Independent cylinder knock control

[Frank Parker]

On Thu, 28 Mar 1996, Edward Hernandez wrote:

> "This is available now in the aftermarket from J&S. I use their box 
> with Bosch sensor. It can retard each cylinder selectively and you
> end up with separate timing curves for ea cylinder. Or it can retard
> all the same."
> 
> Can you describe your ignition system? The two extremes I imagine are
> 1) single coil distributor system or 2) crank triggered coil per plug.
> How does J&S box control each cylinder if it isn't option 2)?
> 
The system is very fast and uses DSP processing. It assumes that if it hears
knock that it is from the last cylinder that fired , so it retards that
cylinder the next time it fires. It works with the revision software that
I have up to 7500 rpm. Last time I talked to designer, I believe he had
a version that works up to 10,000 rpm. Mounting of the sensor is critical.
There was a SAE paper of a few years ago about the best place to mount, the
end result being down low on a rigid rail or boss. I mounted mine near
oil pan railing, low and away from any valve train noise.
The system has a analog output so you can monitor retard. Ouput of 0-1.25
volts corresponds to 20 deg of retard (max). I built a led monitor using
a LM3914 ic to display the output. Also toke retard output and many others
like fuel pressure and turbo boost etc and ran to datalogger and took data
at 100 times/sec. Output in selective retard is a series of pulses, the
amplitude proportional to retard. If I richened up fuel, I could see knock
signal drop off, then out as I got a/f ratio correct. The system is super!!

Frank Parker

93 Civic EX vtec custom turbo
89 S-10/much mod L-98 V-8
96 Contour SE