high speed logging

[Yves]

For some time now I have considered buying a cylinder pressure sensor and logging it to find out about certain conditions. (not looking for a debate on that).
One of the issues is that I would need to use a very expensive daq to correctly log pressure at high speed and combine it with crank degrees.
Not sure how many people are looking into it.

Seems to me it would be possible to have MS record things and TS display a graph showing a pressure trace based on degrees crank rotation.

Bad idea ? Ah well, maybe too much asked...

[whittlebeast]

Here is MS3 Ultimate logging at 200 hz. At the bottom is the engine cycles. My gut feeling is you need way faster data rates to get what you are looking for

http://www.nbs-stl.com/tuning/MS3%20Ult ... il%202.png

MLV HD will handle almost anything you want to open.

Andy

[Yves]

yes, pressure signal is sampled at 50 kHz.

[whittlebeast]

We need to check with James as to what is the sample rate on the ADC channels. It may be way less than 50.

[jsmcortina]

If you really want to log at 50kHz then you need a logger designed to do that. As Andy says, 0.3kHz is the most you'll typically get out of MS3. The diagnostic loggers (e.g. MAP logger) might sample a little faster and can correlate to a crank tooth, but nothing like 50kHz

James

[racingmini_mtl]

By the way, 50kHz is one sample per engine degree at 8133RPM or per one half degree at 4167RPM and so forth. So you need to correlate the engine position and the signal sampling with at least that accuracy. That's likely not an issue at constant engine speed but that may start to be an issue at fast transients.

As James says, you will need a logger designed for that and it will also need to do a good job at wheel decoding.

Jean

[Yves]

By the way, 50kHz is one sample per engine degree at 8133RPM or per one half degree at 4167RPM and so forth. So you need to correlate the engine position and the signal sampling with at least that accuracy. That's likely not an issue at constant engine speed but that may start to be an issue at fast transients.

As James says, you will need a logger designed for that and it will also need to do a good job at wheel decoding.

Jean

Wouldn't a hall sensor suffice for the job of crank decoding ?

[whittlebeast]

Wouldn't a hall sensor suffice for the job of crank decoding ?

No

[Yves]

It seems to me that it can reliable detect crank rotation at speeds of up to 8000 rpm. I think with good timers you can then divide the signals further.

[racingmini_mtl]

Whatever hardware you use, you need the code behind it to determine the exact engine position from the tooth pattern. And that is not trivial if you want flexibility and accuracy under all conditions.

Jean

[Yves]

Whatever hardware you use, you need the code behind it to determine the exact engine position from the tooth pattern. And that is not trivial if you want flexibility and accuracy under all conditions.

Jean

Based on previous answers, it seems that the only possibility remains a national instruments setup. Labview does allow the flexibility to program it.

[jsimmons]

What conditions exactly are you trying to study / research? I'm curious as there might be simpler or cheaper ways to find the info you're looking for

[Yves]

knock sensor characterization, peak pressure point, point at which 50% of the charged burned....

[pmbrunelle]

Digital Storage Oscilloscope to record pressure.

1 pulse / revolution camshaft sensor on the engine.

Use the 1 PPR camshaft sensor to trigger the DSO.

Drive at constant speed. Crankshaft angle can be determined by the time axis, since you are at constant speed.

Output data to .csv, export to Excel.

From estimated crankshaft angle, bore, stroke, TDC combustion chamber volume, compute cylinder volume for each crankshaft angle.

Perform integral of pressure with respect to cylinder volume.

Presto, you have IMEP.

[racingmini_mtl]

That seems to me to be highly optimistic that you can get a good enough resolution from single pulse per cam revolution. Saying that you go at a constant speed ignores all the real world things that will cause some variations and you have a single precise location per 720 degrees where you want in the order of 1 degree resolution.

Jean

[vw_chuck]

No such thing as constant speed in an internal combustion engine. If you have done this type of work before you would know that you need a high data rate toothed wheel. I think the one we had at work was 360 tooth or 720 tooth wheel with an optical pickup.
The reality though for the hobbyist if you want to look at in cylinder pressure sensors on the cheap just buy an O-scope. Preferably one with logging abilities. If you can look at each firing cycle you will be able to see if the engine is detonating or not. You really don't care about where the piston is in this cycle so no real need to know crank angle unless you are doing some serious post processing with expensive equipment to figure out burn rates and VE and stuff like that.
Not sure where you would get a reasonably priced in cylinder pressure sensor though as they are quite pricey. The ones I used to use were like 2500 bucks a piece.