LED knock indicator? [Archive] - SaabCentral Forums

: LED knock indicator?

Johann F
10th May 2002, 08:41 AM
Reading Tweakers site he says (used to anyway as it's changed) that when knock is detected it connects pin 19 to ground. While I had my APC box out the other day I soldered a lead out wire to pin 19 and connected it to the oil warning light ( which lights up when grounded) - no flashing lights though!. Could he mean it outputs a + signal - has anyone done this?

10th May 2002, 11:46 AM
Pin 19 provides an earth for the warning light! I got an LED from maplins which I fitted in the centre consul, got a feed off the sunroof switch and then ran through a wire to pin 19.
Last week I changed things slightly by removing the APC cut-out from the brakelight switch (white wire) I cut this wire and insulated and used the terminal as my connection for pin 19. That way I could remove the soldered wire from the circuit board as I was not happy with it and the connection is now incorperated in the APC mutliplug!!!

18th August 2005, 11:13 AM
I did every step needed to connect the LED to pin 19 -no light! Constant +12 to the anode ,and cathode to pin 19 on APC main connector. No any resistors. And still no lite.
Going too far to think i'm not having knock ever, isn,t it?

18th August 2005, 11:40 AM
With the ignition on, try tapping the knock sensor with a fairly hefty plastic screwdriver handle and see if the LED blinks.

Johann, is the oil pressure lamp a normal LED then? The APC has a built in resistance to drop the +12v supply to what an LED needs (1.5v?) so a normal bulb won't show up.

18th August 2005, 04:47 PM
Johan seems to have last visited in mid-2004.

19th August 2005, 12:54 AM
I did think I hadn't seen him about for a while. Teach me for not reading the date AGAIN! ;oops:

22nd August 2005, 04:43 AM
Johann F (John Griffin) re-registered as "trackside".

Best Car Insurance (http://autoinsurances.wearecares.net) | Auto Protection Today (autoprotection.wearecares.net) | FREE Trade-In Quote (trade-in.wearecares.net)

22nd August 2005, 08:08 PM
Is it possible to add a independant knock sensor? and what would be the best location for it? does anybody know how the knock sensor works as in what frequencie it detects for heavy knock? if this is the case i could add a contact microphone and see the knock levels on a laptop graph as a peak?

sound logical anybody?

This way you can see in a graph how the engine vibrates at different RPMs and different engine loads and fuels and so on, could be useful to detect problem in advance;)

alan forsyth
23rd August 2005, 05:12 PM
sha , as far as i'm aware its ilegal to run on public roads with computerised tuning components (mark from the garage was having a few issues with this and his skyline)ie a computer screen displaying readouts :roll:

24th August 2005, 12:49 AM
Are you sure Alan?

is it because the screen is a distraction or because its a power modification?

What if it's part of the cars built in system? Do you think this is illegal maybe?

alan forsyth
25th August 2005, 04:06 PM
mark had mentioned it in the first issue of fast and modified ,the next time i see him i'll ask about it

30th January 2006, 10:38 AM
Sorry to bring up this old thread, but I just have one small question.

I have a T16, the previous owner removed the APC, and I am looking for a knock sensor. And i happen to have a an old T8 wich I only use for parts, what I am wondering about is how much of the APC has to be connected in order for the knock sensor to work. Obviously the power and the sensor, but do I have to hook up the boost and rev stuff as well?

30th January 2006, 03:35 PM
900aero.com -> Tech -> APC Simulation -> check it out.
This is work done by Anders Olsson, translated and hosted by Widde.

"RPM signal is very important to make the APC not register regular engine noise as knock at high RPM"

It would be worth putting the whole system back in imho. I know everyone harps on about it, but it's a great system! How much would you pay for an aftermarket system that can do what APC does? It's fully closed loop and has that nightmare-fighting knock protection built in.
Is the wiring still there? Have they cut off the connector? If it's all gone you can bet they stole it for their volvo :roll: