Awesome Camshaft Article
07-25-2003, 02:22 AM
#1
Honda-Tech Member
Thread Starter
Join Date: Sep 2002
Location: I taint rich, NJ, USA
Posts: 1,446
Likes: 0
Received 0 Likes
on
0 Posts
Awesome Camshaft Article
camshafts
Power Tech: Camshafts
Lift your Performance to New Heights
Text and Photos by Michael Ferrara
Among all the components that make up an engine, the camshaft plays the most significant role in determining the behavior and character of the engine. As for the engine's behavior, most OEM camshafts offer idles that are smooth and polished. A radical aftermarket full-race camshaft may produce an idle that is rough and raw. As for character, one camshaft may regulate an engine to produce massive low-end torque, while a different camshaft in that same engine may soften up the power production at the low end while allowing the engine to pull strong up to redline. Understanding the function, design, and limitations of the camshaft will allow you to maximize your performance experience.
Function of the Camshaft
The four-stroke process that occurs in your car's engine is as follows: intake, compression, power, exhaust. While the crankshaft's position, crankshaft's stroke and rod length ultimately determine where the piston will be in the cylinder at any given degree of rotation, it's the camshaft that determines the position of the intake and exhaust valve during all four strokes. An engine's camshaft(s) is/are responsible for the valve timing in the engine. Proper valve timing is critical for any four-stroke automotive engine to operate at maximum efficiency. When the valves open, how high the valves open (lift), and for how long they stay open (duration) all determine the performance characteristics of the engine. In the performance symphony, the camshaft is the conductor of valve events. It orchestrates which instruments play (intake or exhaust valves), when they play (opening and closing events) and how loud they play (valve lift). Whereas OEM conductors (cams) offer a classical sound, aftermarket cams can really make your engine rock.
The Band of Power
As mentioned earlier, the camshaft will determine an engine's character. The engine's character in terms of power
production is often termed the "powerband." Where does the engine begin to make power? Where does the engine begin to fall off in power production? Is the power delivery flat and consistent or aggressive and peaky? These questions are answered in the description and understanding of the engine's powerband. Some powerbands are narrow, while other are deemed broad. Some are peaky, some are flat. An engine that makes appreciable power from only 6000 to 8000 rpm (a range of 2000 rpm) would be considered to have a narrow powerband. A comparable-sized engine that makes power from 3000 to 7000rpm (a range of 4000 rpm) might be considered to have a broad powerband. More so than any other internal components of the engine, the camshaft and its complimentary valvetrain components will establish the powerband of the engine.
The Ideal Cam
So how do you get the perfect cam? The cam that has tremendous low-end torque, a 10,000 rpm redline, an idle like mom's car and a powerband from idle to redline doesn't exist. Fortunately, an aftermarket performance camshaft that optimizes the rest of your performance combination to provide the performance that you desire probably does exist. Dollar for dollar there is a good chance that aftermarket cam(s) may be the best performance investment that you make.
Lift, Lobes and Symmetry
For every action, there is always a reaction. From a performance standpoint, the faster a valve opens and reaches full-lift, the better. Why? Horsepower is directly related to how much air and fuel can be stuffed into the cylinder. Air and fuel can't get into the cylinder unless the valves are open. Camshafts that quickly open the valves are said to have an aggressive lobe profile. Unfortunately, the laws of physics govern the maximum amount of possible valve acceleration or "aggressiveness." If the camshaft profile tries to accelerate the valve too fast, excessive wear or valvetrain problems can occur. When returning a valve to its seat, a camshaft once again cannot do this too fast or the valve slams into the valve seat (sometimes valves even bounce off the seat). Most modern cam designs optimize valve acceleration rates by designing camshafts with asymmetric lobes. This style of lobe lifts the valve faster than it lowers the valve. Quite simply, asymmetric lobe designs can be utilized to maximize the performance available while increasing the durability of the valvetrain.
Types of Engines
There are two basic styles of piston engines in production today, the overhead-valve engine (OHV) and the overhead-cam engine (OHC). Overhead valve engines rely on valve lifters, pushrods, rocker arms and a camshaft which rests in the engine's cylinder block. Examples of OHV engines include most of the domestic V8 and V6 engines manufactured over the last 50 years.
Knowing the Specs
Since we have already explored the basics of camshafts, we will now attempt to unlock the mysteries surrounding camshaft specifications. Since the camshaft(s) influence when an engine starts making power, when it stops producing power, maximum power output, fuel economy, idle quality, and engine efficiency, it is important to understand camshaft specifications. With this basic understanding, you will be better able to select the camshaft(s) that will keep you ahead of the competition.
Lift and Duration
The basic function of a camshaft is to open and close the engine's valves. On many applications, a single camshaft controls the opening and closing events of all the valves in an engine. Other applications may implement as many as four camshafts to control the valve events. Regardless of the number of cams, the rules that apply for single camshaft engines also apply to those with multiple camshafts. The most well-known camshaft specifications are lift and duration. Most manufacturers give specifications for lift at the valve, instead of at the camshaft. On some applications that don't use a rocker assembly these two lifts may be the same. If you need to convert from lift at the camshaft lobe to lift at the valve, use the following equation.
Valve Lift = Lobe Lift x Cam Follower Ratio
Lift
Lift is nothing more than a measurement of the maximum distance the valve is opened. Assuming all other specifications remain the same, choosing a camshaft with more lift will increase the flow of air and fuel into an engine and the flow of exhaust out of an engine. As a result, more power can be made. In many cases, camshafts that have increased lifts over stock specifications and near stock duration will offer increased performance without making measurable sacrifices in "driveability". Everything has a limit and cylinder heads will generally reach a point where airflow no longer increases with an increase in valve lift. Before you order that mega-lift cam, please consider the following: when valve lift is dramatically increased, the possibility of valve to-piston contact, coil bind at the valve spring and valvetrain interference is also increased. To avoid bent valves, broken retainers and thin wallets, always use the necessary complimentary valvetrain components and check valve-to-piston clearance when recommended by the camshaft manufacturer.
Duration
Along with how high a valve is opened, how long it remains open also influences the performance of an engine. If you are trying to fill a glass at the sink, how much you open the faucet or valve, as well as how long you have that valve open will determine how much water fills the glass. How long you keep the faucet turned on is a simple measure of duration. The duration specification of a camshaft is measured in crankshaft degrees of which there are 720 in one complete four-stroke cycle. However, the problem with camshaft duration figures is that different manufacturers measure this duration at different valve lifts. The Brand-A manufacturer might measure duration as soon as the valve is lifted .015 of an inch off its seat until it returns to the same lift, while the Brand-C manufacturer might not start measuring until the valve is .050 inch off the seat. The result is that if we had both companies measure the same camshaft, Company-A might measure 306 degrees of duration (measuring at a minimum lift of .015"), while Company-C would measure 256 degrees of duration (measuring at .050"). In essence we have two completely different numbers for the same camshaft. Luckily, most camshaft manufacturers now provide duration figures at either a minimum lift of 1mm (Japan's industry standard measure) or a minimum lift of .050" (the traditional U.S. hot rod standard). When duration comparisons between two camshafts are being made, only compare the figures if the measurements have been taken at the same minimum lift.
Duration and Power
More lift translates into more power and torque across the powerband for most cases. In general, increased duration will shift the torque and horsepower peak to a higher rpm. All other specifications being the same, increasing duration yields more top-end and mid-range power while sacrificing low-end torque. As a result of the shifting of the powerband upstairs to higher rpms, a longer duration camshaft, when used with the appropriate valvetrain components, will also raise an engine's redline. One rule of thumb is that every 10 degree increase in duration (measured at 1mm or .050") will shift the torque peak and redline up by 500 rpm.
A Closer Look-Valve Timing
Believe it or not the explanation of lift and duration has been somewhat simplified. If we only look at lift and duration, we only know how high a valve is lifted and for how long. What lift and duration fail to tell us is when the valves are opened and closed. If we know that the complete four-stroke cycle contains 720 degrees of crankshaft rotation and the intake stroke (when the piston moves down the cylinder when the intake valve is open) makes up one-fourth of the cycle, we easily deduce that the theoretical duration of the intake cycle is 180 degrees (one-fourth of 720). If we could instantaneously open the intake valve at TDC (the beginning of the intake stroke) and have the intake charge immediately start flowing into the cylinder until the piston was at BDC (the end of the intake stroke, 180 degrees later) where the intake valve would instantaneously slam shut, we might have an engine that would run well with only 180 degrees of intake duration.
Early Intake Valve Opening
In practice, there are many advantages to opening the intake valve early and closing it late. By initiating the opening the intake valve early, the intake valve has time to get to a lift where appreciable flow will begin. On a well-designed cylinder head teamed with a free-flowing exhaust, the pressure in the cylinder when the valve is opened early may be lower than atmospheric, so the intake charge actually gets sucked in (in practice, the exhaust valve is still open when the intake valve begins to open). The benefits of early intake valve opening are very rpm dependent. At low engine speeds, extremely early intake valve opening may cause exhaust gases to be sucked into the intake manifold causing erratic idle and other problems. At higher engine speeds, this same amount of early intake valve opening will have no adverse effects since the intake manifold is not operating under a vacuum condition.
Late Intake Valve Closing
Now that we understand why we need to open the intake valve early, let's take a close look at the closing of the intake valve. The reason we leave the intake valve open past Bottom Dead Center (BDC) is inertia: objects at rest tend to stay at rest, objects (or a mass of air in the case) in motion tend to stay in motion. Since we have an intake charge in motion we can experience additional filling of the cylinder while the piston dwells (or remains in place) at the bottom of its stroke at BDC. On engine with high rod length-to-stroke ratios, the piston may dwell around BDC for 20 degrees of crank rotation before the piston starts to move up the cylinder. During this time the flowing intake charge continues to fill the cylinder. If the intake valve closes too late, the piston may pump some of the intake charge out of the cylinder through the intake valve and back into the intake manifold. This reverse flow is obviously undesirable. As you may have guessed, the optimum closing of the intake valve is also very rpm dependent.
Exhaust Valve Open Early
Since we have a good understanding of the intake side out the equation let's take a look at the exhaust side. The major difference in dealing with the exhaust side is that the average pressure in the cylinder is probably more than six times the average pressure during the intake cycle. This makes the task of releasing the exhaust gases easier than trying to get the intake charge into the cylinder. During the power stroke, the majority of horsepower is generated during the first 90 degrees or first half of this 180 degree cycle. This being the case, opening the exhaust valve early has little effect on killing power. In fact, power is usually increased since the residual pressure is released from the cylinder so the piston doesn't work as hard to push the remaining gases out when it begins its upward movement on the exhaust stroke.
Exhaust Valve Closing Late
Keeping the exhaust valve open after TDC can also have benefits. If the exhaust valve is kept open after TDC, the intake valve will also be open at the same time. When both intake and exhaust valves are open at the same time, it is termed valve overlap. The ideal amount of overlap depends on rpm. Higher rpms tolerate more overlap and the intake charge can be drawn into the cylinder due to the draft caused by the exhaust gases leaving the cylinder. When overlap gets excessive, exhaust gas can make its way into the intake manifold, diluting the intake charge. A diluted intake charge limits power production, so a careful balance must always be struck.
The Bottom Line
A camshaft may look simple, but its job is no easy task. Understanding the function, design and limitations of aftermarket cams will allow you to make educated decisions about getting the right cam(s) for your car. Remember to rely on the experts. The wealth of knowledge that the major cam companies possess is incredible. While it is great to have an understanding of cams, there are enough self-proclaimed engineers in the world. Nine times out of ten, the specialist at the cam company will know more than you (that's his or her job). The value of your performance education is identifying the one out of ten instances that you may encounter. As always, remember to consider that the camshaft(s) are just one element of the performance combination. All of the parts in the combination need to work together to produce the maximum in power and reliability. Camshafts will only do there job effectively when complimented with the correct valvetrain component. Installation of the camshaft and complimentary valvetrain components must also be done correctly. Failure to do so will result in a loss of performance and the potential for component damage.
VTEC: Powerband Optimizer
Many bad explanations of the VTEC advantage have been given in the past. The advantage is simple: VTEC allows the engine to perform as if the cams were switched to a different profile at a set rpm. The low profile can optimize idle, meet emissions and provide good bottom-end torque. The high-profile lifts the valves higher and opens the valves longer to improve power at higher rpms.
VTEC does not allow for higher peak power to be made. If a set of non-VTEC cams were ground to match the VTEC high-lobe profile the same power would be made. However, the Non-VTEC cam would not have near the performance of the VTEC cam at lower rpms. Driveability, fuel efficiency and idle quality would all suffer.
The end performance result of VTEC technology is an engine that has an incredible broad powerband.
The site had a duplicate image of the first diagram instead of a diagram for the exhaust. Hopefully the proper image is up soon
-Jalal
Modified by MJ23FE at 2:38 PM 7/25/2003
Power Tech: Camshafts
Lift your Performance to New Heights
Text and Photos by Michael Ferrara
Among all the components that make up an engine, the camshaft plays the most significant role in determining the behavior and character of the engine. As for the engine's behavior, most OEM camshafts offer idles that are smooth and polished. A radical aftermarket full-race camshaft may produce an idle that is rough and raw. As for character, one camshaft may regulate an engine to produce massive low-end torque, while a different camshaft in that same engine may soften up the power production at the low end while allowing the engine to pull strong up to redline. Understanding the function, design, and limitations of the camshaft will allow you to maximize your performance experience.
Function of the Camshaft
The four-stroke process that occurs in your car's engine is as follows: intake, compression, power, exhaust. While the crankshaft's position, crankshaft's stroke and rod length ultimately determine where the piston will be in the cylinder at any given degree of rotation, it's the camshaft that determines the position of the intake and exhaust valve during all four strokes. An engine's camshaft(s) is/are responsible for the valve timing in the engine. Proper valve timing is critical for any four-stroke automotive engine to operate at maximum efficiency. When the valves open, how high the valves open (lift), and for how long they stay open (duration) all determine the performance characteristics of the engine. In the performance symphony, the camshaft is the conductor of valve events. It orchestrates which instruments play (intake or exhaust valves), when they play (opening and closing events) and how loud they play (valve lift). Whereas OEM conductors (cams) offer a classical sound, aftermarket cams can really make your engine rock.
The Band of Power
As mentioned earlier, the camshaft will determine an engine's character. The engine's character in terms of power
production is often termed the "powerband." Where does the engine begin to make power? Where does the engine begin to fall off in power production? Is the power delivery flat and consistent or aggressive and peaky? These questions are answered in the description and understanding of the engine's powerband. Some powerbands are narrow, while other are deemed broad. Some are peaky, some are flat. An engine that makes appreciable power from only 6000 to 8000 rpm (a range of 2000 rpm) would be considered to have a narrow powerband. A comparable-sized engine that makes power from 3000 to 7000rpm (a range of 4000 rpm) might be considered to have a broad powerband. More so than any other internal components of the engine, the camshaft and its complimentary valvetrain components will establish the powerband of the engine.
The Ideal Cam
So how do you get the perfect cam? The cam that has tremendous low-end torque, a 10,000 rpm redline, an idle like mom's car and a powerband from idle to redline doesn't exist. Fortunately, an aftermarket performance camshaft that optimizes the rest of your performance combination to provide the performance that you desire probably does exist. Dollar for dollar there is a good chance that aftermarket cam(s) may be the best performance investment that you make.
Lift, Lobes and Symmetry
For every action, there is always a reaction. From a performance standpoint, the faster a valve opens and reaches full-lift, the better. Why? Horsepower is directly related to how much air and fuel can be stuffed into the cylinder. Air and fuel can't get into the cylinder unless the valves are open. Camshafts that quickly open the valves are said to have an aggressive lobe profile. Unfortunately, the laws of physics govern the maximum amount of possible valve acceleration or "aggressiveness." If the camshaft profile tries to accelerate the valve too fast, excessive wear or valvetrain problems can occur. When returning a valve to its seat, a camshaft once again cannot do this too fast or the valve slams into the valve seat (sometimes valves even bounce off the seat). Most modern cam designs optimize valve acceleration rates by designing camshafts with asymmetric lobes. This style of lobe lifts the valve faster than it lowers the valve. Quite simply, asymmetric lobe designs can be utilized to maximize the performance available while increasing the durability of the valvetrain.
Types of Engines
There are two basic styles of piston engines in production today, the overhead-valve engine (OHV) and the overhead-cam engine (OHC). Overhead valve engines rely on valve lifters, pushrods, rocker arms and a camshaft which rests in the engine's cylinder block. Examples of OHV engines include most of the domestic V8 and V6 engines manufactured over the last 50 years.
Knowing the Specs
Since we have already explored the basics of camshafts, we will now attempt to unlock the mysteries surrounding camshaft specifications. Since the camshaft(s) influence when an engine starts making power, when it stops producing power, maximum power output, fuel economy, idle quality, and engine efficiency, it is important to understand camshaft specifications. With this basic understanding, you will be better able to select the camshaft(s) that will keep you ahead of the competition.
Lift and Duration
The basic function of a camshaft is to open and close the engine's valves. On many applications, a single camshaft controls the opening and closing events of all the valves in an engine. Other applications may implement as many as four camshafts to control the valve events. Regardless of the number of cams, the rules that apply for single camshaft engines also apply to those with multiple camshafts. The most well-known camshaft specifications are lift and duration. Most manufacturers give specifications for lift at the valve, instead of at the camshaft. On some applications that don't use a rocker assembly these two lifts may be the same. If you need to convert from lift at the camshaft lobe to lift at the valve, use the following equation.
Valve Lift = Lobe Lift x Cam Follower Ratio
Lift
Lift is nothing more than a measurement of the maximum distance the valve is opened. Assuming all other specifications remain the same, choosing a camshaft with more lift will increase the flow of air and fuel into an engine and the flow of exhaust out of an engine. As a result, more power can be made. In many cases, camshafts that have increased lifts over stock specifications and near stock duration will offer increased performance without making measurable sacrifices in "driveability". Everything has a limit and cylinder heads will generally reach a point where airflow no longer increases with an increase in valve lift. Before you order that mega-lift cam, please consider the following: when valve lift is dramatically increased, the possibility of valve to-piston contact, coil bind at the valve spring and valvetrain interference is also increased. To avoid bent valves, broken retainers and thin wallets, always use the necessary complimentary valvetrain components and check valve-to-piston clearance when recommended by the camshaft manufacturer.
Duration
Along with how high a valve is opened, how long it remains open also influences the performance of an engine. If you are trying to fill a glass at the sink, how much you open the faucet or valve, as well as how long you have that valve open will determine how much water fills the glass. How long you keep the faucet turned on is a simple measure of duration. The duration specification of a camshaft is measured in crankshaft degrees of which there are 720 in one complete four-stroke cycle. However, the problem with camshaft duration figures is that different manufacturers measure this duration at different valve lifts. The Brand-A manufacturer might measure duration as soon as the valve is lifted .015 of an inch off its seat until it returns to the same lift, while the Brand-C manufacturer might not start measuring until the valve is .050 inch off the seat. The result is that if we had both companies measure the same camshaft, Company-A might measure 306 degrees of duration (measuring at a minimum lift of .015"), while Company-C would measure 256 degrees of duration (measuring at .050"). In essence we have two completely different numbers for the same camshaft. Luckily, most camshaft manufacturers now provide duration figures at either a minimum lift of 1mm (Japan's industry standard measure) or a minimum lift of .050" (the traditional U.S. hot rod standard). When duration comparisons between two camshafts are being made, only compare the figures if the measurements have been taken at the same minimum lift.
Duration and Power
More lift translates into more power and torque across the powerband for most cases. In general, increased duration will shift the torque and horsepower peak to a higher rpm. All other specifications being the same, increasing duration yields more top-end and mid-range power while sacrificing low-end torque. As a result of the shifting of the powerband upstairs to higher rpms, a longer duration camshaft, when used with the appropriate valvetrain components, will also raise an engine's redline. One rule of thumb is that every 10 degree increase in duration (measured at 1mm or .050") will shift the torque peak and redline up by 500 rpm.
A Closer Look-Valve Timing
Believe it or not the explanation of lift and duration has been somewhat simplified. If we only look at lift and duration, we only know how high a valve is lifted and for how long. What lift and duration fail to tell us is when the valves are opened and closed. If we know that the complete four-stroke cycle contains 720 degrees of crankshaft rotation and the intake stroke (when the piston moves down the cylinder when the intake valve is open) makes up one-fourth of the cycle, we easily deduce that the theoretical duration of the intake cycle is 180 degrees (one-fourth of 720). If we could instantaneously open the intake valve at TDC (the beginning of the intake stroke) and have the intake charge immediately start flowing into the cylinder until the piston was at BDC (the end of the intake stroke, 180 degrees later) where the intake valve would instantaneously slam shut, we might have an engine that would run well with only 180 degrees of intake duration.
Early Intake Valve Opening
In practice, there are many advantages to opening the intake valve early and closing it late. By initiating the opening the intake valve early, the intake valve has time to get to a lift where appreciable flow will begin. On a well-designed cylinder head teamed with a free-flowing exhaust, the pressure in the cylinder when the valve is opened early may be lower than atmospheric, so the intake charge actually gets sucked in (in practice, the exhaust valve is still open when the intake valve begins to open). The benefits of early intake valve opening are very rpm dependent. At low engine speeds, extremely early intake valve opening may cause exhaust gases to be sucked into the intake manifold causing erratic idle and other problems. At higher engine speeds, this same amount of early intake valve opening will have no adverse effects since the intake manifold is not operating under a vacuum condition.
Late Intake Valve Closing
Now that we understand why we need to open the intake valve early, let's take a close look at the closing of the intake valve. The reason we leave the intake valve open past Bottom Dead Center (BDC) is inertia: objects at rest tend to stay at rest, objects (or a mass of air in the case) in motion tend to stay in motion. Since we have an intake charge in motion we can experience additional filling of the cylinder while the piston dwells (or remains in place) at the bottom of its stroke at BDC. On engine with high rod length-to-stroke ratios, the piston may dwell around BDC for 20 degrees of crank rotation before the piston starts to move up the cylinder. During this time the flowing intake charge continues to fill the cylinder. If the intake valve closes too late, the piston may pump some of the intake charge out of the cylinder through the intake valve and back into the intake manifold. This reverse flow is obviously undesirable. As you may have guessed, the optimum closing of the intake valve is also very rpm dependent.
Exhaust Valve Open Early
Since we have a good understanding of the intake side out the equation let's take a look at the exhaust side. The major difference in dealing with the exhaust side is that the average pressure in the cylinder is probably more than six times the average pressure during the intake cycle. This makes the task of releasing the exhaust gases easier than trying to get the intake charge into the cylinder. During the power stroke, the majority of horsepower is generated during the first 90 degrees or first half of this 180 degree cycle. This being the case, opening the exhaust valve early has little effect on killing power. In fact, power is usually increased since the residual pressure is released from the cylinder so the piston doesn't work as hard to push the remaining gases out when it begins its upward movement on the exhaust stroke.
Exhaust Valve Closing Late
Keeping the exhaust valve open after TDC can also have benefits. If the exhaust valve is kept open after TDC, the intake valve will also be open at the same time. When both intake and exhaust valves are open at the same time, it is termed valve overlap. The ideal amount of overlap depends on rpm. Higher rpms tolerate more overlap and the intake charge can be drawn into the cylinder due to the draft caused by the exhaust gases leaving the cylinder. When overlap gets excessive, exhaust gas can make its way into the intake manifold, diluting the intake charge. A diluted intake charge limits power production, so a careful balance must always be struck.
The Bottom Line
A camshaft may look simple, but its job is no easy task. Understanding the function, design and limitations of aftermarket cams will allow you to make educated decisions about getting the right cam(s) for your car. Remember to rely on the experts. The wealth of knowledge that the major cam companies possess is incredible. While it is great to have an understanding of cams, there are enough self-proclaimed engineers in the world. Nine times out of ten, the specialist at the cam company will know more than you (that's his or her job). The value of your performance education is identifying the one out of ten instances that you may encounter. As always, remember to consider that the camshaft(s) are just one element of the performance combination. All of the parts in the combination need to work together to produce the maximum in power and reliability. Camshafts will only do there job effectively when complimented with the correct valvetrain component. Installation of the camshaft and complimentary valvetrain components must also be done correctly. Failure to do so will result in a loss of performance and the potential for component damage.
VTEC: Powerband Optimizer
Many bad explanations of the VTEC advantage have been given in the past. The advantage is simple: VTEC allows the engine to perform as if the cams were switched to a different profile at a set rpm. The low profile can optimize idle, meet emissions and provide good bottom-end torque. The high-profile lifts the valves higher and opens the valves longer to improve power at higher rpms.
VTEC does not allow for higher peak power to be made. If a set of non-VTEC cams were ground to match the VTEC high-lobe profile the same power would be made. However, the Non-VTEC cam would not have near the performance of the VTEC cam at lower rpms. Driveability, fuel efficiency and idle quality would all suffer.
The end performance result of VTEC technology is an engine that has an incredible broad powerband.
The site had a duplicate image of the first diagram instead of a diagram for the exhaust. Hopefully the proper image is up soon
-Jalal
Modified by MJ23FE at 2:38 PM 7/25/2003
07-25-2003, 02:23 AM
#2
Honda-Tech Member
Thread Starter
Join Date: Sep 2002
Location: I taint rich, NJ, USA
Posts: 1,446
Likes: 0
Received 0 Likes
on
0 Posts
Re: Awesome Camshaft Article (MJ23FE)
Truth Versus Fiction The Rules of Thumb Meet the Dyno
Truth Versus Fiction
Rules of Thumb Meet the Dyno
Bench Racing: Rules of Thumb
"Every additional point of compression ratio will deliver four-percent more power." "You need to burn a half-of-pound of gasoline every hour to make one horsepower." "An 11-degree drop in air temperature will deliver a one-percent increase in power." "Each additional psi of boost pressure will deliver a five to seven percent increase in power." "Ten extra degrees of cam duration will raise the peak power point by 500 rpm." Maybe you have heard some of these "rules of thumb", maybe you have not heard these yet. When a group of enthusiasts start talking about going fast and what it is going to take to go faster, chances are the rules of thumb will surface in the discussion.
The Value of Thumbs
Thumbs allow our species to function at a level of dexterity not found anywhere else in nature. Rules of thumb while not always 100-percent accurate, often show or explain a performance trend. With regards to the aforementioned rules of thumb, higher compression ratios, lower intake temperatures and higher boost pressures generate more power; it takes more fuel to make more power and longer-duration cams make power at higher rpms. These are all verifiable trends.
The Dyno Results
In this test, we compared a set of Skunk Stage II camshafts to a pair of Civic Type-R cams fitted in a B18C5 Type-R Integra engine. According to the rule of thumb regarding cam duration, the longer duration Skunk Stage II cams should have produced peak power at about 1000 rpm above the Civic Type-R cams (as the duration of the larger Skung Stage II cams is about 20 to 25 degrees more than the Type-R cams). In practice, the Type-R cams peaked at 7500rpm while the Skunk Stage II cams peaked at 8400rpm. While not exact, this rule of thumb proved to be a pretty good guess.
Click Here for cam specs on the Skunk 2 Stage II cams and OEM Civic Type R cams.
Complete Honda B-Series VTEC Cam Specs for those who are interested.
-Jalal
Truth Versus Fiction
Rules of Thumb Meet the Dyno
Bench Racing: Rules of Thumb
"Every additional point of compression ratio will deliver four-percent more power." "You need to burn a half-of-pound of gasoline every hour to make one horsepower." "An 11-degree drop in air temperature will deliver a one-percent increase in power." "Each additional psi of boost pressure will deliver a five to seven percent increase in power." "Ten extra degrees of cam duration will raise the peak power point by 500 rpm." Maybe you have heard some of these "rules of thumb", maybe you have not heard these yet. When a group of enthusiasts start talking about going fast and what it is going to take to go faster, chances are the rules of thumb will surface in the discussion.
The Value of Thumbs
Thumbs allow our species to function at a level of dexterity not found anywhere else in nature. Rules of thumb while not always 100-percent accurate, often show or explain a performance trend. With regards to the aforementioned rules of thumb, higher compression ratios, lower intake temperatures and higher boost pressures generate more power; it takes more fuel to make more power and longer-duration cams make power at higher rpms. These are all verifiable trends.
The Dyno Results
In this test, we compared a set of Skunk Stage II camshafts to a pair of Civic Type-R cams fitted in a B18C5 Type-R Integra engine. According to the rule of thumb regarding cam duration, the longer duration Skunk Stage II cams should have produced peak power at about 1000 rpm above the Civic Type-R cams (as the duration of the larger Skung Stage II cams is about 20 to 25 degrees more than the Type-R cams). In practice, the Type-R cams peaked at 7500rpm while the Skunk Stage II cams peaked at 8400rpm. While not exact, this rule of thumb proved to be a pretty good guess.
Click Here for cam specs on the Skunk 2 Stage II cams and OEM Civic Type R cams.
Complete Honda B-Series VTEC Cam Specs for those who are interested.
-Jalal
Trending Topics
07-25-2003, 10:40 AM
#9
Honda-Tech Member
Thread Starter
Join Date: Sep 2002
Location: I taint rich, NJ, USA
Posts: 1,446
Likes: 0
Received 0 Likes
on
0 Posts
Re: Awesome Camshaft Article (EK-TUNED)
I couldn't resist i had to post it since its alot of useful information for newbs and people you want to review to look at and read so that they can reassure any questions of misunderstandings they had. I myself am still a newb when it comes to the actual dynamics of the engine, so i thought i would lend a helping hand to everyone else out there who is in the same boat as i.
Maybe this can be made a sticky or something.
-Jalal
Maybe this can be made a sticky or something.
-Jalal
07-30-2003, 11:20 AM
#14
Honda-Tech Member
Join Date: Dec 2001
Location: Huntington Beach, CA, USA
Posts: 803
Likes: 0
Received 0 Likes
on
0 Posts
Re: (AzN_Flava)
ok question: after having read those articles, why do they make different cams for different applications? more specifically, why make specialized cams for forced induction? it seems from those links that the supercharger/turbo cams are less aggressive, having shorter duration and smaller lift than the all-motor ones. i guess that would make sense, because maybe you can boost higher because the motor will ingest less air... but what if you were to use aggressive N/A cams, and just boost less? would it not have the same effect? (assuming in both cases the motor burns the same volume of air/fuel, of course.)
07-30-2003, 11:49 AM
#15
Re: (carsaregood)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by carsaregood »</TD></TR><TR><TD CLASS="quote">ok question: after having read those articles, why do they make different cams for different applications? more specifically, why make specialized cams for forced induction? it seems from those links that the supercharger/turbo cams are less aggressive, having shorter duration and smaller lift than the all-motor ones. i guess that would make sense, because maybe you can boost higher because the motor will ingest less air... but what if you were to use aggressive N/A cams, and just boost less? would it not have the same effect? (assuming in both cases the motor burns the same volume of air/fuel, of course.)</TD></TR></TABLE>
It has to do with the in/out dynamics. Typically turbo apps have more pressure on the exhaust manifold side than the intake side. You'll need the cam timing to not let the flow go backwards. Trust me. We've had this happen to us.
It has to do with the in/out dynamics. Typically turbo apps have more pressure on the exhaust manifold side than the intake side. You'll need the cam timing to not let the flow go backwards. Trust me. We've had this happen to us.
07-30-2003, 11:59 AM
#16
Join Date: Sep 2002
Location: Orange County, CALIFORNIACATIONATED, USA
Posts: 1,769
Likes: 0
Received 0 Likes
on
0 Posts
Re: (Rocket)
yeah but superchaged motors dont mind big cams..because you dont have to worry about a turbine holding back pressure..but it could push fresh fuel/air out the exhaust which would kill you O2 sensor and cat really fast..... 
07-30-2003, 01:46 PM
#17
Honda-Tech Member
Join Date: Dec 2001
Location: Huntington Beach, CA, USA
Posts: 803
Likes: 0
Received 0 Likes
on
0 Posts
Re: (Rocket)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rocket »</TD></TR><TR><TD CLASS="quote">
It has to do with the in/out dynamics. Typically turbo apps have more pressure on the exhaust manifold side than the intake side. You'll need the cam timing to not let the flow go backwards. Trust me. We've had this happen to us.</TD></TR></TABLE>
ahhhhhh, of course! thanks!
It has to do with the in/out dynamics. Typically turbo apps have more pressure on the exhaust manifold side than the intake side. You'll need the cam timing to not let the flow go backwards. Trust me. We've had this happen to us.</TD></TR></TABLE>
ahhhhhh, of course! thanks!
08-02-2010, 06:30 PM
#19
Trial User
Join Date: Aug 2010
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
Re: Awesome Camshaft Article
My goal is to find a quality aftermarket replacement camshaft for my 2003 Element. I have the scoring on 2 lobes of the exhaust cam. Any help out there? I don't want Honda due to cost. Nevermind the fact the stock one is obviously faulty. I just want a quality piece to swap it out and keep it moving forward. Any direction would be appreciated.
08-02-2010, 06:43 PM
#20
MiG-21 superfan
Join Date: Mar 2001
Location: near the ocean, Moderator City, NJ
Posts: 8,628
Likes: 0
Received 3 Likes
on
3 Posts
Re: Awesome Camshaft Article
My goal is to find a quality aftermarket replacement camshaft for my 2003 Element. I have the scoring on 2 lobes of the exhaust cam. Any help out there? I don't want Honda due to cost. Nevermind the fact the stock one is obviously faulty. I just want a quality piece to swap it out and keep it moving forward. Any direction would be appreciated.
pics of scoring?
your best bet is to search for cam options for the k24a4 in the '03-'05 accord, if there are any. there might be some other chassis that had that engine but i have no idea which.
here is the 03+ accord forum where you can search - https://honda-tech.com/forums/honda-accord-crosstour-2003-2012-118/
Thread
Thread Starter
Forum
Replies
Last Post
