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Thread: Can MAP trigger a shift?

  1. #1
    Tuner Pector55's Avatar
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    Can MAP trigger a shift?

    Car is a 13 Challenger RT with HC TB, 2.9 Whipple, little meth kicking in at 12psi, Apache heads, HC cam, 6.2 block, long tubes - should be a little over 15 psi in this weather (3.125 with 18% OD) - 2 bar MAP

    I'm noticing that since bumping up the boost something is triggering a shift right as the MAP hits 200-201. I suspected it was torque modeling or airflow related so I've been adjusting those and I thought I was moving in the right direction but then realized that it still shifted right at the same area on the MAP. I have hit 15 psi but I think there is a little more in it if it actually ran up to the actual shift. I've hit this anywhere from 5800-6100 RPM, depending on the weather so I'm looking for some ideas.

    OR - am I just seeing the limit of the MAP sensor since we are already at 1 bar (atmosphere) and 1 bar is 14.5 psi? If so, that makes sense.

    It's not max airflow or airflow to RPM because I've not hit close to that yet.
    I'm aware of Max MAP setting in Engine Diagnostics and that is set up to 225.
    It's not the fuel cutoff settings as those are up at 6600 and my shifts are set to 6300 with my TCM RPM limit also at 6300. I recently moved both up just to make sure I confirmed it wasn't them.
    Torque Management is all on in the engine and trans side.
    Last edited by Pector55; 06-28-2019 at 09:53 AM.
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    On the newer cars with the A8 there are different shift schedule maps for when ESP is active.

    Are you triggering ESP to step in?

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    Quote Originally Posted by spoolboy View Post
    On the newer cars with the A8 there are different shift schedule maps for when ESP is active.

    Are you triggering ESP to step in?
    My ESP is set to use spark. As I understand you can enable it for spark, fuel, and throttle and none of those change. It hits the 200 limit on the map and map collapses whereas everything else keeps going as normal. That's why I was troubleshooting it as a torque modeling or airflow issue at first. See the attached pic. It felt like the throttle body closed but nope.. you can see everything kept going except the MAP. Just for giggles, I will set the MAP limit back to 200 and see if the behavior changes. My 3 bar is on the way from HHP so I believe that will resolve everything.

    This is an older car with a NAG1. I realized that I raised the MAP limit from 200 to 225 and I'm wondering if the car is kept a the 200 limit, will it just continue to operate as normal, just never record over the 200 kPA limit. If boost were to be significantly beyond this, it would be a problem as you could not scale PE_Pratio correctly but a car like mine where the boost is right on the edge between 14.5-15.5 depending on weather, would be fine like this.

    Just so everyone knows, it does not appear to be advisable to raise the MAP limit beyond the MAP capacity. lol It was a "duh" moment for sure.
    MapCollapse.JPG
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    Assuming you're using an SRT-4 MAP sensor, it's actually not a 2 bar, but a 2.25 bar sensor. In which case, setting your MAP limit to 225 would have no Ill effects. A 3 bar sensor isn't going to solve your problem in that scenario.

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    Quote Originally Posted by B00STJUNKY View Post
    Assuming you're using an SRT-4 MAP sensor, it's actually not a 2 bar, but a 2.25 bar sensor. In which case, setting your MAP limit to 225 would have no Ill effects. A 3 bar sensor isn't going to solve your problem in that scenario.
    When I got my Whipple, the map had been smashed in shipping so I got a 2 bar from HHP. I called and checked with them and confirmed that it was just a 2 bar. I always thought the Whipple came with an SRT4 MAP but I have no clue.

    I'm not convinced going to a 3 bar map will solve the shift yet either btw, but it appears to be time to do so, so I figured I would rule that out. If you have any suggestions on what to look for, I'm all ears.
    Last edited by Pector55; 06-28-2019 at 04:15 PM.
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    Quote Originally Posted by Pector55 View Post
    When I got my Whipple, the map had been smashed in shipping so I got a 2 bar from HHP. I called and checked with them and confirmed that it was just a 2 bar. I always thought the Whipple came with an SRT4 MAP but I have no clue.

    I'm not convinced going to a 3 bar map will solve the shift yet either btw, but it appears to be time to do so, so I figured I would rule that out. If you have any suggestions on what to look for, I'm all ears.
    https://www.highhorseperformance.com.../5033224ab.htm

    If it's the above sensor, it's a 2.25 BAR sensor. They (and pretty much everyone that sells it in the aftermarket) have it advertised incorrectly. One way to verify is to look at your MAP Sensor Linear value [ECM 44271]. If the value is 46.38 kPa, then your tune is scaled for 2.25 BAR, and if you check with the scanner at key on engine off and see that your MAP value matches your atmospheric pressure, then you know it's scaled properly.

    All that aside, there's no harm in going with a 3 bar MAP sensor, as long as you rescale for it.

    It would be helpful to make an attempt at diagnosing your issue if you provided a proper log file and corresponding tune file.

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    Quote Originally Posted by B00STJUNKY View Post
    https://www.highhorseperformance.com.../5033224ab.htm

    If it's the above sensor, it's a 2.25 BAR sensor. They (and pretty much everyone that sells it in the aftermarket) have it advertised incorrectly. One way to verify is to look at your MAP Sensor Linear value [ECM 44271]. If the value is 46.38 kPa, then your tune is scaled for 2.25 BAR, and if you check with the scanner at key on engine off and see that your MAP value matches your atmospheric pressure, then you know it's scaled properly.

    All that aside, there's no harm in going with a 3 bar MAP sensor, as long as you rescale for it.

    It would be helpful to make an attempt at diagnosing your issue if you provided a proper log file and corresponding tune file.
    Good info on the 2.25. I specifically called and asked about that sensor too so it's unfortunate that they advised incorrectly. I honestly don't plan on going too much higher in boost so I may not need to go to a 3bar.
    I did the tune myself, never been to a shop or tuner, so we can't trust the value in that field but that's good info on checking vs atmosphere (just checked and both atmosphere and Map were at 14.5psi).

    I did a fresh 3rd gear pull this morning. I'll attach that and my tune and scan.

    Dodge Challenger_6.2_07012019_MAP200shift_A.hpt
    07012019_MAP200_shift_A.hpl
    Last edited by Pector55; 07-01-2019 at 01:49 PM.
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    I will do another pull on the way home. Since the airflow drives the torque numbers I'm hoping that maybe this is just a torque limit somewhere. I scaled back on my airflow table in the higher ranges and increased the max flywheel torque to see if that changes anything. I added airflow numbers to my scan too. I just don't see anything MAP related so maybe it's the underlying "drive-by-torque" nature of these cars or something.
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  9. #9
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    Set MAP limits back to 200 after reading this thread: https://forum.hptuners.com/showthrea...00-under-boost

    She shifted way up around 6500 so I just need to clean up the shift now. Odd that moving the MAP limit to 225 created such a problem.

    It was also odd that it hit 14.50 (200kPa) and then started decreasing until it shifted. I am hoping that swapping to a 3 bar fixes this.
    MAP200Shift.PNG
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    In speaking to Stephen Dixon at MMX, apparently the 11-13 years have a map limit in the pcm that is known. At this point, the work-around appears to be the use of a map clamp.
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  11. #11
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    In case anyone finds this issue: Here is a link to another thread with the workaround - set the Max Map limit to 195 kPa https://forum.hptuners.com/showthrea...h-supercharger
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