Knock Detection

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FeArZ
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Knock Detection

Post by FeArZ » Tue May 12, 2015 3:01 pm

I was looking at getting a PNP and learning to tune.

Are any of you using the knock detection on the Megasquirt to tune?
I was wondering this as I would be doing street tunes and I could log then adjust over and over.
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Kill3rwill
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Re: Knock Detection

Post by Kill3rwill » Wed May 13, 2015 11:55 am

I am not! I've been wanting to get it working myself! Maybe MattCramer can chime in on how this works on our mspnp2 systems. I know it is physically wired in through the wiring harness still, but the megamanual seemed rather vague. I don't know how I feel about simply turning the feature on and hoping it works.

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Matt Cramer
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Re: Knock Detection

Post by Matt Cramer » Fri May 15, 2015 6:24 am

There's two parts to the MSPNP knock circuit.

1. A headphone output that lets you listen to the filtered knock signal. It will show up as a high pitched almost beeping sound through the filter. Useful for tuning if your engine is knock limited.

2. The analog circuit that the ECU uses to pull timing. I recommend dialing it in so a conservative spark map won't make it trigger. Not something you'd want to use as a primary tuning tool, but it could help if you have something unexpected like a tank of bad gas...
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Kill3rwill
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Re: Knock Detection

Post by Kill3rwill » Sun May 17, 2015 2:16 pm

Anything to set up or adjust with either of these options? Or simply turn on and go. I was under the impression that knock sensors pick up and filter certain harmonics, so determining that harmonic seems a little scary. Like if I we had to induce knock to get it working

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Matt Cramer
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Re: Knock Detection

Post by Matt Cramer » Tue May 19, 2015 10:50 am

The frequency is physically set in the hardware. However, there are several trim pots inside the MSPNP you need to adjust. See the MSPNP manual for details: http://www.megasquirtpnp.com/docs/mspnp ... &isModel=2
Matt at DIYAutoTune.com - Megasquirt ECUs, fuel injectors, wideband O2 sensor systems, and more
Nissan plug and play engine management now in stock!

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