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Thread: Dodge aircharge measurements

  1. #1

    Dodge aircharge measurements

    I have a question about aircharge , what does it measure exactly and is it measured accurately by the ecu . Common sense says that more aircharge means more power . And basically boltons freeup the engine to take in more aircharge , is that correct ?

    I noticed something i have two logs of the same car with the same tune when the weather is cold and iats are in 25*c the aircharge reaches 0.8g but in the summer when iats are more the 45*c the aircharge doesn?t go above 0.76 do iats have that much effect ? Of course the engine made more actual torque with more aircharhe

    Now should i see a difference when installing mods like headers boltons or cam or is it hardcoded in the ecu models ? And if the afr is correct and spark is correct can this number be a direct measurement of how high the horsepower is

    On 6.4 liter the aircharge goes north of 0.85 g is that why they make more power ? On boosted setups it goes up to 1.25
    So can a tune have an effect on this or is it strictly parts related
    Last edited by malikib; 07-07-2020 at 04:07 AM.

  2. #2
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    It's a calculation in PCM but if you have same tune and mods to increase MAP you should see higher aircharge as well. I know aircharge gets over 2.0 if you put a lot of boost to one. Typical bolt on Hellcat is maybe 1.8 area if pushing the stock blower hard just for reference.

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    Thinking about it and Hellcat is a good example of this being calculated... Every year and operating system doesn't calculate the same aircharge. Might have two cars running the exact same setup and boost logging the same and show 1.7 and the other 1.55 aircharge or something like that

  4. #4
    Quote Originally Posted by tbrtuning View Post
    Thinking about it and Hellcat is a good example of this being calculated... Every year and operating system doesn't calculate the same aircharge. Might have two cars running the exact same setup and boost logging the same and show 1.7 and the other 1.55 aircharge or something like that
    So can two cars be making the same horsepower with different aircharge? And what about N/A applications . If this number is calculated and calibrated for stock configuration, modding will skew it ?

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    Absolutely. It's just a number and doesn't have to reflect power. If I change displacement doing a stroker it seems aircharge goes up, but if you leave displacement stock and just add extra fuel aircharge will stay closer to stock. Power won't change though

  6. #6
    Quote Originally Posted by tbrtuning View Post
    Absolutely. It's just a number and doesn't have to reflect power. If I change displacement doing a stroker it seems aircharge goes up, but if you leave displacement stock and just add extra fuel aircharge will stay closer to stock. Power won't change though
    so a dyno is always the key , got it thank you very much. One other thing the torque indicated in the ecu like the actual and tge driver is there anyway to recalibrate it to reflect real values ? Or should i just treat it as a limiter that has to be removed ?

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    You can change the torque and airflow models to make indicated torque higher but not really much point. Sometimes it even causes you to get to torque limits you would never hit if you don't mess with it and let it think it's still close to stock power.

    Doesn't have to be a dyno but yeah you need some way other than watching aircharge to see if you're gaining power. Could be GPS acceleration, subtracting times from logs, track, program like Virtual Dyno that compares acceleration from logs. Just mentioning if you don't have dyno you aren't out of luck and there are plenty of other methods.

    There are times when aircharge might even go up but power go down. Cam timing with boost and aftermarket cams this can happen with pretty easily. More boost being measure leads to higher aircharge calculation usually but sometimes with cam timing you will reach a point where boost will go up and power go down.

  8. #8
    Quote Originally Posted by tbrtuning View Post
    You can change the torque and airflow models to make indicated torque higher but not really much point. Sometimes it even causes you to get to torque limits you would never hit if you don't mess with it and let it think it's still close to stock power.

    Doesn't have to be a dyno but yeah you need some way other than watching aircharge to see if you're gaining power. Could be GPS acceleration, subtracting times from logs, track, program like Virtual Dyno that compares acceleration from logs. Just mentioning if you don't have dyno you aren't out of luck and there are plenty of other methods.

    There are times when aircharge might even go up but power go down. Cam timing with boost and aftermarket cams this can happen with pretty easily. More boost being measure leads to higher aircharge calculation usually but sometimes with cam timing you will reach a point where boost will go up and power go down.
    i will be doing my first ever dyno tune session today , i always street tuned . do you have any pointers ?
    i already rescaled the injectors to get to 2% lamda error and set my spark with a little bit of knock somewhere in the realm of 2-3 degress . it's a 2015 charger 5.7 with cai , long tube 1-7/8 headers and no cats plus a catback . i'm really hoping to get good numbers the gas here is bad and the car won't take over 15.5 of timing at wot
    Last edited by malikib; 07-07-2020 at 09:04 AM.

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    Sadly a dyno isn't going to help you tune spark on a knock limited setup very much. You're not tuning for peak power you're tuning against an octane limit. Be cautious too because depending on the dyno sometimes engines seem to like a couple degrees more on the dyno than real world and will knock with the same timing as they were fine with on the dyno.

    What kind of lambda are you running? Try few percent different directions for AFR and also try to run it with cam advanced a few degrees each run a couple different times and compare the results. Might lean out as you get more efficient with cam timing. Something else you can do is just set the cam timing the same across the entire table and do pulls at each then check the highest torque area and what cam timing it was at to build your ideal table.

  10. #10
    Quote Originally Posted by tbrtuning View Post
    Sadly a dyno isn't going to help you tune spark on a knock limited setup very much. You're not tuning for peak power you're tuning against an octane limit. Be cautious too because depending on the dyno sometimes engines seem to like a couple degrees more on the dyno than real world and will knock with the same timing as they were fine with on the dyno.

    What kind of lambda are you running? Try few percent different directions for AFR and also try to run it with cam advanced a few degrees each run a couple different times and compare the results. Might lean out as you get more efficient with cam timing. Something else you can do is just set the cam timing the same across the entire table and do pulls at each then check the highest torque area and what cam timing it was at to build your ideal table.
    Yeah i realize this , that’s why i will first try to tune it on pump gas then i might use an lucas ocatane booster just to see what can be gained , the gas is 91 and i ran two lambdas 0.85 and 0.83 i saw a tad less knock with the 0.83 but not that major i always heard these hemis like to run rich
    I was going to play with cam timing as well i’m using the exhaust cam for this car and i will try different combinations i was think of retarding the cam at lower rpm and advancing it uptop after 4000 rpm or i might do as you suggested to set it as one number and see what works best
    Last edited by malikib; 07-07-2020 at 09:25 AM.

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    Try taking a couple degrees of timing out and leaning it out to maybe 0.88 for a pull also

  12. #12
    Quote Originally Posted by tbrtuning View Post
    Try taking a couple degrees of timing out and leaning it out to maybe 0.88 for a pull also
    i mean that leaner than my liking with such bad fuel ,but i might try it

    i have attached a log i did yesterday wwith the 0.83 lamda if you don't mind taking a look at it and telling me if there's something that needs improving run 12.3.hpl
    and if my injector rescaling is good enough

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    AFR and timing are kind of relative to each other. You can safely run really lean if you don't have too much timing in it. I'm not on the computer right now to look at log. Just run it on several different setups and you will find what it likes the best. I wouldn't pay so much attention to what the AFR or timing ends up at as much as if you find somewhere that's making good power without any extra knock just run it there.

  14. #14
    Quote Originally Posted by tbrtuning View Post
    AFR and timing are kind of relative to each other. You can safely run really lean if you don't have too much timing in it. I'm not on the computer right now to look at log. Just run it on several different setups and you will find what it likes the best. I wouldn't pay so much attention to what the AFR or timing ends up at as much as if you find somewhere that's making good power without any extra knock just run it there.
    Thank you for your advice and help , much appreciated one last thing is there an acceptable knock numbers with the stock knock thresholds ? Or should i always make sure there isn’t any inock at all . I have read that some factory tune with some knock in them

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    It's a bit difficult to say without seeing logs before and after timing changes or with higher octane as a test. Stock knock sensors might be a bit too sensitive if you're getting much extra noise from the long tubes but you're playing it safe leaving it where they are pretty active and pulling a little timing. Add some race gas sometime and if the knock goes away in same tune you probably are running right around knock threshold. If it still has the same kind of knock then dial back the sensors a little bit to just where it isn't picking up knock and that will be your more realistic baseline threshold to represent the normal noise without knock

  16. #16
    Quote Originally Posted by tbrtuning View Post
    It's a bit difficult to say without seeing logs before and after timing changes or with higher octane as a test. Stock knock sensors might be a bit too sensitive if you're getting much extra noise from the long tubes but you're playing it safe leaving it where they are pretty active and pulling a little timing. Add some race gas sometime and if the knock goes away in same tune you probably are running right around knock threshold. If it still has the same kind of knock then dial back the sensors a little bit to just where it isn't picking up knock and that will be your more realistic baseline threshold to represent the normal noise without knock
    Believe it or not , the knock got much less after the longtubes it went from -6 to -1 with no tune changes maybe different pump ?! .currently as it sits im seeing -3 max will test further and hope for the best
    Last edited by malikib; 07-07-2020 at 10:07 AM.

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    Might be real knock then. Another reason I think it might be is that you said when you added more fuel you got less knock. You probably are just at the limit of 91 octane. Cam timing change can help out

  18. #18
    I'm still trying to figure out the Dodge PCM, but one thing to take into consideration is if Dodge has this setup (I assume so) is the knock is recorded and the PCM automatically pulls timing kind of similar to LTFT. So each subsequnt run you can get less knock but still not really be at MBT. So you may want to make sure the PCM isn't doing any additoinal compensation with the timing.

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    You are correct that they do that with learned knock. You can log long and short term for the knock retard to see if it's learned

  20. #20
    Quote Originally Posted by tbrtuning View Post
    You are correct that they do that with learned knock. You can log long and short term for the knock retard to see if it's learned
    Thank you!

    I found it in the tables. Spark\Retard\Long Term Knock\Max Retard.. When dialing in the MBT timing you can set that to 0 and just run off of ST until you get it dialed in, then set your LTK. That way you aren't battling that as you dial it in