Autonerdz forums

Hi Lawrence

Do you have a psd file to show here? There are some great guys willing to help you with your questions.

you will find every running engine has a different wave. But cranking waves are a little bit easier to interpretate.

Mick

the easiest way to use the first look sensor in the exhaust , FLSE , is to use it with AceMisfireDetective .
AMD does the translation and sees things i can not . but i keep trying .

    dont forget that the exhaust pulse you see does  not match  the cylinder fireing , there is an offset , which truly kicked my butt at first and still does off idle.   

the latest version of ANNO wave from AES wave has the ability to put a transparency with pre marked things over the top of saved waveforms and imho you should build that or something like it into your learning curve .       but there really isn't anything quite like it   paint.net  can also build layers on top of waveforms .... but  i dont want to learn to be a graphics designer to operate it  and it uses gobs of memory to save files  ...

anno wave files wont open here but they can be saved as gif files which do open here .   

my thoughts are to create templates in anno wave to overlay on top of pico 6 captures that cover 720 degrees of engine rotation ... so you can sync on spark or ... and see where things happen in the engine the anno wave template can be expanded and contracted without loosing the relative position of things  noted in it ... to match the 720 degrees plucked out of a larger pico 6 capture ....
                          
    but it has been a little busy
    AMD capture with sticking exhaust valve and ...
   

Hi Members,
  This is first attemp to understand the offset.  Not sure really how to read yet.  Trying to understand wich is the exhaust valve.  The link that Romain supplied helped alot (not in the manual I received).  Sure may have tested wrong.  Any help gladly accepted.  Thanks

Jeff

Hi Rich,
  I will try that, always getting buggy before horse.  Thanks

Jeff

Keep in mind that there are 3 exhaust valves open at once
To check for mechanical problems do a cranking test with the throttle wide open
I can do a more detailed version with the exact timing if you like
Need the exact engine cam specs
This is not usually necessary because the exhaust pipe distorts the pulses somewhat anyway

If you do this exhaust test with a 4 cyl it is easier to see since there is only one exhaust valve open at a time
I like to start here to learn because it is so much easier

You can always do your test like you did either running or cranking with one spark plug out and see the result
All engines are a bit different because of different exhaust lengths and bends

Play around
It is a blast

Pretty soon you will be doing it with one FLS hooked to the exhaust and one to the intake and yet another on the fuel rail

Hi Group:


I got an idea , lets take a truck that has a problem and play with it .



I just happen to have a truck to play with.

I have an 95 Ford F150 5.0 with an engine problem the computer shows misfire in number 7 and 8 cylinder.

The engine has a misfire and a knock coming from around #4 cylinder like  a lifter maybe

Here is the pico diagnostics compression test.

Hopfully somebody can fill in the blanks and we will see where we end up.

I have not done any compression test or secondary ignition yet but we can the customer does not want to fix but we can learn from this junker.

It is really storming here so bare with me as I hold my lap top tight.

Here is with TP open cranking

i never had a communication problem with AceMisfireDetective on any version , one version was unhappy and would not record a full 20 screens , it did not like the sync pickup that came with the kit... i dont remember which version .

as a rookie , i have not graduated to 8cyl waveforms yet ...

the overlay is from Tom Clozza's article or discussion about vacuum waveforms .
          every one using the FLS  should read that and Bernie Thompson's article in Motor Mag archive.
        
            i have a copy and i know Wilf has a copy .
here is an overlay on top of a running compression waveform , marking out what happens when , you can make your own by running a running compression test then importing that save into ANNO wave  ,

      DO not use the FLS sensor for running compression , the one i did is with a FLUKE PV 350 ,
         which sux , dont buy it .    useless as mudflaps on a sledghammer . terrible resolution. 

     allow for ignition timing advance and overlay on spark parade to see what intake or exhaust valve is opening when .   
     in ANNO wave you can stretch or shrink or whatever and the overlayed template  image stays in proportion  .

Hello, i have been having a play with my firstlook sensor in the exhaust. I am trying to learn which stage in the cycle each pressure pulse is due to. this test was performed on my single cylinder, 4 stroke, yamaha 125cc motorbike. There appears to be one spark for each 360 revolutuion with one spark at the end of the exhaust stroke (the one with the lower firing KVs due to the lack of compression. . .)
This test was carried out under load at medium revs.

Am i right in thinking that the first positive pressure pulse is due to the exhaust valve opening and the pressure created by combustion being expelled into the exhaust pipe?

There is a second postive pressure pulse about 10ms after, is this the pressure created by the piston pushing the spent charge out of the cylinder? this makes sense to me as the second spark fires at the end of this pulse, indicating that the piston is nearing TDC. . .

finally, what do you think about the negative pressure pulse after the two positive ones? is it due to the relaxation of the sensor's  diaphragm, or the inertia of the exhaust in the pipe causing a depression or could they be due to valve overlap? . . .

I get the same characteristic trace at idle but the pressure pulsations are not as high due to the reduced volume of charge in the cylinder.

i thought that this may make the trace easier to dicipher as there are no other cylinders making any contribution to the pressure in the exhaust.

Thanks for any replies,

heres a trace captured from my single cylinder 125cc motorclcle again. (4 stroke)
the firstlook sensor is in the exhaust, triggered on the HT lead. it appears that once the exhaust valve opens, there is a drop in pressure in the exhaust. (a negative pressure fluctuation) is this the case or am i being confused?
in the example of this test given in the Pico software a similar trace is reported.
is this one of the reasons that when you get a missfire, the pressure drops off (neg pressure pulse as the exhaust valve opens?)

thanks again for any light on the subject. . .

oops, i left that bit out! this was a cranking test. When you see the drop in pressure, can you confirm that that is when the exhaust valve opens? is the slight rise after the initial drop due to the piston pumping the air from the cylinder? sorry if i seem silly, i just want to ret a solid understanding of which parts of the trace represent which parts of the engine cycle and this single cylinder example simplifies it.
Thanks!

this is a trace of a 4 clyinder engine at 2500 rpm. the engine has twin static ignition with the plugs firing 1&4, 2&3. i disabled injector number 4. (firing order 1342)
i used the primary earth for 1&4 plugs, at least according to the wiring diagram i did!
do you rekon this is correct? it almost appears to be a misfire on injector number 2. . .
what do you people think?

i just dont want to get confused over this!!
thankyou

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Rick Hill wrote on Jun 15^th, 2007 at 12:10pm:

Hi Michael,

I'm curious about that slight bump in the pressure waveform, have you made any comparison with the other cylinders to see if this is uniform throughout the engine or just a signature to that one cylinder only ?

With this attachments, I would like to attempt a description of what I think the sudden momentary cylinder pressure drop is caused by,

since the area of the TDC compression is shown, there would have to be a brief pressure relief for the waveform to display the sudden pressure drop,

now since the cam lobes for that cylinder, at this point in time are pointing away from the cam followers, I submit that there is a bad spot / abrasion or irregularity on the base circle of one of the cams, so that the cam follower (Hydraulic) is transmitting it's movement on to the valve, and momentarily releasing pressure, allowing us to witness the resulting drop in the waveform.

in brackets I inserted Hydraulic, as a mechanical valve train would not be able to effect that same condition due to the valve clearance provided .

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fisher wrote on Jun 18^th, 2007 at 10:59pm:

I found out something about the Fluke PV350 and trying to use it for determining TDC.  It was 25 degrees LATE.  I used the CKP sensor to give me the true TDC.  Has anyone else checked to make sure their PV350 was really telling the truth?  This is the only car I've ever tried to verify the PV350's accuracy on, but I don't think I would trust it to tell you the true Top Dead Center on an engine.

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I spoke late; a good man already had clarified the Fluke thing.

http://www.quantex.ru/portal/methodics/gas.aspx

color=#ff0000]Chernobyl sunrise - and how many "hot" spots dot the ocean floor ? from soviet nuclear powered submarines with system failures , crews forever preserved by the radiation that permeates the areas they are now resting in ,  half life of the melted reactors measured in millions of years .
  [/color]

Here are a couple of fls captures on an 04 f 150 5.4 with a vct system. This engine is very sick and surprisingly only one cylinder has no compression according to a relative compression test and it's not where you might think it would be looking at the fls wave forms.  One of these captures is in the intake at about 510 rpm and the other is in the exhaust at about 1760 rpm. See if they will tell you anything about the condition of this motor or is there any useful info there at all.  I will add these in psdata so you can manipulate them and they were done on version 6.06 if it matters.
    Here is one from the exhaust.

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---------------------------------------------------------------

Hi Michael
     I agree those captures are hard to make much of. You may well be right about that exhaust valve leak at the fourth  in the order . I'll check that before it's gets torn down. The firing order here is 13726548.  I can't really slow the engine down and get a more stable capture over a longer period of time. If I let it idle  that wave as you call it running through the wave form will get like the intake capture and I'll have to raise the voltage scale on the scope to the point that you'll no longer see any individual pulses or it will run right off the screen.  It becomes extremely unstable at slower speeds. Did you look at the intake capture and notice how the wave running through the wave form is like the inverse of what you see in the exhaust?  I'm pretty much thinking about what I might see in these wave forms when the valve timing is way out of sync with the piston position.  The only thing that makes me rethink that  is the ignition and injector timing is right according to the crank sensor and the fact that I show eight cylinders in a relative compression test. I think if one cam was 360 out of time I would only see four  cylinders in a relative compression test. The cams are synced together so if one is out of time both are out of time. There was the possibility of one being 360 off but the eight pulses in the compression test kind of ruled that out I think. I can pretty positively say at least one intake valve is wide open or close to it when the piston comes to tdc compression. From the fls wave forms  it looks to be the 4th in the firing order but from the relative compression capture it would logically be the 7th in the firing order.
    Thanks for taking a look at that and giving me your opinion on what you see in there. I know it takes a bit of your time to look through those captures and annotate them as you've done. I know I spend a bit of time looking through them a number of times after I've looked through them the first time for anything that just obviously stands out. I notice it looks like you figure there is a pretty good delay in the fls reporting when compared to an electrical signal. I found about a 3 ms delay in my pv 500 but I've never checked the fls for delay. I have gone under the assumption that it was at least quite a bit faster than my pv 500  and haven't figured on the delay much when looking at these wave forms.  I believe it's a piezo device rather than a pressure transducer and assumed it to be faster to report. Do you figure the delay to be about the same as your pressure transducer? I guess I should check it and find out what the delay actually is so I can figure that in there as well.
 Here is a relative compression capture  to give you a little more info about why those fls waves may look like they do with the blue being starter current and the red being #1 primary.

A lot of the time (always) mechanical integrity is easier to see with the engine cranking and not running.
I use two FLS 100 testers and do intake and exhaust at the same time with a sync.
That way you don't have to deal with any turbulance caused by the misfire.
That is my 2 cents
Take it for what it is worth
Here is an example of a toyota

Wilf

Hi Michael
      I will get those wave forms but I got side tracked yesterday with Dogs and didn't get them done. Friend of mine was running a bear south of here for the game and fish folks with my tracking collars on his dogs. I have my name ph number and address on my tracking collars so all day long I kept getting calls about lost dogs showing up in folks yards. Most folks don't understand those collars are radio transmitters so they don't know what to think when you tell them that the dogs owner will be along shortly. I ended up taking a trip south to help round up dogs. In the old days these dogs had good homing instincts because they always just ran loose on a fellas property and went where they wanted but these days they spend all their time in a kennel so on a hunt after a couple days on track they get hungry and go to the first sign of civilization rather than home. The homing instinct has been kind of bred out of them so to speak.

     I see you and I are roughly on the same page with those wave forms. I came up with the peak in that intake wave being at about 442 degrees after #1 firing event but I also came up with 442 degrees after the firing event in the exhaust wave as being about 42ms after the firing event  you show that point as being a little earlier than 442 degrees. I still tend to think there is a valve timing problem here as well. I guess we'll know more about that as soon as I get those captures done.
     Time wise what do you figure the delay to be with the fls?  Thats something I'm still unsure of.

Michael here are the running compression waves for the cylinders you asked about.There are no revelations here for me as I already knew there wasn't anything wrong with this a new set of heads wouldn't cure.  With a leak tester on #4 the intake is always open but I can hear that the cam is moving the valve as I roll it through. I think maybe that intake is bent or a seat fell out. Do they do that?
  Anyway I'll start with #4 and I'll put up the psdata file so you can manipulate them.

here is #2.

Running with the fls at the dipstick and the maf ac coupled didn't come out so well. I couldn't seem to get rid of the noise and the same with the fls and the cranking waveforms I think mostly over using such a low voltage range to get much of a wave form. Here is running with the fls at the dip stick and the maf ac coupled.

Last is cranking with the fls in the exhaust. This did change some from the running exhaust capture but there is a lot of noise on the signal. I tried wrapping the fls in rags and seting it on a stand not connected to the truck but it didn't seem to help much.

Mike

Could the one slightly shorter exh pulse not be caused by something other than an injector?
Do you have an acompaning injector capture to show us that there is a poorly flowing inj in this vehicle?

Wilf

Michael what is the difference between the two tips?  Smaller opening, larger opening, screen or restriction in the coupling?
   I looked at the wave forms you annotated for the 4.7 and I would agree with your analysis of the waveforms but I kind of wondered about whether the fuel wave pulse problem were really for   #1 and #6 injectors. That would put injection  somewhere around 150 degrees before the intake valve opened which seemed kind of early. I've never looked at the injectors on one of these so I really don't know but  like that ford I was looking at up above the injectors were triggering at about 70 degrees before tdc overlap or intake valve opening. Made me wonder if what we were seeing in the exhaust waveform on that 4.7 was really caused by an injector although it would make sense that it was. I would like to have seen an injector capture on #1 and #6 to go along with the fls exhaust capture.

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Don't you dare Wilf     I think you know that FLS better than anyone.  Certainly better than me 

It's easy to jump to conclusions with that tool as the waves leave a lot to interpretation.  You question everything.  This is good.  With a tool like that you need to substantiate things to draw valid conclusions.  It's easy to assume things that later prove to be less than completely accurate.

Hi Mike,

The difference in 02 content (contained between individual cylinder exhaust strokes) drives differential pressures between the exhaust strokes of good combusting and misfiring cylinders.  The unconsumed O2 (and sometimes HC) from a misfire (or partial misfire) causes a difference in mass between the exhaust strokes (homogeneous gasses and non-homogeneous gasses). Non-homogeneous masses create an obvious pressure differential in the signal created by the FLS.
I think you are equating the “long line” pressure transitions (in the signal created by the FLS) between exhaust pulses as the signature of a misfire and that is correct. Any pressure transition between exhaust pulses is an indication of a differing combustion event between cylinders.  It’s just that the “longer the line”, (greater the pressure transition) the greater the misfire if that helps. Long line misfires are “dead holes” that you and your customers will definitely “feel”. Shorter lines (lesser pressure transitions between exhaust strokes) are partial misfires or combustion inefficiencies that you may “feel” as a quiver or not “feel” at all.

Since the FLS is a Piezo device, I look at the FLS waveforms as the “sound” of each cylinders exhaust stroke. Of course each cylinder’s (entire or total) sound will occur at a predictable point of a 720 degree cycle, differences between individual exhaust stroke “sounds” are easily identified. With the resonance difference that “different design” exhaust systems create through different bends and different muffler baffling however, I’m not sure that that you can dissect and analyze the mini-content of each exhaust strokes “sound” in the same way between “different” manufacturers and engines. What “sounds” like a burnt valve on a Ford may “sound” like a low flowing injector on a Chevy? I dunno, but I think that at least valve "sounds" may be easier done on the intake side of things with the FLS. That’s my take for WIW, but I think that between you and Wilf working these signals so much we'll probably all know sooner or later 


mwebb wrote on Jul 31^st, 2007 at 8:48pm:


A tube within a tube is a venturi (http://en.wikipedia.org/wiki/Venturi_effect) which should smooth the signal somewhat and maybe make the overall pressure differentials easier to pick out but I’m not sure that’s a good idea for what you and Wilf are doing since you will lose some waveform “sound” definition and change the picture.

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Maybe I am confused, you said there was a wave that was between 4 and 8 cylinders in length. I took it to mean that it was not happening every rev or every other rev, relative to the spark firing event or TDC on CKP, say. If it did not sync to th electrical impulses on the car then it would be some kind of noise or whatever.

Hi Sam,
        I remember you told me some things about my own Fluke. I evetually took it to Branom Instruments, here in Seattle and they took care of me as they sell Fluke equipment and service. They dont restrict their business strictly to Fluke however.  The price for me to have them check it was worth it, mine needed nothing.
         You ought call them, I think if it needed repair the cost to fix it would be about 75% that of a new one,  max... You can find them on the web and one number to call is 1 800 767 6051.
          They repair 'process control instrumentation' as well as testing equipment including DVOMs, transducers, etc.
  For sure you can look for a company that repairs and calibrates instruments.

Thanks Mike I will give it a try.  My apadter is just hose connected and clamped to the hose from my compression tester.  I may have been having a problem wiht my usb connection on my pc as well I went to use the scope and the voltage was reading 5v less than what it was wiggling it would correct it.

Here is an image of when the pv350 was apparatly working

Hi Alex,

You'll probably get more responses if you open a new thread for your case.  From your description of #3 failing the power balance, I'd guess that the intake wave is showing you that you are getting pressure in the intake during #2's intake stroke.  That pressure may be coming from a leaky #3 intake valve during #3's power stroke.

I'm busy right now, but when I get home I can put up an image that can show this better.  Perhaps by then others will have seen this, and can chime in.