Diesel exhaust waveform analysis

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Diesel exhaust waveform analysis

Postby ecosse » Mon Mar 17, 2014 9:26 pm

Hi guy's n girls I've got a little citroen c1 1.4 HDI Siemens 508 management with piezo injectors.

Has a misfire and I am trying to work out a quick way of testing to establish which injector/cylinder is causing the misfire, not just on this but any other vehicle for that matter.

I have included a pic/diagram and wonted some views on this.

I will try and include the psdata file too.

any advice on this particular waveform/analysis appreciated

:D
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c1 missfire study.jpg
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Re: Diesel exhaust waveform analysis

Postby Steve Smith » Tue Mar 18, 2014 3:59 pm

Hello and thanks for posting this waveform as exhaust and intake pulsations get you thinking for sure.
The exhaust pulsation will be offset by one pulse to the right after your trigger on this engine, and so your analysis is correct looking at the image attached.
What is interesting is the progressive fall of each peak before your second injection event. (They almost look like they are “stepping” down.
Could you post the psdata file so we can see the events and adjust the settings?
I have been looking at the “First Look” sensor booklet which contains some valuable theories about intake and exhaust pulsations http://www.picotech.com/document/pdf/fi ... nualv3.pdf
Your waveform appears to be missing an exhaust pulsation from number 2 cylinder whereby the above booklet suggests this can be caused by a “lack of fuel”.
Can you confirm the injector was fuelling for number 2 cylinder and on another note were the remaining injectors compensating the fuel trim values to carry the offending cylinder?
Why I ask is because of the size of the exhaust pulse for number 1 cylinder.
Has the fault now been rectified and if so do you have a WPS waveform from the exhaust after fix?
It would be nice to see if the pulsations have evened out or could the waveform reveal potential “near future failures” of other injectors based on a mechanically sound engine but with under performing injectors.
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Re: Diesel exhaust waveform analysis

Postby ecosse » Tue Mar 18, 2014 7:53 pm

I will post the waveform of the fixed vehicle tomorrow.


The number 2 was indeed dead and now with a new injector has made a massive improvement, The other 3 injectors are not perfect they are all under fuelling to some extent especially on the pre injection (proven on my injector test bench) which is bound to cause some drivability issues, though customer wanted to put in S/H injectors i said NO!! as they no doubt could cause even more issues than his own.


one thing i found is that at higher rpm say 3000 the waveform is somewhat unstable, its seems that it paints a clearer picture at idle to 1200rpm.

I did try with the first look but seen as its more sensitive it was hard to make the capture out, i suspect this is why we can't see any exhaust/inlet open close events in the above.

the psdata file is too big for on here i tried to post it last night

I would post the fixed file/picture now but its on my work laptop i will get it popsted tomorrow night at the latest.


I have another one coming right up a mondeo with a misfire which i will get to before the end of the week.

Kenny
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Re: Diesel exhaust waveform analysis

Postby Robski » Tue Mar 18, 2014 8:15 pm

who said No 2 on another forum Mr ecosse ? :wink:

Also WPS/FLS exh pulses, tell me which is which from the pic below of a 2.2 TDCI Mondeo .......
2.2TDCI_Exh pulses_Kenny.JPG
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Re: Diesel exhaust waveform analysis

Postby ecosse » Tue Mar 18, 2014 8:50 pm

WPS-1
FLS-2

what do you mean by no2 on another forum rob? :shock:
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Re: Diesel exhaust waveform analysis

Postby Robski » Tue Mar 18, 2014 8:53 pm

ecosse wrote:WPS-1
FLS-2

what do you mean by no2 on another forum rob? :shock:

Have a read through !
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Re: Diesel exhaust waveform analysis

Postby ecosse » Tue Mar 18, 2014 8:54 pm

cylinders 1- 4 miss on yours?
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Re: Diesel exhaust waveform analysis

Postby Robski » Tue Mar 18, 2014 9:00 pm

ecosse wrote:cylinders 1- 4 miss on yours?

Negative !

I posted it to show you (from the other forum) that the WPS & FLS were not a million miles out were they......
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Re: Diesel exhaust waveform analysis

Postby ecosse » Tue Mar 18, 2014 9:19 pm

negative? please enlighten me o wise one :)
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Re: Diesel exhaust waveform analysis

Postby Fat Freddy » Sat Mar 22, 2014 10:35 am

Hi Ecosse

A choice of staring at your image or Midsomer murders (your jpeg was more interesting) possibly confirmed what you found, showing on the "'5th' channel".
The number 2 was indeed dead


The psdata file would be good, can you chop it?
Did you try Amp clamping all injectors?.

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