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Thread: low boost w/ med compression vs. high boost w/ low compression?

  1. #1
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    Default low boost w/ med compression vs. high boost w/ low compression?

    Medium CR being 9.4 and Low being =< 8.8

    Low boost being 6lbs and high being 9lbs+

    Type 1 = low boost w/ med compression

    Type 2 = high boost w/ low compression
    ---------------------------------------------------
    The following is IMO only.

    So the main difference with these engine setups is going to be the way the power curve looks. Type 2 is probably going to be more rev-happy, where type 1 is probably going to be a better daily driver.

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    Default

    IMO 9lbs is not high boost, 9lbs can be run on factory internals given its not super high compression to begin with, however theres probably reliability issues

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    Hey! how about High Boost and High Compression! BOOM!

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    With low compression motors, you have the ability to run high boost with low octane fuels (pump gas). High compression motors, you will need exotic fuels to run the same amount of boost. Shitty thing with low compression motors, is off boost, there is NO power/torque at all. It's a dog around town, and fuel economy drops (obviously).

    When you lower compression on a motor, you will need more boost to make the same power (less compression, less cylinder pressure). For example, a 11:1 compression motor at 6psi will make the same power as an identical motor but with 8:1 compression motor at 12psi (not exact numbers, but you get the idea). The 8:1 motor will be a dog when the turbo isn't spooled up though, and fuel economy will be worse, but it can make more power with the same octane fuel by allowing more boost before detonation.

    The secret is to find a good balance, like the 911 twin turbo, running mid compression (10:1 I think) and a maximum of 12psi. This will give excellent peak power with decent off boost torque as well.
    Originally posted by SEANBANERJEE
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