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Thread: Newb 2015 Sonic RS Tuning

  1. #1
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    Newb 2015 Sonic RS Tuning

    Hey everybody. I'm new here, just got my mpvi2 last week. I have a 2015 Sonic RS Turbo 6 speed. I've been playing with the tuning over the last week, and so far I've gotten it to run a stable 18psi of boost, 6psi more than I hit stock. But as I've been reading online, people mention VE tables for WOT, partial throttle and decel tables, and I can't see any of that! The only fuel table that specifies WOT in the description is the power enrichment table, and it appears that GM kind of disabled that from the factory. I don't see any decel or partial throttle tables at all. I have 2 tables that relate to boost, one is injector flow rate vs Pressure Delta, and the other is flow rate vs MAP. The Pressure Delta table is set up from the factory, but not the MAP table...? I have no clue what the pressure delta table actually means, and it confuses the hell out of me because the kpas in that table are WAAAYYY higher than anywhere else. The only way I've gotten it to run 18psi stable, is not really the correct way. I put a small vacuum tee in the waste gate line, disabled the overboost code in diagnostics once I confirmed that the boost level was stable and the fueling was okay. As far as the fueling, I just let the stock settings handle it. I read that a stock ECU can handle up to 20psi just in case something goes wrong, so I just did that. Anything to help get my newb ass off the ground would be much appreciated, thank you.

  2. #2
    Senior Tuner cobaltssoverbooster's Avatar
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    pressure delta is pressure difference....typically between the rail and the manifold or manifold and atmospheric pressure. depends on the system section you are in.
    you should have a vve ecu. i suggest reading up on tuning using vve before you play with any boost increases. increasing boost and not correcting fueling is the fastest way to a trashed motor.

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    Thanks for the info. I?m well aware and fully understand that what I did is potentially dangerous, and not the correct way to do it. I was careful and eased into it. I made logs from every step and studied them to make sure nothing was going wrong. But I?m not doing anything else until I have a better understanding of how to tune my fueling, that?s why I?m here trying to get information. I?m very knowledgeable about engines and performance related changes, however I?m new to the EFI tuning world. Pretty much all of my experience thus far has been with carburetors and distributors as well as stators and coils on ATV and streetbike engines. I have no idea why it keeps replacing my apostrophes with question marks no matter what I do lol
    Last edited by Derpy Dylan; 05-14-2019 at 03:26 PM. Reason: Typo

  4. #4
    Senior Tuner cobaltssoverbooster's Avatar
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    that vve tool should be the the thing you are looking for to keep the danger down.
    i believe the driver demand map A table will help you command higher boost without the use of an external modification.

    if you can sneak a wideband in that would help a lot as well.
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    Alright I will definitely check into those when I get off work, thank you. Wouldn?t I have to have a pro model mpvi to integrate my wideband? I?ve just got a regular mpvi2

  6. #6
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    Wideband is step #1

    There are ways to use it in HPT without the pro version but even just having a gauge to keep an eye on is a really good idea.

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    I have a wideband. That?s how I made sure the fueling was okay. I?m not aware of how to integrate it into HPT though without a pro version

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    So I just checked through my whole ECU, and I do not see what you're talking about. I found the map A table in the driver demand section, but it uses accelerator position and vss/rpm to produce axle torque or engine torque, doesn't say which one. Maybe I'm overthinking it but that doesn't seem like I could use that to make boost. As far as the VVE stuff, I do not see VVE listed anywhere at all in my whole ECU. LOTS of VSS stuff but not VVE

  9. #9
    Senior Tuner cobaltssoverbooster's Avatar
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    Yes thee map A table is in torque because its a torque request table. Command more torque and it makes more boost.
    A lot of tables in this ecu work as request or modeling of output. There is a boat load of connected tables. I still suggest you work on walking first... that is figure vve out. Once you understand it and have corrections applied correctly through it, then move to making map A changes and work on try to understand how it works.
    VVE is an editor tool found in the edit tab of the software.
    This forum is good with information but we still expect you to use the search function. Read up on vve, don't disregard the v8 posts because they are the most active. While your there satisfy your curiosity by trying to understand map A between calibration tests.
    If you don't want to blow it you'll learn how to command each section one at a time. Base calibrations, Fuel, then boost, last ignition. Base calibrations not so much for you because you haven't mentioned changing injectors or pressure sensors out.

  10. #10
    Senior Tuner cobaltssoverbooster's Avatar
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    Any non critical sensor that feeds a 5 volt signal to the ecu and can be read by the scanner can be turned into wideband input. Follow the forum posts about setting up wideband through the egr. Works the same way just change egr settings out for the sensor channel you decide to use.

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    I?ll have to look into integrating my wideband. Thank you for telling me where VVE is, I never thought to look there. I?ll definitely start experimenting with it. My flow rate vs pressure table. It?s not used by gm, all the multipliers are at 1. Is there any benefits to setting that table up and using it instead? It seems like it?s a more simple table. If there are benefits, how would I go about getting a base map set up in it? I?m guessing there?s some math I could do to convert the pressure delta table, or a different tables numbers?

  12. #12
    Senior Tuner cobaltssoverbooster's Avatar
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    if your leaving the injector stuff stock just leave the injector stuff stock. they are close enough to not worry about fighting the new changes there.
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    Okay. Yeah for now I?m keeping stock injectors. I wanna get to 25psi eventually and leave it. If the stock injectors are taxed at that level, I?ll upgrade

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    Mr cobaltssoverbooster, I had some time to play with the map A torque table over the last couple days. I wasn?t getting anymore boost pressure out of it though?

  15. #15
    Senior Tuner cobaltssoverbooster's Avatar
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    check your knock airmass table to see if its causing any limitations. map a should request more engine load from the ecu which would in tern give you more boost. knock airmass can limit this if its activated. also look into the other maps b,c,d....etc. they should have descriptions with them to let you know which one goes with which power request mode.....ie normal, tow/haul, 4wd, power. modify the them all to be the same or make the ones you can use different to match your desires.
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    Thank you. I just did some tuning and took it for a test drive. I did get a little more boost this time.

    Something else I?m wondering about though. Why do I make more boost and consume more air/make more power, in second gear compared to third? In second I make almost 19psi and consume 16.4 lb/min of air. According to the guy from BNR that tunes their sonic, the whp on these cars is roughly 10x the peak airflow. In third gear I only make almost 14psi and consume 14.2lb/min. It?s quite noticeable too. I know second will always feel more powerful because of the mechanical advantage from the shorter gear, but I swear I can actually feel and more so hear the drop in boost. I was always under the impression that boosted cars made more boost under higher loads, ie, a higher gear?

  17. #17
    Senior Tuner cobaltssoverbooster's Avatar
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    im not exactly sure why it happens. in my cobalt i would tune 2nd gear and in 3 and 4 i would experience a pressure spike. i controlled the spike with some traction control. since i could take care of it i never looked into the why.
    this is my best guess though. the turbine side of a turbo is designed to spin the compressor of the turbo which forces extra air to the engine. when the engine rpm accelerates quickly the compressor air doesnt build up like a higher gear because the pumping efficiency of the engine is increasing at a fast rate similar to the airflow gain of the turbo. when the motor accelerates slower, higher gears like 3/4, the turbo pushes that extra air but the pumping efficiency id the motor us is not increasing as well as the lower gear with mechanical advantage. the air stuffs the cylinder making boost because thats the only place it has to go. i believe this pressure difference from 2 to 3 you speak of has to due with the pumping efficiency gain rate of the engine under load. This just so happens to be dictated by the gear you are in.
    Last edited by cobaltssoverbooster; 05-19-2019 at 02:24 AM.
    rdrfabrication@gmail.com
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    Ecotec help can be found here:
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