The Trainer #31: A Beginner's Guide On Using In-Cylinder Pressure Testing For Drivability Diagnosis
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- Опубликовано: 22 июл 2013
- #engineperformance #incylindertesting #scope #pressuretransducer #picowp500
Have you ever stood peering into the engine compartment, scratching your head and wishing you could see inside the engine when faced with a drivability complaint? Wouldn't so many problems be easier to find if you could? Imagine being able to see exactly when the ignition event actually happened, or confirm that a valve that wasn't sealing as it should? How about verifying cam/crank synchronization without the need for a "known good" cam/crank sensor waveform or tearing the engine apart to access the physical timing marks?
You could do all this and more in minutes if you were using in-cylinder pressure testing as part of your diagnostic assault!
This test uses a pressure transducer and a digital storage oscilloscope (DSO) to monitor pressure changes in the cylinder while the engine is running. A transducer differs from a sensor in that the transducer is able to accurately measure the pressure while a sensor simply reacts to pressure change. The transducer converts the pressure measurements into a voltage signal that your scope can use to paint a picture of these changes on the scope's screen, bringing the idea of a traditional running compression test into the 21st century!
In the August 2013 edition of The Trainer, we'll show you how what accessories you'll need and how to set up a scope to perform this test. We'll also show you the basic elements of the in-cylinder running pressure waveform, and what they have to tell you. After viewing this video, we're sure you'll see how valuable a technique this is and how it can save you hours of time in the shop!
Bernie Thompson, if not the father of this technique is certainly one of the most well versed in its use, recently authored an excellent introduction to this testing method that was featured in our July 2013 issue. If you missed the print, you can always access the digital version at www.searchautoparts.com/motora...
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This is the best video ive seen in a long time. Thank you very much for sharing this on youtube. Really handy way to diagnose problems.
Excellent explanations. Very clear
Some very good information on pressure waveform analysis!!! Thanks Pete!
hello my friend , good night you took away all the doubts I had left inside me, also work with pressure transducer in my analizes in otto cycle engines. I am extremely grateful for your video lesson , um big hug and already I will sign up for your channel
Automotive Test Solutions (ATS) and Snap-on also make transducers. ATS founder Bernie Thompson is often credited with pioneering this testing method.
The E-Scope Elite is one impressive piece of equipment to boot. Bernie has a lot of videos on it. Pull up the wave form and click on “mark cylinders” and bingo, so simple. Or at least he makes it look simple😅
Lots of good info there Pete. That's for taking the time to share your knowledge.
True, but the peaks are consistent and can be used as a reference point. The distance between them is always 720 degrees of crank rotation.
Thanks for the video.
Thanks for the lesson on this
great video pete, thanks for your time,clearly this is the way of the future and it is exciting to see what the dso and its speed can do for us. happy hunting. the engine is an air pump.
Good Afternoon Pete Meier motor age Take care and have a great day 👍
Great tutorial thank you 👍
From Nick Ayivor from London England UK 🇬🇧
thanks for teaching..
👍 Really appreciate you Pete!
Interesting! Thanks for the observation. Is there a reference you can point me to that explains that?
I would think, being a layman, that even with the heating of the air charge, peak pressure would still occur at the point where the combustion chamber volume is the smallest. ???
Good video 👍
fantastic
Nice video! is there somewhere I can download a chart with the marks at the bottom. like the 0 degree 180 and so no
What is the other brand of in cylinder pressure transducer??? I only knw bout the pico
Pete, great video. I would like to point out something. The peak pressure IS NOT piston TDC. Due to thermal dynamics, as the cylinder volume decrease, even though you are motoring, not firing, the charge will heat up due to compression. This heating of the charge will cause the peak pressure to happen before TDC of piston. Sorry, can't help myself. It's part of being involved in cylinder combustion analysis for over 35 years. :-)
Hi Eric, I realize you posted this few years now but I was jus wondering if you could direct me to some information which supports argument, thanks a lot.
Very cool Pete, that cleared up some things. Thanks. Thank you for subscribing to my channel. I have more videos up, take a look.
Any idea why your waveform from the Zeus+ is not as uniform as the one captured in this video? The Zeus+ intake capture seems to rise / slant upwards shortly after the intake valve opens. One would think that the modern Zeus+ capture would at minimum be as accurate / detailed as this 9 year old capture with older technology. As far as I remember, you didn't mention that the engine had any mechanical issues (in the Zeus+ video)... so the only thing I could think of that would affect the quality of the Zeus+ capture... would be the pressure sensor or the scope. One could end up thinking there's a mechanical issue... when there isn't one (recent Zeus+ video).
Thankyou Pete for the escope testing. I'm learning with the Pico, but seeing is believing.
If others want Pico Scope training, check out "Trained By Techs" on the you tube. There's LOTS of videos by these guys.
Awesome video pete! Do you know of any websites that list OEM cam spec sheets? I found aftermarket cam sheets but very little for stock oem cams
Many of the service information system providers have this info in their data, and you can always access the OEM service sites (most require a fee, though). Check out www.nastf.org for info on accessing those.
Hi. Very good video.
Can you tell me please, I would like to know what model is the sensor shown in the minute 1:58
with a cable from the sensor ending with a BNC connector for the scope
There are several on the market, with some designed for a particular scope platform while others can be adapted to nearly any scope. Check out aeswave.com for a varied selection that are proven performers for automotive use.
can I know why the pressure transducer located at first cylinder..? I read two journal paper about in-cylinder analysis and measurement but it does not state why...
+mohammad muzammil The test can be performed on any cylinder that you suspect has an issue. It can also be used to compare one cylinder to another - as when diagnosing a problem between cylinder banks. Wherever you would perform a traditional compression test, this test can be performed and provide so much more information for the time spent. There is a whole series of articles authored by Bernie Thompson on the Motor Age site.
I'm simply blown away! I am so glad to find your channel cause you are extremely knowledgeable & are very informative. Autel Maxis Elite is on my list for this upcoming Christmas. Would a pico scope work with this?
Glad you found it so helpful! Not sure what you're asking, though. Can you clarify your question?
Will the pico scope work on the Android OS?
I don't think so. It is only available for Windows operating systems. You can go to the pico website (www.picoauto.com/) for details but I'm still running mine on an old HP laptop. And if you're serious about diagnostics, you're going to need a laptop anyway.
True, I just wanted to ask.
No worries! Feel free to reach out and ask anytime. We're always willing to do what we can to help.
I was wondering if someone knows where you can find ready to go budget pre- wired boxes for the 5 volt power supply to hook up to readily available pressure transducers without having to obtain the parts and build your own?
They sell those boxes on eBay, you can then buy pressure transducers that are reliable and use it based on the accuracy you want. The pico version is of course a best investment if you don't want to play around with something you don't 100% trust.
I did an in cylinder pressure test on my 2007 chevy aveo5. I synced the ignition on channel B of my picoscope. The ignition timing was 1 deg after TDC. This is a waste spark ignition system. Is this normal?
If this was a running test then I suspect timing is off by at least a tooth. Verify by looking up the spec. Typically idle timing is 10-15 degrees BTDC
he's making alot of work of it christ
Wouldn’t a leak create less vacuum on the decompression stroke?
A leak creates more vacuum on the descompression stroke because you have less air at the time the piston starts moving down and the volume starts to increase. This creates a higher pressure differential, that is why the pocket goes deeper (more vacuum). When there is no leak at the compression stroke the same amount of compressed air is returned to its original volume at the end of the expansion stroke this means the vacuum is the same as the one achieved at the intake stroke.
what scope are you using for this demonstration? Thanks for the video.
The scope used in this video is the ATS EScope. Check out automotivetestsolutions dot com for information.
I am just getting into using a scope. Can I ask what equipment you're using? Thanks for all your help with these videos.
I use a Pico scope (PC-based) and their WPS500 pressure transducer. There are other options that work just as well, so if you already own a scope be sure to check out all the possibilities.
Motor Age pico scopes it's easy to check timing and fast this way sucks
thanks for the info... but can I ask if this method use in research... the in-cylinder pressure graph will provide what information to us
+mohammad muzammil This testing method provides a wealth of diagnostic information including verification of proper ignition timing, cam timing, variable valve timing, valve sealing issues and much, much more.
+Motor Age thanks but are this infomation can be related to heat release rate... and can you explain how heat release rate vs crank angle was obtain...
+Motor Age thanks a lot for you respon I really apprecite
+mohammad muzammil I think we are talking about two different things here my friend. This is not a research tool, but an every day diagnostic tool for technicians. We are not concerned with heat release rates, and I couldn't even begin to offer any insight into that question. Perhaps SAE has papers published that could be of more help to you?
+Motor Age ouh... i get it now. anyway I still want to say thanks alot for you positive respon and the suggestion..
my knowledge the ignition timing controlled by pcm few degrees before tdc while engine is running ,so is it normal to see ignition out of tds as long as timing is within specification ?
What you see on the scope is what is REALLY happening. Here's a brain teaser for you. The scope shows the timing is out of spec, but the scan tool data says it is in spec. What could be wrong?
i can rephrase to be cleared:
in good engine we can check cylinder compression and we see ignition timing exactly at tdc this in case of test done by cranking engine (injector and coils disabled).
if engine at idle ignition timing will be at tdc and also any degree within timing specification for instance , assume timing is 10-18 btd so timing will be at 10 or 11 or....
in non good engine ( jumped timing chain, ...) engine cranked( injectors & coils disabled) we will see ignition timing not at tdc but few degrees btdc , if it is at 10 or 11 or 18 degree we still say timing chain is jumped because specification taken in mind in good engine and while is idle . in idle, timing will be out of specification as long as chain is jumped .
are all above is correct ?
sorry for my bad English
No reason to say you're sorry! You speak two languages! I only speak one...and that not very well.
Back to your question.
First, don't think "idle". The engine is not running.
Second, the ignition event should occur just before TDC at the peak. Any other position requires further investigation. It could be a jumped chain or belt, or a sheared key.
Third, jumped timing chain or belt will generally change timing 10 degrees or so.
Hope that helps!
Not my knowledge, We're just the middlemen, learning what we can and passing it along!
If you have a bad lifter on the intake or exhaust side how would that affect the waveform?
I would think it would depend on the nature of the failure. If the lifter collapses, the valve will open later than it should and remain open for a shorter period of time. You can see the difference in opening time with this pattern.
Motor Age i need to get me a pressure transducer and do some.experimenting.... lol
If we don't like to test for ignition event, Will it be wise to leave the COP unplugged?
Thanks a lot for ur videos, They r as much helpful as usual.
That shouldn't be a problem. But including the ignition event is an easy way to rule out timing issues, so why not include it? You're already right there! :-)
@@MotorAgeMagazine Fair enough Pete, Thank you very much.
Here's your chance to learn from one of the leading experts on the subject of the use of pressure and vacuum to diagnose all manner of engine/drivability issues: endeavor.swoogo.com/virtualtrainingsummit
Register for the Virtual Training Summit and look up Brandon Steckler - watch every video he has there. Those alone are worth the cost of admission. Then take advantage of the remainder of your 45 day access to dive into the library of over 40 different presentations - many will feature a date/time when the presenter will be available for questions.
@@MotorAgeMagazine Thanks a lot Pete, I will sure check it out.
it's alot easier to use second channel on eignition
after exaust back pressure u can tell exaust manfold lenght ( runner)?
No, you can't determine runner length using this method. Interesting idea though!
hmm if u know back pressure speed wich is speed of sound and time between peaks of exaust is that wave is traveled 2 runners lengt ? (P.S. sor for bad english)
Vladimirs Sinkevics OK, I won't say positively "No"...but it seems to me that there is too many other factors involved - runner length, shape of the bend, location relevant to the cylinder being tested...
Hello
Where can I buy this cylinder pressure sensor
They are available from a number of sources. Try www.aeswave.com!
hello friend good night , Mr. can help me by putting me in a program your learning ? help your friend here from Brazil to develop