Independent cylinder knock control

[Jim Pearl]

I've heard of the J&S system - it sounded great and if not for my DFI.... 
Currently I use a GM sensor hooked into my DFI. I was told to mount it on 
the HEAD (!) and am pretty sure I'm getting false knock from the 
valvetrain. The sensor uses a small box from GM between it and the 
computer. I've seen monitoring boxes for turbo GNs and would love to adapt 
one for my system. Anyone have any ideas? I just want to know when it's 
thinking it sees knock without having to use my laptop. I've done some 
electronics work but it's been years and most of the little bit of design 
knowledge I had has drained away.. TIA!

----------
>From: 	Frank Parker[SMTP:fparker at umich.edu]
Sent: 	Thursday, March 28, 1996 9:43 AM
To: 	diy_efi at coulomb.eng.ohio-state.edu
Subject: 	Re: Independent cylinder knock control



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





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