NZ_87_TURBO

I’ve read that the knock sensor is ignored after 4000rpm. The system goes
Knock sensor --> Knock control box --> ECU
Where does the signal get ignored? The knock box or does the ECU have a system build into ignore it?
From what I can tell the Knock control box has no input feed from the ECU apart from +12v.

Knock sensor in
+12v in

Ground out
ECU signal out

Unless the knock control box has some kind of filter built in that can interpret the extra noise from the motor as rpm increases and then stops sending a signal as it gets to a certain point, then im guessing it must be the ECU.

my enquiry come from the stock ignition map and the USE of a FCD which tells the ECU that the MAP sensor is only seeing 8psi, until this point as PSI has increase from 0 the stock ignition has been retarding the timing 1degree per 1 PSI, so after 8psi the stock ignition is fixed and doesn’t retard any more.

The knock system has the ability to retard the timing up to 5 degrees (can someone second that). If we could log the Knock signal going to the ECU and map it against RPM and BOOST and TIMING curve, we could see what influence the knock control box has on the ECU.

If we can work out the voltage the ECU see's from the knock box and relate it to the timing adjustment, then maybe we could make some sort of controller that uses a reference from a MAP sensor (obviously not the signal to the ECU from the stock item but maybe intercept it before the FCD ) and log a map so that at every PSI above 8 there could be a signal sent to the ECU from the knock control to retard the timing by 1 deg

Icemark

The knock box sends a conventional signal to the ECU and the ECU then controls the timing based off of the running particulars at that moment.

It is my understanding (and mind you this is only from looking at the schematics and not the code) that the knock box simply provides a ground signal when it "sees" a loud enough ping. Simply a switch, based off of a microphone. The reason for the lack of a control at WOT or above 4000 rpm is simply because the design is so cheap there is not the sensitivity to discern above 4000 rpm.

Perhaps there is more too it, but I doubt it.

So, the ECU is sending out a 5 volt signal, that when it sees ground on the knock wire, the timing retards based off running perimeters at the time.

NZ_87_TURBO

Thanks Icemark.

That is some really helpful infomation and allows me to put this case to rest. I though i was onto a winner there and it all depended on what type of signal the ECU received.

From what ive read there is a 3-5V signal going to the ECU but you state it is coming from the ECU and is grounded by the knock control. so that means that it only acts once the ECU actually see's a 5V signal thru its wire to the Knock control.

wouldnt it have been nice tho.