Venturi pipe in engine exhaust flow

[Dteeter]

I would appreciate opinions on this...on which setup would create the best vacuum in an exhaust gas stream? The #1 drawing is a pipe that has a birds eye cut in it. These are sold for engine crankcase exhaust ventilation. There are some that say they work, then others that say they don't work and actually created back pressure in the crankcase. I personally think that #2 would work much better...a better vacuum signal. Thank you.

 

[Baluncore]

Do you intend to use the vacuum for crankcase exhaust ventilation? If so you will need a flame trap to prevent a crankcase explosion.

I do not think you need to penetrate the exhaust flow to such a significant extent. A hole, flush with the internal surface of the exhaust pipe should provide a partial vacuum.

What is the normal positive pressure in a vented crankcase? What is the normal pressure in the exhaust pipe?

Why do you not vent the crankcase to the inlet manifold and burn the blow-by products to reduce emissions?