Test your automobile knowledge

[locost7018]

http://auto.howstuffworks.com/engine-quiz.htm?mkcpgn=i600001953&utm_source=taboola&utm_medium=paid&utm_campaign=CarSmartsEngines(RON-desktop)&utm_term=microsoftsolitairecollection&utm_content=How+Much+Do+You+Know+About+Car+Engines%3F+Take+This+Quiz+T

[NVP66S]

Not a very good test, and just plain wrong in some questions. Q2 asks for the 4 engine strokes. There is no correct answer, and their "correct" answer is the one that includes a combustion stroke. Nope. Combustion takes place in far less than a complete stroke, and it usually starts before the end of the compression stroke. Expansion stroke is the correct answer. Q8, says that a turbocharger is "A turbine that compresses the air traveling to the engine" Wrong. Turbines don't compress, they expand. In the case of an automobile turbocharger, the turbine expands the exhaust gas and extracts work, then via shaft power spins the compressor that compresses the induction air. Q12 says "Internal combustion engines are a lot more efficient than external engines..." Baloney. Tell that to the owners of nuke or coal burning utility power plants. They are both Carnot limited. It's true that early steam cars had less efficient engines, but they didn't even bother to close the cycle with a condenser. There was a push in the 1970s to develop Stirling engines for cars, but the major reason they did not was because they cost more to build. High pressure and high temp continuous compared to bang-bang in an Otto or Diesel. The highest efficiency power plants are combined cycle Brayton-Rankine units. Q13: "What's another name for the 4-stroke engine cycle" Their correct answer is "Otto". I think Rudolf Diesel would disagree. Q21 has Diesel cars getting better mileage solely because the fuel has more energy per gallon (true). But completely ignores the lower specific fuel consumption of the engines. Efficiency goes with the root of compression ratio and Diesels are about a factor of 2 higher than Ottos, and there is no throttle plate. At part throttle, pumping losses across a partially closed throttle plate are Vdot * delta P. This is why the same car with a smaller engine gets better mileage than that car with a bigger engine; it spends more time with a wider open throttle. Q23 and 25 are more of the same. (I got tired of typing)

 

Or did you post the link intending to start a discussion on the quality of the 'quiz' ? :lurk:

Edited July 24, 2016 by NVP66S

[locost7018]

Oh yeah, that's it!!!