#6 - Crankcase Pressure
Long has it been a standard practice in the Rocket 3 community to simply slap a filter on the breather at the back of the motor, and allow the crank case to vent to atmosphere. This might be an acceptable practice in street riding, but, I've never been satisfied that it's a best solution. Sadly, the dry sump system used in the rocket 3 is not strong enough to simply seal off the port and allow the pumps to control crank case pressure.
Meanwhile, its getting severely heat cycled and becoming brittle. The foam inevitably cracks away from the rubber and now you've an unfiltered ingress point for water/particulate.
Clearly this isn't optimal nor is it particularly effective at crank case fume extraction. The filter is shielded on 6 sides, and will not be in a particularly low pressure area, so the effect of "pulling" the fumes out is questionable.
When sitting still or moving slowly there's essentially nothing drawing the unwanted vapors out, it's just sitting in the lower half of the motor and in the transmission cavity collecting on the walls of the cases where it runs down into the sump and is pulled back into the oil tank, to be recirculated through the bearings.
The right fix in my mind is a filtered catch can that connects to the port seen above, and scrubs the fuel/water/oil vapor out of suspension and then has that air drawn in to the intake patch keeping the crank case under vacuum while not drawing in oily air and causing detonation. This one has a dipstick so it's easy to see how much oil is in the storage part of the can. By adding a piece of coarse steel wool in the input path it will scrub most of the fumes out of the air and allow them to drip down into the catch area below.The output will be ported to an added port on the intake system creating vacuum as is normal in the bottom half of the engine. This should have positive effects on both wear and possibly on power (if there were any issues with ventilation/aeration as currently configured).
For the $40 in materials and a small investment in time, there is literally no downside and every upside possible to adding a catch can to the bike, so, I'll be doing so asap.
Very difficult to keep the returning air free of oil mist. Try venting to the exhaust system using a check valve and tube into the start of the collector. A restrictor in the line can help tune maximum flow as this type can draw too much depending on design. No drips, no oil in combustion chamber, no dis-colored plugs. I have this on my R3. Can send pictures if that is helpful.
ReplyDeleteI’ve looked into this since you commented. I think I’ll be going the route you suggest, it just means a little welding work.
ReplyDeleteDo you run a air-oil separator between the check valve and motor or plumb it straight with a hose?
I don’t think too much vacuum will be an issue, but I’v ordered a GM 1bar map sensor to T into the line and monitor vacuum levels, at least during the initial testing of the setup.