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Friday, July 25, 2014

Out of Time for Engines.

Timing, timing, timing.  Being in the right place at the right time can bring possibilities to reality, and can assure that things go according to plan.  Timing plays a huge part in all things life oriented, timing also comes into play with engines (electric motors too).  This article will be fairly short, but the info is crucial to the proper function of any engine.

Without proper timing in an engine, all sorts of issues can arise that include  loss of fuel efficiency and power, overheating and thus warping of metal parts, and even total catastrophic destruction of the engine.  

It is imperitive that all the parts in an engine operate in the correct sequence, at exactly the time they are supposed to.  We must assume that the engineers who designed the engine took into account how different engines require differing timing needs.  

A big, slow turning truck engine compared to a small, high revving motorcycle engine will have very different timing needs, but the basics remain the same. Creating an engine that can make alot of power instantly requires that combustion occurs precisely when the maximum energy can be delivered from the chemical form in fuel to mechanical energy out the wheels.  

In some engines, the timing system must keep the valves and pistons separated physically so that damage does not occur- this is referred to as 'interference'- literally the engine parts interfere with each other.  If a timing belt or chain breaks, the parts meet without any ability to move and thus bend and break.  This usually adds up to very expensive repair bills, or recycling a machine back to its constituent components.  

Combustion, or more commonly, ignition timing is a matter of when the fuel in an engine actually burns.  Igniting the fuel under pressure in the cylinders causes a huge pressure pulse or spike that actually makes the power to turn the wheels.  It is the pressure spike that drives the piston down comes after combustion.  

The burn time is remarkably short and must happen just as the piston comes up to 'TDC' or top dead center, so that the pressure pulse pushes the piston back down as it rolls over the top of the combustion stroke and into the power stroke.  

If that combustion happens too early, referred to as advanced timing, the internal parts in the engine are put under tremendous stress from the piston coming up and combustion pushing the piston down at the same time.  This causes 'ping' or 'knock' at best, engine destruction at its worst.  A tiny bit of ping is acceptable in most engines, but too much will drastically reduce engine life.  

The pinging sound is actually the slap of the piston against the cylinder wall as it cocks slightly sideways from added stress of pre-combustion.  This can seriously and quickly  wear out cylinder walls and piston skirts, or even snap the piston skirt completely off the bottom of the piston.  The loss of the piston skirt not only puts broken metal shrapnel into the engine, but will rapidly cause added wear from a piston that now fits loosely in the bore.  

If ignition happens too late in the process, called retarded timing, instead of too early, the combustion is rapidly quenched by the expansion of the gasses instead of accelerating combustion due to compressing the fuel and air together as ignition happens.  Overly retarded  timing results in engine overheating, burnt exhaust valves, and severe loss of power. 

A properly tuned engine will have the combustion happen at the precise moment when the pressure spike can deliver the most power output from that combustion.  Not a millisecond before or after.  Its very precise.  Generally, a slight advancement from stock settings will result in more power, lower temps, and improved fuel efficiency. 

A bit off topic here, but not by much. The tyrannical EPA and its nonsense emissions rules mean that engine builders retard ignition timing back from its optimal point in order to waste fuel and sacrifice engine life and performance just to keep emissions to dictated levels.  The EPA is run by, and these levels of emissions are set by ex-oil company executives and ex-car company CEOs and other execs.  It is in the interest of these corrupt jerks to get you to waste more fuel and throw away engines to increase the profits of the companies whose stocks they own  I say focus on fuel efficiency, the emissions will follow.  Make engines last as long as they can and the coal burning power plants that power our manufacturing base will save fuel as well.  I will go into emissions more later in another article.

I hope you now understand better what it means to the operation of an engine to have the mechanical and combustion timing perfectly set and maintained within a tiny window of acceptability.  Thanks for reading, and remember, if you have an engine with a timing belt, have it changed out before it can break or stretch and compromise engine performance or integrity.  Check back for more helpful info...

MW outta here and onto the next fix-er-up... 
'Til next time, love your machines!


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