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Thread: Turbo maps - a quick guide

  1. #1
    Welcome to the Darkside! Automotive Encyclopaedia -==L=a=N=c=E==-'s Avatar
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    Default Turbo maps - a quick guide

    After some positive feedback i've had over my quick guide in my writeup (check siggy for link to project) I thought i'd let everyone else have a look, and tell me where i may or might be wrong:

    Copy and Paste
    ================================================== ========
    I promise the guides are coming soon. Half of the list will hopefully be fixed this weekend.

    Anyways, while i was waiting for the ute to be finished, i did some research into turbo sizing. (for my own curiosity)

    Firstly, i needed to make a VE map of a 2.7Litre engine Some quick calculations where done, and setup in an excel sheet.
    http://lance.ugbox.net/Hilux/Technic...3RZFE%20VE.xls

    This CFM map assumes a few things, like stock head, 90%VE and a perfect cam over the range. We all know that isn't correct, but for this situation, it helps to assume as such.

    Turbo maps are available freely now from the garrett we can now use these maps to trace our airflow. www.turbobygarrett.com

    I was unable to map the turbo i have in my car now, as it is a very unknown turbo. But i assume if it is anything comparable to RB25 highflow, it'll be good for around 450hp before running out of usable puff.

    Anyways, using the above calculated CFM curve, and then converted to lbs/min we can now draw on the maps.

    Below are what i did up. For a 2.7L engine, with 90%VE, and the largest housing available for each turbo.

    GT28R GT30R GT35R GT40R

    Now your looking at a map full of lines and squiggles. Ill quickly explain what it all means.


    Using the GT35R map as a guide.
    Straight lines is the amount of airflow moving thru the engine at a given RPM range.
    The 'island' shows when the turbo is giving positive pressure and when it is the most efficient along with what speed it is spinning at.
    The left hand bar represent pressure in relation to atmosphere. So 1Bar is at atmosphere, 2Bar is 1Bar above atmosphere (1bar of boost).

    So assuming a perfect situation. a 1.06 A/R housing on a GT35R will see around 0.3bar at 2000rpm, 1bar at 3000rpm 2.2bar at 4500rpm etc.

    So, if i ever wanted more power (god forbid) from the engine, a 1.06 rear housed is about spot on (assuming rebuild, and lifting the rev limit to around 7000-8000rpm). For quicker spool, each housing step down is about 500rpm quicker spool up. So for 0.86 rear housing, you would see 0.3bar at 1500rpm, 1bar at 2500rpm, 2.2bar at 4000rpm.

    And thats about it. I'm no expert about reading turbo maps, so take the information as a grain of salt.

    I mapped totenkpf's GT35R against the 2L and it comes fairly close. So i can't be completely wrong

  2. #2
    Junior Member Grease Monkey Bored?'s Avatar
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    Default Re: Turbo maps - a quick guide

    I like the approach of drawing volume lines over the graph. It does make reading off the compressor map quite simple.

    Most places I've seen on the 'net explain how to size the compressor. What I don't get is how to size the turbine + exhaust housing, and have it matched to the compressor.

    A few things that might not have been clear in your explaination:
    1) The iso-lines are lines of equal efficiency.
    2) The thick curves are lines of equal turbo shaft RPM
    3) The left-most line is usually marked as the surge point of the turbo

    A few suggestions:
    1) Some of us have sigs disabled, so you might like to post a link.
    2) You might consider using a colour with more contrast. At first I though "that's a weird looking map", then I figured out that you'd added stuff.
    Last edited by Bored?; 21-08-2006 at 08:37 AM.

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    Default Re: Turbo maps - a quick guide

    Bored?: I to don't quite understand the turbine sizing either. All i do understand (with the GT series) is the smaller wheel moves the turbo island to the left, at the expense of efficiency and topend.

    This map i just did up is for Draven:
    2JZ 3Litre with 90% VE, and GT35R

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    Default Re: Turbo maps - a quick guide

    For those that have asked, this is where i got the idea from:
    http://wolfkatz.com/Articles/Compres...on%20Small.pdf
    Turbo sizing for a 2L Turbo (3S-GTE in this case)

  5. #5
    Former User Conversion King Joshstix's Avatar
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    Default Re: Turbo maps - a quick guide

    Garrett also have a really informative writeup on this subject on their own website http://www.turbobygarrett.com/turbob...o_tech103.html.

    On the subject of sizing the turbine my basic understanding is:
    1. Try to get a balanced wheel setup where the turbine wheel is at least 80% of the diameter of the compressor wheel
    2. Make sure the mass flow of the turbine housing is not hugely lower than the mass of air the compressor should be able to move
    3. Try to have the mass flow of the turbine housing max out at the point you expect to make maximum boost

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    Olde ****** Automotive Encyclopaedia ToDa30/4's Avatar
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    Default Re: Turbo maps - a quick guide

    interesting post lance ,turbo sizings a black art to most
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