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Old 08-25-2009, 02:13 PM   #38 (permalink)
mcbrew
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Join Date: Aug 2009
Location: Annapolis, MD
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McBrew's xD - '09 Scion xD
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Quote:
Originally Posted by cottonfox View Post
Sorry for the insultingly new question, but what is the advantage of this over the tach, which shows how hard the engine is working in RPM's?
I know this is old, but it was not fully addressed. Your tach shows how fast the engine is turning, not how hard it is working. Let's say that your engine turns at 2,000 RPM at 50 MPH in 5th gear (for the sake of argument). Going down a hill at 50 MPH, it is turning 2k RPM... on level ground at 50 MPH it is turning 2k RPM... going up a mountain at 50 MPH it is turning 2k RPM. Those three scenarios would see a very different load on the engine, and a very different amount of fuel being used.

A generator is a good example. Most gensets run at a single speed. The more electricity you use, the more load on the engine. The more load, the more fuel is burned. Same speed, different amount of fuel burned.
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