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Oracle · 01-27-2009, 06:30 PM

OHC engines have the ability to use multiple valves. this gives greater high rpm flow velocity, meaning it can cram more air into the cylinder at high rpms, meaning similar HP with less displacement. also, a OHC has less rotating mass than an OHV motor so it can rev higher and faster. because of these traits the technology was conceived for racing applications where displacement was implimented to limit performance. OHC engines allowed engineers to squeeze more out of the limits that were imposed. the reason many manufacturers use this is because they have racing teams that they sponser, and already get a good deal of R&D done on the track. also the ability to make decent hp at smaller displacement means the engines are generally smaller resulting in less parasitic losses that become apparent at times where the vehicle idles often, like at city stoplights.

OHV engines have a trend of 2 valves per cylinder, and those two valves are very big. this large size alows high flow volume, meaning it can cram more air into a cylinder at low RPM. this gives the motor a greater amount of tourque in a range where fuel has time to burn, at low rpms. this is superior for applications which require that extra force down low. OHV motors also have greater rotating mass but less overall mass meaning they are lighter. an OHV engine also has a trend of being large displacement. this large displacement allows for more air in the cylinders at any rpm, meaning once again it has more force at low RPMs. this combination makes this type of motor ideal for providing low end power to move a lot of mass such as towing or heavy vehicles. the reason we see these in corvettes and ford GTs is because of the tradition way back when, sticking the largest truck motor they had into a lightweight sports car. the amount of torque is what made the cars so successful. not the power. the reason a modern OHV engine is so powerful is because of advancements in valve design that increases flow velocity. however these will still find it difficult to produce as much hp as an OHC engine. that is why you will see professional racing series producing 600hp out of a 5.0L NA OHV engine (Chevy Aurora engine out of a V8 supercar) while producing 780hp out of a 2.4L NA OHC engine (F1 car motor). on the plus side of all that torque from a OHV motor it can cruise the highway all day content at 1500 RPMs, which is where its fuel economy numbers will shine.

01-27-2009, 06:30 PM	#9
Oracle Drives: Ford Focus Join Date: Jun 2008 Location: Phoenix, Az Posts: 71	OHC engines have the ability to use multiple valves. this gives greater high rpm flow velocity, meaning it can cram more air into the cylinder at high rpms, meaning similar HP with less displacement. also, a OHC has less rotating mass than an OHV motor so it can rev higher and faster. because of these traits the technology was conceived for racing applications where displacement was implimented to limit performance. OHC engines allowed engineers to squeeze more out of the limits that were imposed. the reason many manufacturers use this is because they have racing teams that they sponser, and already get a good deal of R&D done on the track. also the ability to make decent hp at smaller displacement means the engines are generally smaller resulting in less parasitic losses that become apparent at times where the vehicle idles often, like at city stoplights. OHV engines have a trend of 2 valves per cylinder, and those two valves are very big. this large size alows high flow volume, meaning it can cram more air into a cylinder at low RPM. this gives the motor a greater amount of tourque in a range where fuel has time to burn, at low rpms. this is superior for applications which require that extra force down low. OHV motors also have greater rotating mass but less overall mass meaning they are lighter. an OHV engine also has a trend of being large displacement. this large displacement allows for more air in the cylinders at any rpm, meaning once again it has more force at low RPMs. this combination makes this type of motor ideal for providing low end power to move a lot of mass such as towing or heavy vehicles. the reason we see these in corvettes and ford GTs is because of the tradition way back when, sticking the largest truck motor they had into a lightweight sports car. the amount of torque is what made the cars so successful. not the power. the reason a modern OHV engine is so powerful is because of advancements in valve design that increases flow velocity. however these will still find it difficult to produce as much hp as an OHC engine. that is why you will see professional racing series producing 600hp out of a 5.0L NA OHV engine (Chevy Aurora engine out of a V8 supercar) while producing 780hp out of a 2.4L NA OHC engine (F1 car motor). on the plus side of all that torque from a OHV motor it can cruise the highway all day content at 1500 RPMs, which is where its fuel economy numbers will shine.