I really have no idea... otherwise I wouldn't be asking this!

I get the idea from some people that on TII's, there is knock control box, in the passenger side kick panel, that controls the timing retard when sensing knock.
I always thought the timing retard/knock sensing was just controlled by the ECU... if there is a seperate unit, can it be made to work with an N/A ECU? (My turbocharged N/A)

Now.. is the factory knock sensor any good? I'm assuming maybe it doesn't work too well since TII's still get detonation, and there are aftermarket knock computers for the RX-7...Does it even work at full throttle?

 

Don't think the S4 knock box would work with a 90 NA ECU. On the S5 T2 the knock box is built into the 13BT ECU. It works quite well.

The S4 knock computer/box sends a signal to the ECU to retard the timing.

But S4 or S5, the ECU can only retard timing so much, if you have exceeded the design specs, you can still have knock. I think maximum retard is about 7 degrees at up to 4000 RPM.

There are also aftermarket knock sensors, but last I checked they all ran around $800-$1200 for the better ones that would sense a Rotary's ping. Again the problem of retarding timing enough can rear its head though.

 

Since the NA's don't have knock sensors, the NA ECU probably doesn't have an input for a knock control box.

 

Man.. I wish I had access to a TII sometimes.. so I wouldn't have to ask these questions!

OK. I thought maybe the knock control box functioned as an independant timing retard, intercepting the signal between the crank angle sensor and ECU or something... like a piggy back.
If it sends a signal to the ECU to interpret and corespond to, (instead of retarding timing itself) well, then it's doubtfull the NA one would work at all with it.

 

Not sure about Rx7s, but my Turbo dodge, has a small unit that is in the block and picks up sounds and thus retards the timing, when it hears pings and such..

How would a knock sensor work without being able to hear?

 

Well, if you have one to play with...

On the T2 the knock sensor feed is pin R on the ECU, but on the NA, the power steering switch is on Pin R.

The 338 ECU on the verts, runs a NA engine or a T2 engine, so... the responding function of Pin R must be the same on T2s as well as NA's. In addition to confirm that the ECU, ECM (engine Signal monitor special service tool) is the same for both the S4 13B and 13BT.

What ever the Power Steering switch does, (it switches ground, apparently on power steering pump operation, which would indicate operation at turning and below 45 MPH), must also adjust the timing while turning and below 45 MPH on a NA.

So in theory you could wire in the S4 knock sensor/computer with a relay coming off of the power steering switch to activate the knock computer at under 45 MPH.

But that is on a S4 car... don't know how you would use one on a S5 ECU.