what happens to the vacuum when you go Turbo?

Discussion in '2.3L (N/A & Turbo) Tech' started by madmike1157, Aug 19, 2010.


  1. madmike1157

    madmike1157 the humor is still lost on me SN Certified Technician

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    Since my only experience w/ turbo cars has been w/ either drag cars (that didn't have a single vacuum sourced accessory) or limited use street cars w/the same deal, I got to thinking.....how does it work when you turbo a street car that has power brakes, PCV, and all of the rest of the vacuum operated stuff under the dash for the A/C and heater when the manifold goes from negative to positive manifold pressure:shrug:
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  2. Red_LX

    Red_LX I’m not much help unless you’re looking for porn! Mod Dude Founding Member

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    Can't mess with any of that stuff while you're boosting :)

    I dunno how it works really, you have vacuum basically anytime you aren't boosting. I do know if you try to use your brakes under boost the pedal goes straight to the floor.
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  3. madmike1157

    madmike1157 the humor is still lost on me SN Certified Technician

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    Ohh c'mon! you can't tell me that SVOs and T/C's didn't have some manifold,log,series of one way valves or something that stops 25psi from pressurizing what is supposed to be a vacuum-operated device???

    I would think that the engineers at ford would have thought of this already.
    "dont expect your power brakes to work while under boost" isn't in the owners manual somewhere.........is it?:eek:
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  4. Delray Dude

    Delray Dude New Member

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    There are one way check valves in the vacuum lines - and the engineers on pretty much all cars incorporate a "vacuum storage" cannister - this maintains a vacuum to the systems that need it under boost conditions.
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  5. Red_LX

    Red_LX I’m not much help unless you’re looking for porn! Mod Dude Founding Member

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    Oh wait, mine might be set up a little different...I converted my TC from the original electronic ABS to vac-assisted brakes, so yeah on mine the pedal does go to the floor since I'm probably missing the check valve I'm supposed to have. Other cars wouldn't do this.
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  6. Delray Dude

    Delray Dude New Member

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    I do remember something from my 280ZX Turbo car.....on the vacuum / pressure issue... IIRC they tapped the vacuum just upstream of the Turbo with a check valve similiar to the ones found on brake boosters and teed into a vacuum port on post throttle blade side with a check valve and then to the vacuum can, then it was distributed to the vacuum sources.

    This would be the best solution - full vacuum under non boosted conditions via the norm (post throttle blades), then under boost pulling from in front of the turbo in acceleration mode is pulling from both, then full turbo boost under non-throttle you would get major vacuum from upstream Turbo because the Turbo would be sucking as much air as it can get from the supply.

    Also, the N/A 2.3 PCV taps into pre-throttle blades, and tapping this into pre-turbo would solve this as well.
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  7. Dr_EluSivE

    Dr_EluSivE Founding Member

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    There are check valves in the system to keep vacuum for the stuff that needs it. Mine was originally an N/A car and nothing weird happens when i boost. Of course i let off the gas before i hit the brakes, but i have never notice anything strange. All the Climate control stuff, and the cruise control works under boost.

    Dr.
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