Q: What is a Wankel engine, and are there any still being made?
A: Felix Wankel was a German engineer who did most of his development on the rotary or Wankel engine in post-WWII Germany. The concept of the engine is very difficult to describe with words, and even when you see pictures, it is difficult to grasp the details. Wankel himself described the rotary engine as “part turbine and part reciprocating engine.”
I suggest that you look at a video on YouTube to get an idea of the operation of the rotary or Wankel engine. I recommend this one, but there are several more.
The Wankel engine has the advantages of mechanical simplicity (few moving parts) and light weight. It suffers from poor efficiency and polluting emissions. They are popular for race cars and experimental aircraft because of the high power to weight ratio. Mazda has produced several sporty cars using rotary engines and is currently (2011) scheduled to discontinue production of their latest rotary model, the RX-8.
Q: What is a turbocharger on a car? How does it work?
A: To get more power out of an internal combustion engine, one must burn fuel more quickly. In order to do this, one needs both more fuel to be oxidized and more oxidizer. The turbocharger is an air compressor powered by a turbine in line with the engine exhaust system. The compressor brings air up to a higher pressure so that as much as 50% more air may be introduced to the engine with each cycle at the same volumetric flow rate. The benefits are especially important when operating an engine at high altitude.
Significant technical obstacles have been overcome for the implementation of turbochargers; these include increased pre-ignition (knocking), intake overheating, and boost lag (sluggish response to throttle demand).
A supercharger differs from a turbocharger in that it is powered directly by the engine rather than the exhaust; it does not suffer from boost lag. Sometimes a combination of a supercharger and a turbocharger is used.
Q: What is knocking or pinging in an Otto cycle engine?
A: Knocking or pinging is distinct from pre-ignition (run-on or Dieseling). Knocking occurs when fuel in one or more volumes of the combustion cylinder ignites or detonates abnormally but simultaneously with the main combustion front. It is often accompanied by a clacking or ringing sound, and can cause harm to engine components because of the abnormal forces exerted during knocking.
Causes of knocking are similar to those for Dieseling and can include hot carbon deposits, incorrect timing, bad fuel/air mixture, and poor fuel composition, amongst others.