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Home> Maintaining
your Continental and Lycoming engine
If I put a more powerful engine in my airplane how much faster will it go?
Inputs: original horsepower, airspeed at original horsepower, new horsepower
Horsepower gives you lift and
aerodynamics gives you speed. To illustrate this point lets compute the effect of horsepower changes on airspeed.
Our example airplane has a 180 horsepower engine that pulls the aircraft thru the air at 150 miles per hour. If we put a 200 horsepower engine in the airplane how much faster will it go?
You can compute this yourself if you have a Java capable browser, otherwise the answer is:
155.4 miles per hour. We only gain 3.6% in velocity with a 11% increase in power!
How can you use this information?
I remember a magazine article where they claimed that their aircraft want X amount faster after a port and polish overhaul. Doing the math I figured that they were claiming a 30% increase in horsepower by polishing the last two inches of a four foot long induction system. Obvious rubbish!
Another use is computing how much fuel you can save by reducing power. Lets say our example engine's specific fuel consumption is .6 pounds of fuel per horsepower per hour (found in the engine's operators manual). If we pull back on the throttle 5 horsepower to 175 we only loose 1 mile per hour! But we save 3 pounds of fuel per hour.
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