i have read a post about people getting a fake knock because the downpipe is hitting there crossmember bar......

mine is touching and i get all sorts of random....

just wondering if anybody else has had this issue???

 

that's not "fake knock" at all, it's just a vibration

and yes, lots of others have this issue when running a 3" downpipe. solution is to put a washer or two between the crossmember and the chassis

 

so you saying the vibration that it is causing is causing real knock? not just the sensor picking up the vibration and setting it off?

thanx for the response!

 

Yes, it is "false knock", AKA "phantom knock", if the sensor is picking up those vibrations and thinking it's engine knock.

No it isn't causing real knock. The vibration can be picked up by the knock sensor and it can falsely think it's real engine knock.

 

No, the vibration is not causing knock.

 

Interesting! i will be fixing this ASAP and see if it stops. what are other area that could trigger a false knock?

thanx guys!

 

Oh, I see what you're saying. Why not just get someone to pull logs on the car? Chances are it's real knock and not false knock...

 

You would just log what the knock sensor is picking up so in that case you could still be logging the false knock. Solid motor mounts can also contribute or cause it.

 

I can pull my logs. Im going remove the bar then do some runs and see what it is. It only happens sometimes which leads me to believe it maybe false knock. How can I tell if its false opposed to real knock?

 

How can I tell false from real knock in the evo scan logger?

 

you can't. to the scanner, knock is knock even if it's false

What RPM is it knocking at? What gear? Is it CEL-indicated from a tune that you're seeing this?

 

I'm on tephra v7 so I get cel blink indicting knock

It happens on all gears sometimes

Sometimes at low boost (8-12) 3000ish rpm

Sometimes it won't blink till 6000 at 25psi.

In all gears but only sometime it's not consistent that it blinks

 

well i removed the bar completely went and did some pulls on the way to get washers...... still got knock. any other places where false knock get produced? im going to get re-tuned Sunday and i just want everything solid as i can before i show up

 

I get the same thing but its from my downpipe hitting my T-case. I think the last owner put an 8 downpipe on my 9 with ACD and there is no clearance. Let us know if the tune fixes it.

 

Will definitely post after the tune. Hopefully it will a positive response!