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Thread: How to set your idle with Chrome (the proper way)

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    I lack color... verified
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    How to set your idle with Chrome (the proper way)

    I've walked you guys thru all the idle tables in this post (http://www.3sgto.org/tuning-engine-e...tml#post211650) but it seems a lot of guys don't understand setting the idle. Those of you who experience RPM dips, on/off throttle stumbles, etc... know what I'm talking about. Though you can sometimes get away with setting the target idle RPMs, flashing then turning the key, there's an initial setup you have to go thru in order to ensure your car will idle properly.

    This setup is actually taken out of the Mitsubishi manual for our cars. The process is exactly the same as any other Mitsubishi. This post applies to turbo and NA cars as well!


    This is the procedure:

    *Install NEW/Remanned throttle body
    *Verify TPS is set properly and Idle Switch works
    *Flash ECU with your target idle tables set to whatever desired idle RPMs you wish
    *Drive the car until engine is completely warmed up
    *With the engine still running, put the ECU into SAS mode (make sure your AC is OFF)
    *Adjust BISS/SAS till engine idles at the RPM you want
    *Disengage SAS mode



    First off....

    ***Replace your throttle body!!!!

    All our cars are approaching the 15+ year old mark. The throttle body is the crucial part of the engine which regulates idle and cruise operations. 90% of all issues come from sensor failures, clogged FIAV and leaking BISS and throttle plate screws. To compound the issue, nearly every car gets this oil muck saturated within the small chambers within the throttle body which impact airflow. I'd highly highly HIGHLY recommend you get it replaced with a NEW unit from mitsu, or contact April to get it rebuild. She does great work rebuilding our throttle bodies!!

    http://www.3sgto.org/f62/throttle-bo...ice-10630.html

    If you can afford $1500 for turbos, then you can afford to get your throttle boy rebuilt. Don't be cheap.




    Next....

    After your new throttle body is installed, it's crucial that you don't have the throttle cable too tight. You can verify this by logging TPS with EVOScan. You should see values somewhere between 10% and 13% with your foot off the gas.

    You also need to verify the idle switch is working with EVOScan (it's just a simple on/off). You see a value of 1 with your foot off the gas pedal, and a value of 0 with it slightly depressed.


    Note: Some people are reporting that EVOScan isn't logging the idle switch correctly.

    Verify this is what you're seeing in EVOScan:



    If not, you'll need to edit that log value to match the screen shot (right click, edit data item....)




    Next...

    After you get your injectors scaled, your intake/fuel and timing maps tuned well enough to at least let the car start, run and drive, there's still a calibration that needs to be done with the BISS (also called the Speed Adjusting Screw) in the throttle body. This is what I'm talking about:



    Note: In this image the cover for the BISS is removed (usually it's missing on many cars).


    SAS mode

    If you recall in the chrome manual I talked about the idle timing stability control. The ISC will get the airflow in the right range for your desired idle RPM but it's ignition timing which is used to keep the idle at the desired speed. You've probably noticed that at idle, your timing values are always inconsistent and constantly jumping around. This is why.

    When calibrating the BISS, the ECU has an input switch to disable this function along with the ISC all together so you can properly set your idle without the ECU trying to counter your adjustments. This is called SAS mode. There are 2 ways you can put the ECU into SAS mode. The first method is shown in the WIKI linked above. The second method (the easy way) is to use EVOScan.

    Open up ECUFlash and the .bin file you flash to your ECU. Scroll down to the bottom and click on the Diagnostics tree, then Select MUT Actuator Mask:



    These are a list of all the MUT commands I've found in the ECU. What these commands do is they manually activate switches on the ECU to test a function. In this case we are going to use MUT command C3 to put the ECU into SAS mode.


    So start off by driving your car till the motor is completely warmed up, then pull over and let the motor idle. Open EVOScan and scroll down to the bottom.

    Ever see this?



    If you enter in the MUT command into the Custom Request box, then check the repeat box, you will activate the switch. Very handy feature for testing solenoids/relays/fans to make sure they are working properly!

    So you have your engine warmed up and idling what you need to do now is data log RPM. You can NOT use the stock Tach to set your idle. It's not accurate enough to tell you the exact engine RPM. Start your datalog and monitor your engine RPMs appearing on the screen.

    In this case, we just want to put the ECU into SAS mode so you just type C3 into the Custom Request box then check repeat.



    As soon as you hit enter (with the logger still connected), you'll see some numbers appear in the Response box telling you SAS mode has engaged. You'll also notice your engine idle will change.

    Now is when you pop your hood and adjust the BISS/SAS. A simple flat head screw driver will work just fine. Turning the screw clockwise will lower your idle and counter clockwise will raise it. You'll notice very suttle turns will make a HUGE difference in RPMs. Just a 1/16th of a turn can make as much as 100 RPM difference.

    Stock these cars are setup for 650-700rpms at idle BUT you can make this any value you'd like. I typically go for 8 or 900rpms for better oil pressure and smoother idle with cams. Just remember to match the target idle RPM tables to whatever RPM you're trying to manually set it to in SAS mode!



    Once again, disregard the stock tach while you're setting the idle! Look at the RPM number you see in EVOScan!

    After your idle is set, uncheck the Repeat box and delete C3 from the Custom Request box and the ECU will return out of SAS mode.

    You will be absolutely amazed how much smoother your car will run now.

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  3. #2
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    Some other notes:

    If you can't get the ECU into SAS mode with EVOScan you'll have to ground the brown connector located by the battery. Details are shown in the WIKI linked above


    If your engine dies right away when you select SAS mode, you'll have to unselect it, open the BISS a few turns, restart the motor, then re-engage SAS mode. Your motor probably died from too low of an RPM. Opening the BISS will raise the idle enough for you to adjust. You will NOT be able to start the motor while the ECU is in SAS mode.

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    These directions are great, which means I have something else going on. Here is my sequence of events after replacing the throttle body with one of April's.

    1. checked to make sure the throttle cable was loose (very loose)
    2. drove the car to get coolant temps above 180*F
    3. using evoscan through tactric connection set the ecu to SAS mode (idle dropped and car shut off) The BISS screw was barely open so i adjusted it
    4. started car again and ran better but barely running so I began adjusting the BISS more to add rpm
    5. was able to eventually get to my target RPM but it was not steady and fluctuated between 812, 843, 875 (target 844)
    6. decided to leave it at that and release the SAS connection
    7. car immediately began to idle around 1000 - 1200.
    8. I drove the car home this way (.5 mile away) and investigated further.

    Conclusion - something is out of whack! LOL and I'm not getting anywhere trying to figure it out.

    Happy Mothers Day (to all mothers)



  5. #4
    I lack color... verified
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    You've got another X factor on your car (ProM) so I can't help but wonder if you need to turn down the low knob.

    What are your narrowbands doing in SAS mode? Are you lean or rich?

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    Greg - You may be on to something with the ProM. I think the results "leaned" more lean than rich. Some how my wide band results aren't in the log but I sent it to you for review. Hopefully we can come up with something.

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    Quick Note:

    was able to eventually get to my target RPM but it was not steady and fluctuated between 812, 843, 875 (target 844)
    This is normal.

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    Hey Greg... Your BISS (Speed Adjustment Screw) reference... be careful because there is also a SAS screw on the throttle body, it controls how far the throttle plate closes, and shouldn't be messed with after it's set. If somebody does mess with that, you will need to adjust that first before setting the BISS and TPS. Procedure is loosen for the throttle plate to be completely closed *or until it's not touching the spring plate*, tighten until it touches the spring plate (the part where the throttle cable attaches to), and then tighten it an additional 1-1/4 turns.

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    I lack color... verified
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    Oh that's right... I forgot about that other screw. Thanks for the reminder!

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    Greg, no matter what I do my idle switch will not come on. My car idles at 850rpm where I set it but never drops below about 38-44 steps at idle. Brand new TB, new TPS, new IAC. I have tried everything. No other issues. No boost/Vac leaks. Everything else checks out. Starting to think it's not me and it's an issue w/ chrome or my ECU. I have about 4000 miles on the car already with the ecu but can't figure this one out for the life of me. Every engine related sensor on my car is new OEM.
    I must say the fan control is amazing. My car runs at 186-192 even on warm days with a massive FMIC and a first gen stealth front end with out any ducting.
    Last edited by Pensky3thousand; 05-15-2013 at 01:05 AM.

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    Quote Originally Posted by Pensky3thousand View Post
    Greg, no matter what I do my idle switch will not come on. My car idles at 850rpm where I set it but never drops below about 38-44 steps at idle. Brand new TB, new TPS, new IAC. I have tried everything. No other issues. No boost/Vac leaks. Everything else checks out. Starting to think it's not me and it's an issue w/ chrome or my ECU. I have about 4000 miles on the car already with the ecu but can't figure this one out for the life of me. Every engine related sensor on my car is new OEM.
    I must say the fan control is amazing. My car runs at 186-192 even on warm days with a massive FMIC and a first gen stealth front end with out any ducting.
    What does the idle switch have for a scaling in evoscan? I wonder if you are one of the unlucky guys who got the wrong evoscan XML file. I can email you the correct copy if you need it.

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