Running compression and intake manifold pressure, Idle to High RPM, waveform

Dmitriy Analyst Toronto, Ontario Posted   Latest   Bounty  
Known Good

This request is for people lucky enough to have access to two WPS500 pressure transducers. I would like to calibrate a high-rpm model, so please try the following with an automotive Picoscope for a 4-cylinder NA gasoline engine in good working order, warmed up before the test.

  1. First WPS500 is in Range 2 (no Zoom), connected to the Intake Manifold. Set channel range to +/-20psi.
  2. Second WPS500 is in Range 1, -55..500psi, connected using the supplied compression hose for the in-cylinder pressure test. Disable fuel injection for that cylinder. Disable ignition for that cylinder or use it for ignition sync in a manner that is safe for the ignition system and the oscilloscope.
  3. [Optional] Ignition sync.
  4. [Optional] It would be absolutely fantastic if you had a BNC splitter and could route signal from the in-cylinder pressure transducer to another channel with Channel Range set to -25..100psi (for better precision at lower pressure values).

Perform the following experiment:

  1. Start the engine, let the rpms settle. Start the capture.
  2. Jump in the car, bring engine rpm to … rpms gradually within 5 seconds, release the accelerator.
  3. Wait a few seconds, then snap the throttle fast, release when rpms reach … Stop the capture.

PsData captures are to be performed at 2 sec/div timebase, Number of samples box: 5MS. Both Idle and Throttle Snap events should be present on one 20-second screen.

Please include engine details. Valve timing info would be helpful.

Thank you,


Q. Why Picoscope? A. I can export data and process it using technical computing tools.

Q. Why WPS500? A. I need fast response for the snap throttle part.

Q. Why 4-cylinder? A. I do not want too many events to overlap.

Jürgen Owner
San Cristóbal de las Casas, Mexico
Jürgen Default

Dimitry, not interested in bounty and so on..... Don't have WPS either......BUT: I do have 2 Px35 in-cylinder pressure transducers which are fast enough and the usb autoscope IV. If this is something that could help you I will do your required test. Actually the autoscope software features a script with a similar test procedure and evaluation. Let me know,

0 Default Ð5 Bounty Awarded
Dmitriy Analyst
Toronto, Ontario
Dmitriy Default

Hi Jürgen, using Px35 transducers would be an interesting comparison, even though I wouldn’t be able to export and process the results the same way as with Picoscope. One of the goals is to assess conclusiveness of high-rpm in-cylinder pressure waveforms, which is, as you pointed out, is related to the Px script in Autoscope. To upload an mwf file you would need to zip it first. Thank…

0 Default Ð5 Bounty Awarded
Brian Instructor
Parma, Ohio
Brian Default

Dmitriy , I will ask around if I can borrow 2nd wps from someone in my area. I would be more than happy to do this. I have 2004 civic with a 1.7 that has cable throttle so nice snaps. I am interested in what can be learned here let us know.

0 Default Ð5 Bounty Awarded
Dale Diagnostician
Sioux Falls, South Dakota
Dale Default

Wish I had a 4 cylinder and it wasn't so darn cold outside. Have the recently acquired wps but have yet to sit down and go over use, etc to get familiar with it.

0 Default Ð5 Bounty Awarded
Dmitriy Analyst
Toronto, Ontario
Dmitriy Delay

Hi everyone, the system asks me to post a ‘Delay’ note, so here it is. Thanks to everyone interested in the topic, hope to hear from you soon regarding the waveforms. The bounty is increased to 5 DNTs.

0 Delay Ð5 Bounty Awarded
Florin Technician
Niagara Falls, Ontario
Florin Default

Hi Dimitriy, I have the Pico Scope and the WPS500 in the shop and I will probably have a 2010 Honda civic in the shop in the next couple of days and since this is a slower time for business might be a good time for playing and experimenting. I will get back here when I have some results for you. Hopefully this will help everybody else who is using the scope.

0 Default Ð5 Bounty Awarded
Pj Technician
Pleasant Hills, Pennsylvania
Pj Resolution

Hey Dmitriy! I have 2 waveform captures. I saved one unfiltered and the other filtered. I hope that these help and I can't wait to see what you find with them. diag​.​net/file/f6tleosc7… ​ diag​.​net/file/f7ihqpivk… ​

+3 Resolution Ð5 Bounty Awarded
Dmitriy Analyst
Toronto, Ontario
Dmitriy Default

Fantastic captures, Pj, thank you very much!

0 Default Ð5 Bounty Awarded
Vasiliy Engineer
Vinnytsia, Ukraine
Vasiliy Default

Hi Pj, I analyzed your waveform with the Px script. Here are the results:

0 Default Ð5 Bounty Awarded