Thread: knock sensor
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beepbeep beepbeep is offline
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Join Date: Jun 2001
Location: Sweden
Posts: 5,565
Oh, I played with APC a lot. I even have two of them, one partially disassembled. It's a pinnacle of 70's analog technology and quite advanced for it's day.
I definitely don't consider APC junk. It's good for it's day but it had inherent drawbacks that were recognized by factory and subsequently removed by Trionic:

1. It was "programmed" to taper boost above 4000 RPM as knock sensors went deaf from chain noise in engine.
2. It couldn't control ignition. Only lower the boost. Winding back boost is very slow and engine risks damage under period turbo is spinning due to inertia if pinging. You would prefer to keep motor on edge of detonation on each cylinder instead of collectively (and slowly) lowering boost.
3. It was tuned for looking for knock overtones in iron B202 block (which many didn't quite understand and retrofitted it to another engines, most notably Volvo iron engines). It didn't always work.

Back to present day: Delphi is about to release their own mass-production ion-sensing ignition cartridges in 2012. 15 years late but I sincerely hope that mass production of ion-sensing ignition will give DIY:ers power to adopt it to MegaSquirt just like they adopted EDIS. This will be nirvana of DIY EFI. It will be Linux in IBM and Windows world of aftermarket EFI.

A DIY MSIII + Delphi ion current coils will be a terrific package.

Delphi Ionization Current Sensing Ignition Subsystems

Right now, I'm aware of only handful of manufacturers besides SAAB that utilize it:

Harley Davidson
Bugatti Veyron
BMW (in their new cars).

Regarding my comments on microphone knock detection:

It works (and has been working since early 90's) but is still something that needs to be tuned per engine type to be really effective. Ion-current implementations don't care about block resonant will detect knock after each combustion in any engine, thus very fitting for universal ECU.
Thank you for your time,

Last edited by beepbeep; 11-01-2009 at 06:02 AM..
Old 11-01-2009, 03:17 AM
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