Audible Knock Warning System

[hemi8]

I have a Caspers audible knock warning system and I had to disconnect it because of false knock under cruise conditions. The false knock has always been there and just shows up randomly when cruising down the highway under very light throttle. This creates a problem with the ear-piercing audible knock sensor. My thought is to wire in to a Hobbs switch so it only functions when under boost. Has anyone tried this? I have not been able to pinpoint the false knock but my guess is valvetrain noise, never knocks under boost.
Mike

 

[salvageV6]

It would be easy to implement.

If it only happens under light throttle, the false knock, I guess it would be a viable solution.

Use a relay to interrupt the yellow KR line into the audible gauge I wouldn't interrupt the power to it you want it powered up ready to work under boost.

And if it ever beeps when you aren't under the trigger boost you know it's the sensor or wiring.

 

[KEVINS]

I have a Caspers audible knock warning system and I had to disconnect it because of false knock under cruise conditions. The false knock has always been there and just shows up randomly when cruising down the highway under very light throttle. This creates a problem with the ear-piercing audible knock sensor. My thought is to wire in to a Hobbs switch so it only functions when under boost. Has anyone tried this? I have not been able to pinpoint the false knock but my guess is valvetrain noise, never knocks under boost.
Mike

I like that idea. Everytime I start my car I get a high pitched scream that drives me crazy.

KS

 

[salvageV6]

You could also implement a 10 second relay delay trigger, delaying powering the unit up via the IGN or RUN portion of the ignition key switch at startup.

 

[quadzila]

great idea, i have been battling the annoyance of that high piercing sensor at start up and when i stab the throttle 50 % of the time. and the times it would go off i checked my data logs and i would see a spike where it pulled timing of 4* and then immediately go away , so i believe and understand this false knock and see no knock when in 3rd and roll into full boost. I do like knowing that sensor works, but what i did was taped up the hole in the sensor and now its quiet but still very audible.

 

[salvageV6]

Try using the IGN 3 source which is powered by the ST/BLT fuse.

It's only live in the RUN position of the Ignition switch so it won't be live during cranking.

IGN 1 ports are live during cranking or Start, Ignition key switch position.

 

[Razor]

Those guys that have a FAST XFI can use the Aux2 output and wire it through a relay to interrupt power. The AUX2 switches to ground when parameters active. You set TPS and Boost level. Once those are met, the output grounds.

Use a simple 30A relay.

Terminal 85 to power, 86 to Aux2 output, 87 to +12 ignition(or pink on harness), 30 to audible pink +12 feed.

 

[salvageV6]

I thought all those FAST guys all had noisy lifters and cams. and simply disconnected the KR sensor.

 

[Razor]

I thought all those FAST guys all had noisy lifters and cams. and simply disconnected the KR sensor.

Be amazed how many customers I talk to that have FAST systems on very basic builds. Use to be 10 years ago it would only be on a solid roller, race car, maximum effort setup.. now days I see more and more on simple cars.

People are buying them.. doesnt mean it cant be done with a chip.. but sometimes a FAST in the hands of the right person is 100x better than a chip in the hands of the wrong person.

 

[quadzila]

great idea, i have been battling the annoyance of that high piercing sensor at start up and when i stab the throttle 50 % of the time. and the times it would go off i checked my data logs and i would see a spike where it pulled timing of 4* and then immediately go away , so i believe and understand this false knock and see no knock when in 3rd and roll into full boost. I do like knowing that sensor works, but what i did was taped up the hole in the sensor and now its quiet but still very audible.

Here is an update regarding my audible knock sensor going off. It appears that it was a little lean at 3750 rpm's at 140 kpa (where i got the knock spike at) so i dropped the a/f ratio from 12.9 to 12.4 in the associated cell and that seemed to cure it.
I logged 6 WOT blasts and no knock spike and no sensor going off. Thanks Razor for telling me what to look for.

 

[KEVINS]

Here is an update regarding my audible knock sensor going off. It appears that it was a little lean at 3750 rpm's at 140 kpa (where i got the knock spike at) so i dropped the a/f ratio from 12.9 to 12.4 in the associated cell and that seemed to cure it.
I logged 6 WOT blasts and no knock spike and no sensor going off. Thanks Razor for telling me what to look for.

Kewl Beans.. When I get to tuning again I'll have to try and figure out exactly what you just said and what you did to cure it..
What data logging system are you using? I'm using DirectScan but I haven't gotten into tuning the O2's throughout the entire run yet, only WOT.

KS

 

[Razor]

Kewl Beans.. When I get to tuning again I'll have to try and figure out exactly what you just said and what you did to cure it..
What data logging system are you using? I'm using DirectScan but I haven't gotten into tuning the O2's throughout the entire run yet, only WOT.

KS

He's using an XFI. So he can log actual airfuel through the recorder and figure out the problem by playing it back and making adjustments.

 

[KEVINS]

He's using an XFI. So he can log actual airfuel through the recorder and figure out the problem by playing it back and making adjustments.

Well, that's no fair.. That's cheating...LOL.

ks

 

[norbs]

Well, that's no fair.. That's cheating...LOL.

ks

Lol, its not cheating, time to step up your combo maybe?

 

[KEVINS]

Lol, its not cheating, time to step up your combo maybe?

Yea, my car is in the process of some updates but nothing real serious. I actually just received the new Precision 5831 but I sent the housing off to be polished so I haven't installed it yet, new PTC 2800 stall, Alchy Injection, new 3" DP from G-body (this is taking FOREVER), Tuesday the car goes in for a 3-muffler setup, and I got my electric crankcase evacuation system working the other day.
I can't wait to start tuning it again..

KS