Bestow unto me: Your knowledge on the most basic of vacuum setups| Grassroots Motorsports forum |

92CelicaHalfTrac MegaDork
10/26/12 3:50 p.m.

I have a car i'm working on that i literally only have two things that need vacuum.

1) MAP sensor.
2) Brake booster.

What i have:

1) Vacuum rails on each cylinder bank.

What i don't have:

1) Intake manifold.

What's the cheapest, yet elegant way to do this while keeping the brake booster and the MAP happy? I'm a little worried about volume, don't want the MAP freaking out when i'm on the brakes, and i HAVE to tie both of the rails together somehow before the MAP sensor is in the system.

Elegant and correct takes precedent over "cheapest."

What i'm initially thinking:

Tie rails together, run to distribution block. Run MAP off of block. Run another line to an aftermarket reservoir with check valve, which then runs to brake booster. Is this overkill and needlessly complicated?

Or is something like this what i need?

http://www.ebay.com/itm/Steel-Black-Finish-Vacuum-System-Reservoir-Tank-Universal-Fit-Hot-Rat-Rod-/350626831556?hash=item51a2fcdcc4&vxp=mtr

Run vacuum from rails into one of the threaded holes, MAP out the other, and brake booster off the plastic-y thingy?

93gsxturbo Dork
10/26/12 5:27 p.m.

You wouldnt want to run the MAP sensor off the reservoir, it wont see the dynamic changes needed. The idea of tee-ing all the vacuum rails together and monitoring from there seems like a solid plan. Should have minimal pulsing because essentially, the vacuum rails are your intake manifold.

If your booster doesnt play well with just running off the same tee, go like this..

Intake vacuum rails
-------------- Tee fitting
-----------------------------MAP Sensor
-----------------------------Vacuum Line
--------------------------------------------Check Valve
----------------------------------------------------------Vacuum reservoir
-------------------------------------------------------------------------Brake Booster

or convert your brakes to hydroboost or run an electric vacuum pump for the brakes.

z31maniac PowerDork
10/26/12 5:41 p.m.

Modify your pedal setup and go manual brakes.

HappyAndy Dork
10/26/12 5:45 p.m.

So it sounds like basically you have ITBs. I doubt you will have enough reliably available vacuum to run the brake booster

Kenny_McCormic Reader
10/26/12 6:38 p.m.

Sounds like hydroboost may be in your future.

Trans_Maro SuperDork
10/26/12 7:53 p.m.

I don't think your booster will give you any trouble. There should be a check valve in the line to the booster and unless you're REALLY pumping the pedaul, it shouldn't cause a significant loss in vacuum.

Shawn

noddaz GRM+ Memberand Reader
10/26/12 7:56 p.m.

That seems like a lot of money for a vacuum can with a brake booster valve... But it is 2012... And yes. That does sound like what you need. Something to "store" (?) the vacuum since there is no plenum.

EvanB GRM+ Memberand PowerDork
10/26/12 8:05 p.m.

Could you just make a vacuum can out of a length of PVC pipe with the ends capped off and whatever fittings you need?

92CelicaHalfTrac MegaDork
10/27/12 7:48 a.m.

Trans_Maro wrote: I don't think your booster will give you any trouble. There should be a check valve in the line to the booster and unless you're REALLY pumping the pedaul, it shouldn't cause a significant loss in vacuum. Shawn

Good point... but i don't have the original line, and this is an autox car. There was a much bigger "reservoir" stock than what i've got available right now without using a "can."