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  1. #1
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    4 out of 4 members liked this post. Yes Reputation No

    COBB Tuning: Boost vs Load in ATR

    Hi All, so i have been learning the ATR beast to try to dial in the boost for street & road courses.

    Problem Statement:
    the OTS high boost and fast taper was a bit disappointing to say the least, especially for a 30 minute road course session. High IAT, uneven torque, etc.

    methodology:
    sooooo, i started logging Stage 2+ aggressive and E30 maps.

    plotted boost vs load (Actual), plotted a linear equation, long and behold, a good correlation. and then used this data to get a nice little table to dial in boost.

    i used road course logs (1.5 hours of so) of data to plot this, have over 10k points.

    looks good so far.

    results are attached in the graph.

    conclusion:
    i understand ever car is different but here a quick starter so you can adjust your custom map boost using load values.

    enjoy.
    Attached Images Attached Images  

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    It is somewhat expected to have boost vs actual load to have a linear correlation. What I think you should look at next is how this is mapped to throttle, because this is the only thing you can control and change (throttle angle) while on the road coarse.

    I would recommend sticking to a linear throttle-to-boost correlation as well. You don't want "lumps" of torque coming out of a hot corner.
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    Unfortunately, it's not that simple. Load is calculated using TPS, air mass and RPM(other stuff too probably.) As RPMs climb more load is required to maintain the same boost pressure.

    Just as an exepriment: try running an ATR map that has 160 load targets all the way across, what you'll see is that boost still tapers off as the revs climb.

    If we knew exactly what the calculations for load were that would make "boost targeting" a lot easier to nail down.
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    Although it is not always like this, it's very close most of the time and all in all the calculation is very helpful, thanks ! I did need this a few days ago when I did a lower boost map. No need to spend some gallons of gas and multiple ECU flash writes to find out Click here to enlarge

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    Click here to enlarge Originally Posted by rader1 Click here to enlarge
    Just as an exepriment: try running an ATR map that has 160 load targets all the way across, what you'll see is that boost still tapers off as the revs climb.
    This is because your stock turbos cannot sustain the corresponding boost up to redline, and your intercooler cannot hold constant IAT to redline.

    The dependencies for the same car and the same weather are mostly linear. The IAT does play a role though, but it can be easily factored in when choosing the targets.

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    Hi Vasil,

    i added the linear curves (ran e30 linear at track) same slope and relationship as Stock throttle.

    have you had any luck changing the (throttle angle) at the track? any recommendations?

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    Click here to enlarge Originally Posted by neilvosko Click here to enlarge
    Hi Vasil,

    i added the linear curves (ran e30 linear at track) same slope and relationship as Stock throttle.

    have you had any luck changing the (throttle angle) at the track? any recommendations?
    A good thing to do is to look at COBB linear maps and use them as base for your throttle tuning.
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    Click here to enlarge Originally Posted by marv85 Click here to enlarge
    A good thing to do is to look at COBB linear maps and use them as base for your throttle tuning.

    BINGO! I drive with Cobb's linear maps on the track and I find that it is easy to modulate the engine output via the throttle. So far, I've not had the need to mess with the throttle response on the linear maps.
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    Maybe I'm just dumb, but I've tried analyzing the differences between ST and LT before, and I'm seeing identical throttle tables between the two. I'd really like to have a LT/ST hybrid map; an ST-like power ramp rate in the early rpms, but then linear up top.

    What are the tables I need to edit for this? Because they all look identical between ST and LT maps.

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    Boost and load most probably.
    From all the things I've lost,
    I miss my mind the most!
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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by Sered Click here to enlarge
    Maybe I'm just dumb, but I've tried analyzing the differences between ST and LT before, and I'm seeing identical throttle tables between the two. I'd really like to have a LT/ST hybrid map; an ST-like power ramp rate in the early rpms, but then linear up top.

    What are the tables I need to edit for this? Because they all look identical between ST and LT maps.
    It's actually in the torque request tables

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    Click here to enlarge Originally Posted by DallasBoosted Click here to enlarge
    It's actually in the torque request tables
    I will take a look, thank you!

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    The throttle maps are different between the ST and LT, you need to look at torque tables. I find that ST is a lot more fun and still driveable on track. sure linear is nicer on the tires but late power delivery is BLAAAhhh

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    I figured the throttle maps would be in the... you know... THROTTLE tables. Click here to enlarge Did not expect them in the torque request tables. Got to muck around with it during lunch. Got a stock throttle curve in the early % of pedal position, then it becomes a linear transition after about half throttle. So far its way more fun to drive Click here to enlarge

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    UPDATE

    Quick update, did a few more logs, E30 linear, E30 with 12 psi target, etc...just to make the guide a bit more usefull accurate.
    BTW..i am just trying to figure out the 12 & 15 psi target for street & track.... here it is
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    Click here to enlarge Originally Posted by Sered Click here to enlarge
    I figured the throttle maps would be in the... you know... THROTTLE tables. Click here to enlarge Did not expect them in the torque request tables.

    Well, if you think about it, you press on the gas when you want the car to go faster. Torque is the force that drives the wheels and transmit the power to the ground. So naturally, pressing on the throttle ultimately results in torque to the wheels even though there are complicated algorithms to translate one into the other. Click here to enlarge

    I like where this is going though. This is the power of ATR. All cars are different, different mods, different driving styles, different tracks, different tires. For some early onset of torque and boost may be OK, for others it is unacceptable.

    In my case with S2+ Aggressive, the Stock Throttle mapping delivers too much torque too early and does not allow me to modulate the power output through a corner PREDICTABLY. I was getting max boost at just 30% throttle pedal position. It made no difference if I pressed the gas pedal any further, it still gave out max boost. Worst of it all, the torque came all at once in one big "lump". Yeah, some times I exit the corner perfectly, but more often I either have too much torque or too little.

    Linear throttle maps solve that problem for me and I have more confidence in the car and in me. I am sure after I add an LSD, things will be different. Click here to enlarge
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    i have an LSD, and feel that somewhere between ST and LT is the sweet spot. i need to come out of corners faster than LT and slower than ST.

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    To make the chart (more) useful you'd need to have load by boost by rpm. Click here to enlarge
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  19. #19
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    E.g. 190 load does not equal x psi. It is rpm dependent. Think of load as more of a limit than a direct correlation to boost.

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    OK, here's a datapoint i would like to add to this. I did what i suggested earleir and threw together a map running a 160 straight across the board. What's important to look at is that even with requested load remaining constant requested boost will still taper off. In order to maintain a flat requested boost you'll need to increase requested load as the revs climb(like me, terry and themyst have stated/alluded to above)
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    Click here to enlarge Originally Posted by neilvosko Click here to enlarge
    i have an LSD, and feel that somewhere between ST and LT is the sweet spot. i need to come out of corners faster than LT and slower than ST.
    There are two requested torque % tables (high and low). What are the difference? My only guess is high and low gear

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    Click here to enlarge Originally Posted by Ansch Click here to enlarge
    There are two requested torque % tables (high and low). What are the difference? My only guess is high and low gear
    High is for manual trans(in non "M" mode) or if the car is auto in D mode.

    Low is for when the auto trans is in DS, sport or if you have an manual trans and put it in "M" mode.

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    Click here to enlarge Originally Posted by rader1 Click here to enlarge
    High is for manual trans(in non "M" mode) or if the car is auto in D mode.

    Low is for when the auto trans is in DS, sport or if you have an manual trans and put it in "M" mode.

    thanks! mine is a 6MT 135i so the high table is all I need to worry about then? I am assuming "M" mode being applicable to the 1M only

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    Click here to enlarge Originally Posted by Ansch Click here to enlarge
    thanks! mine is a 6MT 135i so the high table is all I need to worry about then? I am assuming "M" mode being applicable to the 1M only
    YepClick here to enlarge
    If you have any more questions about ATR post in the ATR discussion sticky and there are a few of us that will do our best to help you out
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    newbie in the Cobb world but I just picked an AP up to give it a shot... is it possible for someone to share their protuned 93 FBO map or not? How does this work?

    Thanks
    2007 335i (100% stock with mods)

    N54 is not a German 2JZ lol

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