Results 1 to 9 of 9

Thread: Are Hellcat fuel trims fat by default?

  1. #1
    Tuner fumanchu182's Avatar
    Join Date
    Oct 2019
    Location
    Maryland
    Posts
    50

    Are Hellcat fuel trims fat by default?

    So I was going through some logs today and I noticed on my stock Hellcat the the fuel trims are kind of fat. Is this to make sure nothing goes boom or is it required to ensure max power? So some starter knowledge that I learned during looking at the logs and trying to walk it back. Stoichiometric for the cars is 13.85. I found this value bye doing 1/FAR. FAR in this car stock is 0.0722. The next thing I learned is that the Command EQ Value directly correlates to aircharge or pressure ratio. I don't know the inner workings but I'm assuming this is accelerator pedal commanded or throttle position where the tables switch over or perhaps a blend of both. So as an example I found the following values in the log:

    RPM: 4803
    Aircharge: 1.40
    Pressure Ratio: 1.72
    EQ Ratio Commanded: 0.76
    FA Enrichment: 0.0227

    0.0722 + 0.0227 = 0.0949
    1/0.0949 = 10.53 AFR
    10.53/13.85 = 0.7602....

    So the math checks out! Glad I figured out how to work back the numbers, however I am trying to figure out why the default fuel trims are fat. Is this from the factory that way? Is this to make the car happy? Is it required? I know I plan on making the two tables FA Power Enrich PRatio Based and FA Power Enrich PRatio Based the same and shooting for 11.50 as the number in both tables but is there anything to be gained from this? Will the car perform better instead of washing the cylinders with gasoline?
    Last edited by fumanchu182; 10-08-2020 at 07:23 PM.
    Hellcat PB > ET: 10.942, MPH: 125.66, 60': 1.636, R/T: .242
    Bone Stock Scat Pack PB > ET: 11.612, MPH: 119.52, 60': 1.634, R/T: .000 (gone but not forgotten).


  2. #2
    Tuner fumanchu182's Avatar
    Join Date
    Oct 2019
    Location
    Maryland
    Posts
    50
    Hellcat PB > ET: 10.942, MPH: 125.66, 60': 1.636, R/T: .242
    Bone Stock Scat Pack PB > ET: 11.612, MPH: 119.52, 60': 1.634, R/T: .000 (gone but not forgotten).


  3. #3
    Senior Tuner Ben Charles's Avatar
    Join Date
    Aug 2009
    Location
    Calibrating
    Posts
    2,757
    Yes... they want to keep it safe

    Email Tunes, Bencharles_10@hotmail.com
    96 TA Blown/Stroked, 4L80E/Fab 9
    15 C7 A8 H/C 2.3 Blower/PI
    14 Gen 5 Viper
    Custom Mid Engine chassis, AKA GalBen C

  4. #4
    Tuner fumanchu182's Avatar
    Join Date
    Oct 2019
    Location
    Maryland
    Posts
    50
    Quote Originally Posted by Ben Charles View Post
    Yes... they want to keep it safe
    Would it be unwise to flatten the tables by making them the same and targeting 11.50 throughout? I think with a leaner mixture would it have the potential to run better?
    Hellcat PB > ET: 10.942, MPH: 125.66, 60': 1.636, R/T: .242
    Bone Stock Scat Pack PB > ET: 11.612, MPH: 119.52, 60': 1.634, R/T: .000 (gone but not forgotten).


  5. #5
    Tuner in Training
    Join Date
    Aug 2019
    Posts
    41
    Quote Originally Posted by fumanchu182 View Post
    Would it be unwise to flatten the tables by making them the same and targeting 11.50 throughout? I think with a leaner mixture would it have the potential to run better?
    I asked the same question, looked through the forums and no strait answers, I know other tuners like 11.7 AFR and on these forums I seen in the forums that these cars make the best power around .83 about 12.0 AFR a bit to lean me on average setup with pump or unleaded race gas. You were the guy with the go pro on the roof behind me last friday at MIR correct. If you have cats your going to see a lot of fuel in the 10s, if not and your running mids turn off all those COT parameters for racing you just have to dial it is till it making power and your not getting any gains from leaning it out then I fatten it up a tad personally. Do not get greedy on the timing! I think your running stock boost correct or do you have a lower?

    Unless someone tells me different I will be looking for 11.3 on my next track rental and once I am confident I can make clean passes with data to compare and not hit limiters like i did last weekend i will lean it out to around 11.7.

    My 19 red eye uses aircharge for PE and it was set at 110 from the factory so .722+110=832 1\ .0832= 12.01. for P ratio I am setting the lower tables the same till i get a handle on when or if p ratio is used on demon and red eyes, since it is not selected in the tune. I actually targeted 11.3 for my track rental coming up and will work from there, .722+160=.882 but this with mid pipes and enrichments turned off for them.

  6. #6
    well a stocih is stoich and from what i have seen hellcats crusie at 14.7 if you use a wideband hooked up to the car , the evic just displays the 1 lambda to be equal 13.7

  7. #7
    Tuner in Training
    Join Date
    Aug 2019
    Posts
    41
    Quote Originally Posted by malikib View Post
    well a stocih is stoich and from what i have seen hellcats crusie at 14.7 if you use a wideband hooked up to the car , the evic just displays the 1 lambda to be equal 13.7

    .722 is stoic in my hellcats calibration, 15% ethanol. Stoich is Stoich=1 lambda , under part throttle and cruising great no problem using the method outlined in these forums, 1 lambda for any fuel is Stoich i get that , what I'm taking about is once you get into boost, your PE starts to come in and is added to to that .722 as calibrated stoich, these cars have factory wideband sensors so I have not bothered to install stand alone system at this point , I am working on WOT passes on the track in my case 93 pump for street tune and 100 octane for my race tune until I feel proficient enough to move on to other fuels, I believe I met the OP and he was doing the same.

    I got myself confused over that dash readings for a day or 2 on initial short bursts testing, not even practical to look at going down the track, Ill focus on the data the car and track provides for now.

  8. #8
    Tuner fumanchu182's Avatar
    Join Date
    Oct 2019
    Location
    Maryland
    Posts
    50
    Quote Originally Posted by joeapple View Post
    I asked the same question, looked through the forums and no strait answers, I know other tuners like 11.7 AFR and on these forums I seen in the forums that these cars make the best power around .83 about 12.0 AFR a bit to lean me on average setup with pump or unleaded race gas. You were the guy with the go pro on the roof behind me last friday at MIR correct. If you have cats your going to see a lot of fuel in the 10s, if not and your running mids turn off all those COT parameters for racing you just have to dial it is till it making power and your not getting any gains from leaning it out then I fatten it up a tad personally. Do not get greedy on the timing! I think your running stock boost correct or do you have a lower?

    Unless someone tells me different I will be looking for 11.3 on my next track rental and once I am confident I can make clean passes with data to compare and not hit limiters like i did last weekend i will lean it out to around 11.7.

    My 19 red eye uses aircharge for PE and it was set at 110 from the factory so .722+110=832 1\ .0832= 12.01. for P ratio I am setting the lower tables the same till i get a handle on when or if p ratio is used on demon and red eyes, since it is not selected in the tune. I actually targeted 11.3 for my track rental coming up and will work from there, .722+160=.882 but this with mid pipes and enrichments turned off for them.
    Yeah brother! That was me, next time you go down to MIR let me know, good to know there are some cats in the area that go down. I believe we talked about my windows tablet and how I eliminated my laptop from shooting forward in the car.

    Quote Originally Posted by malikib View Post
    well a stocih is stoich and from what i have seen hellcats crusie at 14.7 if you use a wideband hooked up to the car , the evic just displays the 1 lambda to be equal 13.7
    No the hellcats cruis at 13.85, it's a fat fuel trim, keeps temps down and adds in error for ethanol.

    Quote Originally Posted by joeapple View Post
    .722 is stoic in my hellcats calibration, 15% ethanol. Stoich is Stoich=1 lambda , under part throttle and cruising great no problem using the method outlined in these forums, 1 lambda for any fuel is Stoich i get that , what I'm taking about is once you get into boost, your PE starts to come in and is added to to that .722 as calibrated stoich, these cars have factory wideband sensors so I have not bothered to install stand alone system at this point , I am working on WOT passes on the track in my case 93 pump for street tune and 100 octane for my race tune until I feel proficient enough to move on to other fuels, I believe I met the OP and he was doing the same.

    I got myself confused over that dash readings for a day or 2 on initial short bursts testing, not even practical to look at going down the track, Ill focus on the data the car and track provides for now.
    I don't even look at the gauges. I'm looking at the christmas tree.
    Hellcat PB > ET: 10.942, MPH: 125.66, 60': 1.636, R/T: .242
    Bone Stock Scat Pack PB > ET: 11.612, MPH: 119.52, 60': 1.634, R/T: .000 (gone but not forgotten).


  9. #9
    Tuner in Training
    Join Date
    Aug 2019
    Posts
    41
    This friday 16th, but its a private track rental, after trying to do an actual test n tune and getting 2 crappy passes last Sunday, I paid for a private track rental so I can get a handle on the new power and torq limits, everything was easy stock , OCT 23 MSHS will be next public event I suggest you buy your tickets online!