Hats the point of the vacuum assist on the new jks

 

Power brakes

 

Cars have had vacuum assisted power brakes for 50 years without the need for a supplemental vacuum pump. I don't understand why the Jeep has one. I can see it on a turbo motor where there might not be any vacuum but not on a normally aspirated motor.

 

i was under the impression that it was for the variable valve timing

 

Technical reason.....GDI (gasoline direct injection) eliminates what we know of as the throttle body. We no longer need to limit the intake air charge via a throttle so that we can maintain a stoichiometric ratio. We can allow the engine to pump as much air as desired and we control the fuel charge as needed. This reduces pumping losses as it takes a lot of horsepower to keep pulling a vacuum against the throttle plate. When the throttle plate is gone we can recover all that pumping loss... but we lose vacuum. We need a different way to run the vacuum brake booster, and other devices run on vacuum. Many vehicles add a small vacuum pump to compensate, but others don't use vacuum at all for accessory devices. We also lose most engine braking, but these are minor issues when we gain so much by not pulling vacuum against a throttle plate.


In layman's terms....more horsepower

 

Since when did the 3.6 get direct injection?


This is the more correct answer:

edit to add:
To clarify, it's needed because of the variable valve timing, not for it.

 

My bad...the 3.6 did not get direct injection....YET

 

Absolutely 100% incorrect. It does not have anything to do with valve timing. Valve timing is controlled by the computer.

The Vacuum pump behind the bumper is for supplying additional vacuum to the power brake system.

 

It's to insure the brakes have enough vacuum while you're inching down a hill, pumping the pedal and bleeding off vacuum faster than creating it.

It's a Jeep thing. (duty cycle)

 

Yes, the valve timing is controlled by the computer.
Yes, the vacuum pump supplies additional vacuum to the power brakes, and other vacuum operated systems.
What you are forgetting to say is, the variable valve timing reduces the vacuum in the manifold under some conditions. That's why the pump is needed; to supply additional vacuum.