I'm still a relative newbie into volvo ownership - I've had 3 s60's under my care, 2 NA and 1 turbo; so I'm still learning the tricks to living with them as they age. My daughter currently has my previous 2005 NA and I'm commuting in a high-mile 09 turbo. I had an 01 a while back but didn't hang on to it.
Both have standard vacuum-assisted power brakes. Both also have a brake vacuum boost pump located immediately behind the radiator. it's triggered when vacuum is low and runs intermittently. The primary vacuum source is the manifold, but neither is a simple direct connection to the manifold. In both boosted and NA variants, there looks to be a Bernoulli pump which runs from the high side to the low side of the throttle body. The resulting vacuum from that pump feeds the brake booster. That pump likely has a limited flow rate, so then you have the auxiliary electric pump to supplement.
WHY?
Perhaps with the turbo I get it - there's not a lot of manifold vacuum (though there should be vacuum when not under boost), but you don't need brakes when your foot's in the throttle. Even in a NA car, there's much-less-to-no vacuum when you're in the throttle. In a diesel, obviously you need a different source of boost (do diesels use vacuum?)... but in this case I have to be missing something.
The only thing I can come up with is they standardized for "cost savings" by employing an $80 vacuum switch and extra $265 pump across all of their models .. except that doesn't save any money.
So what am I missing? Remember, the NA cars have it too.
do all gas turbo cars/trucks do this?
(Background - car has 0 brake assist when cold, and that torquey motor will roll it right along during high (1200rpm) idle - I'm not sure my wife could stop it, my butt lifts off the seat myself until idle drops or I pull it from gear - i'm fixing it now)
-m
Both have standard vacuum-assisted power brakes. Both also have a brake vacuum boost pump located immediately behind the radiator. it's triggered when vacuum is low and runs intermittently. The primary vacuum source is the manifold, but neither is a simple direct connection to the manifold. In both boosted and NA variants, there looks to be a Bernoulli pump which runs from the high side to the low side of the throttle body. The resulting vacuum from that pump feeds the brake booster. That pump likely has a limited flow rate, so then you have the auxiliary electric pump to supplement.
WHY?
Perhaps with the turbo I get it - there's not a lot of manifold vacuum (though there should be vacuum when not under boost), but you don't need brakes when your foot's in the throttle. Even in a NA car, there's much-less-to-no vacuum when you're in the throttle. In a diesel, obviously you need a different source of boost (do diesels use vacuum?)... but in this case I have to be missing something.
The only thing I can come up with is they standardized for "cost savings" by employing an $80 vacuum switch and extra $265 pump across all of their models .. except that doesn't save any money.
So what am I missing? Remember, the NA cars have it too.
do all gas turbo cars/trucks do this?
(Background - car has 0 brake assist when cold, and that torquey motor will roll it right along during high (1200rpm) idle - I'm not sure my wife could stop it, my butt lifts off the seat myself until idle drops or I pull it from gear - i'm fixing it now)
-m
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