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Discussion Starter #1
Ok, this is one of the individual throttle bodies I am using on my car, and pictured is the vacuum port. Traditionally ITBs have a needle valve for each single throttle body that you adjust to balance their idle airflow with each other...you do this using a flow meter and adjust the needle valve one at a time...it really is an antiquated way to balance them...evidently BMW thought so as well because as you can see, the vacuum port on each throttle body attaches to common manifold for each bank which are then connected together with vacuum hose to a single idle speed control valve that equalizes airflow for each cylinder....that is the way it works on a BMW M3 anyway....but since the port spacing is so different with the 3.7L Ford engine that these are installed on, the BMW manifold for each bank no longer fits. I am left trying to come up with a way to balance airflow to each cylinder for idle speed and am open to ideas. Currently my plan is to tap vacuum port on each throttle body for 1/4" NPT fittings(since the hole size is just slightly smaller than what is needed for 1/4" NPT) and use either hose barbs or pneumatic quick connect fittings to run 6 vacuum lines to a central manifold and use some type of air control valve to set a controlled vacuum leak to dictate idle speed. The question is whether there is a better way to accomplish this? Maybe I should make some type of common manifold for each bank and then run just 2 hoses to a valve on a T-fitting? To complicate matters...the vacuum ports are on the outside of the throttle bodies and so there is limited clearance to the valve covers making straight hose barbs problematic. There is always the option of using brake line instead of hoses as well...its hard to say what exactly the cleanest look is going to be(well, needle valves are the cleanest, but also a needless PITA to balance)
 

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With my stack setup (Inglese EFI), they created a common vacuum area on the underside of the manifold. Then the IAC value (a chevy style one) taps into that from the top side of the manifold.

It's the Remote IAC with filter on this page:

If you could put your brake lines for vac on the inside, then you could run those to a remote vac tank and plumb that to the remote IAC. Seems like it would be a mess though

What if you made your spacers taller and then drilled into those for the vac lines...That would get the vac lines away from the throttle bodies themselves..lower down and out of sight maybe. Is that an option?
 

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Discussion Starter #3
With my stack setup (Inglese EFI), they created a common vacuum area on the underside of the manifold. Then the IAC value (a chevy style one) taps into that from the top side of the manifold.

It's the Remote IAC with filter on this page:

If you could put your brake lines for vac on the inside, then you could run those to a remote vac tank and plumb that to the remote IAC. Seems like it would be a mess though

What if you made your spacers taller and then drilled into those for the vac lines...That would get the vac lines away from the throttle bodies themselves..lower down and out of sight maybe. Is that an option?
I had not even considered that...not sure it would work though...I have a water pipe running under the injectors in the valley:



its a good idea though, would be much cleaner....I guess in the end it wont be any messier than spark plug wires...I could probably run some blue pneumatic lines and fool people into thinking they are plug wires on a quick glance.
 

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Discussion Starter #4
I just thought of a downright easy solution to this one:


Simply buy a couple feet of fuel rail blanks...cut one to be a manifold for each bank(with holes drilled for each port), then use the remaining section to be a distribution block....then its just a matter of mounting a valve to that block and connecting the 3 with appropriately sized vacuum hose(likely 5/8" heater hose)
 

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Might be possible to use hard plastic line like oem fuel injection uses to be a little cleaner, the kind you heat and slip over the fitting with no clamp?
 

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Discussion Starter #6
Might be possible to use hard plastic line like oem fuel injection uses to be a little cleaner, the kind you heat and slip over the fitting with no clamp?
how to do you make bends in that stuff? just heat it up and use a tubing bender maybe? Also, not sure I have ever seen it for sale anywhere. The fuel rail blank idea might not work after all due to the valve cover space constraints.
 

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You could use a 90 or 45 fitting, but I think the tubing itself is pretty easily bent by using a spring inside to keep it from collapsing. Heat gun or hot water would work for heating. Tie wire or something on the spring to help remove in case it hangs up. Might even try a spring on the outside with heat as it would resist kinking if the sides couldn't push out.
 

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Discussion Starter #8
Circling back to this because its really the last thing I have to worry about with the ITB setup, some pictures for reference:



This is the factory BMW manifold for one bank of ITBs. Sadly it no longer fits because bore spacing has changed(not to mention it was meant for one bank of a v8, not a v6). There are a couple interesting things to note here though...the MAP sensor is installed at the end of this manifold so obviously this setup provided a good enough vacuum signal for engine tuning. Next thing of note here is the short length of the protruding tubes than fit into the throttle bodies. This leads to the question of whether this short tubing to a shared manifold is actually needed for a quickly responding vacuum signal, or whether it was just easier than running individual lines to a central manifold. The last thing of note here is the actual shape of the manifold...its tapered like a real intake manifold...what benefit does this have? Speculation on any of these points is welcome.



This is a picture of the actual space I have to work with with the ITBs instaslled...you can see one of the ports on the ITBs below the throttle bracket I bolted to the throttle bodies
 
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