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Thread: Unlogic's Chrome ECU tuning thread

  1. #1
    Forum User Feedback Score 3 (100%) Unlogic's Avatar
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    Unlogic's Chrome ECU tuning thread

    My build thread is getting way too long so I thought I'd follow the trend and make a separate thread for my Chrome ECU tuning experience.

    Here are the specifications of the relevant parts on my car:
    - Stock boost solenoid
    - Evo 560 injectors (INP-401, 4 nozzle version using short latencies)
    - Supra fuel pump (hotwired ~14v)
    - Montero 482 MAF
    - AEM rail mounted FPR
    - Stock eurospec 11b turbos
    - Gene SMIC's
    - CX Racing 2" pre-intake and intercooler pipes
    - AEM 30-2310 Inline Wideband UEGO
    - GM 3 bar MAP sensor
    - Stock ECU boost solenoid
    - 3" exhaust and downipe with a single large catalytic converter
    - Precat eliminators
    - Stock engine and heads

    I've spent the last couple of weeks fine tuning the VE table trying to get the car to run like stock and with good trim values and accurate AFR values. I now have a tune that runs fine under all conditions except very low engine loads and engine braking where I experience some stutter/hesitation.

    Today I decided that the low engine load hesitation problems can wait until later and instead I started upping the boost. I followed the instructions in this thread and updated the following tables in my ROM:



    Setting all values to zero in the load error correction table made my pulls much smoother. Previously the ECU would start pulling back my boost after about 3 000 RPM since I was overshooting the stock load values. This made it feel almost like driving into a wall halfway through the pull.

    Here is how the boost curve looked with the stock boost values (3rd gear pull):



    This is how it looks with the new values (3rd gear pull):



    Much smoother and steady all the way to redline holding about 11 psi.

    However when I made a pull though 2nd, 3rd and 4th gear I got a very different boost curve with boost increasing a few psi each gear peaking at 17 psi and giving me single count of knock. The chart is cut a bit short because I didn't want to pull 4th gear all the way to redline



    Whats the best way to tackle these boost spikes and slight boost creep?

  2. #2
    I lack color... verified
    Feedback Score 1 (100%) Greg E's Avatar
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    Guess what the load error corrections do.


    What I would do I lower the WGDC in the areas were its spiking while leaving the higher RPM values alone. Don't be surprised if you have to have the base values jump back and forth a bit.
    Last edited by Greg E; 08-05-2014 at 07:24 PM.

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  3. #3
    Forum User Feedback Score 3 (100%) Unlogic's Avatar
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    Quote Originally Posted by Greg E View Post
    Guess what the load error corrections do.
    Thanks for your patience Greg. I'm a rookie when it comes to tuning and my question about boost spikes must have seemed really stupid. After giving it some thought the physics behind it are simple... revving one gear to redline and then shifting up to the next gear which starts at a much lower RPM will naturally cause a boost spike when using a constant WG duty cycle since the turbos will spinning way too fast for the lower RPM right after the shift. So with the load error correction disabled it's best to do single gear pulls or shift slowly between the gears to avoid boost spikes.

    I've slowly worked my way up to 100% duty cycle now which gives me about 17-18 psi at the top and then tapers down to about 14-15 at redline. This give me a ECU load of about 200 and a airflow around 1900. I did 8 pulls today and I only saw a single count of knock (on the first pull) so I think I'm gonna leave my fuel and timing tables completely stock for now.

    Since I'm not aiming for any records I think that I'm going to stick with this level of boost for a while. I can't go any higher anyway without either replacing the boost solenoid or the wastegate springs and even then I don't know how much more breath there is left in my small 11b turbos.

    The annual nordic 3000GT meet is next weekend and it's a 2500 km drive for me. So I'm gonna try and dial in the proper values in the load error correction table this week so that I don't have to worry about boost spikes on the track.

    Thanks again to all the people behind Chrome and the flashable ECU's.

  4. #4
    I lack color... verified
    Feedback Score 1 (100%) Greg E's Avatar
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    It's not hard to understand but it is hard to explain. Sometimes hands on is the only way to learn.

  5. #5
    Forum User Feedback Score 3 (100%) Unlogic's Avatar
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    It's been a while since I posted anything in this thread. I've been very busy at work this autumn so I had to put the car aside for two months.

    Took the car out for a spin today for what was most likely that the last time this year. I've gotten completely rid of the boost spikes now following Greg's instructions in this post: http://www.3sgto.org/tuning-engine-e...tml#post293836

    I still have some tweaking to do to get the boost up the 16-17 psi level where I want it to be. Currently it's staying very flat around 12 psi. Here are the values I'm currently using for boost load error correction.



    Most likely I have to get a bit more aggressive with the compensation table in order to increase the boost further. If I change the base WGDC table any higher I get boost spikes.

    One of the things I've noticed during my sporadic mapping sessions is that I often get 2-3 knock counts during my first 3rd gear pull after starting the car. All following pulls are completely knock free so my guess is that the ECU calibrates the knock sensor voltage levels after the first pull. So if your out logging, make sure the you make multiple pulls.

  6. #6
    Forum User Feedback Score 3 (100%) Unlogic's Avatar
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    During the last runs I did with the car last autumn my boost was substantially lower that I had set it in the ECU and I couldn't figure out why. Took the car of tonight with my laptop so I could do some logging and noticed the same thing. The odd part was that I hadn't touched the boost settings since the summer when they worked perfectly.

    Turns out the WGDC vs Coolant table was the key to this mystery. During cold autumn and spring evenings my car doesn't reach the 180°F required for the ECU to give full boost according to the stock values in the WGDC vs Coolant table, instead I was only getting 75% of the WGDC I had configured...

    My car seems to stay settle just a few degrees below 180°F when I'm doing pulls on the highway so a slight tweak to the WGDC vs Coolant table should take care of the problem and allow me to run full boost during autumn and spring too.

  7. #7
    Forum User Feedback Score 3 (100%) Unlogic's Avatar
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    My car is running really good with Chrome now the only issue that I haven't been able to put my finger on is the hesitation which sometime occurs during engine breaking or low load situations.

    It feels like there must be a table which needs a slight adjustment after the MAF/injector change to smoothen out the jerking issues. My trims are very well tuned so I'm thinking that it must be something else. Maybe closed loop or fuel cut?
    Last edited by Unlogic; 06-15-2015 at 10:02 AM.

  8. #8
    JNS Engineering verified Feedback Score 1 (100%) Jimvr4's Avatar
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    Decel rpm fuel cut resume? In the accel section.

  9. #9
    Forum User Feedback Score 3 (100%) Unlogic's Avatar
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    Thanks Jim, I hadn't noticed that table. Have you had to adjust it on your car?

  10. #10
    JNS Engineering verified Feedback Score 1 (100%) Jimvr4's Avatar
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    Never changed it but I've seen the hesitation on decel and thought that might be a place to start. I just passed emissions and put the test pipe back on and now finishing up installing the big SMIC from Oohnoo. Also changed to MAFT + Z06 intake so I have some tuning to do now

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