I pulled this off of a gasser forum while trying to find some good concepts of the ccv mod not sure if it pertains to diesels but I don't really see why it wouldn't
by Tuner Boost Ľ Jun 25 2013, 12:15am
OK, this is one of the most misunderstood subjects/systems on todays cars and light trucks, and some good replies above.
NEVER open the system. To do so defeats one of the most important functions of the PCV system, and that is to evacuate the damaging combustion by-products from the crankcase while these compounds are still in a suspended or gaseous state. The other is to relieve the crankcase pressure caused by blowby....which is the obvious and the one function most understand.....what is missed is the first function.
Here is a explanation of the function and the unintended issues caused by the oil mist/vapors ingested with the evacuated compounds...and also, only a few catchcans actually stop the oil ingestion...most are no more effective than a beer can with 2 fittings. I will continue this in several parts so it can be studied and questions asked to clarify any part not clear, and will also include my qualifications as many will question this as well. So do NOT get pulled into purchasing a catchcan that is only partially functional, and I will go over most on the market and include test results and pictures of them dissected with explanations as to why some do work and most don't...no matter the price or the brand name.:
Understanding oil contamination from combustion byproducts
The evac system is not for the environment....it is to keep the engine alive and wear free as long as possible. Your not alone and 99% of car owners never think about it or realize whats happening over time. And yes, most will drive 50-75-100k plus miles and never know the damage gradually being done.
over 35 years building race and performance engines.
Mechanical & Automotive engineer by trade
Graduate of the Reher Morrison Racing engine building school (one of the most respected in the world and a GM R&D contractor).
Owner and driver of drag teams with multiple Divisional, National & World championships in both NHRA& IHRA in several classes (this is where every minute detail in an engine matters)
And I tear down and build most every kind/brand of motor imaginable (except diesel) on a weekly basis.
So here goes:
Every motor has a certain amount of blow-by, the bigger the CI & the more boost the more blow-by (with everything else assumed is equal and no piston/ring/cylinder issue).
Most only look at the crankcase pressure portion and deal with that and that is only a small part of the crankcase evac systems function. The most important is the flushing & removal of the harmful combustion products before they have a chance to condense & settle into the crankcase oil.
These consist of:
and several other harmful compounds that when mixed in the crankcase produce Sulfuric acid and as that accumulates past a certain PPM the bearing surfaces, wrist pins, and crank journals begin to be etched and start to damage. This is gradual of course so thatís why like you, most never realize whats happening.
The other very harmful byproduct is the very abrasive carbon particles (near diamond-like in abrasiveness) that many are to small to be caught by the oil filter and accelerate wear as well.
If you have a good cross flow of filtered fresh air entering one side of the crankcase (best is through a flow controlled breather), say the pass side oil fill cap, that fresh air will travel through the pass side valve cover, around the rockers, down the pushrod valley, through the center of the crankcase, (now on the LS6/2/3 valley cover with the fixed orifice it exits there drawn by vacuum so 1/2 the engine is still stagnant with foul compounds...especially the drivers side rocker area) up the drivers side pushrod valley, past the rockers and exits the rear of the drivers side valve cover flushing and pulling the compounds out BEFORE they can settle and condense into the crankcase. Now with out that flow the compounds settle and mix with the oil every time the engine cools. When started and run to operating temp the volatile of those are "flashed off" and again could be evacuated but if just venting with breathers, ONLY the excess crankcase pressure will exit and very little of the harmful compound mix goes with it and once the abrasive carbon particles mix with the oil they are there to stay reducing the protection your oil provides. Now if changing your oil after every track event then this is not an issue. But with a street driven car it is and I can tell you to just look at how dirt your oil gets as far as coloration when you eliminate the evacuation portion of a PCV system, but that tells very little. Send in an oil sample to a good analysis lab and the report back will verify everything I'm saying. The over the road trucking industry does this as a rule, and we do with our race engines as well looking for metal content that tells us a bearing is going away before we could ever detect it and knowing to freshen before a catastrophic failure.
Now back to the LS engine. Any built, big cube, or FI motor cannot breath using the valley cover fixed orifice as it is far to restrictive and excess pressure is a given. So we never use the valley cover vent tube but draw from the rear of the drivers side valve cover. This barb/fixed orfice MUST be drilled out to 1/8-1/4" if using the RX dual valve catchcan. Remove the valve cover to do this and be carefull not to drill through the baffel underneath.
Now we come to the issue of FI builds that pressurize the intake manifold. Turbo or front mount centri SC systems, the problem with the OEM style system is as soon as you are under boost and the intake is under positive atmosphere you are pressurizing the crankcase directly via the vacuum nipple that evacs under non boost.
The only true solution for street driven cars is a oil separating crankcase evac system that will provide proper, continuous evac while operating under non-boost via the intake vacuum, and as soon as it senses pressurization a check valve senses this and closes blocking any chance of crankcase pressurization. Then as this happens a secondary valve opens and uses the suction/vacuum of the head unit to continue evacuation while the separating can traps & removes all the oil in suspension allowing only the gasses that do not effect the energy released per explosive event (you do NOT want ANY oil entering the intake air charge or residue/varnish forming on the compressor wheels throwing them off balance).
No oil caused detonation, no shortened engine life/increased wear, and the best of everything you need for the motor to perform properly & last as long as possible.
This is the end of the first part of this multipart post....more to follow, and ask any questions in detail as there is so much misinformation and most great shops and techs do not understand all the functions either as it is not taught in any tech school, or by any dealers service training.
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