Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Breathing without slobbering

Other forum posts over the last couple of years on the subject of engine breathing got me to thinking (always a bit dangerous) about minimizing the amount of oil mist ingested into the engine during normal operation without losing the benefits of positive crankcase ventilation (PCV) which helps keep the oil on the right side of the seals and keeps bad things out of the atmosphere. Direct venting to atmosphere, even with a catch can if you are a good citizen of the planet, seems not very 21rst century, and again loses the benefit of negative pressure in the crankcase.

The S&S specified system of a small hose from the top of the cam chest into the bottom of the intake throttle body is simple and effective, but, with the downstream placement of the fuel injectors (generally a good thing), oily grunge can build up in the intake tract over time as there is no fuel present to wash it down until just before the intake valve. Theoretically, at least according to some of things you can find to read on the internet, oil vapor in the intake tract can lead to deposits on the valves over time and effectively lowers the octane rating by displacing air/fuel mixture.

But for me, I just wanted to know how much oil froth is getting into the engine, and therefore should I worry about it. The easy answer is no, just drive the damn thing and trust that S&S did their homework. But that's not how my brain works.

Modern autos have for some time had air/oil separator units installed to address these issues while keeping the benefits of PCV. So a little internet searching revealed a huge amount of aftermarket options from simple to somewhat complex with most aimed at performance automobiles and therefore rather large. I kept at it until I found a motorcycle sized air/oil separator from K-Motor performance that was small and inexpensive, perfect for an experiment. It uses the vacuum from the intake to pull the crankcase oil vapor into a small (50cc/1.6 ounce) reservoir where the heavier liquids settle out while the air passes through a sintered bronze filter element before passing into the engine. Not very high tech, but functional. Does it remove all the contaminants from the crankcase vapor? I dunno. I doubt it. It does remove about 20cc of frothy oil mix per 100 miles driven (looks like vanilla latte). Put another way, I need to empty the reservoir when it's time for a fuel fill up. So it's doing something useful, but not sure it was worth the effort. I found it very interesting that the first trial run, about 30 miles, yielded only water, about 30cc. Since then, just the latte.

Install photos are below, and pretty much self explanatory, but some hardware notes may be useful to others seeking to do something similar. The separator is installed inline between the cam chest and the intake and all aspects of the factory sealed system are preserved (except for the oil in the intake!). Threads for the intake and cam chest fittings are 1/8" U.S. National Pipe Thread (aka NPT), tapered. Common in the U.S., not so much elsewhere. I had intended on using AN fitting adaptors at both the intake and cam chest to allow for tidier hose routing, but the cam chest fitting is a proprietary design tube that S&S specifies, so I kept that in place. One could use the existing hose nipples. Hose btw is 5/16"/8mm, and really should be fuel/oil rated.

The change to the breather hose routing is pretty much invisible due to being obscured by the air cleaner, and I chose black fittings to keep the mod discreet. To maintain the S&S specifications, the fitting screwed into the throttle body has been internally drilled/tapped 1/4"-28 and a brass set screw is threaded in that has been drilled with a .100" hole.



The two hoses then run 'round the back of the forward cylinder...



and arrive at the small air-oil separator unit mounted to a chassis tube.



Simple alloy clamp brackets keeps it in place. The forward bracket around the separator came with the separator and the bracket that clamps to the vertical chassis tube is from Speedwaymotors.com, p/n 91032866-1.50. In this location, the separator is shielded from debris by one of the driving lights mounted next to the engine. There is a schrader valve for draining in the bottom of the reservoir, though I have found it faster and easier to simply unscrew it and dump it out.

Nicely done Steve. I bet you are spot on about removing and dumping the froth since it is sticky enough to need to be wiped out.

The separation system I have does not route the air back into the Venturi . I also vented the main oil tank, and the results is no oil leaking and drooling down the side of the tank, less froth in the cam chest vent can.

Steve, how is the system working?

Custom Morgan is working on a replacement for main oil tank designed in such a way as to separate the foam out of the oil/air in the system so the tank can be vented without a catch can.

It's working as intended. But I don't believe it is a worthwhile mod given the hassle of of emptying the collector jar every couple of hundred miles and how little oil gets into the the intake (I allowed the oil froth to condense down for a few weeks once it was full and there was only enough oil to cover the bottom of the collector jar, so just a few drops-after 200 miles of running)

I will likely remove it when I do my winter engine service, as I'm not a fan of complexity with no purpose. So my conclusion is there is no need to second guess the S&S engineers when it comes to crankcase ventilation, as their solution works just fine.

Well done. Thanks for the trial and insight!

That is why Morgan Custom is working on separating in the tank.

my experience with engines is that foaming is only and issue in engines that are run for short times.... e.g. the little old lady who only drives to church and back.

How far do you think running the Three Wheeler is necessary to not get foam/moisture?

Long enough to get the oil up to about 230F for 10 to 15 minutes should do it.

In this climate of the seaside communities of the PugetSound it takes about 8 or 9 miles to get to 180F, getting to 230F would take 40 mile trip if it ever got that high during the winter.

How far, on average, do you all drive when you start the MOG?