Header bang and false knock
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From: Dyess AFB, TX
Header bang and false knock My y-pipe bangs like an Asian hooker at WOT. I haven't Auto Tapped yet but I'm wondering how bad it has to bang before you get false knock. I dynoed yesterday and put down 328/345 with a steady a:f ratio of 13.2-13.5 from 3600rpm to 6200rpm. Just wondering if it's a possibilty my PCM is registering false knock. Mods in sig, '98 A4.
Re: Header bang and false knock Just hook up a scan tool to see if you are generated KR.
If you don't have a scan tool, another tell-tale of KR on the dyno is a very jagged torque / HP curve, or a sudden dip of ~5 HP in power.
Asian hooker <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />
and now the boring stuff.....
False knock from your exhaust is either there or it isn't..... Your exhaust has to actually resonate against the frame at such a frequency that the PCM can percieve it as false knock. The PCM knows when each cylinder fires, so it has to recieve a "thump" at such a time and at such a frequency so as to percieve it as knock.
With that in mind, it isn't how loud your headers have to hit the floor before they cause KR, but rather whether it is going to do it or not. If you are one of those unlucky souls where the exhaust is rattling against your car at just the right frequency, then it hardly needs to touch the car at all to cause KR.
Good Luck,
Kevin
If you don't have a scan tool, another tell-tale of KR on the dyno is a very jagged torque / HP curve, or a sudden dip of ~5 HP in power.
Asian hooker <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />
and now the boring stuff.....
False knock from your exhaust is either there or it isn't..... Your exhaust has to actually resonate against the frame at such a frequency that the PCM can percieve it as false knock. The PCM knows when each cylinder fires, so it has to recieve a "thump" at such a time and at such a frequency so as to percieve it as knock.
With that in mind, it isn't how loud your headers have to hit the floor before they cause KR, but rather whether it is going to do it or not. If you are one of those unlucky souls where the exhaust is rattling against your car at just the right frequency, then it hardly needs to touch the car at all to cause KR.
Good Luck,
Kevin
