Diagnostics using Pressure Transducers

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Re: Diagnostics using Pressure Transducers

Postby Allautos » Sat Aug 30, 2014 3:22 am

I have struggled at times like you but you do start to see things as your experience grows, I biggest aid to verifying problems was the use of some very handy soft ware that has been written by Rod Maher you can watch it it on this link https://www.youtube.com/watch?v=7LFwm_4 ... e=youtu.be

You can contact Rd through his web site www.scandata.com.au

Cheers

Maurice
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Re: Diagnostics using Pressure Transducers

Postby hexibot43 » Sun Aug 31, 2014 6:02 am

This should be a link to the ps data for the ford fusion

https://docs.google.com/file/d/0B7XznVsF_XxtekkyMHBmYXp4X3BMeWY3dUI4cHY4WVl2a1Fz/edit

And here is a link to the psdata for the bonneville

https://docs.google.com/file/d/0B7XznVsF_XxtUEJ0MGxxbHFkZHNOZ081U0V1bC0yQWQ4bmhV/edit

Alright I've figured out google drive now.
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Re: Diagnostics using Pressure Transducers

Postby hexibot43 » Sun Aug 31, 2014 6:08 am

Allautos wrote:I have struggled at times like you but you do start to see things as your experience grows, I biggest aid to verifying problems was the use of some very handy soft ware that has been written by Rod Maher you can watch it it on this link https://www.youtube.com/watch?v=7LFwm_4 ... e=youtu.be

You can contact Rd through his web site http://www.scandata.com.au

Cheers

Maurice


Checked out the link, and I'm very interested from what I've seen. Thanks for sharing.
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Re: Diagnostics using Pressure Transducers

Postby Steve Smith » Mon Sep 01, 2014 10:51 pm

Thank you Maurice for the link which is very interesting with some nice features.

Thank you also Marcello for the Ford fusion waveform which is as clear as a bell. If only they were all as conclusive?

Take care both.....Steve
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Re: Diagnostics using Pressure Transducers

Postby Fat Freddy » Fri Oct 17, 2014 10:11 am

Hi Steve

Any chance of posting up the psd file for the Mazda. I would like to have a play. :twisted: :wink: :D

Am I correct in assuming chB is cyl1 ign trigger?

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FF
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Re: Diagnostics using Pressure Transducers

Postby Fat Freddy » Tue Oct 21, 2014 10:37 am

I have attached my interpretation of the events within the exhaust system of a straight 4 cylinder engine which is far easier than looking at a "V" configuration. There appears to be characteristic troughs in the waveform that I hope I can attribute to valve overlap, but I need more experience and time to confirm these events.


Any feedback


Hi Steve.

I've had a little play. There are a couple of things I feel that don't quite sit well. Because I'm not too good at explaining things I have drawn an image (I actually have a few which may give food for thought but one step at a time).

Anyway this is just my first thoughts about the capture of the Mazda and the valve overlap. :)

Any thoughts about that. I have assumed Ch B is Cyl1 sync

Steve1.png


To me it appears the exhaust valve duration is too short and the overlap too long. But that's just my thoughts.
Also I'm not too sure why you have picked the position of number 1 exhaust stroke. :? - It's way to early.

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FF
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Re: Diagnostics using Pressure Transducers

Postby Steve Smith » Wed Oct 22, 2014 2:30 pm

Hello FF and thank you for the feedback.
I have attached a further interpretation of the waveform using generic figures of a 2.0 Lt. 16 valve 4 cylinder engine.

The Mazda (from memory) had a fixed exhaust valve sprocket but VVT on the inlet.
The spec's I have used look to coincide very closely with the Mazda engine in the image.

Can you let me know what you think?

The number 1 cylinder exhaust gas pulsation is set 1 "peak" to the right of number 1 IGT event as the initial rotation of the crankshaft after ignition will consist mainly of the power stroke (No exhaust gas pulsation from number 1 cylinder during this period)

REVISED EX GAS WAVEFORM.jpg


MAZDA FOR FORUM.psdata
(601.75 KiB) Downloaded 132 times


I hope this helps, take care.....Steve
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Re: Diagnostics using Pressure Transducers

Postby Fat Freddy » Thu Oct 23, 2014 10:59 am

Thanks Steve. Much appreciated. :)

I did find the manual for the FLS and I found some interesting and some what contradicting information about where the exhaust valve timing occurs. But I also found some interesting info too.

I think your capture has given me more questions than answers. It's given me something to think about.

The one thing I am struggling with, is the generated waveform that the FLS produces (I don't own one, so a bit off with interpretation). I remember reading (I think) that the FLS has an inverted output. In other words, an increase in pressure gives a negative voltage and visa versa.

http://www.autonerdz.com/cgi/yabb2/YaBB ... 1284040266

And also mentioned in this article here, "a vacuum to the sensor with a vacuum pump, the voltage output will rise quickly,".

http://www.motor.com/article.asp?article_ID=1016

Is this true?
A comparison with a WPS would be good. 8)

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Re: Diagnostics using Pressure Transducers

Postby Steve Smith » Thu Oct 23, 2014 12:01 pm

Hello again FF and thanks for the feedback.

This really does throw a spanner in the works for sure, but it would appear that a positive pulse felt in the exhaust system during the exhaust stroke is met with a positive pulse from the First Look Sensor

I have attached a comparison made whilst testing the Mazda above using both WPS and First Look in the exhaust system.

Whilst there is a timing offset, they match pulse for pulse.

MAZDA WPS AND FIRST LOOK.psdata
(810.4 KiB) Downloaded 134 times


Looking at the image in my previous post above, if the exhaust valve opening times are correctly marked, then the First Look Sensor would appear to respond with a positive pulse for a positive pressure wave.

What do you think?

Thanks again for the feedback

Take care......Steve
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Re: Diagnostics using Pressure Transducers

Postby Fat Freddy » Fri Oct 24, 2014 10:35 am

Man. this is driving me up the wall. :? :D

I have attached a comparison made whilst testing the Mazda above using both WPS and First Look in the exhaust system.

Whilst there is a timing offset, they match pulse for pulse.


Thanks for that, much appreciated. It sure seems to show a match. So at the moment, I'll settle for that. :)

Looking at the image in my previous post above, if the exhaust valve opening times are correctly marked, then the First Look Sensor would appear to respond with a positive pulse for a positive pressure wave.


I'm still in two minds about this.
What my thoughts is (this should through a cat amongst the pigeons) or should I say were. You are not seeing the inlet valve opening. You are seeing the next exhaust valve open....... -
The decreasing slope as pressure change reduces as the exhaust reaches the end of its stroke. But as it does so the next fully charged exhaust event over laps, giving that 'pop' of an increase in pressure and masks the inlet valve over-lap (after all there is 40* exhaust over-lap). I did have an image to show you which explains it (I may post it anyway).

But, I have a problem. I'm going to assume the two capture's were done on the same vehicle under the same conditions. So why is this the result.

Any thoughts on this? I'm confused. Have I missed something??????????

Steve XXX.png


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FF
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