Date: Wed, 12 May 1999 15:28:00 -0700
From: "James S. King" (james.king@wyatt.com)
The following steps describes how I installed the J&S knock sensor on my '94 RX-7. I used the Mazda factory wiring diagram to verify the colors of wires in the factory harness to splice into. This is highly recommended. It is possible that for different model years the wire colors may be different. I haven't checked this. YMMV and all of that. What you do to your car is what YOU do.
The instructions included with the J&S suggest locating the J&S control unit in the passenger footwell and running several wires over to the driver's side footwell and then through the firewall to the engine compartment. This is not necessary. The only wires that need to go into the engine compartment are those that go to the knock sensor inself. These can be routed through a grommet on the passenger side. The J&S control unit can be mounted beside (on the outboard side) of the stock ECU.
Tools Required:
Procedure:
This write-up covers only the installation of the J&S unit. You are on your own as far as mounting the monitor unit. I plan on mounting the main J&S control unit directly on the back of the engine ECU. I have not done this since I'm still tuning the sensitivity adjustment. It looks like it will fit there ok, but the small "black box" control unit that is mounted there may be in the way. It could probably be relocated without much trouble.
This is a first draft. Any criticisms, corrections, suggestions for better methods are welcome. I will be on vacation for few days, so can't answer any immediate questions.
_________________
Date: Fri, 29 Jan 1999 15:14:43 +0000 From memory, so don't take this as anything but a rough indication:
The knock sensor control unit mounts away from heat--usually under
the dash somewhere or in the glove box.
Mount the microphone on your rotor housing. One of your housings
already has the mic from the stock knock sensor. Use the analigous
space on the other housing. The mic cable terminates in a plug
which fits into the control unit.
There are four wires to run: Two are used to interrupt (and route
through the control unit) the low tension signal that fires the
leading plugs--between the coil and igniter on my 1st gen. In other
words remove the igniter wire from the coil. Attach it to one J&S
wire. Attach the other J&S wire to the coil. The wires are color
coded.
The third wire is hot (switched). The 4th wire is ground. (Note:
If your ground wire comes loose from the body, you will lose ALL
SPARK to the leading plugs. Secure the ground wire well.) These
four wires terminate in a multi plug that goes into the control
unit. The unit comes with a shorting jack that fits into the end of
the multi-plug. Use this if you are diagnosing a problem and want
to take the J&S unit out of the picture. It simply turns the
ignition signal around and sends it back without going through the
box. Pretty nifty. I used it when my ground wire came loose one day
when I was on the road. You should see what happens to exhaust temps
when you are only firing the trailing plugs.
There is an optional 5th (yellow) wire used if you notice the knock
sensor activating during over-run conditions. This can happen if
there is unburned fuel left in the combustion chamber. The knock
sensor is sensitive enough to detect this stuff burning off in an
uncontrolled way. Even though it won't harm the engine, some people
don't like seeing the indication that the knock sensor has activated,
so the yellow wire is provided to hook up to a voltage source like
the TPS. This prevents the knock sensor from operating when your
foot is off the throttle. Note that the knock sensor already knows
not to operate below a certain RPM threshold. I don't remember what
it is--probably somewhere between1200 and 2000 rpm.
The knock/retard readout gauge simply plugs into the control unit.
The A/F meter portion of the gauge has (I think) one wire to T into
the O-2 sensor, and another wire. I don't have this feature so I
don't recall where it goes.
The following controls are on the front of the old model control unit. The
new one may differ:
There is a set of dip switches with which you can select options like
retarding total timing according to the worst knocking rotor face, or
retarding each rotor face independently. There is a sensitivity
control which will probably end up open about a quarter turn from
full counter-clockwise, with the screw slot somewhere around 11 and 5
o'clock.
There is another adjustment for the rev limiter. No one mentions
this because our cars under boost will over-rev on the trailing
plugs alone (not controlled by the knock sensor). Nevertheless,
there is a sophisticated rev limiter included. If I remember
correctly, you tune it with a VOM and a screwdriver so that the VOM
reading corresponds to the red line. The unit cuts spark
intermittantly from that amount of RPM to 10% over, and totally cuts spark
after that. If someone figures out how to make this work for both
leading and trailing plugs on our cars (without buying a second
knock sensor) it would be VERY handy.
Once again, this is from memory after installing my J&S unit well
over a year ago. The new model must have a switch to select the
"10% max retard" mode Shiv mentioned. Take the above as a general
indication of what is involved to install it, and not as specific
instructions.
________________
Date: Thu, 26 Mar 1998 21:56:07 -0800 I have a J&S unit on my car, which is an '85 GSL-SE with an after market
turbo. I also have the read-out for the amount of retard being dialed
in. The object is to set it up so that you get no reading under max
boost. This is as opposed to setting it up to rely on it routinely to
retard the spark under boost. You shouldn't see it activate unless you
are messing with things, and have probably gone too far. You will know
it is right if you have established a baseline where you know boost is
about the max you can safely run. Set the J&S unit to activate at any
point above that.
Of course, if you hear detonation, you need to make it a little more
sensitive. My unit is set so that the screw slot is on a line between
11 and 5 on a clock face, about a quarter turn clockwise from the least
sensitive position. I have also discovered that if the unit is too
sensitive, it will retard the leading plugs past where the trailing
plugs fire. For some reason, this seems to cause pinging.
I have not hooked up the yellow wire because I have not had a problem,
however, I do occasionally see a flicker on the indicator when the car
is off throttle--especially if I have just completed a high boost run.
It isn't worth worrying about.
If you don't already have it, you should get the read-out to tell you
what is going on with the knock sensor. As an alternative you can use a
volt meter hooked up to a mini jack and plugged into the front of the
control box. J&S makes a version of the read-out with a parallel line
of LED's that is an A/F meter. The combination meter takes up very
little room. I wish I had gone that route. Twenty-twenty hindsight,
eh?
________________
Date: Tue, 29 Dec 1998 13:32:27 -0600 I have it in my 93 R1. The pickup is attached by a nut and bolt just above
the rear trailing sparkplug. It uses an unused tapped hole there. My
control unit is located under the carpet under the drivers seat. When doing initial
adjustments, it was placed between the left side of the seat and the side rail, just
behind the release of the seat back. My retard monitor is attached with Velcro to the dash,
just left of the steering column. The control wires connect to the ignition igniter
on the inner left fender. Requires splicing and cutting! I also had to connect
the yellow arming wire due to low rpm engine/trans noise. This can be connected to
the map sensor or the TPS. The TPS connection works best for me. My unit's
sensitivity had to be set to only about 1/16 turn past minimum due to picking up noise
around 4500 and 5500 rpms.
________________
Date: Mon, 1 Mar 1999 08:02:20 -0600 Update on my original comments: since my new engine is fully broken in,
my final setting on the J&S sensitivity is 1/4 turn from minimum. The
retard monitor will momentarily light up (about 1 to 2 seconds) sometimes
when initially accelerating. After the turbos are fully heated up, this
retards stops. Either the turbos are noisy when heating up to max HP, or maybe it's
caused by loose carbon hot spots that quickly burn off. There isn't any
pinging at these times even if the unit is switched off. Another J&S user also once
mentioned this same oddity.
_________________
Date: Mon, 15 Mar 1999 17:04:56 -0600 I set mine by adjusting the sensitivity to just barely retard at normal
boost (10PSI) when the turbos were not fully heated. You will notice that
when first getting on the boost the unit will retard for a couple of
seconds but will stop after the turbos and engine are fully heated up.
Evidentially it is picking up the noise of the various turbo parts
creaking as they heat up. More sensitivity than this will cause the
unit to retard for every gear instead of the first one when boost
was fully engaged.
This is accomplished by starting with too much sensitivity and gradually
reducing it for the above mention affect.
_________________
Date: Wed, 13 Oct 1999 15:04:18 +0000 I just installed my J&S, and wanted to verify the final settings.
Sensitivity is dependant on mods, I guess, but I ended up setting it 1/4
turn from minimum (9'O'Clock position).
Are all the above settings about right?
_____________
Date: Wed, 13 Oct 1999 16:49:09 -0400 Make sure the actual sensor is in tight. I found mine to come lose
after a bit of driving.
Set the sensitivity to maximum and go for a drive.
Give it throttle and decrease sensitivity till you get one or two red lights
on the meter. I have mine set to 1-2 red lights when under throttle up to
redline.
When driving it is hard to tell if it is actually retarding the
timing. The best way to test is to turn on the car, and put the meter on the
dash where you can see it from the outside of the car. From the throttle
cable give the car some gas and tap on the sensor with a wrench; you can
actually hear the RPMs decrease as the timing is retarded. This way you know
if it is actually working.
There really isnt a need to hook up the Yellow
wire to the TPS.
______________
Date: Wed, 13 Oct 1999 20:51:50 +0000 I called Brian of M2 and je told me they do not use the yellow wire.
They say there is no need to hook it up to the TPS.
The instructions for the RX-7 install specifically say not to do that.
In fact they say that it is a common mistake to set it on maximum
sensitivity. Start at mid point and work down.
I also had a very
interesting conversation with Ari of RP-Online, and he mentioned that he
found that the stock knock sensor sometimes interfers too much, he found
in those specific cases that cutting the single wire going to the stock
knock sensor and using a 400-600 ohm resistor a ground would remedy that
problem. You have to remember that the ECU recieves a signal from the
stock knock sensor, not the J&S. The J&S only goes between the ECU and
the igniter, ie it's on the output side.
______________
Date: Wed, 13 Oct 1999 20:52:57 -0500 Actually, it's 400k-600k ohm resistor. There's a big difference!!!!
______________
Date: Wed, 13 Sep 2000 08:51:42 -0500 Try connecting the arming wire to the TPS or MAP sensor and see if the
problem goes away. Without an active arming wire, mine will retard
around 2000rpms even if slowing revving. My sensitivity is now set at
about the 10 o'clock position.
Knock sensor install on Miata.
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[Copyright Notice]
From: "David Lane"
From: "David H. Lane"
From: "Westbrook, Chuck"
From: "Westbrook, Chuck"
From: "Westbrook, Chuck"
From: Wael El-Dasher (wael.el-dasher@efini.net)
switches 1,3,4 up
switch 2 down
From: "Jason Baughman" (jbaughman@columbus.rr.com)
From: Wael El-Dasher (wael.el-dasher@efini.net)
> Also, during the test drive, I cranked the sensitivity to maximum and got no
> indication of retard under cruising conditions. When I went full throttle,
> I did get some retard, as much as 8 degrees on one chamber. I felt no
> butt-dyno loss in power. Is this common?
From: Steven Kan (skan@ticnet.com)
From: "Westbrook, Chuck E." (CWestbrook@tmh.tmc.edu)
>I have a question about my newly installed knock sensor. Last Sunday I was
> messing around with it prior to an autox and left it with the rev limiter at the
> minimum setting... (snip) I know it was reducing power. I understand the rev limiter
>doesn't work as well because it only affects the leading ignition, but now I have doubts
> as to how I have it set up. I'm surprised to have reached the stock rev limiter
> in this condition.
> The main reason I question my installation is that I can only get it to read
> "retard" when it's set to maximum sensitivity and I rapidly floor it from
> highway speeds when I've already gotten the EGT up to 1400F or so from closed
> loop operation. I have the car setup to be as far from detonation as possible
> (duh :) but I'm surprised to be getting none when I'm really getting on it.
>
> I suppose some description of the car is appropriate.
> '87 TII with 8K on rebuilt motor and rebuilt Series 5 turbo with ported
> wastegate (plumbed to the manifold to allow 8 psi boost), UPRD reprogrammed N332
> ECU, open exhaust and TID.
