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Last Post 20 Nov 2013 02:44 PM by  mrazny
Cobalts and Boost-Rule Clarification
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Evolve
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16 Oct 2013 12:24 AM
    A local competitor and I have been arguing about his Cobalt SS and boost.  No protest will come about, mainly we're just curious about what would really be legal in an STX tune.  We've found that the stock boost levels in a cobalt learn down to maintain 260hp, so they'll vary from 10 to 22 psi.  The rules state "...no changes to standard boost levels, intercoolers, or boost controls are permitted. Boost changes indirectly resulting from allowed modifications are permissible but directly altering or modifying the boost or turbo controls, either mechanically or electronically, is strictly prohibited." 

    Is he allowed to alter the limiting of the boost by the ECU?  Is he allowed to change the target power rating of the learn down?
    Is he allowed to constantly run the highest boost the stock ECU would allow?

    Thanks for the help everyone!
    cashmo
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    16 Oct 2013 01:13 PM
    The rules state "...no changes to standard boost levels, intercoolers, or boost controls are permitted. Boost changes indirectly resulting from allowed modifications are permissible but directly altering or modifying the boost or turbo controls, either mechanically or electronically, is strictly prohibited." 

    Is he allowed to alter the limiting of the boost by the ECU?  Is he allowed to change the target power rating of the learn down? Is he allowed to constantly run the highest boost the stock ECU would allow?
    I'm no ST rules expert but at first glance I'd say no to all 3 of your questions.
    Aaron B
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    16 Oct 2013 01:43 PM
    He can't touch the ECU boost tables. If it's programmed for a range, then that range has to remain untouched. The rule is written to allow changes to intakes, downpipes, exhausts, etc, which may result in inadvertent boost spikes/changes because of differences in flow restrictions.
    ratt_finkel
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    16 Oct 2013 03:32 PM

    And on top of what Aaron said. Only fuel and timing tables can be touched anyway. So anything else, including tables that indirectly alter boost, would be illegal.

    Evolve
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    17 Oct 2013 03:57 PM
    So to sum up: A STX Cobalt can't have more than 260 hp (give or take) because altering the learn down is an alteration of boost tables. Sucks to be an STX Cobalt, but good to know the rule. Thanks everyone for getting back to me before the Utah match tour, it'll be good to help a friend dodge protests.
    snaponbob
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    17 Oct 2013 09:42 PM
    Posted By Evolve on 17 Oct 2013 03:57 PM
    So to sum up: A STX Cobalt can't have more than 260 hp (give or take) because altering the learn down is an alteration of boost tables. Sucks to be an STX Cobalt, but good to know the rule. Thanks everyone for getting back to me before the Utah match tour, it'll be good to help a friend dodge protests.

    Is it? The software in the ECM is VERY complex. Tunes for the LNF can address boost tables, or not. It is up to the person tweaking the tune. As a correction, the factory cap on boost is 20psi, not 22. If the LNF tune is rewritten to NOT break through that cap, does it not comply with the letter and intent? I know from personal experience what a tune for a Cobalt SS with only 18psi, high flow cat, and well under the sound limit, feels like. Not shabby, and per some folks that would know, it complies. 


    Evolve
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    19 Oct 2013 08:57 PM
    So we're saying a cobalt can alter boost as long as it could theoretically be possible from the stock ECU, so he can run 20 psi all day long, right?  I look at the stock programming as something that hits its power target by controlling the air fuel ratio using boost.  In my eyes, since that target power controls what the stock boost levels are, changing the learn down is "directly altering or modifying the boost controls, either mechanically or electronically."  That's the letter of the law and to me it doesn't match. 
    Can cobalts gain power since we're changing the boost controls as a derivative of the learn down changes (and what else does that program do besides control boost)?  Or can STX change the boost controls/tables as long as they are still within plausible tolerances?
    Z3papa
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    20 Oct 2013 09:19 AM
    Why don't you focus on making the car be able to put down the power it has, corner, brake and less about getting more power.
    Evolve
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    20 Oct 2013 03:09 PM
    I don't worry a lot about potential power of a cobalt driving my RX8, but in the long off season around here we build and we talk- I didn't think that was unusual- and I thought it'd be useful to see what a national consensus would say about potential upgrades before he put them on the car.  I'm also curious as to the viability and legality of a car at national events. If this isn't the right place for this, let me know.
    gary p
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    21 Oct 2013 10:18 AM
    It's an interesting question. My limited understanding is that factory ECU is programmed to deliver a target torque value at WOT and varies the boost as needed to reach (if possible) but not exceed that. Not sure how the ECU calculates torque. Boost level is variable in the equation to deliver a constant torque output, not a constant that other variables are manipulated to maintain.
    Silverspeed3
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    21 Oct 2013 03:51 PM
    As I understand it, the ECU has a boost target. It has no idea how much HP or torque it produces at that target it just knows the target. The A/F ratio at that target can be manipulated via the fuel and to some extant the timing tables. Adding a cold air kit and or downpipe (and a lesser extent even a cat back exhaust) will change the amount of boost can potentially be produced. The original target still exists, but the motor can, and often will exceed that target under certain conditions (although, based on what I've seen/read, it never exceeds it by very much). Upgrading these parts will above all things, allow the motor to reach peak boost earlier and more often than it would otherwise. If I add a downpipe I am allowing more exhaust flow therefore allowing the turbo to spin faster, sooner, plus the added bonus of increased efficiency of just creating a easier path for the exhaust to exit. Maybe the Cobalt reacts differently than my car, but if it's like most of the turbo motors, with the mods you listed, he is running in excess of 260 HP at the flywheel, but is seeing larger gains at lower RPM's (timing changes also enhance this). An STX legal tune really handicaps the tuner, but there is still noticeable power increases that will be realized using legal parts and a legal tune. As noted by another post, the key is being able to use that power in an autocross setting.
    jfossum
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    21 Oct 2013 04:44 PM

    As I understand it, the ECU is a black box that controls a signal to the wastegate (among other things).  Whether the ECU internally uses an algorythm based on calculated torque/hp, detonation limits or the phase of the moon is pretty much irrelevant.  If you modify the ECU to change the output to the wastegate then you are modifying the boost controls.

    If you modify something else like the ignition timing or fuel/air ratio that doesn't impact the output to the wastegate, but has an indirect effect on boost pressure, then you are OK.  If everything in the ECU is so interelated that you can't separate this out, then you are pretty much stuck as far as the ST rules go.

    gary p
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    21 Oct 2013 07:20 PM
    Posted By Silverspeed3 on 21 Oct 2013 03:51 PM
    As I understand it, the ECU has a boost target. It has no idea how much HP or torque it produces at that target it just knows the target.

    In a lot of turbo cars, boost targets are the tail that wags the dog.  Boost is the primary piece of feedback in the loop.  If boost goes above or drops below the target, adjustments are made to try to get back to the targeted boost.

     

    The LNF ECU has a stock hard boost limit of 20psi, but has no boost targets.  It has torque targets.  A complex algorithm of  multiple engine parameters yields a calculated torque output.  Various variables (including wastegate, throttle angle, injection timing, and ignition timing) are manipulated to maintain the targeted values of the torque equation.  

     

     http://www.andersonperformance.net/GDI_ITModel.jpg

     

     

     

    bruecksteve
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    06 Nov 2013 12:39 PM
    We use that engine in the Jeep. Why not run straight E85 and re-tune the ECU, no change in boost level required? We use a E85 tune from Trifecta that works great. Granted, other things have been changed in our ECU, but substantial gains can be had just by changing to E85, especially on a FI direct-injection motor.
    85rx-7gsl-se
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    06 Nov 2013 01:31 PM
    I think e85 is going away in ST* unless it is a factory flex-fuel motor.
    bruecksteve
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    06 Nov 2013 01:32 PM
    Bummer... but isn't the LNF a flex fuel motor?
    Evolve
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    06 Nov 2013 02:02 PM
    The issue is the legality of altering the learn down, that will effect the other aspects of the engine potential.  If the learn down can't be altered, it doesn't really matter what you do or add, at least to the limits of my knowledge. 
      
    To refine the discussion a little let's recap.
    Cobalts don't have the standard boost table, instead a stock LNF targets -and is therefore limited to- a specific power level. It does that through altering a number of things, one of which is boost level through control of the waste gate. If additional power is gained from a cobalt the learn down was changed.
    Changing the learn down effects the waste gate regardless of other parts, fuels, or upgrades. Changing the waste gate is altering boost controls/tables. So, changing the learn down is altering boost control.
    Additional power is therefore only accessible through altering boost controls as I understand it. Power would therefore seem limited to stock levels for a legal STX cobalt.

    I look at this and see a handcuffed STX car. Is there some technicality to the boost control (or any other) rule that I am overlooking?
    mrazny
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    06 Nov 2013 03:30 PM
    As a note, this place is not *the* national consensus, just *a* potential National perspective. Still a resource, and sometimes a very good one.

    The rules are a language that may have had an intent, but it only exists as the exact words listed.

    "These allowances also
    apply to forced induction cars, except that no changes to standard
    boost levels, intercoolers, or boost controls are permitted. Boost
    changes indirectly resulting from allowed modifications are permissible
    but directly altering or modifying the boost or turbo controls,
    either mechanically or electronically, is strictly prohibited."

    Which is to say, you get to have your version of what this means. And other guys get to have their version of what it means. And if someone throws paper, then the committee the day of gets to have their version of what it means.

    Clarifications would only give you more language to present your case on top of the above.

    So... if what you did "changes standard boost levels" or "changes boost controls", you can't do it. To say it's allowed, you'd have to make the case that it didn't make a "change" to the two specific prohibitions listed.

    If you're asking what things the class typically just ignores and doesn't throw paper on, that's a different argument entirely. There's no additional ST boost rules. The only Cobalt specific clarifications are about a disallowed ECU reflash from GM since it is for competition pruposes, and disallow the GM Steering knuckle that is also "competition only". Appendix F is your clarifications if you want to browse for any other bits of language that have been added but I came across none.
    MrAWD
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    06 Nov 2013 04:19 PM
    From the above written stuff, it looks to me that Cobalt is controlling power levels inside the ECU, which indirectly regulate boost at the given time. I see no prohibition for the ECU to control power output of the car, so if you change that part, which indirectly change boost levels, that should be covered by the allowance from the above -> [Boost changes indirectly resulting from allowed modifications are permissible].

    Fedja
    mrazny
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    06 Nov 2013 05:19 PM
    The caveat I'd put out there though, be certain about what is actually changed.

    If the changing the target output only effectively changes boost, that's a hard case to make that it was an indirect change...
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