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  1. #1
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    2 out of 2 members liked this post. Yes Reputation No

    Are you wondering how much boost is really safe for stock turbos?

    I found this from the other forum and found it pretty interesting.

    So DON't ask me any question because I don't have the tech knowledge needed to respond, unlike my buddy Dzenno!

    Are you wondering how much boost is safe for stock turbos ? Calculations inside !


    Hi,

    Have you ever wondered how much boost is really safe for your stock turbos, and how to calculate it ? The sticky thread about the Mitsubishi TD03 turbo characteristics does not mention any calculations, just speculations. This was driving me mad. I needed real answers based on calculations.

    With the help of a software program that I just made, I have calculated how much boost is safe for the stock N54 turbos, at each RPM.

    Based on the results below and your logs, you can see if your turbos are inside the efficiency range or you are pushing them too hard.

    I used these materials as a reference:

    This tells you how to calculate various parameters:

    http://www.turbobygarrett.com/turbob...Catalog_V4.pdf

    This tells you the Mitsubishi TD03 turbo efficiency maps:

    "Here's some compressor map data for the turbochargers on the x35 N54 vehicles.

    From this we can gather that a pair of these turbos spinning at redline can produce ~1150 kg/hr of airflow, which translates into ~42.25 lb/min. "

    Click here to enlarge

    Algorithm: For each RPM (in steps of 100), check each psi value from 22 down to 0, in steps of 0.1psi, and see if the resulting values (pressure ratio, air flow) is inside the efficiency maps using an algorithm to determine if a point is inside a polygon. Of course, it's a bit more complicated but this is the essence.

    Here are the results for an IAT of 40 Celsius (104F) and a pressure drop (intercooler + piping) of 1.5psi:

    RPM PSI
    1300 4.00
    1400 6.50
    1500 15.80
    1600 17.50
    1700 17.60
    1800 17.70
    1900 17.80
    2000 17.80
    2100 17.90
    2200 18.00
    2300 18.10
    2400 18.20
    2500 18.30
    2600 18.40
    2700 18.50
    2800 18.50
    2900 18.60
    3000 18.80
    3100 18.90
    3200 19.00
    3300 19.10
    3400 19.20
    3500 19.30
    3600 19.40
    3700 19.30
    3800 19.20
    3900 19.10
    4000 19.00
    4100 18.90
    4200 18.70
    4300 18.60
    4400 18.50
    4500 18.40
    4600 18.10
    4700 17.70
    4800 17.30
    4900 16.90
    5000 16.50
    5100 16.20
    5200 15.80
    5300 15.50
    5400 15.10
    5500 14.80
    5600 14.50
    5700 14.10
    5800 13.60
    5900 13.00
    6000 12.40
    6100 11.90
    6200 11.30
    6300 10.80
    6400 10.20
    6500 9.70
    6600 9.10
    6700 8.60
    6800 8.20
    6900 7.70
    7000 7.20
    7100 6.80
    7200 6.40

    Here are the results for IAT of 22 Celsius (74F) - for example if you are using meth:

    RPM PSI
    1300 4.00
    1400 6.50
    1500 15.80
    1600 17.50
    1700 17.60
    1800 17.70
    1900 17.70
    2000 17.80
    2100 17.90
    2200 18.00
    2300 18.10
    2400 18.20
    2500 18.30
    2600 18.40
    2700 18.40
    2800 18.50
    2900 18.60
    3000 18.70
    3100 18.90
    3200 19.00
    3300 19.10
    3400 19.20
    3500 19.30
    3600 19.40
    3700 19.30
    3800 19.20
    3900 19.10
    4000 19.00
    4100 18.90
    4200 18.70
    4300 18.60
    4400 18.50
    4500 18.40
    4600 18.10
    4700 17.70
    4800 17.30
    4900 16.90
    5000 16.50
    5100 16.20
    5200 15.80
    5300 15.50
    5400 15.10
    5500 14.80
    5600 14.50
    5700 14.20
    5800 13.60
    5900 13.00
    6000 12.40
    6100 11.90
    6200 11.30
    6300 10.80
    6400 10.20
    6500 9.70
    6600 9.20
    6700 8.70
    6800 8.20
    6900 7.70
    7000 7.20
    7100 6.80
    7200 6.40

    Now let's have a tuner push these turbos to the max, it seems to me there is plenty of room in the midrange Click here to enlarge

  2. #2
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    Click here to enlarge Subscribed.

  3. #3
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    Cool! I LOVE data such as this Click here to enlarge Bring that dude over here hehehe
    Click here to enlarge

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    That is a lot of taper to stay "safe."

  5. #5
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    Keep in mind this is to be within efficiency at a very high IAT and without using meth...with meth, especially when injected pre-turbo, it serves to stretch the compressor map making the turbos seem more efficient than they really are on their own

    This also shows why on stock turbos people are wasting time past 6000-6100rpm when shifting/racing
    Click here to enlarge

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    Looks cool just not sure how the VE of the engine/turbine is being calculated. Probably just good rule of thumb logic.

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    I have the VE of the engine vs RPM and I think that plot is a little over conservative with boost especially past 6000 RPM. The turbos are small but you can sustain more than 6 psi at 7k we all know that. I have a plot somewhere taking into account VE and IAT vs boost, ill post it up later.
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    Click here to enlarge

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    Click here to enlarge Originally Posted by Rob@RBTurbo Click here to enlarge
    Looks cool just not sure how the VE of the engine/turbine is being calculated. Probably just good rule of thumb logic.
    The guy claimed to use 95% VE across the board. Said he got it from garrett as a rule of thumb.

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    nice info

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    It's interesting and cool no doubt but is it applied to the n54 accurately to be of use?
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  11. #11
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    Click here to enlarge Originally Posted by ATP Click here to enlarge
    The guy claimed to use 95% VE across the board. Said he got it from garrett as a rule of thumb.
    That is a dangerous assumption, the N54 engine VE varies with RPM drastically. It is not very efficient past 6000 RPM. I think it goes down to 83% VE at around 7000 RPM. So in the sense, the turbo will be flowing less because the engine is asking for less, and the compressor pressure can rise according to the flow requirement on your compressor map, which is why that 6 psi at 7000 rpm should be morel ike 12 psi at 7000 rpm.
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  12. #12
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    I think he was open to adjusting his tables with the correct info. If you have it, I am sure someone can send it to him.

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    This has the makingsto be a sticky. Just needs more solid info

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    2 out of 2 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    That is a dangerous assumption, the N54 engine VE varies with RPM drastically. It is not very efficient past 6000 RPM. I think it goes down to 83% VE at around 7000 RPM. So in the sense, the turbo will be flowing less because the engine is asking for less, and the compressor pressure can rise according to the flow requirement on your compressor map, which is why that 6 psi at 7000 rpm should be morel ike 12 psi at 7000 rpm.
    +1 Normally a motor will have ~80% VE. Saying it has 95% VE across the board is optimistic. The 2 biggest factors making up volumetric efficiency can be summed up by A/F flow and in our case turbos. But in the quest of making more power our turbos are pretty much maxed out. The RB turbos have proven that the VE is increased when it comes to adding more air. Of course this whole debate will heat up with Dzenno's head work project which should translate to better efficiency especially in the mid range.

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