Hellcat uncontrollable knock

[slowSRT8]

I have a 2016 Challenger with 2500 miles on it which was recently modded and tuned with ANN on using e85. I have logged my Hellcat many times before the tune and my knock sensors, even on a 100% bone stock car, would report between .80 ~ 1.80v generally and sometimes up to 2.00v. I attributed this to crap gas and figured I'd worry about it after I was modded and tuned on race gas. Well I added a pulley and had it tuned on e85 and the sensors are behaving exactly the same way, indicating it's not the fuel. The voltage readings are exactly the same (maybe a touch higher) so either my e85 isn't doing it's job or the additional sound the motor/intake/exhaust is making from the added power has negated the job of the e85. My tuner told me that he "desensitized them a little bit" and it was still doing it. It was late and I decided to leave the dyno to do some street pulls and see how it behaved just in case it was isolated to that dyno only.

It was better on the street, but not cured. I figured, okay he just didn't desensitize them enough. I checked his tune last night and was horrified to find that he tripled the knock sensor threshold (~1.85v) and it is still pushing beyond that threshold and pulling a lot of timing. The thing is, it's inconsistent and some pulls there is zero timing reduction while others in the same gear it yanks as much as 7 degrees. I am at a loss right now. I know that hemis in general have a knock sensor issues, and the hellcat is supposedly worse, but I'm worried I have a bigger problem here.

The only thing I could come up with was to add another catch can. I had one on the dirty side only and now have ordered one for the clean side. I did find a small amount of oil in the intake. I think that happens after chopping the throttle quickly after a WOT pull, it blows oil mist into the intake. Not sure if this is my issue, but the can isn't here yet for me to test. Anyone know how long it takes to burn residual oil out of the intake? I probably only have 5 miles on the car with the catch cans, so maybe it's still burning that stuff off?

I've only read of others going as much as 2x the voltage threshold, I am at 3x and still can't avoid it. I will be putting the sensors back to 1.5x for safety concerns, but other than the new can I am at a loss. Any tips would be very helpful, thank you .

[Jay@HAP]

A lot of it is the noise from the blower that's picked up as knock. I've ran into the same thing. It did it on pump E85, E98 and 110 race gas.

The harder you spin the blower the worse it seemed to be. How much boost are you seeing?

I went from a stock blower to a Whipple and the knock sensors don't make a peep anymore. Same boost, same fuel and same timing. Only change was the blower.

Also TM uses the knock sensors to pull out timing, I think more so on the automatic cars.

[slowSRT8]

A lot of it is the noise from the blower that's picked up as knock. I've ran into the same thing. It did it on pump E85, E98 and 110 race gas.

The harder you spin the blower the worse it seemed to be. How much boost are you seeing?

I went from a stock blower to a Whipple and the knock sensors don't make a peep anymore. Same boost, same fuel and same timing. Only change was the blower.

Also TM uses the knock sensors to pull out timing, I think more so on the automatic cars.

I'm glad you replied. I believe I've read every single post you've ever made about anything to do with Hellcats lol I saw the one you made about the Whipple and it is very intriguing. My car is an auto and I also read about what you said about the TM. However I am not seeing that in the logs. I have logs where there was zero shifting happening and the knock is still there. I have logs where I shift and no knock was registered. Then again I have logs showing zero knock at all which really makes me scratch my head.

This blower is one noisy son of a bitch. So much so that I waited longer than I wanted to mod the car as I was waiting to see if I had a bad blower. It never changed whole stock, but is definitely louder at idle now that it's pullied. I would imagine it's seeing 19 pounds with my pulley. The sensor stops reading at 17 as far as I'm aware, so that's all it ever shows.

Apart from putting a Whipple on it, how far can I go with the knock sensor thresholds? I am hoping to find someone who has taking them farther than 2x.

[Jay@HAP]

Are you logging the knock sensor voltages? Also what spark plugs are you using?

[slowSRT8]

Are you logging the knock sensor voltages? Also what spark plugs are you using?

Yea I am logging the voltages and stated the values in the OP. The plugs were stock with the stock logs and then when I went modded I switched to one head range colder NGK iridiums plugs gapped at .025

[JoshCP527]

Well I will say on a dyno you can see how much power you gain with the timing. You kind of have to go old school in the fact that when knock happens you wont be gaining power. I think most of the recent gains have been from people accepting the stock blower is a noisy sob when spun faster and with a solid pulley. Your tuner has to be comfy with this fact and just slowly creep up on it and try to find peak torque. Check plugs and go from that. Knock sensors wont be as useful with the stock supercharger but you can change the aggressiveness of the timing retard when it goes over the noisy voltages also. It easy to say that is why most people blow the motors with high octane tunes and low octane or bad gas. the stock sensors cant see past the fog or when they do its only a little.

[JoshCP527]

You have knock thresh holds you use this to filter out engine noise and have to raise them higher. Then you have severity multipliers that tell the computer how much timing to pull after it breaks past that ceiling. If you raise the ceiling you will need to also increase the severity when it pokes through. You have intern went from a conservative quiet motor to one that well isn't so conservative anymore. So when it acts out you need to pull a lot out and do it very quickly. Still might not be enough as that is what you get for playing in a fog but its all you can do at that point.

EDIT* They ran into this very same thing with vets and direct injection. Its been documented with the tuning school and they went as far as not trusting the plug readings and pulling heads only to find its just a knock sensor calibration thing.* Dont go crazy with it lol

[Jay@HAP]

Well I will say on a dyno you can see how much power you gain with the timing. You kind of have to go old school in the fact that when knock happens you wont be gaining power. I think most of the recent gains have been from people accepting the stock blower is a noisy sob when spun faster and with a solid pulley. Your tuner has to be comfy with this fact and just slowly creep up on it and try to find peak torque. Check plugs and go from that. Knock sensors wont be as useful with the stock supercharger but you can change the aggressiveness of the timing retard when it goes over the noisy voltages also. It easy to say that is why most people blow the motors with high octane tunes and low octane or bad gas. the stock sensors cant see past the fog or when they do its only a little.

Agreed. I wish the plugs were easier to check. Freakin Mopar!

[JoshCP527]

Agreed. I wish the plugs were easier to check. Freakin Mopar!

jay you mean freaking hellcat I would love to do the old srt8s any day.

[slowSRT8]

Josh thank you very much for the input. When we had it on the dyno the sensors actually picked up less knock the more timing we added. So we put the timing where it should be for my setup (17) and all was well. The car got hot because of so many pulls so we set it aside for 2 hours to let it cool. Put it back on and knock everywhere. Couldn't figure it out, left with about 13 degrees of timing.

I would rather pull the motor I think than check these plugs again LOL What a design! I don't remember my 300c being that bad at all. Can't remember.

I have the stock tune and logs as well as both for the modded tune file if anyone is curious.

I'm thinking install the second can and give it some time to possibly clear out any residual oil in there and see what happens. Or disable the sensors and get my bible out lol

[slowSRT8]

Jay I can see your response in my email but not here. I don't have cats and have raised my cat temp limit higher. That would probably just richen the mixture though if I went too high on the cat temp.

[slowSRT8]

Turned the knock sensors down to 1.5x and just did 4 long pulls. Only one of the 4 pulls pulled a ton of timing.

Can someone explain to me how on Gods green earth I can do 4 identical pulls but only one time I get bad knock? It boggles my mind. Same gear, same temps, same everything duplicated, but knock on some but not others. I'm thinking it's gotta be the damn oil blowing in there somehow.

I still dont have my clean side can installed yet by the way.

[slowSRT8]

Here is my log from last night. As you can see only the first pull of the four had big timing pulled from the knock sensors. All values seem to be identical between the pulls, I compared them side by side. I need to get some more data, but it is now raining.

[slowSRT8]

Here is my stock read and my custom tune. I did a compare file to look at everything and there is just stuff I don't understand yet. If anyone wants to take a look I have attached them.

[Jay@HAP]

What injectors are you using?

[slowSRT8]

what injectors are you using?

id1000

[Jay@HAP]

Log Throttle Torque Source. The knock sensors seem to be happy when it pulls all the timing out on the last WOT pull. The voltages look good and it showed -.5 of short term knock. I think there has to be another reason it's pulling timing out.

[slowSRT8]

Log Throttle Torque Source. The knock sensors seem to be happy when it pulls all the timing out on the last WOT pull. The voltages look good and it showed -.5 of short term knock. I think there has to be another reason it's pulling timing out.

Also, IMO you are commanding a lot of timing in your WOT base table even though it's not getting anywhere near it.

Okay I will add Throttle Torque Source to the next log I can get. It's raining now so a couple days probably. Also bear with me a bit as I didn't write this tune, only trying to understand it. I don't want to be a huge burden on the community with a bunch of questions, so I will start to research timing and how it relates to the WOT base table.

[Jay@HAP]

Did you get different injector data from ID? The reason I ask is what you have and what is on their site is very different. I ended up getting different data for the 1700's I used because there wasn't enough breakpoints in the data that ID originally provided.
I spent a lot of time with Paul to figure out what I needed.

Also your injPW vs Fuel Mass tables don't match the inverse tables, which they need to.

[Jay@HAP]

Okay I will add Throttle Torque Source to the next log I can get. It's raining now so a couple days probably. Also bear with me a bit as I didn't write this tune, only trying to understand it. I don't want to be a huge burden on the community with a bunch of questions, so I will start to research timing and how it relates to the WOT base table.

I mispoke about the timing. I didn't realize I was looking at the WOT Thermal table by mistake.