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Thread: ECUFlash Tuning 102: Utilizing the stock BCS system

  1. #1

    ECUFlash Tuning 102: Utilizing the stock BCS system

    Introduction and Advantages

    Â* Â* Long past are the days of bleeder T's and sliced boost lines, now replaced with manual (or electronic) boost controllers. But a new more viable option is available for us Evo owners: utlizing the stock Boost Control Solenoid (BCS) system. There are several advantanges to going to such a setup including:

    - Cost effectiveness
    - Full ECU closed loop boost control
    - Fine tuning
    - Stealth factor

    Â* Â* Most MBCs today range from $80 to $100 depending on how you much features you would like, while spending $250 and up on a full electronic unit is not uncommon. For most folks, this is a very good value as it offers a very simplistic way to regulate boost withoutÂ* much hassle. But you could save this money towards other purchases and just utilize the stock BCS system and have the same control and power by spending on a Tatrix cable.

    Â* Â* Why would you do it? Well in addition to the typical benefits of the cable including datalogging and flashingÂ* capabilities, an ECU boost control can offer you something an MBC or EBC cannot: full ECU closed loop boost control! Imagine during a cold start warm up period where you want minimal boost because the oil and engine has not warmed up properly...done! Or you want slightly different boost settings per different gearing....no problem! And how about that darn overboost effect during colder days...eliminated! Those are just some of the basic advantages of integrating boost control using the stock ECU, something a stock basic has already, albeit at a lower performance setting.

    Â* Â* In addition to the above, the stock ECU offers some great tuning capabilities for those who want even more control including fine tuning in 500 rpm increments, correlation back to actual engine load, and of course having boost limiting protection. This will allow precise calibration throughout the rev range to map boost to load properly and still have fully failsafe mechanism in place in case something goes wrong!

    Â* Â* Lastly, due to our locality in the great state of California, for some the greatest benefit is in stealth: there is no visible signs of any modifications. Your harassment-free, easy-going, non-discrimanting popo could pop your hood and *shouldn't*Â* tag you for anything.

    Â* Â*With everything in life, unfortunately there are still some negatives, hence the following disclaimers: 1) The stock ECU is a very complex system and even the slightest wrong values at the wrong maps may damage your vehicle 2) Any attempts to modify your ecu should be done with the proper datalogging equipment including map/boost sensors, evoscan (or MUTs if you don't believe in freeware for the people), etc. 3) there are probably many other maps (some upwards of 600+ O.o) that have not been accounted for in ECUFlash and I by no means, pretend to understand them all; this is just simple guide based on my own experiences so YMMV and do it at YOUR OWN RISK.


  2. #2

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    BCS operation

    The underlying function of the whole BCS system is founded on the manipulation of the stock wastegate. By itself, it is set to boost roughly at 12-14psi. To get around this restriction, Mitsu architected a scheme to "bleed" off boost from the compressor seen by the wastegate thereby keeping it closed for more boost. This is done through a myriad of T's, restrictor pills, and of course the boost control solenoid itself.

    If you follow the below diagram closely boost is derived from the compressor side (turbo nipple if you will) fedback to the wastegate. The boost first enters through one of 2 passage blocks or more common known as restrictor pills. This first pill sets the baseline boost (its zero map level if you will). The smaller the pill, the more boost will enter and be seen by the wastegate and thus less boost. Conversely the larger the pill, the less boost the wastegate will be seen and thus more boost can be produced.Â*

    Now further down the boost hose path, is the T line. One end goes to the wastegate actuator while the other route down to the BCS. The sole purpose of the T is for the bleed off of additonal boost via the BCS. This is how the ECU can electronically govern how much boost to regulate. In the path of the hose is the 2nd of restrictor pills to the BCS. This serves as sort of the Delta to which how much boost can be made/regulated from the baseline (as defined in the first restrictor pill). Removing it altogether will give you the maximum available boost range to work with, however it can also produce some boost spikes if your 1st restrictor is sized improperly (due to the limiation of how much boost the stock bcs can bleed off). Keep this in mind as this is how many eFlash tuners work to increase the stock boost.

    In order to size the restrictor pills properly, you will need someway to log boostÂ* properly. You should try to select a size of pill that is within 6psi range of your target boost. This is because sizing it too little will cause high duty cycles on the BCS and sizing it too large will cause it so you can't go low enough within your boost range. This will be discussed further in the max wastgate duty cycle settings.

    [insert source for off the shelf bcs pill]

    bcs block diagram


    restrictor pill

  3. #3

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    Detailed description of ECUFlash Parameters:

    Now in terms of controlling the actual boost yourself in ECUFlash, you have to understand each of the different parameters affecting it:

    - Max Wastegate Duty (MWDC): This is the main parameter that controls boost itself. It is a percentage based field of the duty cycle of the BCS. Values go from 0-127.5%. Why 127.5%. especially when the stock ECU designates operation to 100%? My belief is that the 100% stock value is expressed as the baseline and not truly 100% open. I am also assuming that 127.5% is basically a 1 byte field binary operation of the BCS, where 0 is fully closed and 127.5% is fully opened. Now, if the stock baseline was truly 100%, there would not be any room for closed loop compensation of the boost should it underboost, thus there is ~ 27.5% for any error correction needed.

    - Boost Desired Engine Load (BDEL): The values here are the target load values the ECU interprets you are shooting for. It is expressed as load ranging from 0-159.4. It is used as a "guideline" to the ECU whether you are over/underboosting, taking into account Boost Control Load offset. COnsider it an outlined trace map of what the computer expects your load cells to hit at.

    - Boost Control Load Offset (BCLO): To achieve above 159.4 boost, the BCLO is taking into account additive to the BDEL. For example to achieve your realized target 259.4 loads (after properly scaling max wastegate duty cycle properly), you would set BDEL to 159.4 and change change this field to 100 (159.4 + 100 = 259.4).

    - Turbo Boost Error Correction (TBEC) : If your target loads are off, the ecu utilizes these values to correct boost on the fly. conversely if this parameter is zeroed out there will be no correction for overboost/underboost conditions. the field is expressed in boost precentage.

    - Boost Limit (BL) : this parameter sets the hard boost limit before fuel cut is realized. it is expressed in kpa relative to atmospheric, so 210 value is ~1.1bar or 1.1 x 14.5 =Â* 15.95psi. It is a ranged over different rpms, typically lower at higher rpms due to boost taper.

    - Boost Delay Timer (BDT) : this is the time expressed in miliseconds after the boost limit is reached before fuel cut is cut in. It is always best to leave it to the stock parameter. Too high of a value would esssentially ignore the boost limit and/or allow overboost/spike conditions to occur.

    - Min Temp for Full Boost Control: This last parameter is your cold start failsafe. it takes into account the coolant temps in degrees Celsius before full boost can be realized.

    How the parameters play out in real world scenarios is as follows: When you first start up, the minimum temp for full boost control will artifically cap your boost to a certain level until that coolant temperature is reached. Once this threshold is scene and you go into wot, your mwdc determines how much your boost is over specified rpms. During this timeframe the ECU will cross check the boost scene w/ bdel values combined w/ the bclo. if the values are lower or higher then expected, the tbec will be initiated to correct however you inputed into the map. If you overboost fast enough and reach the boost limit cutoff, the bdt will count down, and if after it clocks off and you're still maxed out the boost limit, you'll immediately hit fuel/boost cut with a loud BOOM!


  4. #4

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    Tuning and Calibration

    Â* Â*Methodology for calibration is very simplistic if you understand the underlying concepts of the ECUFlash parameters. First, to safeguarding your engine while tuning, you should set your AFR and timing relatively mild (10.5 afrs on pump, and stock timing usually does the trick). Next, to prevent any unwanted intervention from external sources as you set your initial boost, you will zero out your tbec value (remember to save the stock values). At this point, all closed loop corrections from the ECU is basically negated and the bdel+bclo is essentially ignored all together.

    From here, get your favorite map/boost sensor dataloggers out, set your mwgdc to a very low value (say 30% or so) across the rpm range, then run your evo throughout the rev range and check your boost profiles accordingly. Make all necessary corrections to the mwdc to get your desired boost range (tip: set mwdc high to bleed off max boost to the wastegate, so you can spool your turbo faster at lower rpms, but watch out for boost spikes/overboost conditions).

    Once you have dialed in your boost, next with a your favorite MUT logger (EVOSCAN/MITSULOGGER/etc.), log out the engine load cells the ecu sees throughout the rev range (helpful if you have a map tracer here). Then, with these values in hand, check the maximum value seen and compute the BCLO from this (eg, if max is 275, BCLO would be 275-159.4 [max value of bdel] = 115.6) and input it accordingly. After inputting the BCLO, recheck the engine load map tracing values seen across the rev range and input the bdel accordingly (eg, at 4000 rpm, you are seeing 260 load cells, so with the 115.6 bclo before, your bdel at 4000 would be 260-115.6 = 144.4).

    Lastly, you'll need to reinput your TBEC so that full closed loop ecu boost correction is re-enabled. I would use your stock values as a starting guidline, keeping in mind the higher the values, the more it will correct. After setting this up, I would go run your evo with your new boost profile, datalogging boost to see how resilient your values are (there might be slight dips and bumps in the boost profile, which you should correct for by re-evaluating your bdel). Set your final boost limit accordingly throughout the rpm range, with some buffer so it doesnt hit boost cut. Tip: higher gears will typically see higher boost because of much larger loading. It is always wise to set initial boost profile in say 3rd gear for tunability sake, then make a run in 4th / 5th gear for stability of the boost (and also to make sure you don't hit boost cut).Â*


  5. #5

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    3rd party boost solenoid operation w/ stock ECU

    From earlier description, the stock BCS is a bleed type system where pressure is essentially diverted from the main wastegate to achieve the necessary boost. Another mechanism exists called the interrupt / blocking type boost solenoid, like the GM 3 port boost solenoid. In this setup, the T boost passsages is eliminated and in its place is the boost solenoid itself blocking the air from the turbo compressor to the wastegate directly. This manner has much more precision and response time, but the drawback with a 3-port system vs. the stock 2-port is that failure of the solenoid in the energized state would lead to complete loss of boost control, likely resulting in overboost condition. Tuning these boost solenoid is the same as the stock BCS, but it does not require any restrictor pill anywhere, since it initiates the wastegate boost pressure itself.




    Get it from Rock Auto (http://www.rockauto.com) - use discont code from : http://www.fatwallet.com/forums/mess...word1=rockauto

    GM 3 port: 12.69. AC Delco part number 214-474.
    GM pigtails for 15.64. AC Delco part number PT 374.

    YOu can also get from GM dealership:

    GM boost solenoid, GM Part # 1997152
    Pigtails, GM Part # 12102747


  6. #6

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    Good info. I feel the need to sticky this...not sure I know how to do that but it'll get done.
    Hmmm.. So if I never mod/ track my Evo, I shouldnt own it? Well, my reasons for an Evo purchase dont have to match yours.<br /><br />-Chirico<br /><br />Only two things are infinite, the universe and human stupidity, and Im not sure about the former. <br /><br />-Einstein

  7. #7

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    STICKIED.....

    regards
    flip
    illuzionz 1.0

  8. #8

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    Quote Originally Posted by ST
    but the drawback with a 3-port system vs. the stock 2-port is that failure of the solenoid in the energized state would lead to complete loss of boost control, likely resulting in a blown engine.
    Electrical failure of the GM solenoid will give you wastegate boost. 11psi
    Bryan - 05 MR w/5speed <br /><br />Over 400whp of Ethanol love...

  9. #9

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    You should also retain the Boost Limit function (Fuel Cut). Raise it up so it is higher than what you intend to run on that map, but don't fully disable it so if there is a problem with the boost at some point, you have something to catch it.
    All da cars are Nekkid!Â*&nbsp; www.dsmporn.com<br /><br /><br />www.roadraceengineering.com

  10. #10

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    Quote Originally Posted by earlyapex
    Quote Originally Posted by ST
    but the drawback with a 3-port system vs. the stock 2-port is that failure of the solenoid in the energized state would lead to complete loss of boost control, likely resulting in a blown engine.
    Electrical failure of the GM solenoid will give you wastegate boost. 11psi
    If it is stuck open, wastegate pressure would continually bleed off resulting in an overboost condition. Your only safety net is the boost limiter, but you would still overboost temporarily nevertheless...I have reworded that description though...



    Quote Originally Posted by Blak94GSX
    You should also retain the Boost Limit function (Fuel Cut). Raise it up so it is higher than what you intend to run on that map, but don't fully disable it so if there is a problem with the boost at some point, you have something to catch it.
    good point, i forgot to input that...

  11. #11

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    ST do you do tuning? I am looking for some one to tune my car.

  12. #12

    Re: ECUFlash Tuning 102: Utilizing the stock BCS system

    Quote Originally Posted by 714benz
    ST do you do tuning? I am looking for some one to tune my car.
    he is long gone from the evo world.
    Bryan - 05 MR w/5speed <br /><br />Over 400whp of Ethanol love...

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