False knock?

[Stretch2126]

Does anyone here have false knock issues and how they fixed them? My car will sporadically pull 2.9-3.6 degrees KR sometimes but usually goes down as boost and rpm rises. Sometimes in traffic a funny shift will also make it pull timing anytime you touch the throttle. I don’t think it is truly knocking since I’ve run true octane booster, 100 octane, and now have a 50/50 water meth kit. Also since it’s inconsistent and doesn’t change with heat or fuel quality.
I also have the upgraded water pump for the intercooler. IAT rarely sees 120 degrees or more with the meth injection.

 

[Ross]

The knock sensor is like a microphone for the block. I've heard they can be sensitive. I have taken mine off, in order to heat the block and remove the oil plug, then remounted it. Maybe take yours off, clean it / sand it, and retorque it back on?

 

[Gtstorey]

It’s called tip in knock retard and there isn’t anything that you can do about it that I know of. The E69 ECM just doesn’t have enough tables unlocked to stop it. At least with HPTuner. I don’t know what might be available in other tuning platforms.

 

[Stretch2126]

I might try to retorque them. I thought it was tip in but it picks random days I feel like. One night it stayed at 0 all night and could feel different.

 

[Rttoys]

”back in the day”, when knock sensors screwed into the block, we would put a lot of Teflon tape on them to muffle the signal. Things were so basic back when TBI was the new high tech stuff.

 

[Gtstorey]

It not sensing knock. There is an algorithm built in that anticipates knock under certain conditions.

 

[Scott #321]

Have you already clocked your knock sensors to 9 oclock? don.t have the link currently but if helps false knock on the LNF.

 

[Stretch2126]

Have you already clocked your knock sensors to 9 oclock? don.t have the link currently but if helps false knock on the LNF.

I have them both at 3 but I need to try to move the left side to 9. These are also brand new sensors.

 

[Gtstorey]

It not sensing knock. There is an algorithm built in that anticipates knock under certain conditions.

 

[Stretch2126]

Rearranged the left sensor so they are 9 and 3. No real difference in low boost but now it will sustain 2-3 degrees and sometimes slowly fall down. Even with meth injection I don’t know why it would still sense knock at full throttle with added fuel/cooling. Not sure if I want to go into HPtuners and dial back the sensitivity.

 

[Gtstorey]

Why are you so sure that it is actually knocking? Tip-in or burst knock is the ECM anticipating the chance of knock.
If you don’t believe me, add race gas or real octane boost and see if the knock still shows up.

 

[Gtstorey]

And there is no way to “dial back the sensitivity” of the knock sensors on the LNF. You can zero out the knock retard for burst and normal knock retard.

I should say the above is for HP Tuner. I don’t know what is available with other software.

 

[Stretch2126]

I’ve done that. I run meth injection and I have had 100 octane in it before. I don’t think it’s real knock but I don’t like how now it hangs in and doesn’t relieve as fast. I believe you on the tip in, but now with the new sensors it seems like it is not recovering and going back to 0.

 

[Desert Sasqwatch]

Do you still have your old sensors? If so, install them and see if any difference. New sensors may be more sensitive than older 'worn' sensors. Weirder things have happened.

 

[Desert Sasqwatch]

As @Rttoys stated, maybe a dampening mechanism is needed. A Teflon washer that fits the width of the knock sensor face against the block? Or maybe fiber washer? Try different things to reduce the 'sound' the sensors are detecting. If this doesn't work then it has to be the tip-in detection as @Gtstorey has stated.

 

[Gtstorey]

You can probably zero out just the tip in retard and see if it goes away.

if you can find a real good tuning shop that uses the microphone type knock sensor, they can determine if you are getting knock. If it isn’t, zero out the normal knock retard.

 

[Gtstorey]

And the sensors can also pick up other noises so make sure you don’t have any loose exhaust or similar that can cause an issue. I’ve heard clutches can also cause it, but I don’t remember any details about what to look for there.
I don’t remember what mods you have, but if this didn’t reduce going from 93 octane to 100, I would probably just zero out, or at least minimize the allowable retard.

 

[Stretch2126]

I may try the old sensors. I do have an aftermarket clutch and flywheel so it could be picking up chatter. I’ll probably retorque everything I can find in the back to see if it cuts down on noise. A recent autocross may have rattled something.

 

[Stretch2126]

After recent tuning I discovered it was not false. With the help of a friend I added a little more fuel to the main fuel command at 100% throttle and pulled a degree out in certain air/load parameters and it likes it much better. No waiting for recovery or losing 3 degrees all the time.