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Friday, April 4, 2014

What does 2 minutes cost? Pt 2

Welcome back for part 2 of Warm-ups: 

    Tuesday we got started on the importance of warm-ups, today we'll conclude that thought and hopefully convince you to waste some fuel to save some engine.

     Engine parts need to warm up slowly and evenly and turbochargers are another important piece of equipment that should have this rule implemented every start.  A turbo on a small VW diesel can spin at over 160,000 RPM, larger turbos somewhat slower. Tolerances are VERY tight and a slight warp or wobble can be supremely catastrophic- explosive or fiery mess like. A fast heated turbo can suffer from rapid over heating and siezing of the exhaust end of the shaft as it heats and expands while the bearings/bushings are still cold. Shaft and bearings must warm-up together to keep fitment correct.  Most commonly though, the turbo shaft heats first, swells,and proceeds to gall and grind the bearings or even seize up solid if not allowed to heat up slowly and evenly.

 Cold oil is hard to pump because its viscosity is high- its thick, like all oils get: cooking oils, massage oils, engine and machine oils. Because its thicker, cold oil puts a lot of extra stress on the oil pump which is trying to cram said oil down small passages and quickly lubricate rotating parts.  I have seen broken oil pump drive-shafts on older vehicles because of the added stress of cold revving- newer oil pumps are direct drive and thus no drive-shaft, but drive-gears and oil pumps still fail due to this.

     The modern computer and fuel injection system has replaced the carburetor choke system for enriching the cold air-charge in order to get the engine to fire. Just as in the old days with carburetors though, until the engine warms, it is wasting fuel just to stay running as the cold metal inside the cylinders wicks the heat out of the combustion process. The modern computer is holding the injectors open longer thus pumping extra fuel into the engine leading to the same end result: a choked condition.

    Wasted fuel and extra soot are created as long as the engine is cool and warming. That soot is usually soft, fluffy, and burns off when the engine warms more if the engine is allowed to warm before loading the engine stays cleaner. Under greater pressures of loading, that soot gets embedded into the piston top/head/valves gets forced down past the piston rings into the oil. The shape of soot from gasoline engines tends to be sharp and abrasive like small salt crystals, and the longer the engine runs rich (extra fuel) the more abrasive soot the engine produces. The faster and more loaded the engine operates when cold, the less fuel gets used for work and the more gets wasted and turned to soot to grind up the metal of the engine and contaminate the oil.

    Another aspect of warm-up is avoiding acid build up inside the engine. Some of the additives in gasoline combined with incomplete combustion and the small amount of engine oil that gets burnt in the cold engine contribute to acid production. At higher engine speed and load, the added pressure drives these acids with the soot past the piston rings and into the oil. Now, don't get me wrong, modern oils are pretty good at buffering out damaging acids and holding them isolated until the heat of the engine boils out water and contaminants which then get re-burned through the PCV system. However, it is only when the engine gets fully heated up that the oil cleans itself of these acids. Since the more acids the engine generates, the longer it takes at high temp to boil them out, the higher the likelihood that those contaminants will stay in the oil at shutdown and be allowed to do long term damage to the engine from the inside.

     I know it is controversial (and may draw some comments- LOL- bring it!) to say that wasting a bit of fuel to extend the life of an engine is a good idea. I cannot say how many times I have been scolded with “Idling wastes precious fuel!” by a well meaning enviro-yuppie. The cost of engine replacement or repair to both the environment and the pocketbook, the waste of additional resources and electrical generation for production of parts, and the downtime and loss of personal or fleet transport outweigh and justify the small amount of fuel burned to warm the engine and keep it happy and healthy for a much longer time.

     It has been proven repeatedly that it is cheaper to prevent an issue than fixing one, and a small investment in time into your engine will pay you back in lower overall cost per mile, more miles before replacement, and greater long-term reliability. Maybe a few more enviro-yuppies will scold you for it, but just remember that its only because you are an easier target for their misguided angst than the local coal burning energy company and its armed guards.

    So, in my maybe-not-so-humble opinion, a couple minutes of warm up before driving, then driving gently for the first couple miles will add thousands of miles to the useful life of an engine by removing damaging elements inside the engine from the outset.

Thanks for checking in, I'm off to go whisper sweet nothings to another neglected machine...

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