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IWG Flutter

Boost Control

Discussion and questions related to the course Boost Control


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Hi, i've been noticing that i can hear my waste gate fluttering on 3rd gear and above when going through the spool rpms of 3k-4.5k. I believe this is the wastegate being violently controlled by the turbo dynamics, am i correct in my assumption?

I have tried to put a weaker spring in my adjustable actuator to get smoother response in 3rd and 4th, however it really robs me of response in gear 1 and 2.

Previous spring was 1.5 bar

Current spring is 1.2 bar

I had issues with my previous spring in which i'd get spikes of 1.7bar+ for a few hundred rpm, to curb this i pulled my 100% duty values from 3600 to 3400 and this put the spiking to a maximum of 1.7 bar. i can bring this value further down to say 3100 rpm, but that would just kill more response in gear 1 and 2 right ?

First option is to adjust the turbo dynamics table for the 1.5 bar spring to try and curb the over boost, however i'm not sure what values to change.

Second option is to go back to my previous waste gate spring and bring down the 100% spool values a few hundred rpms before to try and curb the spike to a max of 1.6 bar

Third option is leave the spool values alone and put the restrictor pill back in the bleed line.

Fourth option is adjust the preload on the current spring to give a high crack open pressure.

How do you know it's the wastegate? Got a video? It sounds like this is a Subaru. What is your mod list? Do you have a datalog of the problem occurring?

ESL ECU, Ej20, subaru v4 uk2000, 4.11 fd sti drivetrain, exedy pink box clutch, exedy lightweight flywheel, td05-16g straight through 3" exhaust with bellmouth decat, 440cc injectors, Chinese brand FMIC, DV delete, stock sti headers and decat upipe heat wrapped with chinas finest lavawrap, orange MAF (good for 350bhp) connected to a samco silicone turbo inlet.

I dont have a log yet(Ive been doing live mapping with the help of a driver), but i noticed if i create a bigger difference between maximum and min wg duty the noise happens more, i assume its waste gate noise because im trying to get my boost to come on violently AND it got louder when i removed my heat wrap on the downpipe (got new one on now).

im thinking this noise is integral windup because im targeting high levels of boost, and then when the windup settles, everything smoothness out after 4.5k.

using this strategy i can produce 1.4 bar in 2nd gear, and like 1.5bar in 3rd and 1.6+ in 4th. I like the way the car feels, its fun! however, because my spiking is so random, i cant dial in my ignition timing because im scared of making it knock. i can spike between 1.5 bar and 1.8 bar depending on how hot the headers are.

What i want to do is develop a turbo dynamics table so well dialed in, that i can keep my 1.2 bar and 1.4 bar in 1st and 2nd, not by increasing the minimum waste-gate duty, but by having values in the turbo dynamics tables to spike my min waste gate values rather than me explicitly increasing my min wastegate values creating a bigger spike!

I understand I've asked this question before, and that there is certain philosophy to tune boost control. I am trying to abide by that strategy to create a little spike when going through the boost rpm of 3k-4.5k(because i have no gear compensation!). i rarely load my motor like this, i do this for tuning, when i drive fast i stay in 5k-7k powerband and i get no issues with boost control.

What i need is some assistance in the turbo dynamics table, to be more specific the sub table in TD which allows for a TEMPORARY spike of real wg duty to my maximum of 100% in the lower gears and if i want to do a gear 4 pull, the table takes values between my min and max wg duty to achieve the target boost.

ESL ECU, Ej20, subaru v4 uk2000, 4.11 fd sti drivetrain, exedy pink box clutch, exedy lightweight flywheel, td05-16g straight through 3" exhaust with bellmouth decat, 440cc injectors, Chinese brand FMIC, DV delete, stock sti headers and decat upipe heat wrapped with chinas finest lavawrap, orange MAF (good for 350bhp) connected to a samco silicone turbo inlet.

I dont have a log yet(Ive been doing live mapping with the help of a driver), but i noticed if i create a bigger difference between maximum and min wg duty the noise happens more, i assume its waste gate noise because im trying to get my boost to come on violently AND it got louder when i removed my heat wrap on the downpipe (got new one on now).

im thinking this noise is integral windup because im targeting high levels of boost, and then when the windup settles, everything smoothness out after 4.5k.

using this strategy i can produce 1.4 bar in 2nd gear, and like 1.5bar in 3rd and 1.6+ in 4th. I like the way the car feels, its fun! however, because my spiking is so random, i cant dial in my ignition timing because im scared of making it knock. i can spike between 1.5 bar and 1.8 bar depending on how hot the headers are.

What i want to do is develop a turbo dynamics table so well dialed in, that i can keep my 1.2 bar and 1.4 bar in 1st and 2nd, not by increasing the minimum waste-gate duty, but by having values in the turbo dynamics tables to spike my min waste gate values rather than me explicitly increasing my min wastegate values creating a bigger spike!

I understand I've asked this question before, and that there is certain philosophy to tune boost control. I am trying to abide by that strategy to create a little spike when going through the boost rpm of 3k-4.5k(because i have no gear compensation!). i rarely load my motor like this, i do this for tuning, when i drive fast i stay in 5k-7k powerband and i get no issues with boost control.

What i need is some assistance in the turbo dynamics table, to be more specific the sub table in TD which allows for a TEMPORARY spike of real wg duty to my maximum of 100% in the lower gears and if i want to do a gear 4 pull, the table takes values between my min and max wg duty to achieve the target boost.

Ok so based on this article: http://www.romraider.com/forum/topic1814.html

oost Error = Target Boost - Actual Boost'As you can see, if target boost is greater than actual boost, boost error will be positive (you are undershooting your target). If target boost is less than actual boost then boost error is negative (you are overshooting your target). Boost Error is used as input to the 'Turbo Dynamics' tables.'

As Im Undershooting in lower gears and Overboosting in higher gears:

'The 'Turbo Dynamics Continuous' table is active a lot of time. Anytime there is negative boost error or boost error is positive (outside of the disable ranges determined by the activation thresholds) it will act to correct wastegate duty (as long as wastegate is not being cut by other factors such as the speed limiter or idle).'

I assume i will be focusing on continuous over and under boost gains as opposed to burst based on attached test screenshot

How would i manipulate each of the 4 values within the continuous under boost and over boost table:

I am under boosting in gear 1 and 2 therefore i should increase the values in the table:

current wg duty gives me 1.1 bar at 50% current duty + 11.8% from the table which gives me a total of 61.8%, as i want to aim for a realistic 1.3 bar in 2nd, do i then change that 11.8 to for example 15% giving me a total value of 65% and keep adding to the table till i get what i need i.e good spool in lower gears and manageable over boost in the higher gears.?

Attached Files

You've got a really old ECU so that makes this difficult. If it is possible set all your turbo dynamics to 0 to control boost control open loop. Then see if the noise goes away. Use a fixed duty cycle with the initial off idle duty cycle and max duty cycle settings.