Emissions and Cranckcase Ventilation Issues
| OK, this is
the one. It's been up and running for about three months (the last
400 miles) and I'm VERY happy with the way it's been working.
Although at startup, it's a bit 'funky' until it warms up a bit, as it's
pulling air past the carbs and I need to keep the choke out a bit longer,
but after the first few minutes, it runs fine. PLUS... not a drop of oil
anywhere. FINALLY... Big Red is potty trained. No more 'marking it's
Now before you get to the pictures, an update is important. The Exhaust scavenging system is a bust and has been removed. Those one-way valves apparently can't take the heat of the exhaust pipe. The valve on top, between the rocker and intake is OK, but the one down on the exhaust pipe has already bitten the dust, and breaths both ways. so in essence, it simply stopped pulling air out of the crankcase. Exhaust pressure pulse reversion wasn't pressurizing the crankcase, as they were being canceled in the 5/8" breather hose, but it was no longer 'sucking' on the crankcase either. Hence this new design inception.
This one works. This system maintains a 4 psi vacuum in the crankcase, stops the oil fumes from gumming up the intake valves, returns any captured oil to the crankcase, and maintain the original valve cover breather system for emissions.
OK...let's get to it. This description, assumes you've read the other systems developed previously. Firstly I built a vacuum canister filter, that's mounted on the firewall next to the windshield washer bottle. It's an aluminum 'catch tank' designed for today's 'Rice-rockets'. It has a site tube up the side to give a visual clue as to the oil level (if any) inside the tank. I've modified the tank by adding a few screw in barbed hose adapters. One 5/8" adapter, is connected to the breather down where the fuel pump goes. I installed a 1/4 turn valve in the very bottom tap, to allow draining any collected oil, directly back to the engine, via a tube that enters the bottom of the fuel pump mounted breather adapter. One 1/4" barb, attaches a tube to the bottom of the rocker cover oil separator. A 1/4" hose attaches directly to the intake manifold, via small multi-turn screw valve.
So this is what and how it works. Via the vacuum line and small multi-turn valve, I can control the amount of manifold vacuum that is applied to the filter canister on the firewall. From this canister, fumes from the block side mounted breather, are pulled into the lower 1/3 of the vacuum canister. Vacuum is also applied to the bottom of the rocker cover oil separator. The hose size differences, are what balances how much vacuum is applied where throughout the system. The multi-turn valve, allows 'tuning' of the rate/volume of air that gets pulled into the intake from the vacuum canister, thusly setting the vacuum level maintained in the crankcase.
The above layout is straight forward enough. The magic is 'inside' the vacuum canister, and where on the canister the hoses connect. The inside of the canister is stuffed with filter screen and gauze material. I used the guts of an aluminum screened, carbon foam kitchen stove vent hood filter. I put a few cut up sections of the aluminum screen, in the bottom. This leaves a void for oil to collect in. I then stuffed the canister with the foam filter material. Then added one or two more layers of screen at the top. I picked this canister because of its sealed nature and screw on lid. This allows me to inspect and change filter material if needed.
The bottom of the canister, has a 'drain' hole. I mounted a 90 degree elbow, and a 1/4 turn valve to allow controlled draining of any collected oil. Now, since the 5/8" hose feeds in from the crankcase block breather adapter, as too does the 1/8" id. oil drain tube, I've since come to find, I can leave this valve open, and the oil still drains to the crankcase, rather than air or oil being pulled up through this small diameter drain line.
The 5/8" crankcase line feeds in about 1/4 - 1/3 the way up the side of the canister. As too does the rocker cover separator oil drain line. The main vacuum tap back to the manifold is all the way at the top.
At high engine vacuum, (idle and just off idle) the carbs are pulling air through the 1/2" diameter piping from the rocker cover. Now remember there is an oil drain tap in the bottom of the rocker cover oil separator. Since the engine vacuum in the canister is greater than the vacuum from the carbs, most air as well as oil vapors in the rocker to carb path, are sucked into the canister, rather than the intake. The one-way valve in the rocker breather path stops any vacuum draw from effecting the carb emission ports. If blow-by exceeds the vacuum from the canister, the carbs will still take up the slack.
I can dial in from zero, to around 12 psi of vacuum. At 12 psi, I can actually HEAR the air rushing into the front timing cover seal at idle. (using a length of hose as a stethoscope). This kind of vacuum is NOT needed. You only need enough to consume the blow-by gasses that build in the crankcase.
So How do you tell how much you should dial in? I chose to install a simple vacuum gauge/gas pressure tune up gauge, tapped right at the vacuum canister. If blow-by were to exceed my 'dialed-in' setting, I'd see a positive pressure. So after driving around a bit, I simply set the multi-turn valve (thus limiting vacuum) to a level that under all operating condition,s I never saw the gauge go to a positive pressure. For Big Red, at an idle 4 psi of vacuum seems to be just right. Now I was concerned that I might be pulling road dirt and dust IN through the seals around the engine (rather than blowing oil out) so to test for a 'safe' level, I held a lit cigarette next to the seals to see if any smoke was being drawn towards the seals. Nope! Nada! Nothing! So I up'ed the vacuum to see how long or what kind of wear I'd need before it did start. At around 9-11 psi of vacuum at id;e ... 'I think' I could tell the smoke was starting to be drawn towards the seals. So I think this system will be good to go for quite awhile. I've decided to leave the gauge in place so I can watch it for awhile. 400 miles now and all is still well! Still not a single drop of oil on the exterior of the engine. (at least not from any seal leaks or blow-by problems.
Now the fun part. The following pictures, when 'moused over' will turn so it's easy to seethe plumbing and components added.
Emissions and Cranckcase Ventilation Issues
All material copyright© Teglerizer 1996-2008
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