Math channel to control cylinder balancing, from alternator

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Math channel to control cylinder balancing, from alternator

Post by LucaB » Sun Mar 13, 2016 10:29 pm

Hello to all.

I wanted to share with you the possibility to check the cylinder balancing the alternator ripple.

I tried to do some testing but the result is not good, at low speeds the frequanza is incorrect and falls.
Math channel, alternator ripple frequency.png
I tried to create a sinusoidal signal of the alternator ripple.
Math channel, alternator ripple frequency_2.png
When I want to find the math channel frequency that I created, the formula fails
Math channel, alternator ripple frequency_3.png
Any suggestions on how to set the correct equation.

Thanks for your attention.

Ripple alternator.psdata
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Re: Math channel to control cylinder balancing, from alterna

Post by victor2k » Sun Jul 17, 2016 1:12 pm

I think you must use filter for small ripple...or you must check the crankshaft signal for deceleration or acceleration.
Also the cylinder balance from Pico Diagnostics will not give the same results if you check for 3-4 times the same engine...too much noises must be filtered,the connection point is very important...

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Re: Math channel to control cylinder balancing, from alterna

Post by STC » Mon Jul 18, 2016 10:03 am


Pico do have that test in the Pico Diagnostics Software although it works better on older cars and can flunk on later vehicles due to access, interference, smart charge etc.

I have found Cylinder balance is best achieved with a Math Channel riding on the CKP.

Airmass, Exhaust & Intake pulses can be viable alternatives. I guess it would be a case of what works best for you.

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Re: Math channel to control cylinder balancing, from alterna

Post by Steve Smith » Tue Jul 19, 2016 3:06 pm

Hello and thank you for the post and the replies.

It great to see math channels getting such use as they reveal so much more detailed contained within the original capture.

For cylinder balance the crank sensor would be the preferred choice but that's not to say we cannot use the math channel on any signal like ALT Ripple or those mentioned above.

The ALT Ripple can be notoriously unstable regardless of engine condition and for this reason I tend to steer clear unless this is all you have to work with.

Lets face it, we have to work with what we have.

In the scenario above Luca, the frequency math channel is dropping due to the crossing point of the signal falling below the threshold. (See image below)
In this scenario, if you are happy with the output of the alternator (DC coupled) then switch the scope coupling to AC. Here we reject the DC and have the Ripple presented about zero volts.

This then makes for a stable crossing point on which to create an RPM math channel to evaluate cylinder balance.

I hope this helps, take care.......Steve

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