More false knock

[Jeff_oddo]

The knock sensors are very sensitive on these cars and any slight bit of NVH could register as false knock.

Sponsored

 

[205.0]

The knock sensors are very sensitive on these cars and any slight bit of NVH could register as false knock.

I

I just adjusted all the piping on the cold side. It seems that every time I do that, the knock goes away for a couple of pulls. Nothing else I adjust or tighten on the car has the same effect. I have the regular worm clamps right now that come with the car, and every time I go to adjust these pipes, they can be pushed into the coupler a good bit. Just ordered the T bolt clamps and hoping to tighten them far enough to keep them from moving.

 

[ALLKHEINZ]

again if you have identified it as false knock then its just that false knock....you can either chase the issue around for centuries or turn the knock sensors down....if your getting knock on good fuel then its false.....i wouldnt worry about anything else....ifs and buts dont mean anything, just put good quality pump gas in the car and have piece of mind....i had this issue with my car 2 seasons ago....couldnt get rid of the false knock, put 116 unleaded fuse in the car, same thing....turned knock sensitivity down and voila, all good, car ran like a champ, went 9.40 at 146 with a vortech JT trim on only the 3.48" pulley....i was at the track near every weekend never once did i have an issue....so i guess the choice comes down to live with the false knock and dont touch the sensitivity, or turn it down and call it a day....if its me and ive confirmed its "false" im turning it down 10 times out of 10.

 

[205.0]

again if you have identified it as false knock then its just that false knock....you can either chase the issue around for centuries or turn the knock sensors down....if your getting knock on good fuel then its false.....i wouldnt worry about anything else....ifs and buts dont mean anything, just put good quality pump gas in the car and have piece of mind....i had this issue with my car 2 seasons ago....couldnt get rid of the false knock, put 116 unleaded fuse in the car, same thing....turned knock sensitivity down and voila, all good, car ran like a champ, went 9.40 at 146 with a vortech JT trim on only the 3.48" pulley....i was at the track near every weekend never once did i have an issue....so i guess the choice comes down to live with the false knock and dont touch the sensitivity, or turn it down and call it a day....if its me and ive confirmed its "false" im turning it down 10 times out of 10.

I have the knock sensors turned down and a full tank of good 93 with octanium and it still sees 3* knock at 2800 rpm (not sure why its only there) and either 6* on the hit or after a shift. Switching to T bolts and going over the car for the 13th time since ive put the paxton on.

 

[Slamdcoop0428]

Cutting the shit ball and socket flange off my headers fixed my issue completely! Im back to 22 degrees of timing.

 

[Tommy V]

I have the knock sensors turned down and a full tank of good 93 with octanium and it still sees 3* knock at 2800 rpm (not sure why its only there) and either 6* on the hit or after a shift. Switching to T bolts and going over the car for the 13th time since ive put the paxton on.

Man if you the have the ks turmed down and and running 93 with octanium and still seeing 3 degrees of knock, u have to find the problem!!!!.Or be like me and take 2 cylinders out because of listining to all the experts here about false knock.From what u are sayinv it does not sound like false knock to me,it could be but with the fuel u have and ks turned down i doubt it.Ive seen alot of these cars have knock at tip in throttle that was not false.Supposedly my FALSE knock cost me a motor.

 

[markmurfie]

The knock sensors are sensitive for good reason, But they are also filtered for specific frequencies that differ by RPM. They can only pick up knock in a narrow window of crank degrees, only where knock happens. They use a reference window to get a baseline of background noises to filter out during that narrow window. There's even a factor based on airflow, basically it tells the ECU a general idea if knock at a certain RPM and airflow will have minimal energy or a higher energy so it can determine how aggressive it needs to be with spark retard. This is used along with how loud the knock is to determine intensity. Basically its more than just a sensitive microphone and steps are taken to reduce false positives as much as possible. Its always amazing when you see a log where the knock goes straight to its max and then slowly starts coming back down. Thats not false. The false knock hits the max and stays there.

I have solid aluminium diff mounts. It whines and makes a slight clunk every now and again, none of which is registered by my knock sensors.

 

[Jeff_oddo]

Lund emailed me back about my issue.

"Yes, any kind of NVH can cause issues. The knock sensors on these cars are super sensitive."
Jon Jr.

I still have a few things to look over on the car, but on E85 there shouldn't be any knock.

 

[venumous]

"You're on E85 which does not allow detonation easily and you're having intermittent knock at low load events. One pull it is fine and the next it's not. Intermittent, in my experience, is usually false. "

Jon Jr to me.

My knock started right after having Sai Li system installed. Of course this pushed me toward bad install - not likely, bad pump - less likely, clutch - stock so who knows at 800whp, new previously non existent NVH from install or completely coincidental timing.

After checking all exhaust, Headers back swapping back to smaller PC silicone inlet from Mak, removing catch can, and zip tie city being introduced to my engine bay, I had little to no change in knock, specifically on tip in. After all of this I noticed the new return line was pulling on all kinds of stuff with no slack and decided to try going to stock fuel system for multiple reasons including testing new tune against it. I first left the line connected in at the regulator and pulled it off the pump side for the swap. Still had similar knock events. Next I pulled the line off the regulator and took for a drive. Within 3 mins of moving I had a 9 degree knock event barely moving from a stop in 2nd gear with 10% throttle. After that, I have seen nothing more than 0.75 deg rarely and not on WOT in 100 miles. I believe that return line was pulling on the brake lines so much that something was torqued out of place and tapping on throttle application. I've rerun the line and am going to swap pumps out today and swap to e85 and retest but I'm fairly convinced it was NVH and not typical source so there is hope.

 

[205.0]

The knock sensors are sensitive for good reason, But they are also filtered for specific frequencies that differ by RPM. They can only pick up knock in a narrow window of crank degrees, only where knock happens. They use a reference window to get a baseline of background noises to filter out during that narrow window. There's even a factor based on airflow, basically it tells the ECU a general idea if knock at a certain RPM and airflow will have minimal energy or a higher energy so it can determine how aggressive it needs to be with spark retard. This is used along with how loud the knock is to determine intensity. Basically its more than just a sensitive microphone and steps are taken to reduce false positives as much as possible. Its always amazing when you see a log where the knock goes straight to its max and then slowly starts coming back down. Thats not false. The false knock hits the max and stays there.

I have solid aluminium diff mounts. It whines and makes a slight clunk every now and again, none of which is registered by my knock sensors.

My knock will either be -2*, then at the shift it will be 4* and slowly go down from there, or it will be the other way around. Tuned by lund and they said it's false, and I honestly don't see any part of my car hitting anything. One thing to note is that the driver side piping on the paxton is very loose, and these worm clamps are not going to get it any tighter than it already is.

 

[higdominator]

Those with Paxton's should check their oil drain hoses to make sure it is securely fastened at the end.

Otherwise, I had a +4 knock event on my 3-4 shift during a 2-4th pull. I looked it over and I have had zero knock no matter what pull I have done (3rd, 4th, 5th gear log pulls). I assumed it was false then realized I had advance trac on. I disabled it and was rewarded with just .75 knock that immediately disappeared (I assume it's driveline). I know AT can pull timing to keep a car in line and spring hard at 100mph seems like it would trigger that. Car runs like a beast now.

 

[205.0]

Those with Paxton's should check their oil drain hoses to make sure it is securely fastened at the end.

Otherwise, I had a +4 knock event on my 3-4 shift during a 2-4th pull. I looked it over and I have had zero knock no matter what pull I have done (3rd, 4th, 5th gear log pulls). I assumed it was false then realized I had advance trac on. I disabled it and was rewarded with just .75 knock that immediately disappeared (I assume it's driveline). I know AT can pull timing to keep a car in line and spring hard at 100mph seems like it would trigger that. Car runs like a beast now.

The oil drain is zip tied down in like 4 places, and all logs are done with advance trac off. What is strange to me is the way the knock comes back after I fix something. For example, we made support brackets to hold the pipes down extra tight, and I had 0 knock for 7 WOT data logs. After about a week of driving, I get on it again and its 8*, so I just took the brackets off. It's like it's something in the piping, but I really can't see anywhere it could be hitting.

 

[venumous]

Update: After swapping out my stock fuel pump for Sai Li and hooking back up I went from no knock with stock pump and BAP to 7 degrees with Sai Li and new tune. Swap stock pump back and back to old tune, zero issues. Take that for what you will. Pretty sure I have my answer. Will be going AED.

 

[Tommy V]

The knock sensors are sensitive for good reason, But they are also filtered for specific frequencies that differ by RPM. They can only pick up knock in a narrow window of crank degrees, only where knock happens. They use a reference window to get a baseline of background noises to filter out during that narrow window. There's even a factor based on airflow, basically it tells the ECU a general idea if knock at a certain RPM and airflow will have minimal energy or a higher energy so it can determine how aggressive it needs to be with spark retard. This is used along with how loud the knock is to determine intensity. Basically its more than just a sensitive microphone and steps are taken to reduce false positives as much as possible. Its always amazing when you see a log where the knock goes straight to its max and then slowly starts coming back down. Thats not false. The false knock hits the max and stays there.

I have solid aluminium diff mounts. It whines and makes a slight clunk every now and again, none of which is registered by my knock sensors.

Hey Mark do u know what parameter ford uses for max postive knock before it sets a cel off.I find it crazy that some of the knock that some of these guys are seeing and are not getting a cel.

 

[markmurfie]

Despite all the precautions and measures taken knock sensors are still not perfect and false knock can happen. Because of this there isn't a CEL for excessive detonation from sensor activity. They are just given a decent range and have a limit to their total authority over spark advance to just get the spark set to where it is definitely not the issue. In the 2015+ 10* from an already low borderline values is the stock limit. At best that would be no more than 9* total advance. At that low advance it is most likely false.

The CEL for knock sensors are set for voltage high, voltage low, or open. The voltage should remain constant for all detected frequencies. If voltage is not constant or the ecu receives an OL. Either the sensor is bad, Wires are cut, sensor is unplugged, or the ECU is bad.

Sponsored