Running boost gauge off brake booster?

[bpu699]

Was randomly looking at threads on here. Wouldn't mind installing a larger boost gauge.

Figured I would have to run a hose from the motor to the dash, a pain.

There are several threads on here that say you can run the boost/vacuum line off the brake booster???

Is that even possible???

I can't believe that the brake booster sees pressurized air from the path of the turbo...

I always thought brake booster was powered by engine vacuum.

What am I missing here?

Is there a way to add a larger VDO boost gauge that doesn't need to rerun a pressure line to the motor?

[Tippy]

I'm pretty sure I have a check valve on my Carrera 3.2 to not pressurize the BB.

[patina]

Yes absolutely, NHS (North Hollywood Speedometer | NH Speedometer) has an adapter kit that they sell with their VDO clock replacement boost gauges. Very simple install and works great.

[JFairman]

There ya go.. you got the correct answer in the post above and learned something in less than 20 minutes.

If the master cylinder takes a dump and fills the brake booster with brake fluid.. then it's a problem.
Had an E21 BMW do that many years ago.

[Pesch]

You can find the correct MC check valve with additional nipple to plug the gauge from our host in the 924 section.

[T77911S]

that's where mine is plumbed in. I have a RUF boost gauge plumbed into the booster hose. I actually think it was T'd inside the car where it comes out of the tunnel.

[JFairman]

Tee'd into the NHS brake booster check valve with the 8mm ID vacuum hose fitting is an easy install and it gives the car a new brake booster check valve at the same time. They're plastic and don't last forever.

A piece of 5/16" or 8mm inside diameter fuel line around 4 feet long secured with hose clamps will comfortably reach from the special brake booster check valve to the back of a VDO/NHS mechanical boost gauge mounted where the clock goes in a 911 dashboard while you're holding it in your hand before pressing it into the rubber ring in the dashboard.
A little vasaline or silicone grease smeared on the rubber ring ID or OD of the boost gauge will let it slide into the dashboard easier.

[bpu699]

The web link doesn't show an adapter?

Is there a diagram or something? I still don't understand the physics of it...

Are we saying that on a 911 the brake booster is powered off the pressurized intake???

Most cars function off vacuum, not pressure, no???

Still confused...

[Tippy]

The brake booster is not designed to work under pressure, only vacuum. When you boost a car, you need to put a 1-way check valve so the line leading to the brake booster never goes over ambient atmospheric pressure.

Once the 1-way check valve has pressure put on to it, the valves close shut so you don't potentially rupture the brake booster diaphragm.

[Rawknees'Turbo]

Originally Posted by JFairman

A little vasaline or silicone grease smeared on the . . . will let it slide into the . . . easier.

???

!!!

[boosted79]

I teed into the brake booster line right where it comes out of the tunnel on the inside before it goes into the frunk. I have an Autometer vac/boost gauge and a 14point7 data logger that it feeds.

[Bucketlist]

Mine just tees off manifold vacuum to my boost gauge and to the map sensor attached to my lm2. Is this wrong or just different?

[boosted79]

Nothing wrong, does the same. I feed my MSD MAP sensor in the engine compartment off the line to the dizzy that comes off the big T on the front of the TB, one side goes to the dizzy, other to the WUR.

[IMR-Merlin]

Mine is T'd off the booster with no check valve