Vacuum sources for the 420A

[link16]

As we all know, the portfueler takes up one more vacuum source than other turbo conversions setups.


On the stock IM we have 3 vacuum ports on the back and one located on the TB (this one goes to power steering IIRC).


I am going to test out different combinations to see what is best to tee off of what; what units need their own "T" free vacuum source.


I have diverged that the BOV needs it own to help take load off of the turbo.


The wastegate has yet to be tested.


The FPR should have its own vacuum source for obvious reasons.


On a side note, MBC's can be run off the boost source, located on the compressor housing.
Hahn's says to run the FPR off of the boost source, located on the compressor housing, as well. From what I have heard from many other turbo racers you need to set idle fuel pressure with the FPR disconnected from vacuum, but needs vacuum to operate during driving.


Most of us 420A-t guys also have mechanical boost gauges; I belive that the hard plastic vacuum source coming from the TB should be teed off for the gauge.


The setup I will be trying soon will be: the portfueler control box will be hooked up to a shared vacuum source with the wastegate on the back of the IM; my FPR will be hooked to its own vacuum source on the back of the IM; my BOV will also be hooked up to its own vacuum source on the back of the IM; my boost gauge and power steering will both share the vacuum source on the TB.


If anyone has any other advise on the matter feel free to list it, I am messing with different ways to do it, but it is hard to get everything to work.

 

[VelocitàPaola]

If these vacuum actuated devices relied on flow rather than pressure this would be a more important topic, but in reality, it's not that important. Air pressure acts on all points in a system equally, and relatively simultaneously... kinda of like Pascal's Law, but with a compressible fluid -- so more like the ideal gas law.

Usually, it's most important to have the wastegate on a separate line from everything else. The FPR, boost gauge, BOV, etc. orientation isn't too crucial. I've got my wastegate connected to the turbo's compressor housing. The MAP sensor for my electronic boost gauge and FPR use two of the three ports on the rear of the intake manifold. The BOV uses the P port on the throttle body.

I just thought I'd save you some time and tell you not to look into it too much.

 

[link16]

Wait, the P port is the one on the TB correct?

What does that hard plastic line go to, and is it crucial to have its own vacuum source.

Keep in mind I still have a mechanical gauge.

Thanks Paul.

 

[VelocitàPaola]

That P port goes to the EVAP system, which I removed long ago. I suppose that you'd want to keep that line dedicated if you kept the EVAP system, seeing as how it has gasoline vapors flowing through it. Before I removed the EVAP system, I had the BOV tee'd off the boost gauge line.

Mechanical gauge or not, you still need a port on the intake manifold -- the only difference is that in one instance the line needs to be longer.

 

[link16]

So the wastegate does not need to read vacuum, only boost?

I have two ports on my tial gate, one on the top which I have to atmosphere and the one on the bottom which I will run to boost.

That should make things a bit easier for me.

My boost gauge is going back to autometer as "0" psi is simulated by the 6 psi tick mark.

 

[VelocitàPaola]

So the wastegate does not need to read vacuum, only boost?

Correct.

My boost gauge is going back to autometer as "0" psi is simulated by the 6 psi tick mark.

The same thing happened to me... about three times, until Autometer finally gave in and replaced it with an electronic gauge.

 

[link16]

The way Maryland's weather is, I can see it happening to me often as well.