Cam/Crank relationship

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Cam/Crank relationship

Postby RonMcleod » Thu Aug 26, 2010 8:33 am

Hi guys its my first post so please be nice :D . I have a Nissan Pulsar N16 QG18 engine. The problem I have is I think the varable cam system may be jammed in one position ????? I have only just got my Pico so im not real sure on how to use it yet but can I use it to check if the cam timing is out or the varable timming is jammed????
Thanks Ron...
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Re: Cam/Crank relationship

Postby JamesD » Sun Sep 12, 2010 4:24 pm

Hi Ron

You can use your Pico.

Hook into ch 1 into cam sensor, ch 2 into crank and ch 3 into a synchronising signal (injector or ignition).

Set the trigger on ch3 (rising edge) and the timebase to 200ms (engine takes 150ms to do suck squish, bang and blow at 800 rpm). Move the trigger across the screen until you see two complete crank revolutions.

Next, you can look for a repatitive relationship between the cam and crank (count the crank sensor pulses between it and the cam sensor). Use the cursors to help with this lining up process.

Finally activate the variable valve solenoid (use a scan tool or use a jump wire between the VVT solenoid control wire and earth) and look for the reference you took before to have moved to the left (advancing the intake cam).

It is a bit difficult to explain here, but I hope you get the gist?

Let us know how you get on.

Cheers

James.
- author of the Oscilloscope Diagnostics Book

Technical Topics, Bridgwater, Somerset 01278 428 699

www.techtopics.co.uk

technical training, bulletins and picoscope
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Re: Cam/Crank relationship

Postby shay » Mon Sep 27, 2010 1:08 pm

Hi JamesD
Do you have some tip for trigger with 2 channel?

Thanks
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Re: Cam/Crank relationship

Postby elijah » Wed Oct 06, 2010 7:21 am

JamesD wrote:Hi Ron

You can use your Pico.

Hook into ch 1 into cam sensor, ch 2 into crank and ch 3 into a synchronising signal (injector or ignition).

Set the trigger on ch3 (rising edge) and the timebase to 200ms (engine takes 150ms to do suck squish, bang and blow at 800 rpm). Move the trigger across the screen until you see two complete crank revolutions.

Next, you can look for a repatitive relationship between the cam and crank (count the crank sensor pulses between it and the cam sensor). Use the cursors to help with this lining up process.

Finally activate the variable valve solenoid (use a scan tool or use a jump wire between the VVT solenoid control wire and earth) and look for the reference you took before to have moved to the left (advancing the intake cam).

It is a bit difficult to explain here, but I hope you get the gist?

Let us know how you get on.

Cheers

James.


Hi there! My friend also thinks that his cam system is jammed in one position and we're kinda confused how to fix it. You've given instructions but I hate to admit it, we're kinda noobs and don't know where to start. We're kinda lost about setting the trigger on ch3 and counting the pulses on the crank position sensor between it and the cam sensor. Do you have any pictures or manual so we could better see it? I'll appreciate it.
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Re: Cam/Crank relationship

Postby andyz » Thu Oct 07, 2010 1:39 pm

Hi Guys,
I'm certainly no authority on the Picoscope but just to help you get the ball rolling, I'll attempt an answer.
If you're using the same automotive software that I have, the trigger settings will be along the bottom row of the screen next to the stop/start symbols. You'll only be able to set the trigger from channel c once you have switched trigger from 'none' to repeat eg.
you'll also only be able to trigger from channel c if you've got a 4 channel scope with channel C turned on.
What you're trying to see with the scope capture is the relationship between the crankshaft and camshaft positons.
If the variable timing system is working correctly the relationship will alter.


Can anyone expand on this?
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Re: Cam/Crank relationship

Postby Dave Hill » Sat Oct 09, 2010 7:57 pm

Here is an example, where I have triggered off an injector voltage signal, in order to stabilise the waveform. It was easier to use an ignition event, but it proved to be unsuitable as the ignition angle wandered too much & the waveform stability suffered. You need to experiment & find what works for you.

As Andy said, the trigger options are to be found on the lower left area of the screen. You can drag & drop the "yellow diamond" trigger cursor for convenience. Use either repeat or auto trigger, they both work in a similar way, although the repeat trigger will not display a capture until trigger threshold is met. If you select "Auto" then the screen will at least draw a waveform periodically, even if the trigger is not met.

Image

Hope this helps

Regards

Dave
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Re: Cam/Crank relationship

Postby gonzotr » Wed Oct 05, 2011 4:09 pm

Dave, how do you get the mov ing Waveform, I likey! tr :P
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Re: Cam/Crank relationship

Postby Lee » Fri Oct 07, 2011 10:03 am

Dear 'Gonzotr'

The moving waveform is quite a cool feature built into the PicoScope software.

In order to create this image, simply collect a buffer of waveforms within the PicoScope Software. Once you have all the waveforms you need.

Go to the 'File' tab > Click on 'Save all Waveforms' option.

When the 'Save As' dialog box opens, simply give the file a name and a location where you will be easily able to find and identify it.

You will see that under the 'File name' box there is a box called 'Save as type'.

If you click on this box a list of file types appear. The one required to create the animation i.e. moving waveform is 'Animated GIF Image' .

The software will then create the Animated GIF based upon the waveforms stored in the buffer.

I hope this helps to answer your question.

Kind regards

Lee - Automotive Technical Specialist :D
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