KNOCK  SENSOR

Here we go, we are going to build some KNOCK  SENSORS for our GMCs'.!!!!

The Knock Sensor is a Piezo Electric device that when you stress it, a voltage is produced.  This is similar to the electronic lighters for the Gas Refrigerators or the lighter for your BBQ except these sensors do not spark.
The sensor shown is for a Ford but I think all of the single wire sensors are the same.  I say this, because someone told me there are two-wire sensors.  I wonder if they were
 confused with the oxygen sensors? 

Try a NAPA Echlin DKS100 knock sensor.  It has a 3/8 inch coarse thread stud about
a half an inch in length.  Den

KS1 and fits 1980 to 1996 Dodge and Plymouth vehicles. Emery

Anyway, this sensor is screwed into one of the heads , mine will be at the rear , and when a pre-ignition happens ( a Knock or ping ), a shock wave is sent throughout the engine and the piezo device puts out a signal (damped sine wave for your techies).  This signal is about plus and minus 2 volts and the duration depends upon what is causing the knock.  The signal is about 5 thousands of a second.  To light an indicator we have to stretch this pulse to something much longer.  The article:

http://www.gnttype.org/techarea/projects/projectspage.html

shows a circuit that will stretch this signal and light a light for each knock and will also send an audio indication if you can stand the noise.
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This was information that he found on the Internet designed by L. Fisher 1989, 1996. (No relation to Gene). I attempted to build this circuit but it didn't work.

I asked my son, who recently received his PhD in Engineering and Applied Physics from the Univ. of Fl. and who started to work for Intel in August as a Senior Process Engineer, to look at the circuit and see if he could suggest any changes to make it work.  He revised the circuit on paper but indicated that he would need more info on the knock sensor's signal and that I might need a capacitor or different resistance values in that input lead.  I built the revised circuit but it lit and buzzed all the time.  I added a variable potentiometer to the input from the sensor and it now worked great. I guess all that money spent on my son's education has finally started to pay off!!!

I installed the unit in my GMC last November and it got a trial run to Michigan and then to Florida and then back to Santa Fe.  It works just as it should.  Since I have the Caspro EKE (electronic knock eliminator) also installed, if I get pinging or knocking the indicator light flashes and the buzzer sounds (the buzzer can be shut off with a switch if you just want the light).  I can tell if the EKE is working because it will flash 2 or 3 times and then the pinging will stop as the EKE retards the timing.  If the EKE should fail or if the timing is too advanced and the EKE cannot retard enough I will be able to immediately tell that.

If you don't have the EKE, this unit can be used to adjust your timing to accommodate regular gasoline and hilly terrain while assuring yourself that you are not encountering too much pinging.

This is a fantastic thing for me since I cannot hear pinging or knocking.  My wife can but it is outside my range of hearing. However, since we put on Darren Paget's insulation blanket under the floor my wife now even has a hard time hearing any knocking as that insulation does such a great sound proofing job as well as keeping the heat out.  (Darren you owe me one for the plug!)

I think this works so great that I want to share this info with anyone that wants to build one so I have just put up the pictures, parts list, schematic, layout diagrams and instructions on my PhotoPoint site.  Go to

http://www.gmcmhphotos.com/photos/showgallery.php?cat=3059

Look for Knock Indicator Light in the list of albums. You can print the pictures and other data from the PhotoPoint site.

If anyone would rather have the parts lists and instructions in Word format I can email them to you.  If you have any questions please let me know. Have fun. Emery Stora
 
 

I have set up three of these.  One for my coach about 1-1/2 years ago.   One for Walter Drew and Al Chernoff and I did one on his coach just last week.  My recommendations is that the sensor be screwed into the threaded hole at the back of the driver's side head.  Caspro's instructions say the
passenger side head but the hoses, etc., make it very difficult to work on  that side.  I mounted the control unit on the back aluminum angle of the motor box on the left rear, using two of the four holes and letting it hang vertically with the writing upside down so it could be viewed when you lean
over the motor box from the step.

PICTURES BY  MR.C

The instructions are quite clear.  One wire goes to the knock sensor.  One wire goes to ground.  One wire splices into the battery terminal of the distributor and the last two wires go in series with one of the three leads from the lower right of the distributor to the plug on the upper right.  I suggest
that when you cut the distr. wire instead of splicing in the two leads from the control unit that you put a male and a female connector to the two ends of the cut wire.  Then put the corresponding leads to the two control unit wires.  I've found that the round connectors work better with less corrosion
problems than the flat ones.  This would allow you to reconnect the distributor to the original configuration in case of any failure of the knock eliminator.

There are two controls on the control unit.  One sets the amount of degrees  that the system will retard.  You'll probably want to set this at about 3-1/2.  The other is the Sensitivity control.  You adjust this after doing some road trials up hills.  We set Al Chernoff's distributor advance (vacuum
disconnected and plugged) at 14 degrees BTDC.  With a 3-1/2 setting on the worked great in Albuquerque but Al found that on his trip to California (from 5000+ elevation to sea level), that our original setting of 3 worked very well at Albuquerque but it started to ping in California.  He stepped it up to 3-1/2 and set the sensitivity up about 1/8" turn and now says that it works properly at sea level.

Those of us who have advance the timing have found that the engine is running much better and with more power.  However, you probably can't advance the timing much over the stock 8 deg BTDC unless you have a unit like this knock eliminator to prevent knocking when loading the engine uphill or when burning low octane gasoline.

One reason that I bought it is because I figured it would take care of the poor gasoline one encounters crossing the country but also, once set up properly, will prevent the knocking.  My hearing is poor at the frequencies of pinging so I have to depend on my wife telling me that the engine was knocking.  I used to then retard my distributor "on the fly" until the ping went away.  Now it is done automatically and then advances when the load/octane permits.

Another thing that I did and we also did on Al's GMC is to mount a small terminal strip to the back lip of the motor box and run our leads to it including the tach terminal and the fuel injection wires so that they could be easily accessed and also to eliminate the problems often caused by crimp-on terminals.  Again, Al could probably supply a picture.

I give a big thumb's up for this product.  Should take about 1 hour to install and another hour to adjust with test runs.

Emery Stora

FAQ

<< is the EKE a "set it and forget it" device, or is there a manual control? (I can't tell from the catalog.) Also, does it connect to the vacuum circuit to the distributor, or how does that work?
Larry >>

Once you have it set up properly it is a "set it and forget it".  Just listen to see if you get a ping once or twice and then it goes away.  That is the only way that you'll know that it is working.  There are two controls.  One that sets the amount of retardation that it will give.   The other is a sensitivity adjustment that you set so that the system will "hear" a ping and retard the timing.  This is a trial and error.  Al Chernoff and I both have ours set at 3-1/2 to give about 10-12 deg. of retarding (this is from memory and I don't have the chart in front of me.)  We have set our sensitivity, following the instructions, by driving the GMC up a steep hill until it slows down to about 45 and listen for pinging.  Readjust this control until you hear a ping or two and then they go away.

We found that setting the initial timing (with the dist. vacuum line plugged off) at about 12 to 14 degrees was a good point.

The EKE doesn't connect to the distributor vacuum line.  Rather it is put in series with a dist wire so that it electronically "delays" the signal to the coil. Emery