why volvo I6 engines use brake vacum pump?
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    1. #1
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      why volvo I6 engines use brake vacum pump?

      Why not designed with simple (and more reliable) manifold vacum for the brake booster like most gasoline powered vehicles?
      2013 XC70 T6, Flamenco Red
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    3. #2
      Senior Member ScottishBrick's Avatar
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      Because there's no vacuum assisted brakes if you need to brake and you had just been accelerating and making boost.
      2003 V70 T5 - Mystic/Graphite - M56LK - 206k - K24/Greens/Do88/Quaife/SMF/P2R Clutch/DW300C/H&R/Bilstein TC/316mm & 308mm Brakes - SteveO Tuned
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    4. #3
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      Volvo (and other manufacturers) have used vacuum pumps for longer than just the I6 motors. They are plenty reliable.

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    6. #4
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      Quote Originally Posted by ScottishBrick View Post
      Because there's no vacuum assisted brakes if you need to brake and you had just been accelerating and making boost.
      So this has more to do with turbocharged engines?
      GM Yukon for example is NA engine, but still has vacuum pump driven via pulley and belt (stupid design I think):

      https://www.youtube.com/watch?v=9RVylpKEU4s&t=2s

      These things don't appear to be 'plenty reliable', even our Volvo one typically starts leaking oil at around ~40-60kmi maybe?
      2013 XC70 T6, Flamenco Red
      2020 Jaguar F-Pace S
      2013 Jaguar XKR Convertible

    7. #5
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      Volvo has used them on naturally aspirated or turbocharged engines for a while.

      Yeah, they leak but I was referring to them producing vacuum when I mentioned reliability. The electric ones would sometimes seize and blow the fuse or the vacuum switch would come apart. Resealing an I6 pump is cheap compared to replacing the others.

    8. #6
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      Quote Originally Posted by Tech View Post
      Volvo has used them on naturally aspirated or turbocharged engines for a while.

      Yeah, they leak but I was referring to them producing vacuum when I mentioned reliability. The electric ones would sometimes seize and blow the fuse or the vacuum switch would come apart. Resealing an I6 pump is cheap compared to replacing the others.
      Agree. Our XC70 has only 30kmi, vacuum pump is a little damp - enough for dirt to collect on it at this point. I'm keeping an eye on it.
      2013 XC70 T6, Flamenco Red
      2020 Jaguar F-Pace S
      2013 Jaguar XKR Convertible

    9. #7
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      Quote Originally Posted by ScottishBrick View Post
      Because there's no vacuum assisted brakes if you need to brake and you had just been accelerating and making boost.
      The 33-year-old one-way check valve in my Porsche 944 Turbo is still working fine and allowing me to have vacuum assist even when getting onto the brakes immediately after extended periods of 1 bar of positive manifold pressure. It's plenty possible to have a turbocharged engine without resorting to a separate vacuum pump to provide brake assist for standard braking.

      That said, my guess is that the vacuum pump is more a result of the traction control and brake-based torque vectoring needing to apply the brakes even while the driver is still on the gas which would quickly deplete the amount of vacuum reserve in a typical brake booster.

    10. #8
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      If you look in to performance car options for adding a vacuum pump to cars with poor engine vacuum,( big cams), several pics of the vacuum motor used in these conversions look very much like one from a Volvo.
      Not sure they are related, but automakers seem to be removing as much as possible from the engine to limit parasitic drag and increase mileage. An electric vacuum pump probably creates more stable vacuum and allows brake systems and other vacuum reliant systems to operate without being influenced by engine performance

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