The engine that breathes the best wins not only in fuel economy but also power. How well an engine breathes is a measure of efficiency.
Now, theoretically, breathing efficiency can only be 100 per cent. That means an engine can only fill itself with as much air at atmospheric pressure as it takes to fill it. So that 5.7 litre hemi Ram could theoretically process 5.7 litres of air every time all eight cylinders are filled and exploded for power.
Every engine design has an engine speed sweet spot. That is the engine speed or rpm (revolutions per minute) where everything comes together and the cylinders are filling to capacity and exploding completely. Push your gas pedal to the floor when starting from a standstill.
At low engine speeds (less than a thousand rpm) not much happens but as the engine speed (or rpm) climbs your vehicle starts to pull or push harder. When the acceleration rate is quickest your engine is in its sweet spot.
In days gone by that sweet spot was a pretty small rpm range.
Recent engine designs are letting us have our cake and eat it too.
The advent of variable valve timing and lift is upon us. The timing of when valves open and close is now variable and controlled by electronics. Some valves are also controlled as to how far they open under differing operating conditions.
This means the sweet spot is no longer only a short range of engine speed. Now the sweet spot can cover thousands of rpm.
These variable valve timing and lift systems are controlled by electronics operating hydraulic systems. The hydraulics are using the same engine oil that lubricates the rest of the engine.
These hydraulic systems must be fast reacting. The oil passages are tiny and they require good clean oil of the correct viscosity. Low oil levels and dirty engine oil raises havoc with these systems.
When it comes to maintaining that large sweet spot some obvious and not so obvious maintenance is the key. The obvious: keep that air filter clean.
The not so obvious. With time and miles your engine is building deposits. The air path into the engine is shrinking. The intakes valves are getting coated in carbon and varnish. The air just cannot get in and out like it used to. This progression is relatively slow and unrecognizable. Use of high quality fuel slows down this process. Air intake cleaning and decarbonizing procedures will get you back that original big sweet spot. When you get that big sweet spot back those Chambers’ trucks will hold you back no longer.
Trail’s Ron Nutini is a licensed automotive technician and graduate of mechanical engineering from UBC. E-mail: firstname.lastname@example.org.