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Thread: Understanding the Dodge ETC system: Tuning for a linear throttle response with a S/C?

  1. #1
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    Understanding the Dodge ETC system: Tuning for a linear throttle response with a S/C?

    I've read countless threads about the Dodge ETC system and how to tweak (trick it) into achieving improved throttle response. Implementing these methods such as altering the DD tables, flywheel % power, throttle body airflow etc have definitely helped and slightly enhanced the response on my 3.6/NAG1 Sprintex S/C'd Pentastar. However, I'm still finding the part throttle response vague, jumpy and somewhat disconnected from the actual pedal input.

    While I can (just) live with this type of response onroad under normal driving conditions, it becomes absolutely woeful offroad! This is where predictable throttle response throughout the whole pedal range is crucial, especially when it comes to technical driving such as rock crawling.

    The 2 major problems I have observed so far is that with a fixed pedal position, the actual throttle blade opening also seems to be dependent on (1) RPM, and (2) aircharge/manifold pressure/pressure ratio. Eg: the throttle opening increases with RPM and with aircharge/manifold pressure/pressure ratio irrespective of the pedal position. This makes it very difficult to drive as you always have to alter the user input to the system (the pedal) to try and compensate. This is further compounded with the NAG1 somewhat shifting at will.

    So, does anyone know exactly how this Dodge (I assume torque-based request) ETC system works and what tables/parameters I need to target to gain predictable throttle control? I'm hoping that the people in the know could chime in with their 2c.

    From researching various threads, I suspect the ETC system works as follws: (Please correct me if I'm wrong)

    1. Pedal % Power Request - [ECM] 35060. Pedal voltage vs NVRatio (RPM/VSS) requests a driver demanded power %
    2. Power % Request (Flywheel) - [ECM] 34542. Takes the driver demanded pedal % request and RPM to request a % of the maximum available torque.
    3. Indicated Aircharge to Torque per Cylinder - [ECM] 19645. This is the maximum torque per cylinder model. The torque request is determined by applying the power % request flywheel to this maximum torque.
    4. Friction Torque - [ECM] 12882. Friction torque losses are added to the torque request to get a total torque request. *(not too sure on this one)*

    So now we have our torque request per cylinder. Multiply by the number of cylinders to get the engine torque request. According to the HPT info bar this torque request then gets converted to an airflow request by:
    Airflow = (Torque - Offset) / Factor or according to 06300CSRT8 it may actually be: Airflow = (Torque/Factor) - Offset https://forum.hptuners.com/showthrea...ue-Correlation
    using:

    5. Torque/Airflow Factor Offset - [ECM] 44386. Torque offset by RPM vs PRatio.
    6. Torque/Airflow Factor - [ECM] 35032. Torque to airflow conversion factor by RPM.

    From this airflow request I believe that the throttle body opening (voltage) is determined by the following throttle volts vs mass airflow tables which have to be equal and inverse to each other.:

    7. ETC Throttle Body Airflow - [ECM] 35035
    8. Desired Throttle Small Range - [ECM] 44388
    9. Desired Throttle Large Range - [ECM] 44387
    Last edited by HaasExp; 06-08-2020 at 02:26 AM.

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    With that apparent theory cobbled together I made some significant changes to the tune in an attempt to minimize the variables and gain full control over the throttle opening.

    Firstly I must list a few precursors that may or may not affect the whole system:

    NN is disabled, VE tuning mode.
    Sensed MAP is enabled (if disabled changes to the throttle body airflow tables also dont seem to do much at all you will eventually throw a P2173 code and go into limp mode).
    Sensed MAP PR threshold set to 0.25.
    Set the pedal WOT limit to 5V so its always in part-throttle mode and doesn't just snap the throttle wide open.

    I started by eliminating the effect on the NV Ratio in the Pedal % Power Request table by making all the columns the same value:
    PedalPowerRequest.JPG
    The Pedal Expected table was set to be the inverse of this.

    Then eliminated the effect of RPM in the Power % Request (Flywheel) table by making all the columns the same value:
    PowerRequestFlywheel.JPG

    I flattened out the torque in the Indicated Aircharge to Torque per Cylinder table to eliminate any RPM and aircharge effects at and above 400mg:
    TorquePerCyl.JPG

    Zero'd out the Friction Torque and Torque/Airflow Factor Offset tables and set all the Torque/Airflow Factors to 1.

    The idea behind all these changes was to allow the pedal to drive the whole system. Eg Pedal at 0.6V = 35% pedal power request, 35% pedal power request = 35% Flywheel power request = 35% of the max available torque. Thus above 400mg aircharge the only influence on the throttle opening should be the pedal as the torque has been flat-lined.

    All the throttle body tables have been significantly tweaked from stock to "trick" the ECU into thinking the sonic airflow is much less than stock in an attempt to gain better response as per the info i found in this thread https://forum.hptuners.com/showthrea...-Throttle-Body

    With all these changes and variables eliminated the throttle opening (throttle voltage in white) is still effected by RPM and aircharge/manifold pressure/pressure ratio even though the pedal voltage (red) remains fairly constant:
    ThrottleLog.JPG

    So what else is still influencing the throttle here? I've set a reference line at 400mg Aircharge so above this nothing should alter the throttle voltage according to the perceived theory....

    Other weirdness also includes:
    Engine torque losses are not zero even though the friction torque table is zero'd. Where is this coming from?
    The trans engine torque is not exactly flat-lined above 400mg even though I have set it as the same values in the Aircharge to Torque per Cylinder table. Engine torque losses don't seem to entirely account for this.
    Even when the trans engine torque has flat-lined in the log and the pedal voltage is fixed, the throttle voltage still increases with RPM and aircharge/manifold pressure/pressure ratio.

    This has got me stumped and going around in circles hence the call out to the tuner community that know more than I do.

    Where do I go to from here? What am I missing? Any discussion, tips or info would be greatly appreciated.

    Tune and datalog attached.
    03-06-20v3.hpt
    03-06-20v3_2.hpl
    Last edited by HaasExp; 06-08-2020 at 01:09 AM.

  3. #3
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    You don't actually really want a direct connection between pedal and TB.
    Drive a blower car with a cable throttle and you will FEEL the non linear response.
    All the ETC tables are there to get the required feel to the pedal (and you can pretty much make it feel however you want, touchy/lazy and anywhere inbetween).
    We tweak the tables to get the right pedal feel (which is still subjective) and will be quite different on a 500hp vs 1000hp set up..
    But be aware that when you tune the engine and get more power/response it will need to be altered....
    Even a pulley swap changes things up as the blower works harder and now gives you more engine for the same amount of pedal.
    Then the trans needs to be adjusted to utilise the newfound tq increase (and pedal %) ....So around and around we go......
    All this can take way longer than simply tuning the af and timing, but really makes the difference between a good tune and a great one.
    Last edited by Hemituna; 06-08-2020 at 06:06 PM.

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    I have been doing a good bit of remote tuning lately and ask people for feedback and make adjustments and have found different people like very different things. I've had people want what I know I would not want to drive it's so touchy or so firm shifting and then have others that want a pretty lazy pedal feel.

    Being able to adjust by drive mode allows for best of both worlds really though. Can have the nice and comfy and sporty aggressive feel at the same time.

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    Appreciate the discussion guys. I've lost count of how many tunes/datalogs I've done trying to get my head around this system. Maybe I'm just looking in to it too deep and have missed something very simple. Hence the call out.

    Quote Originally Posted by Hemituna View Post
    You don't actually really want a direct connection between pedal and TB.
    Drive a blower car with a cable throttle and you will FEEL the non linear response.
    I understand what you are saying here Hemituna. If it were a direct connection I guess you would be riding the actual engine torque curve of X% throttle opening which will feel non-linear as it will "take off" through the rev range etc.

    This is currently what I'm experiencing, however it is further amplified as the throttle seems to open up more due to RPM and aircharge/PRatio/Mani pressure. This happens regardless of my fixed pedal position.

    The RPM and aircharge/PRatio/Mani pressure seem to be independent influences that are opening up the throttle as shown in the following data log.
    ThrottleBehaviour.JPG

    Circled in blue is where the throttle seems to open due to RPM. Pedal pos, aircharge/PRatio remain fairly constant.
    Circled in white is where the throttle seems to open due to aircharge/PRatio. Pedal pos and RPM remain fairly constant.

    I guess my questions are:

    1. Which table(s) should I focus on to tweak/tune and eliminate the throttle dependence on RPM? Power % Request Flywheel | Torque/Airflow Factor | Torque/Airflow Offset | Aircharge to torque? All these tables are based on RPM.
    2. Which table(s) should I focus on to tweak/tune and eliminate the throttle dependence on aircharge/PRatio? Torque/Airflow Offset | Aircharge to torque? These tables are based on PRatio or Aircharge.

    Thanks for your time.

  6. #6
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    Looks like your airflow values are still too big.

    The OEM numbers for airflow max are tiny and raising them does not raise the PT limits....they stay the same.
    So at PT it is following the OEM airflow limits vs rpm...and yes they do increase at higher rpm. (you will need to log total airflow also, aircharge has its place but airflow is what is limited here)

    Say your TB/large airflow is set at 100gs at 1.0v and the OEM limit is 100gs at 3000rpm, you wont ever be able to get more (no matter what you do to the tables) than 1.0v TB at 3000rpm unless you go WOT.
    To get more from PT, lower the airflows alot....for rough example, make - 1v 50gs - 1.5v 75gs - 2v 100gs - 2.5v 125gs etc (obviously keep idle and off idle same as you had it but blend into the new numbers from there up)...
    You will find it will still only allow you 100gs but that is now a 2.0v TB opening.

    (As a reference, I use a lil bit less than the OEM NA airflow numbers as the 3.8v number which is from memory about 160 gs max on a maggie 3.6L V6 and 320gs max on a 6.4L Hemi whippled with 100mm TB, so dont be scared to go small).

    Obviously you will now need to calm down DD flywheel power and maybe DD a little to get it to feel nice (it will be suuper responsive with those changes).
    There will no longer be a step between PT and WOT (set it back to 3.7ish) if done correctly as TB is already open enough and you should get a heap of super-controllable boost at all rpm.

    You will also need to rejig the trans tune to work with the new numbers (TQ wont be anywhere near reality, it will read similar to stock but be making a heap more)
    Treat the PCM like the IRS and only tell it what it needs to know and it will co-operate.
    Last edited by Hemituna; 06-09-2020 at 02:58 AM.

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    The Tuning School just put out a short video on this subject. Looks to be a little different way to do it, but it is on a Hellcat Charger, so it might help.

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    That video shows a very hack way to get full throttle at lower pedal positions that is definitely not what I would recommend for a linear throttle feel. You wouldn't want throttle body to suddenly open all the way at something like 3/4 throttle because you end up with a really weird part throttle effect in that area where you go from 70% throttle opening to 100% with barely any change in pedal. On a blower car in particular you want a longer more linear pedal feel without sudden transitions

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    Quote Originally Posted by Hemituna View Post
    Looks like your airflow values are still too big.
    The OEM numbers for airflow max are tiny and raising them does not raise the PT limits....they stay the same.
    So at PT it is following the OEM airflow limits vs rpm...and yes they do increase at higher rpm. (you will need to log total airflow also, aircharge has its place but airflow is what is limited here)
    Cheers for the advice! I ended up reverting to all stock tables and set the TB airflow model, small and large range to roughly the values you recommended, blending them to the stock idle and off idle values.
    ThrottleAirflow.JPG

    Focussing on the DD flywheel power table I dropped the % significantly in the upper RPM ranges which managed to tame it down and mostly avoid the RPM "take off" effect I was experiencing earlier. Still needs a bit of work but its definitely a step in the right direction.

    However, now I have come across a rather unnerving/worrying situation where the throttle wants to remain open even though the pedal is at 0.00V after a high RPM (>4500) stint. In the following datalog it takes over 4 seconds after I've lifted off the pedal before the throttle starts to close and another ~5s to close to idle opening values. What is causing it to stay open like this?
    ThrottleOpen.JPG

    Quote Originally Posted by Hemituna View Post
    (you will need to log total airflow also, aircharge has its place but airflow is what is limited here)
    Now this total airflow PID has some very weird behaviour. I can only get it to around ~50g/s just before I get on boost (PR<1.0). Once PR>1.0 it actually drops significantly even though the aircharge is still increasing. The only way I've managed to get realistic total airflow numbers that don't drop on boost is by disabling Sensed MAP. However doing so really kills the throttle response and eventually trips a P2173 code as I've previously discovered: https://forum.hptuners.com/showthrea...l=1#post610137

    Am I running into some sort of airflow limit or something that's causing these messed up total airflow numbers?

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    It will do this on overrun so the the vehicle continues to "roll" when you lift off the gas.
    Increase the airflow numbers in this area so it will shut the TB a bit more to remove the cruise control effect....this is part of the "blend" I mentioned.
    Idle and off idle need to stay big enough to close the TB so it idles nice and runs down off throttle, but above .75-1v you can run the much smaller numbers than stock.
    Some OS's carry on with airflow readings, most just quit as we are using sensed map, but it will still limit tb airflow to rpm table numbers even though it doesn't show a reading...so just continue with small airflows and DD until you get it to feel the way you want.

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    I have been making significant changes to the power % request flywheel table and along with the large reduction in the throttle body airflow/small range and large range tables I've got this supercharged Jeep driving 1000% better than it ever was!!! Now the throttle blade actually tracks the pedal input and doesn't change significantly with RPM.
    An added bonus is that the trans isn't downshifting near as often and this thing just crushes hills without dropping gears and revving its tits off now. Amazing transformation!
    Still working on the flywheel table under higher % power requests but for normal daily driving its great!

    One thing I still can't seem to get on top of is the power surge when I just get into boost. The throttle seems to open by itself when just coming on to boost (Im guessing this is the point where the bypass is closing) which I cannot tune out by the RPM based flywheel power tables. The throttle behaviour seems to track the sharp increase in aircharge/PRatio/torque here.
    ThrottleBoost.JPG

    From the datalog (circled in red) this behaviour seems completely independent of the RPM and pedal position.
    This is very different from the RPM dependant behavior (circled in blue) which I can tune out through the flywheel power table.

    This increase in throttle results in a very noticeable (unwanted) surge in acceleration especially in the lower gears.

    What do I need to tweak to remove/control this throttle behaviour and eliminate this surge coming onto boost?
    Do I need to rejig the torque table here? The aircharge axis on this table is still stock and only goes upto 750mg. This value is easily exceeded on boost.
    Last edited by HaasExp; 06-16-2020 at 06:29 AM.

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    So according to the HPT info bar you can apparently demand upto 200% of the available torque from the power % request flywheel table.
    Has anyone had success using values above 100% in this table? Or does the PCM just cap it off at 100% regardless?

    Im struggling to achieve throttle openings greater than 1.2ish V at low RPMs (<2500) regardless of how high my pedal voltage is. Seems like i need to demand much more than 100% of the available torque to achieve this.

    At higher RPMs (>3500) I don’t have any issues making it to WOT openings (even though I’ve temporarily disabled the WOT threshold for ETC tuning purposes). I’m assuming this means my throttle airflow values have been reduced enough to achieve this. Currently I’m at ~130g/s at 3.8V so I don’t think i need to lower them any further?

    @Hemituna have you managed to achieve full range throttle response at low RPMs? Eg have you been able to get a linear pedal response right upto WOT with low rpms? (<2500)

  13. #13
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    You are probably hitting a torque or airflow limit down low if you have raised the Max Throttle Voltage and still get limiting. Log Actual Torque and Expected Torque where it happens. Also Throttle Torque Source

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    That’s what it almost feels like tbr.

    I’ve raised the max throttle voltage to 3.8V across the board to make sure that was never a factor. Could Max Indicated Torque have anything to do with it?

    The only torque related PIDs I can log are engine torque and trans engine torque. I guess I could ask support to try and add the expected and actual torque PIDs to my ever growing request list. Any other useful PIDs that I need to request to aid in ETC tuning?

    Ill double check what the throttle torque source is doing when this happens but I’m pretty sure it never changes from “pedal”

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    How much boost are you getting with the 1.2v TB opening at low rpm?

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    So this screen shot clearly depicts the issue with the throttle not opening above a certain amount at lower RPMs.
    ThrottleNotOpening.JPG

    Circled in red you can see the pedal voltage is still increasing but the actual throttle opening (volts) seems to be capped and even starts to slightly decrease, which in turn slightly reduces the RPM (this is a descent hill I'm testing on).
    These pedal voltages (~1.3 to 1.85V) convert to a power % request from ~60% to ~75% according to my power % request table. The torque request source remains on "pedal" throughout this problem area.

    Transposing this request range into the power request % flywheel table I should clearly be demanding an increase in the available engine torque but this is not being converted into a throttle request for some reason. HPT info bar says that upto 200% can be requested hence my values above 100%.
    PowerFlywheel.JPG

    It's only until the auto downshifts and the RPM rises to ~2.7k+ that the throttle opens significantly which is quite annoying as there's now too much power on tap and I have to back off to maintain the speed. Definitely not seamless.

    Do I have to reduce my ETC airflow table further? It's currently only at 130g/s @ 3.8V and the throttle does open up fully (even with the WOT switch disabled) but it needs ~3000rpm+ to do so.
    ETC Airflow.JPG

    My Max Demanded Throttle table is set to 3.8V from 1100rpm up. I've tried maxing out the Max Indicated Torque table.
    In the engine diag I've also maxed out the:
    Torque Delta
    Toque Delta Fault
    Airflow Max RPM

    I have a supercharger and thus the potential torque available down low so I shouldn't have to wait till the RPMs rise to be able to use it. Kind of defeats the purpose...

    So the question remains: How do I get the throttle to open further at lower RPMs? What is limiting me here?

    Current tune and log attached:
    19-06-20v2.hpt
    19-06-20v2.hpl

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    Quote Originally Posted by Hemituna View Post
    How much boost are you getting with the 1.2v TB opening at low rpm?
    MAP of around ~130kPa (PR = 1.30) @ 1800rpm @ 1.22V Throttle. So around 4.5psi in my latest example.

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    Sounding like tq limit.
    I would look into what tq it reads at low rpm

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    From my PID list I've only got Trans Engine Torque and Trans Converted Engine Torque. They mostly read the same.

    Are there any other PIDs I could request that would possible help in this situation? Are there any PIDs related to driver demmand?

    To give a few examples of the tq at lower RPM where I seem to be capped:

    ~250nm @1250rpm 0.64V throttle 1.00PR
    ~312nm @ 1850rpm 1.22V throttle 1.30PR

    Are there any other RPM based torque limiter or throttle limiter tables besides the Max Demanded Throttle table that you are aware of?

  20. #20
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    Look in the section with Driver Demand for a Max Flywheel Torque or something like that and see if you're stuck following that at low RPM. I don't really know what the stock 3.6 tunes look like but that's a common one.