 24V truck just change the signal to the ecm? or the signal to the pump? Does it change it with resistance? Or does it amplify the signal somehow??

What i'm wondering is, if it uses resistance, could a person just wire up a potentiometer and run it in to the cab? Or a setup with 3 or 5 different positions? If it amplifies the signal, then I guess a person would have to go another route...

All of this would be ran with an EZ... I don't think you'd want to do somethin like this without that.

I was just a little curious... That's an expensive pump to be tinkering with...but.....................I need something to do after work

Also, where is the cheapest place to get TST PM, PM2, or PM3??

Thanks,
-Ryan

CTD NUT

The Wire taps do not have anything to do with the ECM. The wire tap is just a wire that taps or tees into the VP44 pump solenoid. The solenoid opens and closes a valve that sends fuel to the injectors. The fueling module that taps into this solenoid wire does not alter the original signal it receives from the ECM but rather builds a larger signal ahead of it and behind it. The wire tap allows for an increase in timing advance by adding an addtional signal ahead of the original and can add duration by adding an addtional signal behind the original signal. This is all done seamlessly so as to trick the solenoid into seeing one earlier and/or longer signal. There is still only one injector firing event. The wire tap can only build around the original signal and not alter it. They are a piggy back method of additional fueling - they are only building on top of what is already there. The wire tap boxes are somewhat complex and require input from the ECM and engine sensors to be able to be able to dynamically control the signal it sends to the solenoid....so, I don't see how you could send your own signal to the pump solenoid and expect anything good to of it without some type of dynamic control and sensory input from the ECM.

AAmeeting

I wonder if the comps voltage backfeads into the Vp's electronics? Possibly causing a dead Vp. If it is Dc current the a Diode should be used to isolate it away from the Vp circuit board and only travel to the solenoid, I realize that there are engineers that have designed this but there are a lot of people that claim there comp killed their Vp after they tapped it. I wish I knew more about what the comp put out. Anybody ever hook up a multimeter to their pump wire? Might be interesting. Keep it real

duallydave

if what ctd nut is saying is the ecm is sending a signal to the vp and the tap box is altering that signal before and after the original signal making the signal in a sense longer then why cant the ecm be programmed to make that longer signal all the time and give you the effect of a comp all the time?sounds simple but maybe its not that easy.

phox_mulder

No, the wire tap signal is in addition to the ECM signal.

The ECM is talking to the electronics on the VP44, it is the computer actually controlling the pump portion of the VP44.

Boxes such as the Edge EZ are already doing as much extra fueling as the VP44 electronics allow,
ECM upgrades, such as the Catcher or Smarty also are doing as much extra fueling as the VP44 electronics allow, albeit differently,
so wire tap boxes had to come into play to allow more fueling than all the electronic's allow.

The wire tap opens the solenoid right before the VP44 electronics tell it to open,
and hold it open after the VP44 electronics tell it to close.
Remember, we're talking milliseconds here.

This is how I understand the intricate workings.

phox

AAmeeting

What if the Vp is sending lets say 8 volts to the solenoid, the comp box could add voltage and bump it up to say 10 volts and further adjust timing. So 2 volts are pushing back into the Vp's main board against an IC or somesort of mosfet or type of voltage regulator. A comp then might be able to create spikes that might damage the pump, and or cause the electronics to get hot ie "5x5 and my pump died". Not mechanical but electrical. If a large diode were placed between the pump ecm and the solenoid and before the tap it would not allow voltage to flow backwards. But then you might have an alternate load for the Vp ecm via the pump wire and the comp box. So a diode could be placed there. What is the ratio of smarty's frying Vp's to wire taps? I know its completely different and thats the point. Timing advancement through the ecm and no extra loads on any factory wiring or electronics. This is all speculation and very well could be BS. But it makes me wonder. Someones has to have more info on how the vp works. I hope this stimulates some interesting conversation.

jrs_dodge_diesel

AAmeeting, Voltage isn't whats operating the solenoid, only digital signaling pulses are operating the solenoid. Adding more voltage to the solenoid circuit isn't going to help put any more fuel in the engine, making the timing pulses bigger is. A diode won't do squat either, unless someone puts it in backwards which would kill the solenoid signal completly and the engine won't run without that signal.

Heres a diagram I made which shows how the digital signalling works, and how an Comp box will modify that signal.




Electronics Technician 2nd Class
U.S. Coast Guard

Ph4tty

Have you read any I added a ez/va/smarty/catcher and my vp died threads? These all allow the vp44 to work at the level it was designed to. Any time make something work harder than it was designed to do, increased wear and premature failure are to be expected be it the vp44, clutch, turbo,.. did I mention clutch

AAmeeting

I am not refering to the load on the Vp. I am wondering if the electrical pulses/voltage/whatever could hurt the inert electronics because it is added on. I doubt the signal is digital because there are only two wires going to the solenoid to operate it. This solenoid is most likely DC, and actuates something requiring specific voltage and ampereage. I really think none of us know for sure how it is opperated. This is all speculation still. I am sure the Vp's capabilities are not met with these boxes. I wonder rather the way these box's derive it from the Vp and if there is a better way.

Mike D

Maybe it's just using a ground to hold the solenoid open.

Bart Timothy

Tapping the wire has the potential, and, in actual experience, has been shown to sometimes blow the VP44 electronics. But then the same thing can be said about adding an EZ.

jrs_dodge_diesel

Digital only requires 2 wires for most items. A signal/triggering line, and a ground/return line. Digital also gives the ability for precision timing and control, something that is very hard to do with analog signals.

Digital is easy to understand, operates in 1's and 0's (or highs and lows) A 1 is considered ON/enable and a 0 is a OFF signal. Now, this solenoid for example is most likely using a high enable to trigger it on. That means for every high pulse the solenoid is opened and when the signal goes low(0) the solenoid turns off. Doesn't matter what the voltage is that triggers it as long as the high and low signal is defined. Like 0 volts is the low signal and say 10 volts is the high signal. Now if you put a variable resitor on the line with digital signaling and have it adjust to where the high signal is below 10 volts, the solenoid won't trigger because you haven't reached the 10 volt threshold.

If someone could tell me what wire on what plug I can check I could put an O-scope on it to see what the signal looks like.

Marco

Gang,
I don't want to rain on anybodys parade but the wire tapping boxes do NOT do their thing the way you're saying here.

Background. The VP meccanical part has been designed by Bosch for two injection strokes. Pre and main injection. To my best knowledge they've never been used except than by the fuelling boxes. The VP electronics have never been implemented for the second injection stroke, thus there's no way to obtain two injection strokes via the ECM

Wire tapping boxes add a second injection impulse after the "main" impulse that was commanded from the ECM has been done.

If you look at jrs_dodge_diesel diagram " original signal to solenoid from ECM"
immagine a second impulse that follows the "ECM impulse" about half as long as the first one. That second impulse is generated from the wire tapping box. That's how it works.

Clear as mud?

The signal to the fuel metering valve is straight 12 DC. No digital signals here, only a good Mos-Fet transistor.
The fuel metering valve actually is normally open, to build pressure it has to be held closed. The fuel for the second injection stroke comes from the membrane chamber or pressure reservoir in the VP.....

Helps?

Marco

HOHN

Well, I guess I will throw my understanding of it out there.
(begin opinion that I can't prove).

There is an electronic computer built into the VP44 call the Fuel Pump Control Module, or FPCM. This computer controls the timing and fueling of the VP44.

The FPCM is responsible for carrying out the instructions sent to it by the engine-mounted ECM.

The engine's ECM has fueling limits programmed into it that the FPCM will never exceed-- remember, it's just taking orders.

Every type of add-on box works by manipulating signals, either the signals that the sensors send to the ECM (thereby "tricking" it into producing an outcome it otherwise would not produce), or manipulating the signals AFTER the ECM (sometimes both).

The stock ECM has a number of fueling curves built into it, calibrated to the engine's rating and emissions certifications. Note, these are CURVES-- they gradually increase fueling as more air is added to the engine.

In a stock 24V, the fueling curve "peaks" at 2700rpm. Both above and below this rpm, the ECM is commanding the pump to deliver less than 100% of the fuel that the ECM is allowed to command (within it's programming limitations).

A non-wire tap box like an EZ works by taking this peak value (at 2700 rpm) and making it available at other, lower RPM conditions. So instead of having to rev to 2700rpm to get max fuel, all you have to do with an EZ is achieve 3psi of boost at any rpm lower than 2700. This is why you get such a bottom end enhancement from an EZ. It converts the sloping fueling curve essentially to a flat plateau. So, you get full fuel at 3psi of boost, regardless of RPM

When the ECM is commanding the pump to give 100% fueling, it's only commanding 100% of THE PROGRAMMED FUELING LEVEL. So no matter how hot a box you put in, you CANNOT exceed the fueling level programmed into the stock ECM. Unless...

This is why you have to "tap the wire" to make the big power. When you tap the wire, you are intercepting the ECM's command to the pump and manipulating it before the pump sees it, like a spy intercepting orders in an effort to change a military's actions.

The wire tap boxes DO NOT extend the injection pulse earlier. Remember, they are intercepting a signal-- no signal, no interception!

So, the ECM sends a signal to the pump to give 100%fuel. The fueling box's wire tap intercepts this signal, and ADDS ITS OWN COMMAND. Essentially, the fueling box adds a second injection pulse that's calculated based on the first pulse.

Say you have a TST powermax3, which is a "63%" fueling box. What this means is that it can add a second pulse that contains up to 63% of the fueling of the primary pulse.

In effect, it works almost like the pilot injection on a HPCR truck, only instead of small pilot injection followed by a main pulse, you get the main pulse followed by a smaller (post) injection.

The reason these boxes are known to destroy VP44 has to do with the bypass solenoid (electronic failure) and they dfistribution head (mechanical failure). The mechanical failures are described on Blue Chip's site here: http://www.bluechipdiesel.com

The electrical failures are almost always due to excessive heat caused by the much higher duty cycle of the bypass solenoid within the VP44. This is the solenoid that closes off the internal bypass within the VP44 and forces the fuel into the high pressure section, thereby initiating the injection event. A fueling box MUST increase the duty cycle of this soenoid in order to have it carry out the second injection pulse. The more aggressive the box, the longer it will attempt to hold the bypass solenoid closed, reducing the "rest" time between injection events-- this both generates MORE heat while allowing less cooling time for the existing amount of heat generated-- a double whammy! It's essentially converting cooling time to heating time.

This will show up in EGTs. For two trucks of identical HP level, the wire tap will ALWAYS have a little higher EGT relative to the non-wire tap assuming both have decent injectors. The late secondary injection pulse also explains the massive torque gains that come with many of these boxes-- 350+ lb-ft.

Compare that to the 180lb-ft claimed for a non-tapping EZ.

That's my understanding.--jh

Bart Timothy

Hey...you just dicovered how Edge got started.