Request for test to see if long tube headers impact ghost knock

**Redfox0099** · 04-29-2008, 02:34 PM

So I have been thinking about this for a while and it not only deals with my car but really any one that puts larger springs in the valve train or long tube headers.

Does adding long tube headers effect ghost knock? Do the longer chambers of the headers carry the sound differently than shorties? Is there a way to combat this? I have stood under my car on a lift and listed to the sounds travel down the headers...it is like they are being amplified.

Any thoughts on testing this?

**Hemi31** · 04-29-2008, 04:09 PM

I doubt it........Alot of us have LT's and no knock.

**Redfox0099** · 04-29-2008, 04:11 PM

I can sit and hit my headers with a wrench and register KR on my Diabo while datalogging, I just thought it was something to look at.

**FlyByU** · 04-29-2008, 05:38 PM

Odds are if you stop hitting your headers with a wrench, the KR will not occur

**MattRobertson** · 04-29-2008, 06:59 PM

Originally Posted by FlyByU

Odds are if you stop hitting your headers with a wrench, the KR will not occur

I wuz just gonna say that :D

**Cam** · 04-29-2008, 07:03 PM

Originally Posted by FlyByU

Odds are if you stop hitting your headers with a wrench, the KR will not occur

OMG LMAO!.

**Hemi31** · 04-29-2008, 07:20 PM

Originally Posted by FlyByU

Odds are if you stop hitting your headers with a wrench, the KR will not occur

Hey Doc......It hurts when I do this......lol

**MikeEast** · 04-29-2008, 07:21 PM

Y'all are cracking me up.. I was thinking the same thing myself.

BUT - on a serious note, what if, all of sudden like (well, over a weekend) my valve springs are now the SRT8 exhaust ones and I now have the fabled 'Hemi Tick' that I never did have before - could that have an effect on knock sensors?

I haven't looked to see yet, and performance sure hasn't suffered at all, but he might have a point there...

Mike

**CoolVanilla** · 04-29-2008, 07:40 PM

Ohhhkay at the risk of getting all serious here...

Nate, try taking that same wrench and tap on the block with the same force. I'm willing to bet you get the same result.

That doesn't answer your question but it does prove a point; knock sensors are there to read knock, no matter the source. A wrench is an anomaly, adding headers (or springs or...) is not. A wrench means something has gone way wrong, and you WANT the PCM to try and save your motor... aka you want the wrench to be seen as knock.

So what about just normal operation (no wrench)? A good tuner ought to be able to tune your motor as a "system"; a combination of parts. So when on the dyno and being tuned, if you're getting knock from the headers, your tuner will see that and desensitize them at that given condition just enough to account for the mods.

Knock sensors, contrary to popular belief, are a really good thing. If yer not seeing knock, you're motor aint tuned to its fullest. In my experience, you want to tune right to the edge of where you'll see knock, and then let the knock sensors do their job when external conditions push your system over that edge. If your tuner has his ear on the motor, physically hears no knock but yet sees the PCM sense knock, he/she ought to figure out the knock sensors are too sensitive. They can desensitize them a touch, and try again and again and again, repeating untill the false knock is not seen anymore and/or real knock actually shows up.

**GasGunR** · 04-29-2008, 08:21 PM

CV, you just used Knock and up in the same sentence

Nathan, be careful!

**Redfox0099** · 04-29-2008, 08:27 PM

Oh I know mine is ghost knock.....we put 100+ octane in the car and the knock was the same...and ran a 11.66.

I wasn't trying to make this about my car, just curious on sound travel....forget I mentioned it.

**GasGunR** · 04-29-2008, 08:36 PM

Nathan it is / was a valid question IMO, but unless the headers are hitting the car somewhere I doubt there is a problem with them. The sensors are tuned to a specific frequency, unlikely that combustion sounds are in their range, but who knows until you test for it.

Now, how would they go about developing the test for this? And if their is a way alraedy known to adjust the sensitivity as CV has already mentioned, is it worth the time to develop and test.

Its Matt and CV's show, but I think they are willing to test anything if there is something worthwhile to be learned by it and it falls within the cost time constraints of the MOFO.