If I rev my engine past its rated horsepower peak, why doesn it produce more power?
Your peak power is exactly that. Why does torque drop off after a certain amount of revs. Basically it all has to do with engine efficiency. As the engine speeds up, the duration of each cycle gets shorter. This means less time in a cycle. Since air is a compressible fluid, it takes time to fill a gap or evacuate a high pressure area. As the engine speeds up, there is less time for the cylinder to fill with fresh air and expel exhaust gases. In simple terms, the engine’s efficiency drops as revs increase. Once you hit your peak power range, power will slowly drop off as its efficiency drops away. The other big factor in engine power and torque profiles is the camshafts. Camshafts are a compromise – unless they are adjustable like the newer variable valve timing or VTEC, they are designed to give maximum economy and performance in a certain rev range. They are not efficient outside of those conditions. Most passenger cars are designed for efficiency, and midrange power. Racing cars have
It depends on the design of your engine. It is likely a matter of airflow. If you think about it, your car’s (gas) engine has to suck all its air through a hole in a throttle body. Even with complete vacuum in your intake manifold, there is only so much air that can be pushed through that (relatively) small hole. Likewise the hole between the intake manifold and the cylinder. When the air would have to be moving near the speed of sound to feed an engine moving fast enough, there are substantial losses. Most vehicle gas engines advance the spark earlier and earlier before the top of the compression stroke as RPM goes up so the peak power from the heat of the gas burning is pushing on the piston at the right place in the power stroke. This also means it may start pushing down on the piston before it gets all the way up the compression stroke, reducing power. Another limit of the speed at which the gas burns: at really high rpm (over 12000 rpm perhaps), the gas may not have finished burni
First off, if you rev the engine to 9000 RPM, you’ll probably kill the engine, possibly explosively. At a certain point, the engine can’t draw in enough air to burn more fuel, resulting in a drop in torque at higher RPM. Remember, power is a product of Torque and RPM, calculated as: HP = ( Ft_lbs * RPM ) / 5252 There is an area on the power curve where the RPM part of the equation raises HP faster than the declining Torque decreases HP. However, there is a point where the torque drops faster than the RPM rises, resulting in a drop in HP. EDIT – The math is a little hairy, but it all has to do with the engine’s inability to breathe at high RPM. The intake system has various restrictions that only allow it to take in a certain amount of airflow. If you attempt to draw in more air than your intake tract will take, torque will go drop quickly and horsepower will suffer. “In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially
