[Diy_efi] Crank sensor for knock detection?

[Bernd Felsche]

On Wed, Mar 12, 2003 at 11:35:40AM -0600, PuffnSmoke wrote:
> Ok, too much sour mash, the question was supposed to be was it possible
> to use the crank sensor to detect detonation in an engine...

Possible; yes. As to reliability and feasability, that's another
fettle of kish.

First, knock occurs very near TDC so the brief pressure increase
from knock that would produce rotational _crank_ acceleration would
be small. If you then have to transfer that acceleration to the
flywheel which is explicitly intended to absorb the higher
acceleration components.

> Yeah knock sensor for knock detection is easy, lol.  What about
> analyzing the crank sensor waveform in real time to detect detonation.
> Is it possible, and is it done on production engines that don't come
> with knock sensors?

It's not done on production engines AFAICT. The ignition mapping is
conservative if there's no knock sensing by either acoustic or ion
means.

-- 
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