Another Hellcat STKR Question - What's up at 4000 RPM?

[Speedy!]

Been working with the Hellcat a bit. I'm seeing strange STKR that I'm fairly confident is false right around 4,000 - 4,100 RPM. I saw it in a stock calibration (4 deg STKR right around 4K RPM) and in pullied cars it's worse unless the knock window or knock sensor thresholds are heavily adjusted. We bumped the octane up to about 103 - 105 and still see the STKR in this area. I enrichened lambda to .82 - .83 just to be sure it wasn't a lean issue.

I'm still learning these cars so how do you guys determine when to adjust the knock window, the knock volt thresholds or both, and by how much?

Playing with the 103 - 105 octane fuel I'm finding I have to really work with the knock sensors to get the STKR to disappear. Lots of threshold increase like double the volts in the 3840 - 4320 RPM range and 1450 aircharge range on some cylinders. Seems like a lot but unless it's changed by these amounts the STKR is 3-4 deg.

Assuming it's false with 103-105 octane of course? Commanded timing in this area is like 6 - 7 deg as the tune is for 93. Pratio around 2.11.

[Blue Bee]

Peak cylinder pressure, they usually always pull timing heavily in that area. There is a lot of background stuff happening on HC with multipliers and such that are quick on the trigger because it's a factory boosted engine that has a warranty...so they have to account for hot days, a heat soaked engine, and someone running the worst gas possible in the car. Running good fuel, stock boost and timing, most likely it's false. Verify and adjust until it JUST isn't pulling timing.

[Hpindy]

Been working with the Hellcat a bit. I'm seeing strange STKR that I'm fairly confident is false right around 4,000 - 4,100 RPM. I saw it in a stock calibration (4 deg STKR right around 4K RPM) and in pullied cars it's worse unless the knock window or knock sensor thresholds are heavily adjusted. We bumped the octane up to about 103 - 105 and still see the STKR in this area. I enrichened lambda to .82 - .83 just to be sure it wasn't a lean issue.

I'm still learning these cars so how do you guys determine when to adjust the knock window, the knock volt thresholds or both, and by how much?

Playing with the 103 - 105 octane fuel I'm finding I have to really work with the knock sensors to get the STKR to disappear. Lots of threshold increase like double the volts in the 3840 - 4320 RPM range and 1450 aircharge range on some cylinders. Seems like a lot but unless it's changed by these amounts the STKR is 3-4 deg.

Assuming it's false with 103-105 octane of course? Commanded timing in this area is like 6 - 7 deg as the tune is for 93. Pratio around 2.11.

Hi Speedy
I have noticed the same thing . Mine would start from 3800 up to 5000 some times . Usually .5 deg up to 2.5 deg. I pulled out 5 deg of time in every one of the cells and it still did the exact same thing . It doesn't do it all the time either for me .

[Speedy!]

Exactly Hpindy, I can remove the timing and yet the knock persists. I can add good fuel, and it persists but only around this RPM range at 4,000 - 4100 ish. Seems adjusting the knock window in that spot is the easiest solutions. I'm going to chat with Mike on it next week to try to understand it better.

These cars also have a knock multiplier for low rpm and high rpm. My theory at this point is that with single knock sensors on each side of the engine monitoring 8 cylinders, and the tune having knock voltage tables per cylinder the sensors are tuned to listen for frequencies that they think are knock based on each cylinder. When we add pullies that make the blower a bit louder some of those supercharger frequencies of sound overlap the programmed frequencies of the knock sensors setting them off when no knock is occurring.

I've heard not to even trust the knock sensors at all from a couple folks to just tune the car for what you know is right timing/boost/fuel wise then tune the knock sensors around it. Apparently Ford knock sensors are MUCH better.

[Flipfloptrader]

Experiencing this exact same problem with my Trackhawk. I back out the timing and it still persists. Fuelling is good, E90. Rich lambda at 0.78-.79.

It also occurs in the 3,800-5,200 window. I'm only seeing 13 degrees of timing at 1,700 g/s and 4,800 RPM so it shouldn't be knocking 1.5-2.5 degrees.

[Hpindy]

Exactly Hpindy, I can remove the timing and yet the knock persists. I can add good fuel, and it persists but only around this RPM range at 4,000 - 4100 ish. Seems adjusting the knock window in that spot is the easiest solutions. I'm going to chat with Mike on it next week to try to understand it better.

These cars also have a knock multiplier for low rpm and high rpm. My theory at this point is that with single knock sensors on each side of the engine monitoring 8 cylinders, and the tune having knock voltage tables per cylinder the sensors are tuned to listen for frequencies that they think are knock based on each cylinder. When we add pullies that make the blower a bit louder some of those supercharger frequencies of sound overlap the programmed frequencies of the knock sensors setting them off when no knock is occurring.

I've heard not to even trust the knock sensors at all from a couple folks to just tune the car for what you know is right timing/boost/fuel wise then tune the knock sensors around it. Apparently Ford knock sensors are MUCH better.

I have been sending my logs to Mike. All my knock settings are stock so I know they are super sensitive . Im sure SRT sets them like that for warranty purposes . We will see what Mike tells us.
I'd love to hear some thoughts from other tuners as well with experience in this matter .

[Hpindy]

Experiencing this exact same problem with my Trackhawk. I back out the timing and it still persists. Fuelling is good, E90. Rich lambda at 0.78-.79.

It also occurs in the 3,800-5,200 window. I'm only seeing 13 degrees of timing at 1,700 g/s and 4,800 RPM so it shouldn't be knocking 1.5-2.5 degrees.

Are you knock table stock as well?

[Flipfloptrader]

Are you knock table stock as well?

I've started to add 15% in the cells being repeatedly hit, namely 3,800-5,200 rpm. So far I'm up to 30% higher in those cells but still keep seeing the same knock. I'm hesitant to keep going higher as I'm not experienced enough. I may have to get a proper knock box and see what's going on.

[Hpindy]

I've started to add 15% in the cells being repeatedly hit, namely 3,800-5,200 rpm. So far I'm up to 30% higher in those cells but still keep seeing the same knock. I'm hesitant to keep going higher as I'm not experienced enough. I may have to get a proper knock box and see what's going on.

That's what I'm nervous about too . I know the factory over compensates but by how much .That's why I left mine stock for now until hopefully someone figures this out properly.

[richhurley]

Wondering if it could be the Tip-In Throttle Spark and Throttle Spark Knock tables.

[spoolboy]

What RPM do these make peak torque? If it coincides with peak torque....

[ShannonSRT]

What are your plugs telling you, wont be hard to see if your detonating

[Blue Bee]

It's almost like I didn't post earlier. Yes, it's going to line up with peak torque, (peak cylinder pressures), plugs are crazy hard to read for those running E and being told to look at plugs. I've experienced the same on double pullied cats on E90R and 12 degrees of timing, so no, it's not knocking. But I have also got rid of all the knock with one quick simple adjustment which I hinted to earlier as well and left the actual KS voltages settings stock! And another thing! get a knock box? No, Dodge has a pretty good base/floor noise for you already stock and you are having trouble, so what makes you think a magical knock box is going to do when you have no noise floor set up at all with an aftermarket system? You would have to knock the engine to figure out the floor.

Good luck!

[Jay@HAP]

stock blowers are freaking noisy and cause a lot of false knock. the harder you spin them the worse it gets.

[Hpindy]

It's almost like I didn't post earlier. Yes, it's going to line up with peak torque, (peak cylinder pressures), plugs are crazy hard to read for those running E and being told to look at plugs. I've experienced the same on double pullied cats on E90R and 12 degrees of timing, so no, it's not knocking. But I have also got rid of all the knock with one quick simple adjustment which I hinted to earlier as well and left the actual KS voltages settings stock! And another thing! get a knock box? No, Dodge has a pretty good base/floor noise for you already stock and you are having trouble, so what makes you think a magical knock box is going to do when you have no noise floor set up at all with an aftermarket system? You would have to knock the engine to figure out the floor.

Good luck!

I'm running gasoline as there is no E85 or any variation here in Canada. I have looked at all my plugs just recently and if anything the car is running a tad rich but there is zero signs of detention.

[06300CSRT8]

It's almost like I didn't post earlier. Yes, it's going to line up with peak torque, (peak cylinder pressures), plugs are crazy hard to read for those running E and being told to look at plugs. I've experienced the same on double pullied cats on E90R and 12 degrees of timing, so no, it's not knocking. But I have also got rid of all the knock with one quick simple adjustment which I hinted to earlier as well and left the actual KS voltages settings stock! And another thing! get a knock box? No, Dodge has a pretty good base/floor noise for you already stock and you are having trouble, so what makes you think a magical knock box is going to do when you have no noise floor set up at all with an aftermarket system? You would have to knock the engine to figure out the floor.

Good luck!

I purchased a knock box and it was EXTREMELY helpful, strongly suggest you stop "knocking" (pun intended) on using one. Stock knock sensors were reporting high voltages, knock box with headphones I heard ZERO sounds of knock, none. and yes, I did get to a point where i did hear knock through the headphones, and was very easy to hear. So yea, they work, and are useful.

Your advice, which I am sure is based on years of experience, is still just a "IT CANT BE KNOCKING BASED ON MATH" assumption. I made the same assumption but then went ahead and actually listened to the motor to verify that assumption was right. I think that is a better approach.

And since when does ethanol make seeing knock evidence on the plugs more difficult? flakes of pistons are flakes of pistons, regardless of fuel type. if anything this is the ONLY way to find knock with ethanol as it has such a high burn rate often stock or close to stock settings for knock sensors will never actually hear the detonation or pre-ignition as the flame front timing is much different than gasoline, need a different crank timing window and highly sensitive threshold.

[Blue Bee]

I purchased a knock box and it was EXTREMELY helpful, strongly suggest you stop "knocking" (pun intended) on using one. Stock knock sensors were reporting high voltages, knock box with headphones I heard ZERO sounds of knock, none. and yes, I did get to a point where i did hear knock through the headphones, and was very easy to hear. So yea, they work, and are useful.

Your advice, which I am sure is based on years of experience, is still just a "IT CANT BE KNOCKING BASED ON MATH" assumption. I made the same assumption but then went ahead and actually listened to the motor to verify that assumption was right. I think that is a better approach.

And since when does ethanol make seeing knock evidence on the plugs more difficult? flakes of pistons are flakes of pistons, regardless of fuel type. if anything this is the ONLY way to find knock with ethanol as it has such a high burn rate often stock or close to stock settings for knock sensors will never actually hear the detonation or pre-ignition as the flame front timing is much different than gasoline, need a different crank timing window and highly sensitive threshold.

So you bought a microphone style knock box? Not the actual add on knock sensor for say cars that never had knock sensors? Sure the mics let you here some things, all you did was prove my point of a modded engine can't use the stock knock floor and voltage settings. You have to calibrate them just like airflow...and fuel. It's not hard. Yes, reading plugs on an ethanol car is more difficult, I wouldn't suggest going until you see metal flakes on the spark plug burning E, I hope you are joking. My advice was based on experience and having done this combo dozens upon dozens of times, but again I did have the disclaimer of, it needs to be verified but I can say without a doubt you can't do these mods and leave knock system settings stock. That would be no different than swapping injectors and thinking you can leave stock injector data...

[06300CSRT8]

So you bought a microphone style knock box? Not the actual add on knock sensor for say cars that never had knock sensors? Sure the mics let you here some things, all you did was prove my point of a modded engine can't use the stock knock floor and voltage settings. You have to calibrate them just like airflow...and fuel. It's not hard. Yes, reading plugs on an ethanol car is more difficult, I wouldn't suggest going until you see metal flakes on the spark plug burning E, I hope you are joking. My advice was based on experience and having done this combo dozens upon dozens of times, but again I did have the disclaimer of, it needs to be verified but I can say without a doubt you can't do these mods and leave knock system settings stock. That would be no different than swapping injectors and thinking you can leave stock injector data...

Its a combination of microphone and has a logging box/laptop connection with its own software.

I didn't prove any of your point. You continue to tell us that the stock knock floor doesn't work, but aren't offering anyone on here how you establish a new one. Anyone can log voltages across rpm, but how you are determining if you are already knocking or not in your approach is just experience, "ive done this forever" etc. Sorry, i am more scientific than that. The frequency and pitch of each of the voltage spikes cant just be stared at and determined to be knock or not. I like to listen to the motor and observe torque on a dyno. Never heard a peep about either of those from anything you've posted. Cant fault me for pointing that out. I fully expect your next remark to be something about how you charge for that level of advice or some other reason you didn't offer it up.

Also we can skip the whole "put race gas in and log, that's your knew knock threshold" I will send you pictures of two windowed blocks of guys on E who obviously started with a base tune they "knew from experience" shouldn't be knocking and went up from there. A $100 microphone would have provided invaluable info on their baseline, no way its knocking, tune.

[Blue Bee]

Its a combination of microphone and has a logging box/laptop connection with its own software.

I didn't prove any of your point. You continue to tell us that the stock knock floor doesn't work, but aren't offering anyone on here how you establish a new one. Anyone can log voltages across rpm, but how you are determining if you are already knocking or not in your approach is just experience, "ive done this forever" etc. Sorry, i am more scientific than that. The frequency and pitch of each of the voltage spikes cant just be stared at and determined to be knock or not. I like to listen to the motor and observe torque on a dyno. Never heard a peep about either of those from anything you've posted. Cant fault me for pointing that out. I fully expect your next remark to be something about how you charge for that level of advice or some other reason you didn't offer it up.

Also we can skip the whole "put race gas in and log, that's your knew knock threshold" I will send you pictures of two windowed blocks of guys on E who obviously started with a base tune they "knew from experience" shouldn't be knocking and went up from there. A $100 microphone would have provided invaluable info on their baseline, no way its knocking, tune.

Exactly, anyone that does this for a living isn't going to spill ALL the beans! I can say I've never windowed a block, blown one up on the dyno, and have many 1k+ builds that lasted years on my tune and was tuning long before HP Tuners existed. So my experience has to mean a little, that and again from doing this combo several...several times and OP as well as another using good fuel and with what they have done to try and fix this mystery knock-it's not knocking. Of course it's a given that the guy tuning NEEDS to make sure it's really not, but with what's been tried and known it's most likely not. To even begin to find a new floor, need to run the fuel it's always going to run, I don't believe in adding race gas to get rid of knock if the vehicle isn't going to run it all the time. On any fuel if you have a spot of knock after mods and dropping timing doesn't get rid of it and it lost even more power on the dyno is a pretty good hint it's false. I'll monitor crankcase pressure as well if it's a high profile build, that will tell you a bunch as well, but at that point mess with some things to keep it from pulling timing when it's at a low set-point and closely monitor torque on the dyno. Add timing until torque seems to level off then bring back in multipliers, background filters (with KS voltage stock the whole time) until it's wanting to pull .5 or 1 in those trouble spots. Drop timing a degree plus maybe a half to verify no knock line and it shouldn't lose much of any noticeable power. And there you have it, a new knock floor for your mods and fuel you are using. Make a couple of hard loaded long pulls so you can check plugs, bore scope, verify power and knock line. Return knock box/mic and PM me your CC info... I get scientific as well, but once you have done the same combo several times...science isn't needed. As in what's going on in here. The mic style (chassis ear) stuff can be pretty handy, but let's be real, how many are really going to know the exact sound of knock? I've listened through those and really powerful engine can be pretty damn noisy so it didn't help. Helped a shop once using that chasing their tails for hours on knock when it was actually the valve train having to weak of springs creating a "knock". Point is, there's a lot of ways to tackle this, not one is for sure and will lead you down the right path quickly.