Using the S&S reed style crankcase vent is a moot point now. It's not for '06 Dynas/'07+ TC engines. If the oil reservoir vent isn't a solution, what the hell do I do with this annoying puking. Right now I have Doherty Mystfrees in the rocker cover, instead of the stock umbrella valves. The stock setup puked, which is why I tried the mistfrees. They don't work either. Can it be cam profile/timing? The stock setup was used with stock cams, and puked just the same when I got some proper breathing and a tune into the system. How do I eliminate this? What do you recommend to control this problem? It's annoying as hell.
I put a few random thoughts together regarding the issue of oil carryover to the air cleaner. This can be challenging because there are a number of things going on that rely on a balance inside the engine which is sometimes altered when the engine is modified. I don’t have any good first hand experience with products like Mystfree, but it seems to me that the manufacturers and distributors of these devices make bold claims that often seem to go unrealized.
I believe that air cleaner oil carryover issues can be broken down into four basic categories:
1. The quantity of oil present in the crankcase, camchest and heads. I believe that increasing the quantity of oil in the engine effectively increases the density of the oil mist carried throughout the engine.
2. The air pressure differential between the crankcase and the air cleaner.
3. The effectiveness of the method used to direct crankcase vent vapors into the intake is relative to the amount of oil condensing inside the air cleaner assembly, eventually ending up on the right side of the machine.
4. Air/oil separator modifications and malfunctions.
I advise against increasing the amount of oil that is pumped into these engines. A number of my previous posts cover this perspective in detail. IMHO, these engines are adequately lubricated and adding additional oil only increases the density of the oil mist suspended in the air moving throughout the engine. This ultimately increases the load on the air/oil separators in the heads.
The big variables relative to crankcase/air cleaner pressure differential is blow by as well as modifications like the S&S reed valve assembly which alters the airflow and pressure inside the engine. The blow by piece of this most certainly increases with engine load and speed; bottom line is that in a healthy engine, blow by is what it is.
Crankcase vent modifications are a wildcard which may have significant negative impact on oil carryover. I recall reading on the board that certain modifications require you to increase the diameter of the drain holes in the rocker arm supports for the air/oil separators. If the rational for the larger holes is that they will allow more oil to be drained from the separators, I believe this will only return heartache and misery if used with the OE separators.
It is my sense that the small drain holes for the air/oil separators are designed specifically to work with the umbrella valves in order to create a pressure differential between the inside of the separator and the rocker box cavity; evacuating more oil than gravity alone would allow. Increasing the diameter of the drain holes effectively reduces the pressure differential, reducing the air circulation designed to evacuate oil from the separator chamber. Gravity drainage may increase but anyone that has “shot” a can of beer knows, a little pressure differential makes all of the difference in the world when it comes to moving a lot of fluid in a short amount of time. Excess oil which is not drained from the separators will eventually be carried through the vent and into the air cleaner.
In my experience, the change that has had the most impact on reducing oil collecting in the air cleaner is the direct routing of the crankcase vent into the induction module. This approach reduces condensation and accumulation of crankcase vapors on the inside of the air cleaner. Aftermarket air cleaners that don’t retain the OE vent exit points will most certainly have more oil collecting on the inside of the air cleaner, or wherever the vent ends up exiting to the atmosphere.
IMHO, a reasonable approach to dealing with oil carryover is to refrain from introducing additional oil into the engine; maintain the integrity of the OE air/oil separators as well as the late style intake vent routing; ensure that blow by is within limits; do not alter the normal airflow through the engine.
In my experience increasing displacement does not negatively impact oil carryover, because the positive and negative pressures while greater, are relative and don’t significantly impact the balance of pressure between the crankcase and air cleaner.
As always, the above ramblings presented along with $4 (borrowed or otherwise procured) will get you a cup of genuine Starbucks coffee.
djkak
Author
Topic: Thoughts about air cleaner oil carryover (Read 1869 times)