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Old 12-27-2018, 07:47 PM
VTtransam VTtransam is offline
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Default Vacuum brake system design - switch input needed

I'm in the final stages of planning out my vacuum assisted brake system on my 1st gen camaro. Due to my ITB intake manifold on lsx454, vacuum for the brake booster isn't ideal. I've decided to go with the GM vacuum pump to combat this issue, similar to the supercharged builds by Mr. Stielow. I'm looking for recommendations on a reliable vacuum switch. I found a company who custom makes adjustable switches: https://www.worldmagnetics.com/our-s...flex-switches/ but was curious what others were using for a reliable vacuum switch (OEM solution?)

In theory, the switch would kick the vacuum pump on at 17 inHg, and off at 23 inHg. I'm also thinking about running a vacuum canister if space permits between the pump and the brake booster. The sensor would read vacuum in the canister. Hopefully this extra volume would prevent frequent cycling of the pump during autoX and track events. Is this necessary or am I overthinking it?

System components: dual 8" booster with Wilwood 1" bore master, Wilwood Superlite 6R front with 14" rotors, Superlite 4R rear with 14" rotors.

Thank you!

Last edited by VTtransam; 01-06-2019 at 11:09 PM.
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Old 01-02-2019, 02:50 PM
stan65 stan65 is offline
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here is one I have seen used.

https://www.amazon.com/Superior-Univ.../dp/B00BZODN9A

I built my own using a GM booster vacuum sensor and some electronic components only a sparky can love. If you are up to a soldering / circuit board project, here's a schematic, you would also have to add a 5VDC power supply.
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Old 01-06-2019, 11:11 PM
VTtransam VTtransam is offline
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Stan that is impressive, and likely above my paygrade. I'll have to break out the old EE books to figure out what's going on here! Thank you for the reply!
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Old 01-07-2019, 09:11 PM
VTtransam VTtransam is offline
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Has anyone tried GM PN 20819275? Its a brake booster sensor from a 2011-16 Cadillac SRX. I can't find any details on it, but its a three wire switch. Anyone have any info on this switch?
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Old 01-07-2019, 09:32 PM
stan65 stan65 is offline
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That is an analog sensor. Itís TTL (uses 5vdc as control power) it is the sensor I designed the circuit I posted earlier.

It puts out 0-5vdc for 0-29 inches of vacuum.

The switch in the link I posted earlier is what the aftermarket add on vacuum pump manufacturers are using. Itís a simple switch using a diaphragm with a spring adjustment to be able to set the on/off vacuum setting. Not sure if the ability to set the hysteresis.
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Old 02-18-2019, 09:21 AM
VTtransam VTtransam is offline
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Closing the loop on this one (hopefully):

After a bunch of searching, I didn't find many good reviews on a reliable and simple aftermarket solution. Stan's method would be great, but beyond my electrical skill level. I decided to try Volvo PN VOL-31400692, found in S40, S60, XC70 and XC90 SUV's. Its a 3 way switch with integrated checks. The switch is wired to a relay which provides power to the vacuum pump when the switch is closed. One line goes to the intake manifold, another line to the vacuum pump, and the last line to the brake booster. My thinking is when the car is running, the engine can make "base vacuum", maybe 12 in HG. The vacuum pump can then kick in and make up the rest of the vacuum. Currently I have a vacuum canister inline as well, mounted between the inner fender and firewall. Upon testing with just the vacuum pump energized, it satisfies vacuum within 3-5 seconds. I'm using a GM (Hella) vacuum pump found in the SRX and Equinox. Below are a few photos of my setup. I still need to route the line from switch to intake manifold, and vacuum canister to brake booster but this should give you an idea. I'll report back with its behavior once the engine is running and the car is driving.
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