adding a knock sensor to DIYPnP 1.6
11-15-2010, 09:03 PM
#3
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11-16-2010, 04:14 AM
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The KnockSense won't provide you with anything useful, either knock detection below 4k and false knock above, OR knock detection above 4k and no detection below (audiable by the naked ear knock, yet the KS did f'all...) BTDT.
The KnockLite, is a far better solution as it has rpm noise filtering. It does have a spare output as ianferrell states, it's not directly compatable with MegaSquirt though, it's signal requires conditioning, as a bonus it's also a shiftlight :P. I quite like my KnockLite, though it's not an advanced piece of kit like a J&S.
Savington, MS's knocksensing input is a switch, there's no filtering etc, (though you can tell it to ignore a signal above x rpm), so you need something to decipher the knock sensors output and then sens a 5v signal to the MS to tell it that bad stuff is happening.
Advanced it is not, however with a good external box conditioning the signal it can be a useful sfatey device.
The KnockLite, is a far better solution as it has rpm noise filtering. It does have a spare output as ianferrell states, it's not directly compatable with MegaSquirt though, it's signal requires conditioning, as a bonus it's also a shiftlight :P. I quite like my KnockLite, though it's not an advanced piece of kit like a J&S.
Savington, MS's knocksensing input is a switch, there's no filtering etc, (though you can tell it to ignore a signal above x rpm), so you need something to decipher the knock sensors output and then sens a 5v signal to the MS to tell it that bad stuff is happening.
Advanced it is not, however with a good external box conditioning the signal it can be a useful sfatey device.
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11-16-2010, 07:15 AM
#7
http://www.turboxs.com/uploaded_images/558.pdf
it appears the knocklite has a signal output. Is this what needs conditioning? isn't that conditioning done in the set up and tuning of the device?
I understand knocksense has a mode that will retard timing at knock detection, then start adding it back in. This seems more advantageous.
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11-16-2010, 08:16 AM
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The KnockSense doesn't retard anything, it outputs the afformentioned 5v signal to the MS which then does the retard thing.
Yes the KnockLite has that signal output, I've not had chance to scope it thus far, but I highly doubt it's a 5v signal the MS requires (likely it's an analogue signal for the DTEC-FC), to condition it you just need a simple circuit to turn whatever it outputs into an on/off signal the MegaSquirt can understand.
Yes the KnockLite has that signal output, I've not had chance to scope it thus far, but I highly doubt it's a 5v signal the MS requires (likely it's an analogue signal for the DTEC-FC), to condition it you just need a simple circuit to turn whatever it outputs into an on/off signal the MegaSquirt can understand.
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11-16-2010, 08:31 AM
#9
The KnockSense doesn't retard anything, it outputs the afformentioned 5v signal to the MS which then does the retard thing.
Yes the KnockLite has that signal output, I've not had chance to scope it thus far, but I highly doubt it's a 5v signal the MS requires (likely it's an analogue signal for the DTEC-FC), to condition it you just need a simple circuit to turn whatever it outputs into an on/off signal the MegaSquirt can understand.
Yes the KnockLite has that signal output, I've not had chance to scope it thus far, but I highly doubt it's a 5v signal the MS requires (likely it's an analogue signal for the DTEC-FC), to condition it you just need a simple circuit to turn whatever it outputs into an on/off signal the MegaSquirt can understand.
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DIYPNP
11-16-2010, 08:36 AM
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If you don't filter and don't set pre-ignition sample period...you don't have usable knock control. This is the difference between an $800 computer and $3000. I don't see this as a problem on a turbo car considering you can retard spark and "up the boost" to compensate.
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11-16-2010, 09:34 AM
#16
this is a way out there thought.
If the problem is background engine noise. Why not drill the mounting bolt of the sensor to a given wall thickness that's resonant with the knock. Then fill the bolt with silicone/epoxy/something to dampen it mechanically? Shouldn't this insulate some if the non resonant noise?
If the problem is background engine noise. Why not drill the mounting bolt of the sensor to a given wall thickness that's resonant with the knock. Then fill the bolt with silicone/epoxy/something to dampen it mechanically? Shouldn't this insulate some if the non resonant noise?
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11-16-2010, 09:57 AM
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Brain whilst it's true the DIYPNP has a knock sensing circuit, even DIY admit it's not particularly good. It's just a copy of the circuit in the MSExtra manual.
90R, I don't see how your idea would work, you want it sensitive at lower rpms and less sensitive at higher rpms, drilling a hole in the body.... I dunno how or if that'd work, a knock sensor is a sensitive device, drilling into it is likely to destroy it.
Hustler, whilst an $800 Knock sensing device is awesome, the KnockLite works really very well, until you've tried it don't 'knock' it
As a preventative measure, (not something to tune against/rely on to run on the bleeding edge), it's perfectly acceptable.
90R, I don't see how your idea would work, you want it sensitive at lower rpms and less sensitive at higher rpms, drilling a hole in the body.... I dunno how or if that'd work, a knock sensor is a sensitive device, drilling into it is likely to destroy it.
Hustler, whilst an $800 Knock sensing device is awesome, the KnockLite works really very well, until you've tried it don't 'knock' it
As a preventative measure, (not something to tune against/rely on to run on the bleeding edge), it's perfectly acceptable.
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11-16-2010, 09:58 AM
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The DIYPNP knock circuit has a bit of a bug in it - we have a work around if you need to use it, but it's not as sophisticated as the KnockSenseMS or other options. It is neither tuned nor does it change sensitivity over RPM. It's just the standard MS1/Extra knock circuit, which is designed to send a signal when the voltage level from a knock sensor exceeds an adjustable set point.
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