I've read posts from several people that have deleted their balance pipe for one reason or another. I've also read that they do little other than ensure a balanced idle even if the throttle bodies are slightly unbalanced.

I've noted that the two intake manifolds on my 5.3L are perfectly balanced vacuum-wise. While my TBs are as in-balance as I can get them, I would still expect a slight variation side to side without the balance pipe; particularly if, like my engine, there is any irregular firing. But vacuum drops and rises again in perfect unison in both manifolds when a miss on bank B occurs. This leads me to believe that, as expected, this large diameter tube is freely carrying any pressure variation between the two plenums.

Here's my question:

If these two plenums are so well connected, then isn't an "A bank" cylinder that is on the intake stroke really breathing through both throttle bodies? If so, at high CFM flow rates does the balance pipe effectively cause the two plenums to act as one with dual TBs?

Obviously that far TB is fairly restricted by the balance pipe diameter and shape.

Very curious.

 

I think, but do not know, that the intake strokes are so close to each other on a V12 at anything above 1500 rpm that there is no time for the airmass to move between the two intake manifolds down such a small pipe, so any doubling effect on the plenums seems a bit unlikely.
The balance pipe ensures the ECU sees an average vacuum signal, that the engine cold start system and tickover can be controlled at one point and also that the brake servo (on non ABS cars) has vacuum available from both engine banks, which Grant told us is a requirement in some markets.
Greg

 

My write up on AAV removal years ago, This includes the removal of that balance pipe.

AAV Removal write up.pdf

 

Thanks Dave and Grant.

I agree Dave, there's far too much restriction for there to be any significant air transferred through the balance pipe. Airstream would be limited by the speed of sound and the air in the tube would become a piston oscillating back and forth. But that oscillation would allow some additional intake as it reduces vacuum for the plenum breathing in.

The reason I asked is because I'm considering a mod to increase the volume of the plenums and I'm running mental simulations since I don't have software for it. Hard to type it all up so here's a visual aid.





Balance pipe / plenum mod concept.