https://www.thedieselpageforums.com/...hp/t-7595.html

While not a pulse adapter, maybe we can take another route or maybe this will spark an idea in somebody.

On another note I have been researching. I have been troubleshooting my IP I have made a recording with a piezo element stuck with a magnet onto the injection line trying to get this pulse I will put a recording of it up here for all to listen to. I think the "clinks" are the injector opening and slamming shut? Anybody Got any idea?

 

 

Above is a "picture" of the audio heard in the clip I have uploaded. I am trying to clean it up more but it looks like a potential signal can be gotten from that. Thats about 50 Cents worth of piezo and 50 cents worth of wire. So far my setup has $1 into it.

I need some help though. Does anybody know when you hear the "clack-clink" in the audio....what is that? Is that the injectors slamming shut? Remember this is not just a recording of the engine with a microphone but it is a piezo element hooked by magnet right onto the injection line next to the injector. Some people call them contact mics.

 

Hm, now we just need a magnetic sensor(like the tach sender, I forget what it's called), plug it in, and then hook it up to the /other/ channel of a cheap USB ADC(sound card mic input).
Now, we should be able to use software to compare the two signals(left and right channel) and get a timing number out of that - Just need to find the closest pulse of the piezo before the pulse on the magnetic sensor.

Also, +1 for Linux.


It's recording the same thing as a microphone would - instead of the vibrations in the metal of the engine vibrating air that you then hear, you are picking up those same vibrations directly.

edit:
OK, so here's the interesting part: I can see all 8 pulses clearly by zooming in. Including several that aren't quite right. This may be because of 'not firing quite evenly' (as you can hear in the lope) or simply due to distance. I believe you are running at about 750 RPM at idle.
I think the pulse to RPM calc is (1/X) / 4 * 60 - so if you measure .020 seconds per injection event, that corresponds to 750 (crank)rpm.

I *really* want you to see if you can rig up a second sensor for reference.
We may be able to take a recording of this and spit out a timing signal, plus possibly an 'injector balance' type reading.

 

Thats an idea I had not even thought of but would probably work awesome under the correct circumstances. (just using left vs right or vice versa) I am a thinking about how to get that magnet to send it's wave at precisely the time it needs to. I think it would be easiest to "measure out" where the magnetic sensor needs to be down by the dampner to be at 8.5 BTDC. I have not even looked yet maybe and 1/4" to 1/2" from Zero. In doing this we can make sure the sensor trips at exactly 8.5 BTDC and then make sure that channel corresponds with a pulse exactly. IE they overlap when the engine is run at 2000 RPM (you have an engine timed 8.5 BTDC)

Who knows where we could put an 8.5 BTDC mark on this engine it doesn't need to be for number one. Actually the easier it is to get to the better. Maybe it's easiest to extrapolate from the marks already on the dampner.

 

I would probably just use the zero mark. Then, we just calculate timing by measuring the time between two pulses of the mag sensor by 360(which equals 1 degree of rotation time), then measure the time from mag pulse to closest piezo pulse, divide by the earlier time = degrees.
And since time-between-pulses is pretty low, we don't need to worry much about it varying between when we measure it and when we calculate the mag-to-piezo degrees.
(We'll probably end up averaging it over at least a dozen cycles at least to remove noise anyway).

 

I forgot to add the way I think we could measure this is just by taking left and right (left is pulse from injector line and right is mag sensor pickup signal) into a headphone jack and recording on a laptop or I use one of those little personal digital recoding things that has a headphone mic input but as long as you could open the file later to reveal the actual signal, left vs right like in the program Audacity you can get your visual representation.

Thanks for the idea Macrobb

 

I am a little bit confused but I will come back and try to work the numbers to see what you mean for sure. I gotta go eat for now.

 

Yeah - I'd use a cheap USB sound card with two microphone channels(stereo recording). That way if something goes wrong and you over-volt the input, all you've killed is a cheap USB sound card and not a laptop/desktop/phone.

 

Okay I think I will probably try to use these ports on the timing tab to rig up something. Does anybody know if these are threaded? If they are what size?
Next question is the dampner itself magnetized at that timing groove cut in it? OR is that groove just there to facilitate a visual marker along with potentially modulating a magnetic field (sensor trigger function) In theory it would cause a blip if you had a mag pickup in one of those ports and "less iron" passed by the pickup for that split second.

 

Yeah, you need a "variable reluctance sensor" - it's a coil of wire around a magnet. Change of steel passing in proximity(like a gear tooth) will generate an AC pulse in the coil.
This is what the factory tach sensor is.

 

I made a sensor from nail and a small piece of wire and a couple magnets. I took the leads from the coil that I wrapped around the nail and hooked them into a headphone jack on a digital recording device. (I made sure to make sure I was not going to generate a lot of voltage) Here is the first attempt at spacing magnets and strength of magnets and all that mumbo jumbo.


So I think we have our RPM sensor made for about 30 cents but we will need to fine tune this thing a little. I am going to increase the strength of the signal just a touch because even what I am showing here had to be "amplified" through the software. It would never show up with that piezo signal I was producing off the injector lines. Next up probably in a couple two or three days will be to try and get both right and left channels recording at the same time so comparisons for timing can actually be calculated like Macrobb was talking about. Macrobb, I hope you are still up to the math.

I might also add one thing I cannot get this sensor mounted where I want to it is mounted further clockwise from the typical zero mark by about an inch because of my cheap sensor. I hope we can calculate this into our equations because getting it right on zero is going to take some more custom made stuff. I would rather not.

 

Just for fun here is what the amplified weak signal from the homemade sensor sounds like to a digital recorder with the signal plumbed right into it.

 

Man.....& I thought I was smart! You guys so far ahead of me I feel I need to just go sit in the corner facing inward. LOL
But you all got my interest up so I'm watching!!!

 

Probably. I'd want to know the diameter of the damper and position "around" the damper your actual sensor is, and see if we can figure out what angle in degrees it would be at.