Vacuum port question.....EFI

[Gumba11]

Hey guys,

I am kind of a newbie with this aspect of the car so I need help. I need to know how many vacuum ports I need and what sizes should be acceptable.

Please tell me if Im missing anything here.

1. Brake booster
2. Waste gate
3. ECM (for internal MAP sensor)
4. Blow off valve
5. Fuel pressure regulator

Last, is it possible to tap the manifold for one large vacuum hose to go to a remote mounted vacuum manifold that has all the required fittings on it? I would like to do it this way to keep my custom manifold as clean as possible.

Thank you for any thoughts here.

[Jim2]

Chris, I considered an external manifold for mine but I found it was easy to route all vacuum lines and wires bundle together so they came from the front drivers side of the engine bundled with the brake booster hose.

A couple other ports to consider:

Air temp probe for EFI system
Vacuum/boost port if you run a mechanical boost gauge
Boost port if you add a mechanical adjustable boost regulator

I also added ports for diagnostics so I could measure pressure and temp both upstream and downstream of my throttlebody as well as before and after intercooler.

It was easy to hide all the ports on the rear or underside of the intake plenum and also in hidden areas of the inlet plumbing.

Regarding ports size I used both 1/8 and 1/4 npt. Only need 5/32" vacuum tubing for devices like boost gauges and FPR, but I used the 1/4 npt ports and 5/16 tubing to minimize signal response lag to items like the wastegate and brake booster.

[Gumba11]

Very helpful! Thanks Jim

[David]

I used two ports on the TB for the fuel regulator and BOV as shown with the red and blue hoses in the pic. For the waste gate valve I got put a port on the pipe from the intercooler to the TB. For the MAP sensor I used the air bypass valve port on the manifold, but if I install an air bypass valve to improve cold starting I'll have to add another port on the intake. I used the stock booster port on the Carrera manifold for brake and boost gauge.

[spuggy]

Hi,

I'm still trying to get a handle on most of this vacuum stuff too, so I had a few questions - the first being anyone got good vacuum diagrams for a 930? Does one even exist, and why isn't it in the factory manual?

I thought the wastegate had a vent line on the top, which just goes to atmosphere, and the control line on the side, which actually only needs boost, rather than boost/vacuum?


From memory, a post by beepbeep a while ago (regarding boost gauge plumbing) said:

Intake after butterfly: shows vacuum, no boost spikes.

Intake before butterfly: no vacuum, boost spikes.


I guess that if there's vacuum, it wouldn't hurt the wastegate(? this is a question, not a statement) to take off the control line post-TB because the wastegate doesn't need to be doing anything whilst there's vacuum, and if there's boost, there's positive pressure in both the throttle body and the intercooler?

Only thing is, you might get better boost control if the wastegate can "see" boost spikes and respond, and isn't the factory setup pre-TB?

Nice looking motor there, 125shifter....

[David]

That's correct, the wastegate top port is open to atm, the side port goes to boost. I have a port on the pipe between the intercooler and TB that goes to the wastegate control valve which is then connected to the wastegate side port.

The red hose coming off the TB goes to the BOV which needs vacuum to open when the throttle is closed.

My MAP sensor is also after the TB so it can read vacuum and boost.