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Discussion Starter #1
This is from my car, 2015 Dodge Challenger with 25k miles, bone stock except for a catch can and lower grill vent mod or whatver is called, when you remove the brake duct plastic piece for the lower fascia :)

This are 3rd gear WOT runs, i bet the house the amount of KR in 4th is even worst, i'll have some work to do in the timing department once i get my unlocked PCM


3rdgear_wot_pull_StockTune by Wrangler RSM, on Flickr

3rdgear_wot_pull2_StockTune by Wrangler RSM, on Flickr
 

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92 octane pump gas is just adequate for the 392 in stock tune.

4th gear would put more load on the engine since your 1:1 ratio at that point.

10.9:1 CR + pump gas, thankfully we have the engine management software that keeps things in line. Trying run the older cars with that much CR would be tough.
 

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And that's why is is so important to run the best gas you can, which in my area I was told by a reputable tuner is Shell and Chevron. We don't have all the brands here like BP and Sunoco etc...
 

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In my both srt8 jeeps the 07 had cai and 91 octane cmr dyno tune and my 2012 was bone stock and I ran union 76,mobil,shell and chevron with 91 octane. I never ran the 2012 with only 91 at the track. The 07 ran the same times with the 4 diff gases. I selected 76 because it was the cheapest with my 91/vp109 mix. I also ran some mobil with my 91/vp109 mix and there was no diff than the 76.
 

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You need to run 93 octane if you can. The stock tune has the knock sensor sensitivity turned way way up. If you get a custom tune they dial them back just a little. I saw up to 3.0 ST KR on the stock tune running good 93 pump gas. With my custom tune I generally see 0.0 or occasionally 1.0 in the higher gears. It's normal to see some at shift points.

I bumped my timing up a few times at the track and ran 96 octane and then 98 octane mix one time and with the 98 octane the knock basically went away. 11:1 compression is borderline even on 93 pump gas. On an older car it would be bad news, would really need 95-96 octane to be safe. But the PCM will pull timing if it senses knock so it will save you to some extent.
 

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Discussion Starter #6 (Edited)
Unfortunately i have no access to anything higher than 91 octane, unless i want to pump 100 octane at $9-$10 a gallon, i'm located in sunny Southern Cali.
I'll back out of the timing a couple of * in those areas and be done with it, i'm also surpised to see the amount of timing we run from the factory at WOT, 7-12 detonating, i'm used to GM LSX stuff, so they're more in the 20-22* range.

I'll also back out the timing in the low load /rpm areas, i get some rattling from now and then, when i'm just launching the car in 1st gear, and it's not because i don't know how to clutch :) i saw the low load cells have a bunch of timing as well in the PT timing table, so i'll take care of that too.

In terms of WOT fueling, Dodge seems to use the approach of leaner down low, then then rich up top, at least looking at what they're commading in PE, i'm not adding LT's or any other big mods for now, but i thought i'll get a WB and dial WOT fuel as wel if it was needed, and shoot for .82 lambda flat across the board.

This is the factory PE, wonder how close we're in reality from what the factory is comading in PE ?
Posting as a pic, as i don't know how to create a table yet in his forum, it seems lean up to 3000rpm, (anywhere between 12.9-13, to 12.6 afr) then a little richer from there on until like 4800rpm (12.6-12.5), then closer to 12's flat past that rpm, is it accurate to say that in stock trim if i change my commanded to all 12's that'll be close to that ?, it has been my experience in GM or Ford that it works as long as the is no big mods influencing airflow, so i'd assume it'll be ok to use .82 lambda, (11.96AFR according to the stoich defined in the calibration of .0688 lambda or 14.53afr)

Stock_PE_Table by Wrangler RSM, on Flickr
 

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This is from my car, 2015 Dodge Challenger with 25k miles, bone stock except for a catch can and lower grill vent mod or whatver is called, when you remove the brake duct plastic piece for the lower fascia :)

This are 3rd gear WOT runs, i bet the house the amount of KR in 4th is even worst, i'll have some work to do in the timing department once i get my unlocked PCM


3rdgear_wot_pull_StockTune by Wrangler RSM, on Flickr

3rdgear_wot_pull2_StockTune by Wrangler RSM, on Flickr

Ahh.... I know this problem well.

I strive to not have ANY ST KNK and I have found that the stock timing curve is basically the max on pump gas.

Before you drive yourself crazy... try this:

Desensitize the knock sensors by multiplying their values by 1.5 in HP Tuners.

Get the AFR around 12.5 and then adjust timing until you don't have any knock. Don't sweat it if it's actually lower than stock in some places, as this isn't going to hurt your power.

I basically have my knock sensor values doubled in some places and my timing curve is basically stock. I can add a degree or two above 5,800 rpms.... not that it makes any real difference.
 

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Discussion Starter #8
Ty sir, looking forward for my unlocked pcm to arrive, to get my hands in the factory tune and improve from there :)
 

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Unfortunately i have no access to anything higher than 91 octane, unless i want to pump 100 octane at $9-$10 a gallon, i'm located in sunny Southern Cali.
I'll back out of the timing a couple of * in those areas and be done with it, i'm also surpised to see the amount of timing we run from the factory at WOT, 7-12 detonating, i'm used to GM LSX stuff, so they're more in the 20-22* range.

I'll also back out the timing in the low load /rpm areas, i get some rattling from now and then, when i'm just launching the car in 1st gear, and it's not because i don't know how to clutch :) i saw the low load cells have a bunch of timing as well in the PT timing table, so i'll take care of that too.

In terms of WOT fueling, Dodge seems to use the approach of leaner down low, then then rich up top, at least looking at what they're commading in PE, i'm not adding LT's or any other big mods for now, but i thought i'll get a WB and dial WOT fuel as wel if it was needed, and shoot for .82 lambda flat across the board.

This is the factory PE, wonder how close we're in reality from what the factory is comading in PE ?
Posting as a pic, as i don't know how to create a table yet in his forum, it seems lean up to 3000rpm, (anywhere between 12.9-13, to 12.6 afr) then a little richer from there on until like 4800rpm (12.6-12.5), then closer to 12's flat past that rpm, is it accurate to say that in stock trim if i change my commanded to all 12's that'll be close to that ?, it has been my experience in GM or Ford that it works as long as the is no big mods influencing airflow, so i'd assume it'll be ok to use .82 lambda, (11.96AFR according to the stoich defined in the calibration of .0688 lambda or 14.53afr)

Stock_PE_Table by Wrangler RSM, on Flickr

I have FA Stoich set to 0.0699, which is 14.3 AFR. My fuel is typically around E7 here. With my Innovative LC-2 programmed for 14.3, I tune for a lambda of 0.87, or 12.44 AFR.

0.82 would be pretty rich with E0 fuel and very rich with E10. A lot of people seem to think these cars run best at 12.0 or so; however I believe the best results come in the 12.4 - 12.6 range.

At E0, that would be 0.85 or 0.886 with E10.

A leaner mixture will always generate a faster flame speed, but people compensate for excessive timing with a richer mixture. I think it's better to back off on timing and lean it out.

This is an awesome article to read:

Spark Timing Myths Debunked - Spark Timing Myths Explained:: Application Notes

IMO, it is best to rescale your Injector Pulse Width vs. Fuel Mass to give you more tuning control at WOT. This will prevent you from really having to whack up your PE.

Set both PE tables to the same values. (Aircharge vs RPM and PRatio vs RPM).

With ANN on, I've gotten really good at tuning my car with bolt on's. I have a custom grind cam being installed right now and I'll have it professionally tuned; however I will certainly attempt to "reverse engineer" the tune and learn from it.
 

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The Bacon Hauler (‘12 Cop Charger)
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*And that's why is is so important to run the best gas you can*, which in my area I was told by a reputable tuner is Shell and Chevron. We don't have all the brands here like BP and Sunoco etc...
You, sir, are correct!!

I try to stick to Top Tier brands for gas fill-ups when possible, and definitely I try to avoid stations which are 'out of the way', especially given that I'm guying their slowest moving gasoline grade (premium/93 octane). I don't want to risk getting some stale crap that's phase separated in the tank, which is more likely if I shop for gas in light-traffic areas.

And when in doubt, data-loggging is always my best friend.

There have been times when I've gone against my better judgement and purchased some gasoline which I knew was suspect at best, but the lure of low cost or fear of running out convinced me to take a chance, and sure enough, the datalogs do not lie!!

My last self-administered spanking came from my desire to save $5 off a fill-up at a local Kroger filling station. I know their gas is low-grade swill, but I had that $5 savings burning a hole in my pocket, and so I used it on a tank of 93 octane from the Kroger station.

Even after dialing my tune back to only require 91 octane (normally needs 93), my datalogs were a horror show of STKR and LTKR spikes during almost every single WOT run (5 out of 6 anyway).

I ended up spending $7 on a can of octane boost just to salvage that tank of gas that I originally saved $5 on by purchasing from Kroger, and even then I still had to dial my tune back to 89 and 91 just to keep the KR from showing up.

:headbang: :cursin: :mad:

Lesson (re)Learned - you get what you pay for!

That, and it's a good thing the gasoline around here isn't carded before each fill-up, because I can say without a doubt that Kroger's 93 octane couldn't pass for an 89 blend with a fake ID and a "handy" for the bouncer!! :nono:
 

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The stock tune will get knock retard showing up because the sensor sensitivity is way up there on the stock tune. All the tuners turn them down some and they're still pretty conservative. I found running 95 octane or so would get rid of all KR all the time. But most of the time my custom tune on 93 pump gas will show 0.0 all through the gears. Pump gas isn't all that consistent, sometimes you get a bad tank of gas, etc. Make sure you're not pulling timing out where it's not necessary due to a bad tank of gas or a blip at a shift point, etc.
 

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How do you check for retardation? That sounds funny, but seriously, is it with something like the Trinity or Diablo tuner?
 

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You can datalog with a Trinity or Intune. Even on the stock PCM you can still monitor and datalog. You just can't upload a tune file to the stock PCM.

You just need to log or monitor the parameters Short Term Knock Retard and Long Term Knock Retard. When doing a datalog it's also good to log other parameters like engine RPM, vehicle speed, spark cyl 1, engine coolant temp, IAT, fuel trims, etc so you can see what's really going on.

I always check for short term knock retard. Most tuners will say anything under 2.0 ST KR is nothing to worry about, especially if it only shows up for a split second and goes away. The sustained KR that lingers and doesn't drop off is the bad stuff. You can see the spark timing drop for the amount of KR that shows up. For instance, if I'm running 19 degrees of timing and then 1.0 ST KR shows up, my timing will then show 18 degrees. The PCM will pull that degree out instantly and then return it once the KR goes away again. That is short term knock retard.

Long term knock retard is when the PCM has had to pull timing in a certain area over and over and it finally just pulls it permanently until so many cycles of not seeing it there anymore pass, then it will restore it. Long term knock retard is bad news. With a good tune you shouldn't ever see this.

Ideally you want 0.0 ST KR all the time, but that's pretty hard to achieve without getting too wimpy on your ignition timing. Aim to get 1.0-2.0 ST KR blips here and there, maybe around shift points, and try to keep it around 0.0 all the time and you will have a pretty solid tune.
 

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Thanks for that! How can I datalog with the stock PCM? We have 91 octane here only, curious what it does...
 

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Thanks for that! How can I datalog with the stock PCM? We have 91 octane here only, curious what it does...
Just hook up your Trinity to the OBDII port under the dash near the driver door, then follow the prompts on the tuner to start datalogging. Or you can just monitor if you want too and not record anything. It's pretty straightforward though.
 

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The Bacon Hauler (‘12 Cop Charger)
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Thanks for that! How can I datalog with the stock PCM? We have 91 octane here only, curious what it does...
Here is a write-up I did a couple of years ago about datalogging with the inTune-DCX: http://www.challengertalk.com/forums/f108/datalogging-diablosport-tuner-266682/

Give it a read and see if anything clicks...the whole datalogging process is a little daunting at first, but if you're mildly technical and even slightly curious about how things work, you can figure out what's going on pretty quickly. It's just a matter of developing a process which is then comfortable for you to repeat and easy for you dissect and understand.

Whatever you do, just remember it's a passive interaction with your PCM, so don't worry you might mess something up while datalogging. Don't be intimidated by all the PIDs; start small and work your way up...and practice, practice, practice! After all, nobody ever broke their car by datalogging, but a lot of folks have managed to fix their cars by doing it :bigthumb:
 

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I usually fill up at sunoco or marathon but have no idea what sort of KR I may have. Would a 50/50 e85 blend, or less maybe, be a bad idea? Not sure if the stock system can give more fuel due to the e85. If it can, wouldn't that help with KR?
 

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You might try giving this stuff a shot > ACES IV Gasoline Formula « BND Automotive

Been running it and it seems to help. I'd be curious if it eliminates KR for you?
I've been datalogging with Aces IV and I've found that it does make a difference. My SRT 392 has the factory tune.

With 93 octane and no additive I get 0 LT KR and occasional ~ 1 second blips of up to 2 ST KR on WOT.

With 93 octane and Aces IV, I get 0 LT KR and almost never see any ST KR on WOT (very difficult to do a WOT pull with any ST KR registering).

When I run 89 with Aces IV, I get identical behavior as running 93 octane with no additive (0 LT KR and occasional ~ 1 second blips of up to 2 ST KR on WOT).
 

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The Bacon Hauler (‘12 Cop Charger)
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I usually fill up at sunoco or marathon but have no idea what sort of KR I may have. Would a 50/50 e85 blend, or less maybe, be a bad idea? Not sure if the stock system can give more fuel due to the e85. If it can, wouldn't that help with KR?
If the KR were a result of insufficient octane of the fuel, the higher ratio ethanol blends could theoretically help since they would provide a bump in octane rating of the fuel. However, that would only be possible if the engine in question has the ability to detect the differing ratios of ethanol and adjust the fuel injector widths accordingly (stay open longer to spray more fuel to compensate for the lower energy return of burning ethanol), i.e. the engine would have to be a FlexFuel engine. If it was not, the engine's tune would have to be specifically adjusted to account for the higher ethanol percentage blend, which is not something that could happen on the fly obviously.

Now, I do not know if the newer Hemis are FlexFuel or capable of handling different ethanol blends above the standard 10-15%, but I was always under the impression that the early versions were not (pre-2015). I could be wrong there, and hopefully someone will correct me if I am.

Either way, it would not be my choice to run a higher blend ethanol to try to mitigate any observed KR. My personal preference would be to address it with minor tune adjustments first (assuming the root cause was verified to be insufficient octane), and then try more ethanol as a last resort if nothing else worked. But that's just me, and I've been called weird, strange, anti-social, a corn hater, and every other slur you can think of... :icon_lol:
 
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