On Emissions Deletes and the Importance of Positive Crankcase Ventilation

Progress has worked against mechanical design almost as much as it has worked for it, and there is no better example of such than in emissions equipment. One can chart in his mind's eye the positive progression of engine technology as a steady climb from the infancy of automobiles up to the 1960s, in which decade automotive design hit its stride, and cars were built for roads not unlike ours today. But 1975 saw the most stifling laws put into place on emissions and efficiency in America, which saw the quality of automobiles as a whole dip into unsustainable mediocrity, which opened the way for Japan to take over. American cars indeed were too bloated and pollution was an issue -- this was American decadence and automaker hubris at work -- but at the point in time that the laws were made, the technology for combatting emissions was nowhere near what it needed to be, and American engine design was far too bloated to achieve efficiency, so the 1970s were largely a whole decade of every engine being miserably choked down with experimental technology that was as faulty as it was obtrusive.

The most terrible legacy of the time is that those laws made back then were so absolutist and never slacked up. Californians are not free to modify the fuelling systems of automobiles that are now entering antique territory, and for the rest of the country as far as I'm aware it is a federal offence to remove a catalytic convertor from a vehicle originally equipped with one, no matter how old. Did you know the early catalytic convertors got red-hot due to unburnt fuel fouling them, and even today in modern vehicles they serve only to decrease performance and eventually plug up completely, rendering the engine unable to run, cracking exhaust components, causing excessive heat? Did you know they're good for nothing at all but cleaning up tailpipe emissions, and that with the vast majority of cars on the road being modern and unmodified, a vintage vehicle here and there having no catalytic convertor affects nothing and no-one?

Those who live in states with no automobile inspections benefit greatly from the freedom to modify, but given that I work mainly with 1980s vehicles I see a lot of people ignorant to the beneficial technology used on them, and go in with the mindset of "ripping it all out," "cleaning up the engine bay" which in all frankness is retarded. In fact, no system ought ever to be removed or modified without full understanding of what it does.

The Difference Between Emissions and Efficiency Equipment.

The best reason to ensure that one understands what something does before removing it is to ensure that the system is emissions equipment hindering performance, efficiency or longevity. Systems designed to help efficiency and longevity are a great thing to keep, and are usually harmless, when designed well and working as designed. Air injection on the Toyota 22R-E, for example, gives the cylinders extra air at a certain point in combustion to ensure that all possible fuel is burnt. The aftermarket community sells blockoff kits for this, but it's actually a good thing to keep, except... the 22R-E fuel filter is horrific to access, and one of the main things preventing any access to it is the air injection equipment on the intake side, so one must pick his poison. Datsun had Air Temperature Control, which measured incoming air in the air cleaner housing and opened flaps to maintain a 100 degree temperature. This was great for efficiency, not great for performance, but for a daily driver there's nothing wrong with keeping it. One can remove each and every one of these "unnecessary" measures, but consider how many of them remained present on engines that have reached 300,000 miles, or even 600,000 miles! If the engine in question is American, however, the unnecessary fodder might well be best removed. Hell hath no fury like a General Motors system acting up.

Exhaust Gas Recirculation

EGR is undoubtedly the most misunderstood emissions technology, and it is important to make an informed decision as to its future on your aged vehicle. It feeds some exhaust back into the intake at a certain point in the throttle opening, and it is designed to -- and succeeds in -- lowering combustion temperatures when active. Progress in engine design has led to higher compression which results in more power, but also more harmful nitrogen oxide emissions due to the higher combustion temperatures. EGR has proven to be the best way to mitigate this through the years. The main drawback is that on a vehicle with multiport fuel injection, like a 1980s through 2000s Toyota, the carbon soot from the EGR and the oil from the PCV both fill the intake with a black gunk that is impossible to clean without removal of the intake, and if not cleaned after about 200,000 miles it will begin to interfere with the throttle plate, making it stick and wear out. (Do not spray an intake full of throttle body cleaner with it attached to the engine, serious damage can occur, I have learnt this lesson.) Rather than an indictment of either EGR or PCV, this issue really highlights a huge problem with multiport fuel injection, which is the intake plenum having only air travel through it, with no gasoline to clean it, since the gasoline is injected at a much lower point. With a carbureted system, air and fuel enter the intake together, and will clean any EGR soot or PCV oil completely out. EGR is best deleted from a multiport fuel injected engine, unless you like cleaning your intake, but is best left on and maintained on a carbureted engine. Lowering combustion temperatures at all likely helps with longevity, especially on aluminum head engines. If EGR is kept, the gate that allows the exhaust in will need to be cleaned with throttle body cleaner every so often, or it will stick open or shut, and if stuck open will hurt engine performance dramatically.

Positive Crankcase Ventilation

This is the meat of the article, the "emissions" system that is not necessarily for emissions or efficiency. PCV generally works by putting manifold vacuum to the crankcase, which sucks out blow-by gases, which are toxic byproducts of combustion that escape past the piston rings. A second vacuum line is usually run that allows fresh air to be pulled into the crankcase to replace the air pulled out, and under hard acceleration (or with lots of blow-by from an aged engine) allows air to blow out, thus the two lines both can serve to evacuate blow-by depending on the situation. These gases coupled with hot oil really stink in a funny way, but the motive for having the engine eat them is more than just due to smells or the environment: no matter the form that PCV comes in, a crankcase should always have a vacuum placed on it to pull out blow-by. PCV is not under any circumstances to be "deleted", you do not want to go back to a draft tube or put a little breather filter on your valve cover. Blow-by gases when not actively sucked out of the crankcase will contaminate your oil so fast it's not funny, and this is the main reason that engines before the 1970s were known for poor longevity. The toxins from combustion are bad even for engines! I have run a couple engines with the crankcase vented to atmosphere, and I found my oil black in 1,500 to 2,000 miles. Oil is supposed to last 5,000 miles before needing changed, but if you have no crankcase vacuum then the oil change interval will need to be as early as the aforementioned. Crankcase vacuum also helps to increase compression and reduce blow-by, because the pressure in the combustion chamber contrasted with vacuum on the other side of the piston rings helps to increase ring seal. So the system that purges blow-by also can help to reduce its emergence in the crankcase, and it does increase performance. I've read that drag racers run an electric vacuum pump on their crankcases, because they need the improved ring seal but without the drain on vacuum from the manifold. If I were to own and maintain an antique engine designed before PCV, I would block off the draft tube and find a way to retrofit PCV. Another thing, while PCV and EGR together contribute to clogging up fuel injected intake plenums, simply not having one or the other could eliminate any mess. PCV can be run through an oil catch can to ensure that no oil reaches the intake.

Now, all of the said benefits suppose that the PCV system is in good working order on your vehicle. The unfortunate aspect is that as engines age, their piston rings lose sealing strength and will allow a lot more blow-by past, and thus the stock PCV system will be overwhelmed and will blow air out both tubes without manifold vacuum being any help. At this point in your engine's life, it will need a rebuild. But in my research I found a very overpriced product called the Envalve, which I cannot afford but I do believe it's a highly beneficial system for those who need it, or those looking to make an engine go many hundred thousand miles with minimal intervention. It replaces the standard PCV valve which is hooked to vacuum, and involves removing and capping off the second tube. It then manages a constant metered vacuum on the crankcase. This means that instead of blow-by being partially sucked out and still building up over the course of your oil change interval, your oil should stay clean for as long as its viscosity is good. It also means that ring seal will be perpetually better, oil seals won't leak oil out while running because there will be no outward pressure on them, and all of these benefits will remain even after blow-by reaches a normally critical point due to worn rings.