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Thread: Boost control explained 6 different types of control

  1. #1
    Davezj's Avatar

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    Boost control explained 6 different types of control

    this info is a copy and paste but there are so many questions about boost control i thought i would post it up as it sensible info.
    there is a link to a video at the bottom.

    Today we're talking about something that is as important as boost itself, and that something is control and we will cover all the boost control setups, starting with the most basic level 1 setup and proceeding to the most complex and performance oriented level.

    LEVEL 1 BOOST CONTROL - wastegate + wastegate actuatorThe most basic setup consists of nothing but your wastegate and your wastegate actuator. This simple setup works by having a boost reference line connected to a boost source. Boost pressure is exerted onto the spring and diaphragm inside the wastegate actuator. Once boost pressure gets high enough it compresses the spring and opens the wastegate. Having quick turbo spool up with this setup is next to impossible as the spring inside the actuator is exposed to boost pressure all the time. Your wastegate will be fully opened when you hit the boost the spring is rated for, but your wastegate will actually start to open way sooner than target boost.

    LEVEL 2 BOOST CONTROL - manual boost controllerA manual boost controller will alloy you to make boost than your spring would allow by delaying the boost going through the reference line. Inside a manual boost controller is a spring and a ball. Adjusting a knob or turning the controller itself will change the spring pressure on the ball. Lifting the ball up from it's seat will require more boost pressure than compressing the wastegate spring so your turbocharger generates more boost. Although the manual boost controller is very simple to install and increases boost pressure it doesn't do anything else. It's dumb just like the level 1 setup and references nothing other than boost. It has no idea about your throttle opening, intake air temperature etc. which can result in full boost at half throttle or a setting that needs readjustment for different weather or or altitude.

    LEVEL 3 BOOST CONTROL - 2 port boost control solenoidThe simplest electronic setup involves a 2 port boost control solenoid. The 2 port solenoid is connected into the boost reference line with a T fitting and it bleeds boost pressure from the line between the turbo and wastegate actuator. Essentially the 2 port boost solenoid is lying to the spring in the wastegate actuator by making it "think" there's less boost being made than actually is. The great advantage between a 2 port boost solenoid and any manual boost controller is that the solenoid is connected to the ECU and the ECU can manipulate the solenoid's duty cycle based on throttle opening, air temperature, coolant temperature, etc. so you'll never get full boost at half throttle again. The downside is that with the 2 port solenoid and the t-fitting the spring still sees boost pressure all the time so the 2 port solenoid still can't prevent it from being slightly opened before it needs to be.

    LEVEL 4 BOOST CONTROL - 3 port boost control solenoidUnlike the 2 port solenoid which is installed with a t-fitting, the 3 port boost control solenoid is installed directly into the boost reference line and it interrupts the boost pressure going from the turbo to the wategate actuator. Because it has one more port the 3 port boost solenoid can control boost more accurately and with less duty cycle compared to a 2 port solenoid resulting in better turbo responsiveness, quicker spool up and more power, as well as more headroom to increase boost later on.

    LEVEL 5 BOOST CONTROL - 3 port boost control solenoid + external wastegateWhen hooked up to an external wastegate a three port solenoid can be used to direct boost pressure to the top port of a two port wastegate helping reinforce the spring and keeping it closed. This is a superior setup to "lying to the spring" and it results in even better turbo responsiveness and more aggressive spool up.

    LEVEL 6 BOOST CONTROL - 4 port boost control solenoid / 2 X 3 port solenoids The 4 port boost control solenoid can do something a 3 port cant'. It can control the top and bottom of a 2 port external wastegate at the same time. A 3 port solenoid can make twice the boost pressure of your base spring, but a 4 port solenoid can make 5-6 times that which means it's capable of generating some extreme boost. The only real downside is poor resolution. Changing a 4 port solenoid duty cycle by just 1-2% can result in 3-8 psi of boost pressure change. To correct a bumpy boost curve generated by a 4 port solenoid you can use two 3 port solenoids, but this will require a very capable ECU and some pretty complex tuning.



    Bye for Now!

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    dazjb's Avatar

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    Handy stuff to know. Cant have enough info when it comes to boost

    Sent from my BLA-L09 using Tapatalk
    Last edited by dazjb; 18-10-2020 at 09:19 PM.

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    Davezj's Avatar

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    The reason i have posted this information is because at every dyno day i have attended there is always 2 or 3 people that have trouble with boost control on the dyno. and it is either a faulty boost solenoid or the solenoid is plumbed in wrong.
    with the info provided able there is no reason why anyone should turn up to a dyno for a tuning session or a power run with a boost control issue.

    it is embarrassing to be honest, how frequently this happens.

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    elnevio's Avatar

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    Quote Originally Posted by Davezj View Post
    The reason i have posted this information is because at every dyno day i have attended there is always 2 or 3 people that have trouble with boost control on the dyno. and it is either a faulty boost solenoid or the solenoid is plumbed in wrong.
    with the info provided able there is no reason why anyone should turn up to a dyno for a tuning session or a power run with a boost control issue.

    it is embarrassing to be honest, how frequently this happens.
    Dave, would you be able to do a complete How To guide on testing the VR-4 for boost leaks - i.e. tools needed and how to do it? This would be a useful guide for so many people (including me!) as it is indeed a common issue.
    October 2020 fleet status: 75% operational 25% furloughed!


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  5. #5
    Confused's Avatar

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    In case anyone was wondering, our cars are "LEVEL 3"

    I've re-done the vacuum line diagrams from the service manuals in higher quality than is currently floating around on the internet, so I hope this helps!

    6A13TT-Engine-Vacuum-Auto-TCL.png 6A13TT-Engine-Vacuum-Manual.png

    And if you wish to move to "LEVEL 4" and install a 3-port solenoid, this is how you would plumb it up. (Note, this will likely require a retune)

    6A13TT-Engine-Vacuum-Auto-TCL-3port.png 6A13TT-Engine-Vacuum-Manual-3port.png

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    Boost leak testing would be fairly straight forward on these cars it seems. However, since there's two turbochargers and thus two inlets, you wont be able to test from the turbo onward. Frankly testing from the turbo inlet isn't the most accurate way anyway, since boost pressure still makes its way past the journal bearings and into the crank case (while the car is not running, of course).

    So, if we assume the turbo compressor housing gaskets as well as the outlet O-rings are intact and sealing, the first area you'd have a potential leak is at the steel Y-pipe that joins both turbo outlets and goes into the rubber intercooler pipe. If I'm not mistaken, that rubber hose is 2.5" in diameter, so all you'd need is a standard PVC cap fitting 2.5" wide (63mm) from your hardware store. Then, you drill a big enough hole through the center so you can fit a standard tyre valve stem. Usually I add either some silicone or PVC glue to make sure the stem wont leak.

    From then on, all you do is you clamp the testing unit at the rubber intercooler hose and start applying compressed air slowly, either going by the boost gauge (which you should have installed) or the compressor if fitted with a gauge. I usually test my cars at 1.5 bar regardless of actual running pressure. Using a mix of dishwashing soap and water, you spray at every possible airway; main charge pipes, couplers, intercooler tanks, BOV, intake gaskets and throttle body shaft seals, and most especially the tiny vacuum hoses that are endless it seems. Wherever you see bubbles foaming, it is a leak that needs addressing.

    From my experiences, fixing all possible boost leaks amounted to the most impact both to performance, as well as better fuel economy. That said, I have yet to boost leak test my brother's Legnum, but like I said, the tester should simply attach to the upper intercooler hose (both compressor housing gaskets and o-rings are new in his case, so no leaks there!).


    Hope this helps.

  7. #7
    Nick Mann's Avatar

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    Nice diagrams Garry - it might be worth labelling the "air intake hose" as the pre-turbo hose or something similar? For a second I was reading the diagram back to front as I saw air intake hose and assumed it was the boost reference point rather than the solenoid waste outlet point.

    Also worth mentioning is that if you have a facelift auto you will almost certainly need to refer to the manual diagrams, not the auto with tcl. (Unless your name is Nev.)

    Diagram 3 for me!

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    Good points, @Nick Mann, I've amended the diagrams in my post - hope that makes it clearer!

  9. #9
    Davezj's Avatar

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    This was my original setup in this thread.
    https://www.clubvr4.com/forum/showth...t+leak+testing

    it is a bit of a word post but you can see the pictures and get the gist.
    i have moved on from the MDF bung and now use the drain pipe capping off bung.
    which does fit perfectly in the flex boost pipe after the metal Y pipe that comes out of the turbo. as described above by kryndon

    i will try and find some other threads where i did a proper parts write up.
    i think i even did a parts list and links to parts.

    here is a pressure regulator 0-30PSI which is perfect for our turbo setup as we are never going to go over 30psi boost and it give good control over the actual set point for the pressure. (£25)

    https://www.ebay.co.uk/itm/Air-Regul...s/121040398913

    here is a pressure regulator you could use but it is 0-145psi so you can set it to 20psi but it might be 30psi it might be 10psi the set point is not easy to set and you could massively over pressurise the boost system of the car quite easily if you are not very careful. (£7.50)

    https://www.ebay.co.uk/itm/1-4-Mini-...e/353251389638

    drain pipe blank 75mm and 50mm might be a bit flimsy but will probably work (£1.50)

    https://www.ebay.co.uk/itm/PVC-Cap-E...kAAOSwcF5fXHUO

    or something like this blank with the extra blank insert and some PVC glue

    https://www.ebay.co.uk/itm/PVC-Eccen...IAAOSwyR5fXHUw
    https://www.drainagepipe.co.uk/push-...-white-p-WP30/

    you can get one piece version of the above blank at DIY stores like B&Q and Home Base screwfix tool station. like this one below but a small diameter as this one is 100mm

    https://www.ebay.co.uk/itm/PVC-Eccen...IAAOSwyR5fXHUw

    Then you will need a bulkhead fitting this one works with push fit 8mm tube capable of handling about 100psi.

    this is the type of tube i am referring to
    https://www.ebay.co.uk/itm/NYLON-TUB....c100005.m1851

    then you can just get the appropriate fitting for the regulator to connect it all up.
    Last edited by Davezj; 27-10-2020 at 10:12 PM.

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