Mths chaneel

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Mths chaneel

Postby s4c » Sun Jul 01, 2012 9:41 am

Hi

Is the a way to show the RPM on a trace using the maths channel, taking ths info from say a crank or cam sensor?

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Re: Mths chaneel

Postby Autonerdz » Sun Jul 01, 2012 2:30 pm

The short answer is yes. You can graph the RPM with a math channel. The higher the resolution of the sensor, the more detail. With a high resolution sensor you can even see the individual cylinder acceleration.

The formula is based on frequency math. So....for example, if you had a 60 tooth CKP, the frequency would be RPM. Each type of sensor requires a unique formula. You have to create a math channel that converts the signal frequency to RPM.
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Re: Maths chaneel

Postby s4c » Tue Jul 03, 2012 10:09 am

Hi

Can you give me an example of a formula so I can see what I have to work with?

I have had a look but do not know where to start.

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Re: Mths chaneel

Postby Autonerdz » Tue Jul 03, 2012 2:04 pm

OK. Here is an example of how an RPM channel was the clue that solved this case from one of our Picogroup members in Australia.

1992 BMW 318i E36 Symptoms:
Cold misfire, backfiring through exhaust and barely running, car runs perfect hot

60-2 CKP RPM channel in black and based on this CKP. Formula freq(B) in this example.

Do not use this picture for a reference waveform. Something is terribly wrong here and we can deduce what it is from the picture. Note how you can see the individual cylinder acceleration as the RPM is being increased.

This is a simple example of an RPM channel. Each application will be different. We cover this in our Picogroup discussions. In fact, we looked at this one in our last live online Group Therapy with the Picotologist session.
Attachments
bmw318irpm2.gif
92 BMW 3181 E36 Known Bad with RPM channel based on channel B CKP.
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Re: Mths chaneel

Postby s4c » Tue Jul 03, 2012 6:50 pm

Hi

Yes, that is what I am trying to do. However, not being great at formulas I need an example of a formula to have a starting base.

When I open the math channel to try I do not even know were to start. Can you give me a working example that I can build on?

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Re: Mths chaneel

Postby Autonerdz » Tue Jul 03, 2012 7:13 pm

Simon,

When you are ready for that scope upgrade, you can have all your mind can absorb. I can't really go into more detail on a forum but we have movies on this as well as forums discussion.

Here is another example from our forums where it came in handy before this feature was even released:

http://www.autonerdz.com/cgi/yabb2/YaBB ... 308802930/

You'll need to be logged in to access this. For those that are not registered....registration is free.

That example is your base formula. Then you have to figure out the math to convert the frequency to RPM if needed (in this case, no conversion was needed). I myself am math challenged and it can be quite the brain teaser. We have been expanding our minds with this aspect of LSD for some time now..... 8)
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Re: Mths chaneel

Postby Dave Hill » Tue Jul 03, 2012 9:58 pm

Autonerdz wrote:
I myself am math challenged



Yeah right!

Get away with ya! :lol:

If you are Math (Maths in the UK please :D ) challenged then I am Henry the VIII.

Of with ya head! :lol:

I have to say though, that for anyone who wants proper Pico support, where you can find the answer to all of your scoping questions, then Tom at Autonerdz is the way.

Best to buy the tool from Tom & gain the benefits of "Full Access", rather than pay annually for it.

For the serious scopist, it really is a no brainer.

I look back & realise that this is the way I should have gone.
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Re: Mths chaneel

Postby Autonerdz » Tue Jul 03, 2012 10:44 pm

Hi Dave,

Thanks for the good words. It's not that we are any smarter then the average bloke, we just put more effort into it than anyone else can. :wink:

So, what's wrong with the Bimmer?
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Re: Mths chaneel

Postby s4c » Wed Jul 04, 2012 12:44 am

I have to apologize for the spelling. I did it on my phone, big fingers and small keys!

The BMW looks like it has a harmonic balanced issue.

Tom. The upgrade will happen. The tax man is getting his cut before you!

I realise you don't like to give much away and you protect what you have for your group members (as you should)

I will endeavor to plug on in the mean time as I do want to work out this RPM issue

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Re: Mths chaneel

Postby Autonerdz » Wed Jul 04, 2012 1:36 am

The BMW looks like it has a harmonic balanced issue.


Good call, Simon. Right on.

We can see that it is not a speed variation responsible for the CKP amplitude changes. Therefore it has to be a change in distance from the reluctor to the sensor.
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