klue":g47k2xmf said:
since a race engine usually has a considerable amount of blow by building pressure in the crankcase, this must be overcome to produce power and conquer the pumping loss. when the engine is under high rpm conditions/load the port vacuum becomes high and can easily pull the excess pressure created by the blow by gas. this is turn reduces the pumping loss created by the pressurized block. -> this gives you the performance gain.
if you have the pcv connected in the exhaust with a properly designed stem to creat a vacuum you can get the same effect as running the pcv to the intake(except you dont have to deal with the residues)
my problem with the catch can is that they hamper the flow of the pcv.
as for the sealing of the rings-> it is my understanding that the vacuum that a good operating pcv system produces helps to oil control ring effectively under loaded conditions.
Klue I have to argue your comment about excessive blowby. Any engine, commuter, or race will perform the best being built to the higest tolerances afforded and thus having the least amount of blowby.
Yes I can see the increased vacuum decreasing pumping losses but overall you are not getting a net gain because the engine still is doing the work to create the vacuum. That is simple first law of thermodynamics(output energy is never greater then input). A block breather would actually give you better performance because you are not recirculating blowby gases which displace good cold air and gas going into the engine.
The exhaust concept sounds sound with proper setup. That would include a free flowing exhaust and a check valve to manage the exhaust pulses.
While a catch can may decrease the velocity of the air in the PCV system, if you are using a check valve between the catch can and intake, you will both eliminate that issue and any possibility of problems with bypass valve dumps.
Towels, regarding tubing height it will not affect the performance but considering you are dealing with airflow things like length and sharp bends will greatly affect the performance.