Miata Mailing List: February 1996, Message #204
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   From: Dlralt@aol.com
Subject: Re: 18 deg timing - results and a question
   Date: Sun, 4 Feb 1996 11:39:12 -0500

In a message dated 96-02-04 02:32:40 EST, you write:

>> Nope, no knock sensor, unless you add one of J&S's units.  No advantage to
>> higher octane if you're not pinging on regular.  Advancing the timing on a
>> car with a knock sensor could still make it perform better, 'cause you
>would
>> be getting your advance in earlier where it's not likely to ping. FWIW
>> 
>> bill
>> Dealer Alternative
>> 1-800-FLY-MX5S
>> ps  I should qualify--I haven't seen a '96  or a '96 book yet, but I doubt
>> that they have added a sensor. The engines aren't generally ping prone.
>
>Bill,
>
>Do you have any experience with the J&S units? Where can I find out more
>about these things? I have never seen anything about them before this week.
>
>-dg
The J&S consists of a box that wires into the cam sensor leads, with one wire
going to the air flow meter. The knock sensor itself mounts in a special bolt
on the rs motor mount. Basically, the knock sensor is a sensitive microphone,
filtered to be sensitive to the characteristic sounds of pinging or
detonation. When it detects pinging, the box retards the timing until the
pinging is gone.
We used these units years ago, when they were not quite as well developed as
they appear to be now. We had some problems with hard cold starting and RFI
interference (the pump for the water injection would give off some RFI from
its brushes and cause the ignition to skip a beat) (Before you ask, this was
on early turbo systems with no intercooler) on the first units.  John from
J&S just sent me a new one to see if the bugs had been worked out---I haven't
thoroughly tested it  yet.  I know Stepen Goode (on the list) has had good
results with one. I will post once I am happy with it.

bill
Dealer Alternative
1-800-FLY-MX5S