Scope view of Cummins CR injection events. Pilot is always active.

Why is there a big voltage spike upon initialization, then an oscillating voltage in the opposite direction for the duration?

I guess I don't know how injectors are wired. My imagination blissfully assumed a steady voltage for duration then a self-induced voltage spike after the solenoid was closed.
 
from what I remember, the initial open needs more juice to open the injector, then not quite as much to hold it open. of course I could be way off here.
 
Initialization draws a greater current, but a supply voltage? That would be a cool way of doing it.

Each one is a waveform of the same injector, right? The timing is moving around so much that one some of them you can see the missing tooth and on some you can't?
 
5150ram said:
I did some testing on a 07 the other day and I used 2 channels, one for bank one the other on bank two. The problem I had was one bank was much higher in voltage than the other. Is that normal or is the computer jacked up. Thanks Chris.
Click to expand...

I could see some variance in high side voltage between the two banks, since they are isolated from each other.

But not a large spread, like say 15 volts lower, that side might have a charging diode crapping out, weak caps ect.



Toolman said:
This is cool stuff, what are you using to scope it? It't too bad we couldn't have seen something like this a few years ago if would could have gotten someone to change it we might have saved a quite a few engines.
Click to expand...

I'm using a Fluke 199C scopemeter, 200MHz 2.5GS/s. Portable, rechargeable and has built in math functions, and measurements via cursors. The logging function is pretty sweet.



onetun said:
Chris I take it you are on the road again/ intense info, will call you in a few.
Click to expand...

Yeah, at it again, I'll be posting a shot pretty quick here that you'll be interested in......
 
No, you're right - the solenoid requires more energy to lift the pintle than to hold it open.
 
Here's a interesting one 4000 RPM full load, injector duration.

1.6 ms that translates into 36 degrees.

I'm interested in how long the dmax's are holding them open up there?

I know there have been quite a few with de-fueling issues on top. Not sure if thats been worked out for everyone yet.

I've always been positive that my truck at least with the Smarty TNT/r fueled great right to 4k and the scope shot confirms it.



4000rpminjectionduration.jpg






Can't put that third event totally to rest........:hehe: thought I would load the STOCK software for a look see...

There it is full load 3000 rpm third event.

Pretty easy to see why there is a significant egt drop when you load the smarty.


Stock3k.jpg
 
Good info thanks for posting. The 07 I was playing with was almost 10 volts different. I want to try on another truck to see what it does.
 
5150ram said:
Good info thanks for posting. The 07 I was playing with was almost 10 volts different. I want to try on another truck to see what it does.
Click to expand...



Chris here is the comparison between the two high side banks on my truck, pretty much identical, maybe a couple of volts different. Your right 10 volts sure seems fishy.


highsidebankcomparison.jpg





Idaho CTD said:
Some of the Dmax guys run as high as 3600+ micro seconds.
Click to expand...

Was just talking to Rob and we figured you might add that info.....

Ok wow, thats a lot more............Ooof at 4000 that would be 84 crank degrees.

I measured 3200 micro seconds at ~1700 and thought it was pretty good.


Just trying to round up a 03-04 to compare to my 04.5.
 
XLR8R said:
No, you're right - the solenoid requires more energy to lift the pintle than to hold it open.
Click to expand...

Exactly, it's called a "peak and hold" circuit where you hit it with high voltage (drawing higher current) to lift the pintle off - then you can drop the voltage and the pintle remains open at a much lower current. It's a way of reducing the average current on the driver circuit, reducing the heat generated in the solenoid, etc. etc. Pretty slick.
 
nwpadmax said:
Exactly, it's called a "peak and hold" circuit where you hit it with high voltage (drawing higher current) to lift the pintle off - then you can drop the voltage and the pintle remains open at a much lower current. It's a way of reducing the average current on the driver circuit, reducing the heat generated in the solenoid, etc. etc. Pretty slick.
Click to expand...
Man I'm excited for the standalone controllers! Who would have thought 10 years ago that we'd be discussing peak and hold injectors on a diesel forum! That almost brings a tear to my eye.
 
Why does the voltage hang around 30 volts when the injector is closed?

Why does the voltage oscillate between 0 volts and 12 volts after the initial open pulse?

nwpadmax said:
Exactly, it's called a "peak and hold" circuit where you hit it with high voltage (drawing higher current) to lift the pintle off - then you can drop the voltage and the pintle remains open at a much lower current. It's a way of reducing the average current on the driver circuit, reducing the heat generated in the solenoid, etc. etc. Pretty slick.
Click to expand...

How does the ECM generate a range of voltages like that?
 
Begle1 said:
Why does the voltage hang around 30 volts when the injector is closed?

Why does the voltage oscillate between 0 volts and 12 volts after the initial open pulse?



How does the ECM generate a range of voltages like that?
Click to expand...


What I've been probing is one of the the high side banks of 3 injectors with reference to ground. So you see the whole show, high voltage discharge, low voltage maintenance current and high side charging.


The ecu in the driver stage has a booster circuit that brings the voltage up to ~60 - 80 volts by capturing back emf from the solenoids themselves.

I should draw up a circuit that would give a better idea of whats going on.


Here is a shot of a single injector, directly across the injector. It will be more easy to understand.

single.jpg
 
Joesixpack said:
Can't put that third event totally to rest........:hehe: thought I would load the STOCK software for a look see...

There it is full load 3000 rpm third event.

Pretty easy to see why there is a significant egt drop when you load the smarty.


Stock3k.jpg
Click to expand...

What else did the stock program show? Is the 3rd event always there?


And I wonder if all Smary tunes have the effect on the 3rd event, or if its just TNT?

I know my mileage suffers above 2200, but that could be for other reasons.
 
AH64ID said:
What else did the stock program show? Is the 3rd event always there?


And I wonder if all Smary tunes have the effect on the 3rd event, or if its just TNT?

I know my mileage suffers above 2200, but that could be for other reasons.
Click to expand...



Didn't spend much time on the stock tune, my only goal was to check for the third event at high rpm. I'll profile it more for comparison.

I can't say if all the Smarty tunes pull the third event, for that matter, this is only one truck, and could be an anomaly for that matter, so no one should take this as the gospel.

One sled puller told me he thought the Regular revo pulled harder than the TNT/r, so I'll load it and have a look at it as well.
 
I was also wonder if the 3000 rpms on the stock tune made a difference. The OE software starts to defuel at 2900 rpms, and that could also effect the 3rd event since the load decreases?
 
Joesixpack said:
Can't put that third event totally to rest........:hehe: thought I would load the STOCK software for a look see...

There it is full load 3000 rpm third event.


Stock3k.jpg
Click to expand...


So I loaded up the stock software again and so it seems this chart above is a complete anomaly.

I can not for any money reproduce that.

So for the record at least on my truck there is only two events under full load.

Three events only under light load up to ~2200 rpm.
 
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