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5.7L Throttle body on 4.6L?

Discussion in 'Performance and Tuning' started by mass-hole, Feb 15, 2021.

  1. Feb 15, 2021 at 10:32 AM
    #1
    mass-hole

    mass-hole [OP] New Member

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    This is actually related to my Lexus GX460, but the throttle body and manifold part numbers are the same as the 4.6L Tundra.

    Is it possibly to bolt up the 5.7L throttle body on the 4.6L? I know the bore is 76mm on the 5.7L and 70mm on the 4.6L, at least that is what I have found. Other than that the two look almost exactly the same.
     
  2. Feb 15, 2021 at 12:53 PM
    #2
    mass-hole

    mass-hole [OP] New Member

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    I actually could be wrong here about the 4.6L TB being 70mm. I found a few sources that said it was but now I think it maybe 76mm as well. Maybe someone can confirm?
     
  3. Feb 16, 2021 at 9:57 AM
    #3
    dirtydeeds

    dirtydeeds Exhaust Fabricator Vendor

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  4. Feb 18, 2021 at 12:03 PM
    #4
    mass-hole

    mass-hole [OP] New Member

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    I called but no definitive answer.

    I have a 5.7L throttle body on its way from ebay that was dirt cheap so I will compare.
     
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  5. Feb 19, 2021 at 6:30 AM
    #5
    mass-hole

    mass-hole [OP] New Member

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    I got the Tundra TB in the mail yesterday. I will need to pull the TB on my GX, but I am pretty sure they are the same.
     
    HulkSmurf14 and AZTundra like this.
  6. Feb 22, 2021 at 1:37 PM
    #6
    cquilichini

    cquilichini New Member

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  7. Feb 22, 2021 at 2:00 PM
    #7
    mass-hole

    mass-hole [OP] New Member

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    I suspect they are the same size but did find a shop that can bore out the stock TB to ~80mm and cut a new butterfly. I already spoke with the guy and will probably send out this tundra TB once I know it works on my GX.
     
  8. Feb 22, 2021 at 5:06 PM
    #8
    Nick T

    Nick T New Member

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    Are you adding boost or building the engine for 9k rpm? I dont think the throttlebody is a restriction on NA engines. Would be nice to find out if a rcf throttlebody would increase power on a 4.6 1urfe but the 2urgse have high flow heads, d4-s injection etc to utilize the 'potential' higher flow.
     
  9. Feb 22, 2021 at 5:39 PM
    #9
    Tundra_power

    Tundra_power New Member

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    If he is n/a, alot of low end torque loss. Maybe higher end hp but is the throttle body a restriction.
     
  10. Feb 22, 2021 at 5:45 PM
    #10
    mass-hole

    mass-hole [OP] New Member

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    I am using it more as a tuning device. No one is tuning the 1UR in the GX.

    After reviewing the Tundra 5.7 tune in HPTuners and datalogging my GX, its become clear that the tune targets a certain throttle angle for a given RPM and load. If you install a larger TB you will get a larger opening for the same throttle angle. This will improve throttle response and allow the engine to make some more low end power where it was not previously opening the throttle all the way.
     
  11. Feb 22, 2021 at 5:47 PM
    #11
    mass-hole

    mass-hole [OP] New Member

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    The stock tune doesnt even open the throttle all the way. I have logged throttle and and MAP on pulls. The throttle angle starts at 78° at 3000 rpm and closes to 73° by redline. At the same time, the manifold pressure drops with it, which suggests to me that it is a restriction.

    I don't have the option to tune it. So my thought is that if I run a bored TB it will get me some more low end throttle response and may even open up a little power up top.
     
    Last edited: Feb 22, 2021

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