8Stack efi & manifold vacuum pressures

[Dimis]

I'm looking at an 8 stack EFI system either - Eightstack or TWM.

TWM I believe use tubing that connects all the t/bs (similar to bobs pic), but it's located above the manifold, which is housed under the center pivot of the linkage below the fuel rails, to reference for vacuum pressure.



Eightstack have developed this manifold (which isn't cheap).



Not there are 8 small holes drilled (4 of which you can see) on the underside of the manifold, inside the chamber, just beneath each of the runners.


They then seal it off by screwing in the bottom plate to create a plenum for reservoir for vacuum pressure.




What I was hoping someone could tell me is what do I need to do to ensure I can create suitable and consistent vacuum pressure for reading MAP having Brake boost, to have a street-able, and easier to tune EFI system.

Engine will be 482 cubes - mild cam, but details yet to be finalized.
Open to your thoughts, knowledge and opinions.


PS: Thanks Redmt... but I need it for an FE


Many thanks,

[Dwight]

picture of my Eight Stack for a small block Ford plenum
you can call Dale or Bob at Eight Stack and I'm sure they can help you.
Eight Stack Injection- home
Dwight

[bobcowan]

Originally Posted by Dimis

What I was hoping someone could tell me is what do I need to do to ensure I can create suitable and consistent vacuum pressure for reading MAP having Brake boost, to have a street-able, and easier to tune EFI system.

I have the manifolds shown above, on a 427W small block. It's a large plenum with plenty of reserve. With a moderate cam, you'll get a balanced vacuum signal just like you would with a single plane carb manifold.

The deciding factor would be your camshaft. A moderate to mid level cam will create a strong signal off idle. If you have a big cam, you will probably need a reservoir for the power brakes, just as if you were using a single carb on a single plane manifold.

I also have EFI. Because my cam is gigantic, I don't get much of a vacuum signal. My primary fuel and ignition maps are based on TPS and RPM. And then I supplement those maps based on vacuum. As my vacuum drops, it adds in a bit of fuel, and takes away a bit of timing.

It's an excellent system and a real joy to drive. And the looks are just killer.

[Gaz64]

Anthony,

I'd plumb the large port from the back of the manifold plenum to a vacuum reservoir tank for your power brakes. The input to the tank should have a brake oneway valve fitted.
Your map sensor can be plumbed to one of the other smaller fittings at the rear of the manifold.