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Thread: Magnuson Silverado throttle oscillation help

  1. #1
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    Magnuson Silverado throttle oscillation help

    Hello, what would cause this throttle oscillation, any help how to fix it? thanks
    all stock, only magnuson supercharger.
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    no one?

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    Any hint? driver demand tables, virtual torque tables?

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    Senior Tuner SultanHassanMasTuning's Avatar
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    lower your PE enable

    your seeing boost and still 1 lambda target
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    Quote Originally Posted by SultanHassanMasTuning View Post
    lower your PE enable

    your seeing boost and still 1 lambda target

    Yes, wanted to take care of that too, in other scenarios it will go into PE without being in boost, i will look into this. any sugestion for the throttle oscillation? thank you

  6. #6
    It's usually from the actual torque being higher that the commanded torque. It can also come from not raising the peak torque table enough in the rpm range its oscillating. Try adding 5-10% to the peak torque table in those ranges. If that doesn't fix it bring peak torque back down and move on to the vve tables, then driver demand, then virtual torque.

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    Quote Originally Posted by 32vape View Post
    It's usually from the actual torque being higher that the commanded torque. It can also come from not raising the peak torque table enough in the rpm range its oscillating. Try adding 5-10% to the peak torque table in those ranges. If that doesn't fix it bring peak torque back down and move on to the vve tables, then driver demand, then virtual torque.
    thank you ill give it a try, should i add in the affected area in the vvt too?

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    It's most likely your DD just glancing at some things. Could be your map torque model, but the airmass one doesn't look like it would be trimming you.
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    do you have a facotry camshaft setup?

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    If I had a dollar for every time I've answered this one lol. You installed a supercharger but the ECM isn't aware of it. So as the bypass valve begins to close, boost comes in and exceeds the target torque which caused the throttle to close to correct for it. Then the bypass opens, dropping MAP and forcing the throttle open again... The overshoot is happening because of the relative vacuum behind the throttle body as boost comes in. Once the blower begins to generate a pressure ratio, the desired throttle angle becomes incorrect due to the higher pressure delta across it. The real solution is installing and enabling an SCIAP sensor to make the controls aware of the inter-stage pressure drop and correct the throttle position. Ford, Chrysler...every manufacturer has issues almost identical to this when installing a PD blower.

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    Quote Originally Posted by smokeshow View Post
    If I had a dollar for every time I've answered this one lol. You installed a supercharger but the ECM isn't aware of it. So as the bypass valve begins to close, boost comes in and exceeds the target torque which caused the throttle to close to correct for it. Then the bypass opens, dropping MAP and forcing the throttle open again... The overshoot is happening because of the relative vacuum behind the throttle body as boost comes in. Once the blower begins to generate a pressure ratio, the desired throttle angle becomes incorrect due to the higher pressure delta across it. The real solution is installing and enabling an SCIAP sensor to make the controls aware of the inter-stage pressure drop and correct the throttle position. Ford, Chrysler...every manufacturer has issues almost identical to this when installing a PD blower.
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    Quote Originally Posted by smokeshow View Post
    If I had a dollar for every time I've answered this one lol. You installed a supercharger but the ECM isn't aware of it. So as the bypass valve begins to close, boost comes in and exceeds the target torque which caused the throttle to close to correct for it. Then the bypass opens, dropping MAP and forcing the throttle open again... The overshoot is happening because of the relative vacuum behind the throttle body as boost comes in. Once the blower begins to generate a pressure ratio, the desired throttle angle becomes incorrect due to the higher pressure delta across it. The real solution is installing and enabling an SCIAP sensor to make the controls aware of the inter-stage pressure drop and correct the throttle position. Ford, Chrysler...every manufacturer has issues almost identical to this when installing a PD blower.
    And now you DEFINITELY have my attention!

    Whipple PD blower on an L83.

    I've been chasing an annoying issue at 30%-40% accelerator pedal position during steady state cruise. A light load will cause throttle position to quickly spike and build considerable boost. Lots of polishing on Virtual Torque and Driver Demand have helped, but the issue still persists.

    1) Can an LT4 SCIAP sensor be added (post throttle body, pre supercharger) and successfully wired in and read by the ECU?

    2) I'm already running an LT4 TMAP (GM 25203651). Can the air temp wire be pinned to IAT2 and the original intake air temp sensor in the MAF be pinned to IAT?

    3) Will the L83 ECU OS recognize two pressure sensors and two IAT sensors if properly pinned to the ECU and MAP sensor type changed to SC-SCIAP-BARO?

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    Do you guys know the location of the sciap sensor signal pin location on the ecm connector ?
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    This typically can be resolved in the driver demand table.

    With the blower it is making more torque and it knows this because the airflow is way up over stock. ECM says wait we are only asking for this.. rolls throttle back. It gets into a oscillation quick trying to chase torque in the DD table.

    Add 5-10% exactly in the region were this is happening. (RPM or VSS X throttle pedal position)
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    Yeah, that's why I pointed it out earlier. DD, vve and cam tables will usually sort it right out. You really need a baro breakout to be 100% fixed with staying correct with your dialed in fueling.
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
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    Quote Originally Posted by GHuggins View Post
    Yeah, that's why I pointed it out earlier. DD, vve and cam tables will usually sort it right out. You really need a baro breakout to be 100% fixed with staying correct with your dialed in fueling.
    He shouldn't need a baro breakout with a magnacharger.
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    Quote Originally Posted by Alvin View Post
    He shouldn't need a baro breakout with a magnacharger.
    Exactly.. baro will never see boost on a PD app.. only needed on centri or turbo setups that pressurize the sensor in the MAF

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    Quote Originally Posted by castorjames View Post
    Do you guys know the location of the sciap sensor signal pin location on the ecm connector ?
    E92 X1 Pin 4 is the signal for the throttle inlet pressure on the NA cars or if you have a factory SC can they use that pin for the supercharger inlet and use X2 pin 45 for the throttle inlet. So you could probably wire it up to work as the OE engineers know you need this set up to control the throttle as smokeshow pointed out.

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    attached is the last file and log, i didnt had much time to play with it any more. i couldnt replicate the issue, i wasnt able to feel it. i see in the logs that it opens or closes the throttle body ocasionally while im steady in the throttle but in a smooth way, i wasnt able to feel anything weird while trying to replicate the issue. i think this is the way this ecm works.. im not sure the SCIAPs sensor is enabled correctly .
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    Quote Originally Posted by castorjames View Post
    attached is the last file and log, i didnt had much time to play with it any more. i couldnt replicate the issue, i wasnt able to feel it. i see in the logs that it opens or closes the throttle body ocasionally while im steady in the throttle but in a smooth way, i wasnt able to feel anything weird while trying to replicate the issue. i think this is the way this ecm works.. im not sure the SCIAPs sensor is enabled correctly .
    I take it that you installed a SCIAP sensor?

    That's good to know it fixed it for you.
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