JLeake

Just wondering if anyone had wired a light to indicate when the DME is sensing engine knock and therefore pulling back the timing. I think that would be a good tuning aid as I imagine the sensor is more sensitive to knock than my ears. I've got the manuals and intend to look into the idea, but thought I'd check first and see if someone had already figured it out.

Danno

That's what the KLR does. It listens for knock on the sensor and has the DME dial back timing. MSD makes an aftermarket knock-sensor with a display.

Billy W

jleake Sorry that I did not make it out to the auto-x the other weekend. What part of charlotte are you in?

adrial

Danno weren't you guys talking about hooking up a LED to something in the KLR to see when the knock sensor was seeing knockin?

I'm interested in this now with the increased boost on the way

Jim Nowak

Summit racing sells the knock detector light.

Jim Nowak

JLeake

Said DME, meant KLR. I was just wondering if anyone had wired a light or LED to the KLR...what the signal was like (were any logic gates required...is the signal present for an instant when knock is detected, or is the duration long enough to light an LED)? I guess I'll look into it myself whenever I get the time...just wondering if someone else had tried it. If and when I figure it out I'll share

Toolmaster

All -

Well, knowing full well that a post up above has stated that there are places that sell these, you'd sorta need an interesting circuit to get it to work.

The knock sensor is nothing more than a microphone, set to detect frequencies that are "knockish." The problem though is that just like if you were talking in a microphone, you'd have a silence between words, or knocks.

So, you'd first need an op-amp circuit, to raise the voltage coming out of the sensor, which would have to feed logic to decide if it was actually a bad knock (like 6+ knocks per second) or actually noise of some other kind. This circuit would then have to feed a latch of some sort, so that when triggered we could drive a light.

You'd also have to build some sort of reset function, somthing like if knock isn't heard for 10 seconds after the light goes on the light can then be turned off.

It's unfortunately not a very simple circuit...

But it could be done.

HTH!

951Tom

In the DME/KLR Test Plan, it labels KLR plug connection #15 as: knocking yes/no (output)

I've wondered if this connection gets a signal when knocking is detected? If I remember, I'll post the scanned page tonight.

Toolmaster

tom -

I'll save you the trouble...



That line signals the DME when knocking is happening. Meaning that you 'could' tap that line for your light, but chances are any major tap on that line will reduce it's function for the DME. You'd have to tap it with a high resistor, and amplify...

HTH!

slevy951

If that line is "yes/no", doesn't that suggest it may be a "logical" yes/no. And you could tap it and feed it into a led driver to light an LED???

Danno

yeah sure sounds like a fixed digital signal. However, you'd want a high-impedance tap on it. Then amplify to drive an LED. Also would probably need a timer circuit to keep the LED lit for a pre-determined interval so that you can see it; like around 0.10 sec or so.

slevy951

So, any electronic guru's listening in here? I have a buddy who's into the whole circuit thing. I'll see what he says.......

keith

Yes, somebody with brains make us some knock lights! (a little LED to mount in instrument cluster...?)

Perry 951

If someone has the manuals handy at work, and can get the output specs, I can ask some of my elecrical engineers here (who design radio transmitters) to figure out a setup. Bet they could have it in a matter of minutes if they know the output.

951Tom

I have the electrical diagram here with me. It doesn't show any wires for pin #15 at the klr. Just #11 is KS ground, #13 is the signal from the KS, and #12 is the grounding for the shielding. We need to put a voltmeter on that terminal, induce knock, and see what it does. Anyone up for trying it?