Quote:
Originally Posted by 572Camaro
In the 1980’s, I was a vibration engineer and using vibration analysis equipment, I diagnosed wear in bearings, pump/motor misalignment, imbalance, journal bearing wear, etc.
All in nuclear power plants.
COULD this be a technology useful for hot rods?
I think I could detect things like a weak cylinder, valvetrain wear, imbalances, A/C compressor bearing wear, etc.
Basically use an accelerometer mounted at specific points on an engine, hold rpm steady, and take readings. Then perform an FFT algorithm on an iPad, and read the frequency spectrum.
COULD IT WORK?
HAS IT EVER BEEN DONE?
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Vibration analysis is very useful to quickly narrow down the source of an issue, and it's done all the time in the automotive industry-- usually by good techs who'd rather properly diagnose an issue rather than just throwing parts at a car until the issue goes away.
The tool of choice for the automotive industry is typically a Picoscope NVH kit.
https://www.picoauto.com/products/no...-balancing/nvh
The software easily identifies frequency peaks, and the software also links up with the OBD2 port for datalogging so you can overlay the various accelerometer readings and vibration peaks with vehicle speed, engine RPM, driveshaft RPM, axle/wheel RPM, etc, so you can figure out what order of vibration you're dealing with and what component it's coupled to so you can narrow down your diagnosis.
I'd love to have an advanced kit from Picoscope for those times I need to trace down a pesky issue on a car I'm working on, but as an occasional home user I'd never break even on the $4800 purchase price... so I just borrow one from a local dealer where I know the service manager on Sundays when the service department is closed.
As far as engine diagnosis… a vibration/NVH analysis setup is helpful for engine and accessory drive related issues (I’ve used a picoscope NVH kit to diagnose dual mass flywheel issues on several occasions, and also narrow down a persistent vibration on another car to an out of balance mechanical clutch fan along with an optical tach) but what’s also extremely helpful for engine diagnosis (weak cylinder, lifter issues, gasket issues, spark issues, injector issues, etc) is a scope with inductive clamp probes for the spark plug leads, in-line connectors to monitor the injectors, and a vacuum/pressure transducer for manifold vacuum or exhaust backpressure pulses. You can easily plot the coil current waveform (or injector waveform) and the manifold vacuum pulse waveform on a per cylinder basis and you can rapidly narrow down a cylinder with an issue based on the waveform of the spark event and manifold pressure pulses in the intake. If you keep one inductive clamp on cylinder #1 and use that to sync your scope data you can move through the firing order with a second inductive clamp you can compare each cylinder and narrow things down really quickly. I was working on an engine last year that would very occasionally have misfire issues and very occasionally pop back through the intake but all the usual things looked ok; I hooked up an inductive clamp to #1 spark plug wire for a TDC sync and attached a pressure transducer to the vacuum line and started logging. Noticed some occasional unusual spark waveforms and manifold pressure pulse shapes for cylinder #3, turns out a lifter on #3 was starting to have some issues.
Just a note… none of this is new to the automotive industry, it’s just become more compact, refined, and powerful over the years. Various shop scopes have been doing this since at least the 60s in one form or another. Scopes to monitor spark waveforms have been around since at least the 60s in the automotive world, and such scopes were built into the flight engineer’s stations on various large aircraft since the late 40s. Somewhere I have a set of early 1960s era reed vibration analyzers I got from an old automotive shop for very rudimentary vibration analysis. Computerized scopes with individual cylinder & firing order sync that could do cylinder balance tests have been around since at least the 80s (The Snap-On Counselor 1 and 2 come to mind, and are still very handy machines for quickly diagnosing issues on carbureted vehicles.) Nowadays though the units fit in the palm of your hand rather than being on a large rack you have to wheel around the shop, and the software is certainly a lot more powerful and versatile now.
As far as you assembling a diy setup... That sounds like a fun project, and will probably be far cheaper than buying an off the shelf solution.