Desensitizing Hellcat Knock Sensors

[jonx96]

Are most desensitizing knock sensors on these cars? I see a fair amount of STKR on take off with a 2.85 and e85 using stock timing down low. Ramping it in up top I get no STKR. I feel I should be able to add 5 to 7 deg down low without getting any STKR.
I'm thinking I'm going desensitize a little to a little bit in the ranges I am seeing the KR.

 

[ChargerChallenger]

I think someone around here is taking VACATION TIME😂😂😂😂😂😂

 

[jonx96]

I think someone around here is taking VACATION TIME😂😂😂😂😂😂

I'm back to work today. But I have over a week worth of thoughts built up in my head. I actually couldn't sleep last night going over a few things in my head. My mind really wonders. I have woke up at 2am and fixed issues I've been dealing with for days.
Every year in July I take a lot of time off because in August I lose it. I rarely take PTO and I get 19 days or something like that a year and can only carry so much over.

 

[fumanchu182]

In your logs are you seeing LTKR? If so do not desensitize the sensors, you may have a legitimate issue.

 

[jonx96]

In your logs are you seeing LTKR? If so do not desensitize the sensors, you may have a legitimate issue.

I have no long term.
I will say the only thing that worries me for future issues is this car in the spring with the originally tuner I had with Diablo he wrote me a 93 tune told me to go wot and the car pulled 14 deg. For that pull. Not good. What really worries me is when that happened to @Speedy! in his video his engine went boom. But that was in March and I have left that tuner and went e85.
It was Legitimate because octane booster took the knock out........ I should have sold the car after that but to late now I'm pretty invested with this one.

 

[fumanchu182]

I have been up and down this road. I have had knock because of bad gasoline (went from royal farms to BP only now). I have had knock because of running a Boost-A-Pump. I have had knock because I turned the car on. Now that I have good fuel (104) and use a dual pump setup I don't worry about the knock issues @Speedy! had anymore. It was what it was. If you have small blips of knock like the following image then I say desenzitise a little by little. Keep in mind that there might be other nefarious things going on... Such as banging gears with hard shifts that will resonate through the body. I also have solid motor mounts so all of the vibrations...

Boost-A-Pump Yeeted, scaring the living shit out of me, ran a 10.2 though...:


Dual Fuel Pumps = fuel pressure for days!

 

[jonx96]

I have been up and down this road. I have had knock because of bad gasoline (went from royal farms to BP only now). I have had knock because of running a Boost-A-Pump. I have had knock because I turned the car on. Now that I have good fuel (104) and use a dual pump setup I don't worry about the knock issues @Speedy! had anymore. It was what it was. If you have small blips of knock like the following image then I say desenzitise a little by little. Keep in mind that there might be other nefarious things going on... Such as banging gears with hard shifts that will resonate through the body. I also have solid motor mounts so all of the vibrations...

Boost-A-Pump Yeeted, scaring the living shit out of me, ran a 10.2 though...:
View attachment 49439

Dual Fuel Pumps = fuel pressure for days!
View attachment 49441

I'm not seeing anything that bad. Maybe what I am seeing isn't even bad enough for me to worry about.

 

[jonx96]

Hmm actually glad I just went back and looked at this. That log actually wasn't from a tune I touched at all and was from an e85 tune that I paid for that I reviewed. But looked at the fuel. It went a little lean for a quick second and when it richens back up it slowly goes back to no KR. STFT aren't bad there though which is odd.
Glad I made this thread to catch that. Still a good question to be asked about the sensors. I haven't been back to the track with the tune I've been working on. I have been updating injector data on the street. I'll have to head to the track and make a few runs and see if fuel stays where it is supposed to before I try anything else.
I have a hard time tuning for take off on the street because no traction.

 

[Speedy!]

Spinning the supercharger faster with smaller pullies sets off a resonance effect (noise) that the knock sensors pick up.

One of the best pieces of advice I received was to log the knock sensor volts in the charts area of HPTuners. Then look for commonalities at various timing settings. If a pattern emerged you could bet it was false knock. For example one trouble spot on my car was 4,000 rpm. I'd see 2V from the knock sensors right at 4,000 RPM whether I had 0 deg or 5 deg in the tune. Now I knew it was false. This helped me feel more comfortable about having to adjust the threshold. The knock sensors are a 0-5V sensor FYI.

I started with known good fuel in the car and set the knock window on mine to match that of a Redeye which has a 20% narrower knock window than the Hellcat. This means it looks for knock in a smaller range than a Hellcat which was a surprise to me when I first saw it.

Finally, when I thought I had it dialed, I had my buddy chase me in his car as I made some highway pulls looking for little puffs from the exhaust. My next video will actually show some of that as I was dialing in the E85, so this thread was timely LOL. We did find a surprise and I learned something but I'll save that for the video thread when I post it. Looking at the exhaust at WOT for puffs of smoke is a good indicator there is knock.

 

[jonx96]

Spinning the supercharger faster with smaller pullies sets off a resonance effect (noise) that the knock sensors pick up.

One of the best pieces of advice I received was to log the knock sensor volts in the charts area of HPTuners. Then look for commonalities at various timing settings. If a pattern emerged you could bet it was false knock. For example one trouble spot on my car was 4,000 rpm. I'd see 2V from the knock sensors right at 4,000 RPM whether I had 0 deg or 5 deg in the tune. Now I knew it was false. This helped me feel more comfortable about having to adjust the threshold. The knock sensors are a 0-5V sensor FYI.

I started with known good fuel in the car and set the knock window on mine to match that of a Redeye which has a 20% narrower knock window than the Hellcat. This means it looks for knock in a smaller range than a Hellcat which was a surprise to me when I first saw it.

Finally, when I thought I had it dialed, I had my buddy chase me in his car as I made some highway pulls looking for little puffs from the exhaust. My next video will actually show some of that as I was dialing in the E85, so this thread was timely LOL. We did find a surprise and I learned something but I'll save that for the video thread when I post it. Looking at the exhaust at WOT for puffs of smoke is a good indicator there is knock.

That does surprise me with the window.
I’ll start there. I also think I’ll pick up a 55gal drum of e85 so I know I’m using good fuel with the knock sensors turned down a bit. When on pump and street tune I’ll leave them alone. I’m going to have to make a test n tune day here real soon and spend the day dialing things in

 

[Speedy!]

I also recommend doing a little background research on the differences between E85 and gasoline. The way the flame kicks off at combustion is different for E85, so the way the timing ramps in needs to be considered. I'm not an E85 expert by any means as I just started working with it over the past year, but I've been told it's not like race gas where timing comes in real early down low in the RPM range.

And obviously if you're having to set the knock thresholds to 3V somethings wrong LOL.

 

[jonx96]

I also recommend doing a little background research on the differences between E85 and gasoline. The way the flame kicks off at combustion is different for E85, so the way the timing ramps in needs to be considered. I'm not an E85 expert by any means as I just started working with it over the past year, but I've been told it's not like race gas where timing comes in real early down low in the RPM range.

And obviously if you're having to set the knock thresholds to 3V somethings wrong LOL.

Right. I was thinking of like 10 to 15% change in a few spots to start. Right if I set it to 3v and it hits it I’ll see you over in the build projects forum 😂
Ya I know ramp in his different. I need to do some more reading. I was actually talking to a friend I went to college with the other day. He is a big science and math person. Not a car person at all but said what we were talking about really interested him. He told me he was going to send me some reading over that interest me on different fuels. He was one of those people who got a 3 on his act. Which it is a max score of 36…….
Haven’t quite got to the point where I want to see let’s go for max power. I will do 5 or 6deg Extra through the low to high middle range of the tune and at the very end ramp it up. I’ll start with that and see how I feel. I may also put it on a dyno before doing anything more than that. There’s one down the road they don’t charge very much I don’t think. He is at the track quite a bit I think I’ll talk to him next time I see him there and see what he’d charge.

 

[Speedy!]

Just be real careful with the timing and the sensor thresholds. Make sure you really understand it, the table Y axis, scaling etc. This is one area where you can have problems real fast if you get it wrong.

 

[Hpmaniac]

I have been up and down this road. I have had knock because of bad gasoline (went from royal farms to BP only now). I have had knock because of running a Boost-A-Pump. I have had knock because I turned the car on. Now that I have good fuel (104) and use a dual pump setup I don't worry about the knock issues @Speedy! had anymore. It was what it was. If you have small blips of knock like the following image then I say desenzitise a little by little. Keep in mind that there might be other nefarious things going on... Such as banging gears with hard shifts that will resonate through the body. I also have solid motor mounts so all of the vibrations...

Boost-A-Pump Yeeted, scaring the living shit out of me, ran a 10.2 though...:
View attachment 49439

Dual Fuel Pumps = fuel pressure for days!
View attachment 49441

Most of that is probably noise. 4500 to 5500 they will show false knock.

 

[16GoManGoHC2]

I had a simular issue to where during the gasoline tuning portion for a flex tune I had an event that pulled 14 degrees of timing also during the pull. I fought knock afterwards for like ever, it would come and go, only 2-3 degrees if that and in the same place always when it would happen, around 3500-5500 rpm, I’d have a clean run once in a while then STKR once in a while at different levels sometimes only .5-1 degree this while on E85, good tested E85, I even bought a barrel of E98 to bring E80 up to 85 even 90%, Knock would be there and not be there, was driving me NUTS. So over winter I did a leak down test and sure enough I had a hurt cylinder, #7 had 25%. Mind you the car made 925 wheel HP like this but would knock and not knock, on the dyno same day one pull there next pull not there, I thought for sure it was false knock. My suggestion from experience which sounds exactly like yours, same pulley size even, is check your plugs and do a leak down test. Start with 7, it’s the easiest plug to pull. I’ll post some logs and pictures later this morning. @Speedy! you seen these log screen shots and some of my journey, bring back any memories?

 

[16GoManGoHC2]

PS, I would not recommend desensitizing the knocks sensors, not even 2-3% I tried the same thing and it didn’t make things any better. If the knock wasn’t there at one time and it’s now they’re especially after an event that pulled so much timing something happened during that event and engines don’t heal themselves usually.

 

[jonx96]

I had a simular issue to where during the gasoline tuning portion for a flex tune I had an event that pulled 14 degrees of timing also during the pull. I fought knock afterwards for like ever, it would come and go, only 2-3 degrees if that and in the same place always when it would happen, around 3500-5500 rpm, I’d have a clean run once in a while then STKR once in a while at different levels sometimes only .5-1 degree this while on E85, good tested E85, I even bought a barrel of E98 to bring E80 up to 85 even 90%, Knock would be there and not be there, was driving me NUTS. So over winter I did a leak down test and sure enough I had a hurt cylinder, #7 had 25%. Mind you the car made 925 wheel HP like this but would knock and not knock, on the dyno same day one pull there next pull not there, I thought for sure it was false knock. My suggestion from experience which sounds exactly like yours, same pulley size even, is check your plugs and do a leak down test. Start with 7, it’s the easiest plug to pull. I’ll post some logs and pictures later this morning. @Speedy! you seen these log screen shots and some of my journey, bring back any memories?

I hope it’s not the case. I’ll at least pull 7 today. I was hoping if I had to do an engine it’d be after my barn was up.
seems like you and I have had a lot of similar issues.
both make to much boost on a 2.85 and we see the consequences.

 

[jonx96]

Also with the knock you saw on e85 were you getting smoke out of The exhaust at any point? Or did you have any other symptoms besides knock in the logs?
Also in this log it looks like knock sensor 2 is the one that spiked.
I’m not sure about other logs. But looking at a chart of placement it’d be my guess that would be the one that picked out the most blower noise.
But cylinder 7 is also on that side.

 

[16GoManGoHC2]

Also with the knock you saw on e85 were you getting smoke out of The exhaust at any point? Or did you have any other symptoms besides knock in the logs?
Also in this log it looks like knock sensor 2 is the one that spiked.
I’m not sure about other logs. But looking at a chart of placement it’d be my guess that would be the one that picked out the most blower noise.
But cylinder 7 is also on that side.

When I experienced knock at the track on gasoline yes puffs of grey smoke when it would do it. Don’t know on corn as I didn’t have a camera to mount back there to look for it. Right now I’m in start up tuning of rebuilt engine and I won’t desensitize the knock sensors or use octane booster in gasoline any longer based on what I saw during tear down. Only real symptom in the logs where knock, my 1/4 MPH hit 142 in cold air negative DA. Something I wondered about is I was condensing alcohol in my UPR catch can when it was in the 30’s back in November, from blow by, I bet that does not happen this year when it gets cold out as now I have little to no blow by. I’ll look for those knock screen shots during lunch break today. Plugs 1, 3, 5, and 7 are easy to get out, I’d look at them all and leak down test while your at it, it’s the only way to really know. You could also borescope the cylinders. BDC and look for missing piston material in the valve relief areas if you don’t have a compressor to do a leak down test but it’s very hard to see and not really conclusive info.

 

[jonx96]

When I experienced knock at the track on gasoline yes puffs of grey smoke when it would do it. Don’t know on corn as I didn’t have a camera to mount back there to look for it. Right now I’m in start up tuning of rebuilt engine and I won’t desensitize the knock sensors or use octane booster in gasoline any longer based on what I saw during tear down. Only real symptom in the logs where knock, my 1/4 MPH hit 142 in cold air negative DA. Something I wondered about is I was condensing alcohol in my UPR catch can when it was in the 30’s back in November, from blow by, I bet that does not happen this year when it gets cold out as now I have little to no blow by. I’ll look for those knock screen shots during lunch break today. Plugs 1, 3, 5, and 7 are easy to get out, I’d look at them all and leak down test while your at it, it’s the only way to really know. You could also borescope the cylinders. BDC and look for missing piston material in the valve relief areas if you don’t have a compressor to do a leak down test but it’s very hard to see and not really conclusive info.

I have a compressor to so. I just don't have the tool to test. I see harbor freight has one for $70 but I'm not sure how much I would trust that. I have to have a friend with one.
Edit friend down the road has one