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Thread: Deceleration Rate Tuning

  1. #1

    Deceleration Rate Tuning

    I'm running a 5.7 with a 274 Cam 2.9 Whipple with 10lb boost. I'm trying to figure out the tables to increase the deceleration rate. When I let off of the gas the deceleration rate is very slow. Doesn?t actually run like cruise control but it's kind of like feathering the pedal to slow down very gradually.

    Do I need to adjust the numbers within table 35101 Desired TQ Minimum FW Tq?

    UPDATE:

    Almost a year to the day later I have some good updates to post on this one.

    I recently went through the process of working through disabling the decel fuel cutoff as I had issues with bucking. I started out with almost zero deceleration and I ended up with throttle hang with the clutch in/in neutral in a specific RPM range. I was able to dial that out using the friction loss table. I was actually able to dial in my overall deceleration rate, I now have a nice smooth transition from coast back to acceleration and a good deceleration rate. Also if you are having issues with the car stalling after say a rev then going back to idle this area will help with that as well. I have a bigger cam so you will notice in the idle rpm area I have it bumped up again in the lowest RPM range to catch the rpm without stumble or stall. One more point to mention, I had to drop the numbers above where I had the throttle hang for it to level out properly. I ended up smoothing out the transition with the needed drop for my trouble zone above and below the range. Attached is stock vs. updated. I haven't tried it yet but I assume this will address the 10 minute return to idle from a rev on the 5.7.
    Attached Images Attached Images
    Last edited by McCloud; 07-27-2021 at 01:56 PM. Reason: Update

  2. #2
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    Quote Originally Posted by McCloud View Post
    I'm running a 5.7 with a 274 Cam 2.9 Whipple with 10lb boost. I'm trying to figure out the tables to increase the deceleration rate. When I let off of the gas the deceleration rate is very slow. Doesn?t actually run like cruise control but it's kind of like feathering the pedal to slow down very gradually.

    Do I need to adjust the numbers withing table 35101 Desired TQ Minimum FW Tq?
    That'll be your ticket if that's the issue. Reduce the 'zero pedal torque'.

  3. #3
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    I don't think that's going to fix your problem, as smokeshow alluded.

    Can you share your file?
    If in doubt, multiply everything by 1.1.

  4. #4
    Quote Originally Posted by spoolboy View Post
    I don't think that's going to fix your problem, as smokeshow alluded.

    Can you share your file?
    I need to check to see if the person that provided the tune is okay with me posting it. Also do I want to post a tune I paid $1k for.. LOL.. I guess if I want help right!!! Anyway the tuner I used is slammed right now and it’s taking weeks to get a revision back, that is what gave me the final motivation to dive in and learn this stuff. Pay $1k for a tune and have drivability issues for months is far from ideal. And this won't be my last build.. If he is okay with it I will post it up.

    Either way appriciate the help.

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    Wow, I need to start doing the mail order stuff.

  6. #6
    Quote Originally Posted by smokeshow View Post
    Wow, I need to start doing the mail order stuff.
    It did also included a remote Dyno session wich actually worked out pretty well, my WOT is spot on. But yeah even if you spend a couple of hours setting up the intial tune and do upteen revisions (probably 10 min a pop) along with a few hours on a dyno it's pretty good money!

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    Quote Originally Posted by smokeshow View Post
    Wow, I need to start doing the mail order stuff.
    There is a lot of demand for the Hemi stuff and a lot of so-so tunes and tuners in the game. I think the main culprit is LS guys that don' t understand this platform.

    I only tune for friends/myself and admittedly I am a novice and know my limitations and stay within them.

    I think there is a reason there aren't many good Hemi tuners and the ones that are out there are backlogged indefinitely.
    If in doubt, multiply everything by 1.1.

  8. #8
    Quote Originally Posted by spoolboy View Post
    There is a lot of demand for the Hemi stuff and a lot of so-so tunes and tuners in the game. I think the main culprit is LS guys that don' t understand this platform.

    I only tune for friends/myself and admittedly I am a novice and know my limitations and stay within them.

    I think there is a reason there aren't many good Hemi tuners and the ones that are out there are backlogged indefinitely.
    Yeah Dodge tuning seems to be a secret trade... I've taken quite a few classes on tuning and I'm wrapping up another one now where they are going through working sessions.. 6 of them and not a single one is Dodge.. I'm hoping as I get through a few more that some of the manufacturers have similar layouts.

    IMO I think the lack of Dodge tuning knowledge is because Dodge was not much into the aftermarket performance arena up until quite some time after the Hemi was re-introduced. GM and Ford never missed a beat.
    Last edited by McCloud; 07-27-2020 at 11:53 AM.

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    Quote Originally Posted by McCloud View Post
    It did also included a remote Dyno session wich actually worked out pretty well, my WOT is spot on. But yeah even if you spend a couple of hours setting up the intial tune and do upteen revisions (probably 10 min a pop) along with a few hours on a dyno it's pretty good money!
    In that case, maybe I won't do any how-to's on the Chrysler throttle black magic. I've told you guys enough lol.

    GM's platform has had the benefit of being the easiest to relate to. Ford has always been the biggest pain in the ass in my opinion because they hate MAP sensors and use radial basis function nonsense to save a buck. And Chrysler historically being the opposite is a fair bit difficult to understand as well because the software has to be more robust and oddly complicated with only the MAP sensor. But GM doubled down...and people flocked to it. lol

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    Quote Originally Posted by smokeshow View Post
    In that case, maybe I won't do any how-to's on the Chrysler throttle black magic. I've told you guys enough lol.

    GM's platform has had the benefit of being the easiest to relate to. Ford has always been the biggest pain in the ass in my opinion because they hate MAP sensors and use radial basis function nonsense to save a buck. And Chrysler historically being the opposite is a fair bit difficult to understand as well because the software has to be more robust and oddly complicated with only the MAP sensor. But GM doubled down...and people flocked to it. lol
    Well, you'll be a perfect dodge tuner. Keep all the secrets.
    If in doubt, multiply everything by 1.1.

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    Lol. Is that what they do

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    to the OG question, i would look into the TB tables more. These whipple setups need a lot of adjustment in this area to get the throttle to feel good as well as the driver demand tables. I would start by lowering your TB tables more in small and large rang along with the airflow table. The lower the number the more the Tb opens. I try to keep all the tables close in respect to each other. If your getting the small cruise control affect you might need to make some adjustments in those areas, just play around with them and you figure them out.
    6.4 Whipple Diamond pistons Manley rods, Demon Plus Cam

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    Black magic indeed, although Hemituna's approach to the air tables seems to work pretty well even if it does not fit the "chrysler" way. Sure makes throttle response feel as it should especially when running FI on a hemi that was NA from the factory. This is where the "chrysler" way may not work as your TB has not changed but the way the engine "breathes" has.

    These are some of the post that come to mind regarding the approach.
    https://forum.hptuners.com/showthrea...l=1#post466902
    https://forum.hptuners.com/showthrea...hlight=airflow
    https://forum.hptuners.com/showthrea...nse-with-a-S-C

    In stock form, the 5.7s seem to be the worst of the bunch when it comes to throttle "hang" or throttle down which seems to take forever...especially when revving in park/neutral. In fact, when Roman & Nathan did a review comparing the 2015 6.2, 6.4 and 5.7 challenger I remember them revving ea model and the 5.7 sounded the least "muscle" of the three (even Nathan's face showed his disappointment) and I also remember it taking forever for the 5.7 to come back down to idle. Anyways, there are several posts about guys complaining about this but with no clear cut solution (at least not to us non-freemasons) which we chalk it up to being an emissions thing that cannot be changed. One would think the tuning school would shed some light on this in their 5.7/6.4 tuning course but no mention of it which has me thinking they don't know either.

    BTW if you don't know Roman & Nathan...this is their review I was referring to.
    https://www.youtube.com/watch?v=VnT7BAtZSU8
    Last edited by Homer; 07-28-2020 at 09:21 AM.

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    Hey I wouldn't know about the Chrysler way, I mostly worked on Fiat engines lol. I will say the most accurate and adherent piece of hardware is one where the physics of how it works is totally understood and accounted for in the controls that manage it. At least that's the goal. That's why we've been able to improve literally everything about engines...we understand them better than we ever have. The software can be really complicated but I don't think the calibration has to be. I've been doing quite a few how-to's lately and I'll be addressing the Chrysler throttle body issue in the near future. I do like to keep it simple, so it will involve a lot of the task being automated by math parameters and probably a spreadsheet.

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    Well it is one thing to get the physics/math squared away but another to actually convert it into something that works with the engine controller and calibration as defined and mapped out by HP tuners. For most tuners figuring out which table does what is probably 60% of the challenge. I remember just trying to change idle and was like...why the hell are there so many tables to accomplish one thing?

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    I won't make any false promises, if there is something that needs to be changed in your file and you don't have access to it (yet), then it will not work as well or it may not work at all. Though HP Tuners is getting better about it by the day and support seems to be pretty helpful. But if you really want something that has one table for all of idle, you could get a speeduino and run your Dodge on that

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    Already using a can bus shield on the arduino but only to sniff the bus (was helping a member try to decode the instrument cluster so he can use it in a resto mod application) and that's as far as I care to take it. Besides I live an emissions state so running a speeduino on my 2015 challenger sounds like a good way to fail.

    Anyways, lets get back to fixing throttle hang and how to make it go away.

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    Quote Originally Posted by smokeshow View Post
    Lol. Is that what they do
    Actually, I don't think the majority of them know either and want to keep that fact to themselves.
    If in doubt, multiply everything by 1.1.

  19. #19
    Thanks for all of the feedback!

    The majority suggest working with the TB tables. I have looked through a few and it seems the trend is to remove the arch from the stock tables, along with some overall airflow, but it seems the biggest impact is removing the arch. Pics attached.
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    Last edited by McCloud; 07-28-2020 at 05:04 PM.

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    What i normally do is just start taking away 20% from around 1.5v and down then just blend the transition. From my experience i drive the car a day or so to let the throttle adaptives to come back into play. Then readjust if necessary. I also try to make all 3 tables relatively close in regards to how they look as far as data, you wont get exact numbers for each spot but just generally close to each other.
    6.4 Whipple Diamond pistons Manley rods, Demon Plus Cam