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Because I am novice racer, I am trying to learn as much as I can about tuning and important parameters. What I am learning may be old hat to some but perhaps not all. So I am starting this thread in hope it may help some.



Air-fuel ratio, lambda and engine performance
Please allow me to revive this thread.
Im a pretty avid tuner and try to stay up to date with the new platforms. I use HP Tuners i mainly tune the G3 Hemi Platform. I have tuned over 50 vehicles with great success from Nitrous to Superchargers. i have not done a Hellcat engine yet. About to dip into my Hawk. I forgot to mention I do hold a Degree in Automotive Engineering, Specializing in High Performance Engines. (so please do not be afraid to use very technical terms ans also i encourage those who want to know what some things mean please let me know ill be happy to explain) Now there are guys out there that are more proficient then myself and have much more time to practice their craft. Hopefully one of those guys can find this thread and chime in. Hemi Tuning is a close guarded secret. I hope we can change that and have the type of support we see with the LS community.
On to the fun stuff. Anyone else notice that their TH Air/Fuel ratio running around 13.5 at a cruise?? Seems a bit rich to me. "safe but rich".
Im open to opinions on this. I found going through the tune file the Stoich FAR is set to .0772 (dodge talks in fuel/air ratio instead of air/fuel) this comes out to 13.85:1 A/F ratio. Why? I get the Hawks weren't engineered for fuel economy but why not get the best you can. unless the reason was NOx. which you see more of in a lean running engine.
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On to the next thing the Power enrichment tables. These tables are use to set the desired Air/fuel ratio during a power enrichment event such at Wide Open Throttle. There are two of them. Air charge based and Pressure ratio based why might these be populated slightly different? and set at 11.99 on the P ratio based and 12.02 on the Air charge based. and also why is the same commanded ratio regardless of rpm and aircharge. normally i would see lower AFR (more fuel) commanded in the higher air charge area (foot closer to the floor area) and a slightly more lean mix in the upper sections of the scale. Im wondering if some of these settings are not being used or are being corrected in the Artificial Neural Network that these systems run.
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I have a lot more that i'm going to be posting if you guys are interested please let me know. Along with questions
I will also begin tuning and reporting the outcomes of certain adjustments.
Also Please feel free to post your tune files. i will be posting mine along with the modifications list to match the tune.
the first being a CAI only tune.
 

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Thanks for sharing with the community. I wish I could be of some help, but I only have a basic understanding of tuning in the NA world, so I am ready to learn. I came from the LS world too and there is lots of knowledge sharing across all platforms. I was unhappy to find out the Mopar community is not the same especially since these Hellcat motors have been around and modded often enough for parameters to be well established.
 

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Looking forward to learning more on this. Please keep this thread going and it's much appreciated.
 

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Stoich is always going to be where your O2's begin to oscillate. That is a lambda of 1.00. FCA ia calling the AFR 13.5 because with E10 fuel that is what you would expect stoich to be. With 100% gasoline the stoich would be 14.7 That would still be lamda of 1.00. So don't get hung up on the 13.5 number. If you put 100 % gasoline in your Trackhawk the stoich is still going to show 13.5 even though the actual AFR is now 14.7. Does that make sense?
 

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Stoich is always going to be where your O2's begin to oscillate. That is a lambda of 1.00. FCA ia calling the AFR 13.5 because with E10 fuel that is what you would expect stoich to be. With 100% gasoline the stoich would be 14.7 That would still be lamda of 1.00. So don't get hung up on the 13.5 number. If you put 100 % gasoline in your Trackhawk the stoich is still going to show 13.5 even though the actual AFR is now 14.7. Does that make sense?
That does make perfect sense. So that’s the calculation dodge used to represent stoich. I’m glad you brought that up. The standalone wide band I use to tune most cars for WOT reads in lambda. Since actual AFR for most fuels is not exact. Lambda is no matter what’s in the tank.
thank you
 

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This also makes me wonder why FCA is even using FAR in their tuning (other then it makes it more difficult for aftermarket) even my 08 Charger SRT uses the same confusing data.
 
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