J&S Knock Sensor

[8/3/2000] Reviewed by Mike Powers - m5powers@aol.com

Applicable to '90 - '97 '99 +

Early style J&S Knock Sensor with dual monitor

I bought mine used to install with a Sebring supercharger on my 1991 1.6L Miata. I installed the control unit under the passenger floor pan, directly wiring it to the engine computer wiring harness. These connections were both crimped and soldered. I did not use the "quickie" style pinch-on connectors that come with the kit.

Installation (combined with the Miata.net instructions) was straightforward and took about 2 hours. The Dual Monitor shows both an air/fuel ratio and the amount of ignition retard being applied by the unit.

The unit worked great the first time and did require tuning. I just used the indication on the dual monitor to watch for knock. Tuning consisted of several third gear acceleration runs. It was possible to completely eliminate any audible knocking.

I have mine set just a tad on the conservative side. It usually takes some timing out at lower rpms (typically 4 to 6 degrees up to 3000 rpm) and then leaves the top end alone.





Under 30 minutes to remove completely

Reviewed by: John Calvit - jcalvit@psrw.com

The J&S is an ignition retard unit. It has a microphone that listens for knocking, and then moves the timing back until the knock goes away. This let you dial up the ignition timing (for more power), without melting your engine.

Last summer I installed a Sebring on my blue '92. The power was gratifying, but the bottom end suffered a little and with a timing of 8 degree past TDC it still knocked. I bought a J&S Knocksensor through Performance Buyer's Club. PBC did a first rate job installing the unit and the optional monitor, but I chose a poor position for the monitor. It's a matchbox-sized thing with a bunch of lights on it, and I had it placed right next to the radio -- and completely obscured by the steering wheel. I have to lean over to look at it. Anyway, after installing the J&S, Brandon at PBC bumped the car's timing up. The pokeyness at the bottom end is gone, and when I mash the petal, there's no more knocking at 5,000+. The difference in power isn't night and day, but it is noticeable. The advanced timing also seems to have helped my mileage a little (though it's hard to tell as I have to take every opportunity to spin up the supercharger, which tends to have the opposite effect on mileage).

The unit is just what the car needed. I feel far more secure when cracking it up. I also bought the Monitor II, which not only displays the ignition retard, but also the fuel/oxygen mixture. Though I like knowing when the J&S is working, the fuel/oxygen bounces around so much that for me it's more of a pretty light show than a useful indicator of engine health. But it sure looks neat. All in all, I wish I had bought the product early in spring instead of late in summer.
Over 30 minutes to remove completely

Back to Product Reviews 15 December, 2001