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Thread: Gear Based Throttle Limits

  1. #1
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    Gear Based Throttle Limits

    Hello everyone!

    I'm new to HPTuners and tuning, but not new to Tundras; bought my regular cab short box 2WD brand new on December 19, 2007 while I was working as a Toyota tech. Considering I am new to the tuning world, please don't be afraid to point me in the right direction if I'm focusing on the wrong thing.

    Let me explain my goal here; I race my truck in a consistency-based brackets system at my local track. While I like to think I do alright, I'm not as consistent as I'd like to be, as I have to "feed the throttle" (depress the accelerator pedal to the floor more slowly than usual) at the starting line to prevent tire meltdowns. What I'm looking to do is take that variable out, and be able to fully depress the accelerator pedal while staging, then just be able to let go of the brake and have the truck "feed its own throttle" as it starts moving.

    I came across Gear Based throttle limits for 1st gear and 2nd gear in Engine > Airflow > Electronic Throttle (located directly above Sec Air Fault), which would be perfect for me, as it appears to work off MPH, so I could simply adjust the table parameters and values for proper throttle angle at, say 0mph, 1mph, 2mph, etc until I reach wide open throttle. Stock calibration file shows all the table values set to max throttle angle opening (89.84). The problem I'm running into is no matter what I change on this table, the truck doesn't seem to recognize it. I've tried leaving the table parameters alone and just changing the values, changing the table parameters and values, and still nothing. I've tried placing the truck in different modes, such as Auto LSD, traction control turned completely off, sport / manual shift mode (I even modified the sport shift mode to hold gears so I knew I was in 1st), and tow-haul. Nothing I've done so far makes the truck realize "hey, this guy wants less throttle opening while he's stopped".

    The truck does recognize other throttle limits such as Fwd/Rev and Secondary Air Fault (and yes, I unplugged my secondary air injection system to test this, haha), so I'm wondering if there's something I'm doing wrong? Maybe a specific mode that the truck has to be in for those settings to work? I wouldn't imagine that HPTuners would put that table there if it couldn't be adjusted, would they? Maybe there would be a better way for me to achieve what I'm trying to do?

    I tried reaching out to HPTuners support about this, and was directed here by the agent I was speaking with. Any and all input is much appreciated. Thank you!

  2. #2
    try optimum engine torque table it should do what you are looking for but its based on engine load.

    you could also try torque based limit low/high load.

    the stock ecu traction control strategy is not as advanced as standalone ecus, its not based on speed, its based on engine load and estimated torque, so its not gonna be consistent but it should allow you to floor it from dead stop and not lose traction its just gonna make you alot slower in my opinion.

  3. #3
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    Quote Originally Posted by QTR FMS View Post
    try optimum engine torque table it should do what you are looking for but its based on engine load.

    you could also try torque based limit low/high load.

    the stock ecu traction control strategy is not as advanced as standalone ecus, its not based on speed, its based on engine load and estimated torque, so its not gonna be consistent but it should allow you to floor it from dead stop and not lose traction its just gonna make you alot slower in my opinion.
    Thank you for the response! Correct me if I'm wrong, but changing the optimum engine torque would allow for a slower ramp-up of engine power, but likely would not allow me to keep the accelerator pedal on the floor at the starting line while the truck is stopped for any period of time, correct? Power would basically keep creeping up until it simply reached the normal engine load settings, correct? Basically, I could slam the accelerator to the floor, but not until the light went green? I have tried what I believe to be something similar to this by limiting throttle at specific Engine RPM using the 1st gear maximum throttle angle table in the Fwd / Rev section. I was actually able to get the truck to hold a specific RPM on the starting line, which was awesome, but when launching, the RPM would either hold where it's at or drop (tight torque converter?) and this would make launches extremely slow.

    While I definitely agree that the stock ECU is behind standalones, I am still wondering if HPTuners has found a way these trucks may control throttle output based on vehicle speed. Here is the table I'm looking at;

    Gear Based 1.png

    Gear Based 2.png

    This basically seems to do just that; limit throttle based on vehicle speed, correct? I just can't get it to work at all. Considering an example that HPTuners doesn't have any 4X4 tables available for a non-4X4 truck, or that there's no tow haul tables on a non-tow haul truck, I have to believe they have that table in there because changing it could modify how the truck drives somehow (why would they put it in if it doesn't do anything?). Because changing those values does nothing in a normal scenario, I have to imagine that something triggers it, similar to the max throttle angles for limp mode scenarios like secondary air malfunctions. It would be much more desirable to be able to control throttle based on vehicle speed if possible. Anyone know how the truck might recognize the table above?

  4. #4
    Can't say that I've ever done any work with the throttle limits by gear table, only the 4Lo tables (most want to always go the opposite direction and have the least possible throttle intervention), but there may be other conditions that need to be met before those tables are active; that said, I'm not confident that you'd really find the results to your liking even if they were working.

    Assuming you're willing to give up your normal Tow/Haul, try modifying the Tow/Haul Desired Throttle Angle tables, specifically for 1st and 2nd. Here's how to approach it:

    Logging throttle angle, TPS, Engine RPM and Vehicle Speed, capture a few launches - some leaving a little too soft, some with moderate wheelspin, and some leaving as close to perfectly as possible (Engine RPM and Vehicle Speed will help identify these).

    From those logs, determine the throttle angles approximately corresponding to each of those points and map them onto the 1st gear Tow/Haul Desired Throttle Angle, with ~25% TPS corresponding to the low end (leaving soft), ~75% TPS corresponding to the high end (moderate wheelspin), and dead in the middle corresponding to your best launches. Below 25%, just blend in to get good drivability, above 75% ramp up to WOT, for 2nd blend those values towards the regular throttle mapping. Obviously, those boundaries and how TPS/Throttle Angle ramp throughout can be adjusted (I would suggest a linear mapping of TPS to torque in the window), the main concept is to put most of the TPS travel (and, thus, fidelity to the user) around the area you care about. It still leaves the launch in your hands (or foot), but your sweet spot around a good launch goes from a small fraction of TPS travel to nearly half.

    If you want, post a copy of your file and I'll create an example for you to look at later this evening.

  5. #5
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    Quote Originally Posted by QTR FMS View Post
    try optimum engine torque table it should do what you are looking for but its based on engine load.

    you could also try torque based limit low/high load.

    the stock ecu traction control strategy is not as advanced as standalone ecus, its not based on speed, its based on engine load and estimated torque, so its not gonna be consistent but it should allow you to floor it from dead stop and not lose traction its just gonna make you alot slower in my opinion.

    Does it really makes the car alot slower? just asking to make sure.

    i usually increase the torques base by 30% and some by 20%
    but i never felt that the car became slower. but when i decrease the numbers i can feel that the car became slower and even while shifting btw gears.

    also some cars can not add more than 25% as the TPS goes off.

  6. #6
    Quote Originally Posted by Mr.AT View Post
    Does it really makes the car alot slower? just asking to make sure.

    i usually increase the torques base by 30% and some by 20%
    but i never felt that the car became slower. but when i decrease the numbers i can feel that the car became slower and even while shifting btw gears.

    also some cars can not add more than 25% as the TPS goes off.
    The newer ECU uses the optimum engine torque table to reference cruise control on those ecu's I don't recommend tuning the optimum engine torque.

    If you have the older ECU, you can just max out the table, and you won't have any traction control, which will be faster.

    You are correct. Decreasing the value makes it slower, OP wants to make his car slow to make it hook better and improve his 60 feet.

  7. #7
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    Quote Originally Posted by QTR FMS View Post
    The newer ECU uses the optimum engine torque table to reference cruise control on those ecu's I don't recommend tuning the optimum engine torque.

    If you have the older ECU, you can just max out the table, and you won't have any traction control, which will be faster.

    You are correct. Decreasing the value makes it slower, OP wants to make his car slow to make it hook better and improve his 60 feet.
    Thank you for your reply.
    is there another way to control the traction control with the new ecu.
    also i found out that some Lexus ecu shot of the throttle as soon as you increase the optimum engine torque.