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1bad383
02-07-2007, 15:20
If I am not mistaken, the tach gets its signal from the alternator. Now, being that we all drive fine Chevy products here, we have all swapped alternators a few times. My spare is behind the back seat..... After swappipng the alternators around, the pulley size is bound to have been changed from factory. Is there a way to check the RPM, without using the alternator as the signal source????? Thanks guys, with out the Diesel Page I would have sold my truck YEARS ago.
DmaxMaverick
02-07-2007, 15:26
If you have a Tech scanner tool, you could read the RPM's from the crank sensor on an EFI engine. Doesn't work for MFI, no crank sensor.

Otherwise, you could use an application called "RPM from sound". It's a Windows program that can read engine RPM's using a computer and a connected microphone. It works, and in my experience, very accurate. I don't recall where on the web it's available, but I can send it to you via email if you want.
1bad383
02-07-2007, 15:52
If you wouldnt mind sending it to me, that would be great!!!! Thanks!
DmaxMaverick
02-07-2007, 16:17
Better yet, download it from HERE (http://www.thedieselpageforums.com/tdpforum/media/rpmsetup.exe) (exe), or HERE (http://www.thedieselpageforums.com/tdpforum/media/rpm.zip) (zip).
1bad383
02-08-2007, 07:14
Quick question. Can I use a recording of the truck on the computer, or do I need to bring a mic connected to my computer out to the truck?? Thanks for the program, pretty neat stuff!
DmaxMaverick
02-08-2007, 09:59
I've never tried it, but I think I remember an option for using a .wav file for the sample. If you mean using a tape recorder, the program doesn't care where the sound bytes come from. As long as your computer's audio adapter can use an input from a recorder/player, it should work. There may be some degree of quality loss, but it should work. I haven't used it in a couple years, so I'm a little rusty with it.
1bad383
02-11-2007, 17:02
I tried to get it working. I recorded the engine @ idle 1500, 2000 & 3000. The program was telling me I had a 1800 ish idle (showing 400-450 on the tach) and it went all over the place from there. Any tech tips?? It is a cool program and would like to use it in the future. I used my digital camera to record the engine, in first gear with only the engine running, no radio ect.
JohnC
02-12-2007, 13:47
Put the mic closer to the engine, or the tailpipe. Also, IIRC, there are some "ajustments" you can make to get it to hear the right harmonics.
DmaxMaverick
02-12-2007, 14:16
I tried the tailpipe. The turbo made the sample completely worthless. It would be a good source for N/A engines, I think.

Try placing the mic in contact with an engine (or motor) part. The best result I had was using a long screwdriver in contact with the intake manifold, and the mic touching the screwdriver bit. Another possibility would be in contact with an injector line. All you need is a pronounced ignition or combustion pulse, and you can adjust the program settings according to the sample you have.