FW: Electronic timing advance

[rauscher at icst.com]

I guess it's mostly curiosity, with the thought that I may need to tweak the
tuning of the unit for other apps. It's been mentioned that the knock freq
is relative to the bore size. Being that I've several 305 ESC's and none from
a 350 (hard to find), well, I was just having some fun...

My results seem to be a little different then what you have found, but I'm 
not done yet. My first step was to hook the knock sensor output up to the
scope and rap on it with a metal rod. It looks just like you would expect
from a microphone, with a max output of ~3v (with a 'good' strike).

So, the ESC module is on the bench, +12v supply, scope on output, and
a function generator (sine wave), on the input. The ESC module is a HKM
from a '87 305 Chevy van.

It appears as though the module responds mostly to a rapid change in signal.
Either a sudden increase in amplitude, or a sudden change in frequency.
It appears that the freq range need be in the 2KHz to 17.5 KHz range.

I haven't found a 'sweet' spot that would cause a continuous knock signal
output. The max p-p volts input that I've been testing with is 2.5v. If I really
crank up the volts, I can get a continuous output at almost any input freq.

For the curious amongst us, the circuit is built on a thin ceramic plate
using silk-screened on resisters, some SMD capacitors, and a single
SMD chip (18 pin). The board was 'encapsulated' with a clear jelly like
substance that cleaned off with a toothbrush. The resisters are laser
trimmed for value.

BobR.

Who at this point is thinking that verifying the above on another module
would be a good idea. No sense in doing all this with a module that might
be/is bad.

Who is also thinking that a tape recording on a running auto, of the
knock sensor 'sounds' like something to try.


Bruce Plecan wrote:

>At one time I had a dozen or so esc on the bench, what exactly do you need
>to know?.
>In crash testing them, using a 555 to generate the KS they all seemed to
>listen
>to 2 frequencies.
>If you want I think I got the diagrams for the 555s to generate the KS
>signals.
>The 555 generators kinda overwhelm the ESC so the results aren't terribly
>accurate, if your tuning them.
>Bruce

BobR wrote:

>>Who now has a 305 truck ESC module on the bench, trying to find
>>out the how/what/why/where of this unit.


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