boost taper?
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This is a discussion on boost taper? within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; hi guys as alot of use probably know i have a big 16g td05 with a mbc at 20 psi ...

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    Registered User sxcrxy's Avatar
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    boost taper?

    hi guys as alot of use probably know i have a big 16g td05 with a mbc at 20 psi but doesnt taper , obviously its better gives me good top end but is there any down points for not tapering? once it hits 20 psi it fluxcuates from 18 to 20, 20 at 3600rpm from, 3600 to about 5000 its 18- 19 from 5000 to 7300 it creeps and sits solid at 20psi, the car has good top end because of this but is this bad in anyway? the reason why it doesnt taper is probably because the wastegate size

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    Moderator Donkey's Avatar
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    It has to with compressor efficiency. You also can't force/control boost taper with an MBC. These are kind of basic fundamental things to know if you are tuning your own car.
    Stealth 316 - Turbocharger Compressor Flow Maps
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    and the Funky Bunch Calvinball's Avatar
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    Quote Originally Posted by Donkey View Post
    It has to with compressor efficiency. You also can't force/control boost taper with an MBC. These are kind of basic fundamental things to know if you are tuning your own car.
    Stealth 316 - Turbocharger Compressor Flow Maps
    Wonderful link there.
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    Admiral Ackbar the 1st mycologist's Avatar
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    What do the logs look like on the top end?
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    Registered User Heide264's Avatar
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    Re: boost taper?

    Quote Originally Posted by Donkey View Post
    It has to with compressor efficiency. You also can't force/control boost taper with an MBC. These are kind of basic fundamental things to know if you are tuning your own car.
    Stealth 316 - Turbocharger Compressor Flow Maps
    This.

    When a turbo is pushing boost at a higher rpm, it must efficiently supply a larger volume of air. If the turbo is way out of its efficiency zone, you will make less power even with a higher psi..... Mostly due to the turbo heating the air up too much. Hotter air is less dense and hence delivers a smaller mass of air per valve opening than colder air.
    Quote Originally Posted by Trainrex
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    Registered User sxcrxy's Avatar
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    Quote Originally Posted by Heide264 View Post
    This.

    When a turbo is pushing boost at a higher rpm, it must efficiently supply a larger volume of air. If the turbo is way out of its efficiency zone, you will make less power even with a higher psi..... Mostly due to the turbo heating the air up too much. Hotter air is less dense and hence delivers a smaller mass of air per valve opening than colder air.
    when i bought this turbo the seller was from a performance shop and a big 16g td05 he said this turbo would pull of 25 - 27 psi tops, i do not understand flow charts so please dont send them to me unless if you could break it down and just tell me an easier way i dont have time to learn how they work

    logs are here:
    https://docs.google.com/spreadsheet/...5eVk1blE#gid=0

    ive done the maf hack reason why everything is halved

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    Subaru Newb MainFrame's Avatar
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    What 16g is it, Forced Performance?

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    Registered User sxcrxy's Avatar
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    Quote Originally Posted by MainFrame View Post
    What 16g is it, Forced Performance?
    claimed to be an australian brand large td05 16g brand name TTS

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    Moderator Donkey's Avatar
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    Quote Originally Posted by sxcrxy View Post
    when i bought this turbo the seller was from a performance shop and a big 16g td05 he said this turbo would pull of 25 - 27 psi tops, i do not understand flow charts so please dont send them to me unless if you could break it down and just tell me an easier way i dont have time to learn how they work
    Seriously? Okay....................
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    Admiral Ackbar the 1st mycologist's Avatar
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    Quote Originally Posted by sxcrxy View Post
    when i bought this turbo the seller was from a performance shop and a big 16g td05 he said this turbo would pull of 25 - 27 psi tops, i do not understand flow charts so please dont send them to me unless if you could break it down and just tell me an easier way i dont have time to learn how they work

    logs are here:
    https://docs.google.com/spreadsheet/...5eVk1blE#gid=0

    ive done the maf hack reason why everything is halved
    It looks like it might be OK if not an ideal solution. The map runs very rich on the top end, which may be helping you out. The IAM is maxed out, which is good, but you need to log Fine Learning Knock Correction (FLKC) Feedback Knock Correction (FBKC) and IAM to get the whole picture. Knock Correction Advance is useless because it just shows you what is going on relative to the max values in the table, which frequently are variable. I.e. you have to compare them back to the max table in the map cell by cell instead of just looking at the corrections directly. The other parameters show you if corrections are being applied due to knock.
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

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    Registered User sxcrxy's Avatar
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    Quote Originally Posted by mycologist View Post
    It looks like it might be OK if not an ideal solution. The map runs very rich on the top end, which may be helping you out. The IAM is maxed out, which is good, but you need to log Fine Learning Knock Correction (FLKC) Feedback Knock Correction (FBKC) and IAM to get the whole picture. Knock Correction Advance is useless because it just shows you what is going on relative to the max values in the table, which frequently are variable. I.e. you have to compare them back to the max table in the map cell by cell instead of just looking at the corrections directly. The other parameters show you if corrections are being applied due to knock.
    Maf scailing towards top end is bad hence the rich problem, no knock ive gone over my map alot of times learning veiw other logs and stuff shows me no knock

  13. #12
    UnBanned Sinister's Avatar
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    Quote Originally Posted by Donkey View Post
    It has to with compressor efficiency. You also can't force/control boost taper with an MBC. These are kind of basic fundamental things to know if you are tuning your own car.[/url]
    Injector duty cycle is the percentage of the stroke that the injector is open. Injector Pulse width is the amount of time that the injector is open and spraying. At low RPM the length of time that the injector has to be open is large. At the highest RPMs there is very little time between strokes and IDC goes up. So a lot of times you have to tune the car to taper at the top to be able to keep a conservative IDC / IPW.
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    Registered User Heide264's Avatar
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    Quote Originally Posted by sxcrxy View Post
    when i bought this turbo the seller was from a performance shop and a big 16g td05 he said this turbo would pull of 25 - 27 psi tops, i do not understand flow charts so please dont send them to me unless if you could break it down and just tell me an easier way i dont have time to learn how they work

    logs are here:
    https://docs.google.com/spreadsheet/...5eVk1blE#gid=0

    ive done the maf hack reason why everything is halved
    I didn't link you a compressor chart. I was seconding what was said, and I also offered an alternative (non numerical) explanation of why your boost would taper. I don't know your specific turbo or anything.

    If you don't have time to learn, go talk to a tuner.
    Quote Originally Posted by Trainrex
    He was throwing balloons filled with sulfuric acid and shrapnel at the swat team. They finally had to take him down with rubber bullets.
    2011 STi Build Log
    -Part 1 - Reading, Data Logging, and Analyzing Data
    -Part 2 - Turbocharger 101 & Basic Boost Control
    -Part 3 - EcuFlash, Experimental Defintions, and a Drive By Wire Intro

  15. #14
    Admiral Ackbar the 1st mycologist's Avatar
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    It isn't that complicated, especially when someone has annotated it for you.



    Flow is how much air - it increases with RPM. Pressure is boost relative to atmospheric pressure (multiply by atmospheric in psi then subtract atmospheric to get boost). Your car will move through the map during a pull. It will start at low pressure and low flow at low RPM and build higher pressure and flow over time. The question is whether you need to drop pressure at high flow (high RPM) to stay on the efficiency islands.
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

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