Bruce Amacker Posted August 28, 2007 Share Posted August 28, 2007 I had the opportunity today to go to the training center and play with a 6.4 for a while. I removed the DPF sensor and connected it to a push-pull MityVac that will generate up to 20psi manually. With the IDS I checked datalogger to see if the MityVac and DPF PID agreed, and they were exactly the same. I applied 12psi to the DPF sensor and was able to force it into a Regen with the IDS. (For those who weren't watching, IDS won't force a Regen if the DPF doesn't show a restriction.) The Regen took 35 minutes to complete, but some interesting things I noted along the way: During Regen: The downpipe measured 175F, the rear of the DOC 350F, DPF inlet 600F, outlet 650F, ahead of venturi 650F, after venturi 222F, tailpipe surface temp 160F, but the gasses were 500 if you point the IR in the center of the gasses. I was surprised at how cool it ran- I was expecting much hotter temps. The amount of temperature drop through the tailpipe venturis was quite surprising, too. I hooked up my scope and took a bunch of waveforms which were interesting, also. First was glow plug amperage, which one side (measured at the power lead into the module) measured 40 amps with a cycle time of 40 seconds at 75F. That would mean total amperage (both sides) of 80 amps initially, that would taper off to about 40 amps after about 20 seconds. I was surprised the cycle time was so long KOEO at 75F. Next was cranking amperage, which went off my max scale of 600amps initially, but showed cranking amperage to be about 350 continuous, which is really low for a diesel. Next was fuel lift pump, which showed only 1.58 amps, which I didn't believe until I hooked a DVOM up and got the same reading. The pump appears to be a 10 bar and spun at 3750rpm, which is pretty slow for the low pressure it gives. It was interesting to see that if you pull the FP fuse, the engine dies within 1-2 seconds, which surprised me. Most HEUI motors would run all day without the FP. I also tried using the IDS to enable the FP, which worked. I heard a rumor that you couldn't turn on the FP with IDS, but on this truck with my IDS, I was able to. The next test was injector amperage, which agreed with the book stating it's a triple strike system at an idle and reverses the polarity to collapse the field quicker. It almost looks like an AC sine wave and shows 8 amps peak in each direction, with the duty cycle increasing on each of the three hits to total about 3ms. Next was injector voltage, which surprised me. I couldn't find specs in the book about this, and found the waveform to be a peak and hold style with the peaks measuring 200 volts and the hold measuring about 130 volts. Does anyone know where to find this in the book? I looked in the service manual and coffee table books and didn't see it. I also did CKP, CMP, and a few other waveforms, but they weren't as interesting as these. Just thought I'd share these with you. Have a great day! Injector amperage: Injector voltage: Current clamp installed on FP fuse for Jim: Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted August 29, 2007 Share Posted August 29, 2007 Cool stuff Bruce. It is interesting to "see" what these things do while they are running and it would be nice to be able to play around with one. Unfortunately, these 6.4's don't seem to be breaking around here. If I wasn't so backed up and short handed I might go out to a salesman's demo and disconnect something. /forums/images/%%GRAEMLIN_URL%%/smirk.gif We had a discussion going about regens and temperatures that fizzled... likely due to the lack of hands on. I failed to make another post with some road test screen shots I made with a customers vehicle that was at the end of regeneration. It is interesting to watch the temperature changes through the system like you mentioned. Even with normal driving it would be s good idea for a tech to make a few data recordings just to get a better idea of what is happening. If I have time I will post my screen shots. Oh, the customers truck? It was in for a high idle at stop lights. This was due to the first regen he and his truck were experiencing. I updated his PCM with the update to address the regeneration issues and idle... also printed out the customer information sheet and placed it on his dash. /forums/images/%%GRAEMLIN_URL%%/wink.gif Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted August 30, 2007 Share Posted August 30, 2007 I'm still absorbing..... the idea that inverse voltage (reverse polarity) is being applied has me intrigued.... 07T07 has us replacing injectors that had reverse polarity applied during testing... and the 6.4 bible tells us that reverse volts is applied to de-energize the injectors.... But we don't see inverse volts on your volt trace (other than that interesting little tail on the intial spike). And the decay of both amps and volts is fairly generous in spite of the time scale you have selected. I have to admit that I had trouble dealing with the abscence of coil oscillations and kept thinking "old school" injectors. My only familiarity with piezo crystals is from their use in knock sensors and, possibly, from other vibration sensors.... This will allow me to plead ignorance if I have overlooked enough stuff to look foolish. Instead of applying inverse volts to close the injector, could it be that a piezo stack has a good deal of capacitance? In this light, we might see the initial sharp peak and decay (but what about that pesky inverse voltage before the peak and hold?) as the piezo stack energizes... When the injector "turns off" could the mirror image inverse amps be caused by the PCM shorting INJ+ to INJ- on the injector side? Rather than applying inverse volts? Also worthy of note... I understood that these injectors operated in the 80 volt range... far below the 200+ volt initial spike and the 130ish volt hold plateau.... Again, I am "almost expecting" typical coil oscillations and trying desparately to reconcile what I'm seeing in their place. I hope we'll see lots of traffic on this subject... not so much because this is stuff we are likely to check, but because it helps us understand what is going on inside of these little miracles and it get's us used to looking at scope traces (something I think we all underutilize) and, perhaps, using the lab scope in the VMM (IMHO, much better than the cartoon in the WDS) in our daily work. More amazing... some fat old f$*k that dropped out in grade 8 is asking these questions and not some young lion.... Sorry about that, I think I'm on a crusade.... But, reality has to raise it's head and bark every now and again.... I'm sitting here swilling a beverage or 5, giving Bruce a hard time ... the house ain't getting done .... and I have a fistful of 08 keys and free reign of the shop from "beer thirty" PM to 7:30 AM.... And my wife likes reality shows - and Kieth is hiding the "puke" smiley.... Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted August 30, 2007 Share Posted August 30, 2007 Jim the reason the young lions are not asking the questions is likely due to the fact that using a scope, while not very difficult, is not as common place as it once was. An old fart that goes way back in this industry that used to use scopes daily to diagnose ignition systems has a leg up on this one. When I started in this business, many of those scopes were already beginning to collect dust. Only recently have I begun to start using the scope functionality made available to us. The problem is that getting the scope set up properly requires me to do a little research and then connect everything while reading an instruction sheet or by the book. Then, interpreting the data... well if the display is set correctly we can compare what we have to some "examples" saved in the IDS utility. I wish there was a web course for using the scope that would at least give us base knowledge to work from. If I knew what the hell I was looking at and understood what the graphs represent then I would definitely use the scope more often, and have something intelligent to add to this topic. /forums/images/%%GRAEMLIN_URL%%/rotz.gif Oh, and /forums/images/%%GRAEMLIN_URL%%/puke.gif Quote Link to comment Share on other sites More sharing options...
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