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Is balancing throttle body vacuum with cylinder compression a good idea?

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  • Is balancing throttle body vacuum with cylinder compression a good idea?

    Hi everyone,

    Here are the readings of compression test and intake vacuum per cylinder (intake vacuum measurements are normalised to 100)

    1. 200-100
    2. 205-107
    3. 175-104
    4. 190-100

    Low compression on cylinder 3 is not good.

    Normal procedure to synch the throttle bodies is to get the average of vacuum readings and set all to that. However, if the cyl compressions are not the same, this will end up in less air to the low compression cyl.

    The idea is to adjust the vacuum in a way that it balances out the compression difference, hence a smoother idle and throttle response. As an example, cyl 3 needs more air (less vacuum reading) that the other cyls.

    Average compression is 192.5, so I will take no 4 as the reference, recalculating vacuum to be set:

    1. 200-105
    2. 205-108
    3. 175-92
    4. 190-100

    Does this make sense to you? Is it a common practice?

    Thanks,

    Mehmet





  • #2
    Do a leak down test to find out why there is low compression.
    75 M2 Zinno
    88 M3 Henna

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