Explain Cams to me...???
#1
12-21-2010, 12:31 PM
Explain Cams to me...???
I was reading the below recent thread on adding Cams to a 2011 HD with a 103 PowerPack. Im picking up a 2011 RGC with Power Pack in late February, and the only mods I know that I'm doing for sure are V&H Monster Rounds exhaust, along with V&H Air Cleaner and Fuel Pack. But its sounding like adding Cams might be a good idea at some point if I want to maximize power output.
https://www.hdforums.com/forum/touri...-question.html
On page 4 of the thread, there was more in depth talk of why to go with a TW-555 Cam over a SE-255 Cam due to fuel issues, especially with a heavy 103 touring bike. There was also talk about proper tuning of the Cams, with one forum member saying to set the 555's somewhere between 10.3-5 cr, and if you get your heads moving 160-5 cfm @ 10", @ .600 lift, which should result in north of 120 ft/lbs.
Can some of you knowledgeable gear heads please povide me with a 101 education on Cams? In other words, what they are, what they do, and what they cost to buy, install, and tune? Also any warranty issues.....
https://www.hdforums.com/forum/touri...-question.html
On page 4 of the thread, there was more in depth talk of why to go with a TW-555 Cam over a SE-255 Cam due to fuel issues, especially with a heavy 103 touring bike. There was also talk about proper tuning of the Cams, with one forum member saying to set the 555's somewhere between 10.3-5 cr, and if you get your heads moving 160-5 cfm @ 10", @ .600 lift, which should result in north of 120 ft/lbs.
Can some of you knowledgeable gear heads please povide me with a 101 education on Cams? In other words, what they are, what they do, and what they cost to buy, install, and tune? Also any warranty issues.....
#2
12-21-2010, 12:59 PM
#3
12-21-2010, 01:04 PM
Cruiser
I was reading the below recent thread on adding Cams to a 2011 HD with a 103 PowerPack. Im picking up a 2011 RGC with Power Pack in late February, and the only mods I know that I'm doing for sure are V&H Monster Rounds exhaust, along with V&H Air Cleaner and Fuel Pack. But its sounding like adding Cams might be a good idea at some point if I want to maximize power output.
https://www.hdforums.com/forum/touri...-question.html
On page 4 of the thread, there was more in depth talk of why to go with a TW-555 Cam over a SE-255 Cam due to fuel issues, especially with a heavy 103 touring bike. There was also talk about proper tuning of the Cams, with one forum member saying to set the 555's somewhere between 10.3-5 cr, and if you get your heads moving 160-5 cfm @ 10", @ .600 lift, which should result in north of 120 ft/lbs.
Can some of you knowledgeable gear heads please povide me with a 101 education on Cams? In other words, what they are, what they do, and what they cost to buy, install, and tune? Also any warranty issues.....
https://www.hdforums.com/forum/touri...-question.html
On page 4 of the thread, there was more in depth talk of why to go with a TW-555 Cam over a SE-255 Cam due to fuel issues, especially with a heavy 103 touring bike. There was also talk about proper tuning of the Cams, with one forum member saying to set the 555's somewhere between 10.3-5 cr, and if you get your heads moving 160-5 cfm @ 10", @ .600 lift, which should result in north of 120 ft/lbs.
Can some of you knowledgeable gear heads please povide me with a 101 education on Cams? In other words, what they are, what they do, and what they cost to buy, install, and tune? Also any warranty issues.....
The info on this site should tell you what you're looking for.
#4
12-21-2010, 01:05 PM
Cam shafts are matched to rotate in conjunction with the crankshaft. They have oval shaped lobes on them that the lifters ride on. The lifters move the push rods which in turn open and close the valves.
The shape of the oval lobe on the cam shaft determines how much the valves open and for how long they stay open. Different cams have different shapes which provide different lift and duration of the valve opening. This determines fuel flow in your engine. Fuel flow is obviously a factor in performance and fuel economy.
Matching the performance level of your cam the the other components is critical.
Cams can be installed at any time since they are accessed through the side of the crankcase but if you're building an engine it makes sense to do it now so everything can be matched to the other parts in your project.
I won't comment on cost but warrantee is a big issue. Not many companies will allow you to modify an engine and still cover it if something goes wrong. Some dealers will mod a new engine and cover it themselves. Ask the dealer about doing this before you pick it up and you might get warrantee coverage, at least through that dealer. Good luck and enjoy your new bike.
The shape of the oval lobe on the cam shaft determines how much the valves open and for how long they stay open. Different cams have different shapes which provide different lift and duration of the valve opening. This determines fuel flow in your engine. Fuel flow is obviously a factor in performance and fuel economy.
Matching the performance level of your cam the the other components is critical.
Cams can be installed at any time since they are accessed through the side of the crankcase but if you're building an engine it makes sense to do it now so everything can be matched to the other parts in your project.
I won't comment on cost but warrantee is a big issue. Not many companies will allow you to modify an engine and still cover it if something goes wrong. Some dealers will mod a new engine and cover it themselves. Ask the dealer about doing this before you pick it up and you might get warrantee coverage, at least through that dealer. Good luck and enjoy your new bike.
#5
12-21-2010, 01:22 PM
A cam swap for a 96 or 103 motor makes a lot of sense, mostly because the stock cams are so bad. The moco has done a bunch of work for us in the last few years. The 06 and later heads flow much bettter than the earlier ones, the increase in displacement adds torque across the entire rpm range, and the closed loop fuel injection system can bring both increased performance and better fuel economy. On the other hand, catalytic converters in the exhaust will rob performance, and the stock cams are designed to reduce emissions, not boost performance.
The good news though, is that a simple cam and header swap will boost performance in a big way, more so than with the earlier 88 motors. The 88's had better cams and no cats, but less displacement and a less effective head design.
Guys get hung up over one cam spec or another. When I was a young hot rodder, we were all about duration. It's human nature to want the biggest bang for your buck, and it's tempting to push a bigger cam in your motor than it needs. Adding too much cam is one of the most effective ways to make a fast bike slow. Generally, too much of anything in a cam will hurt low end power. Your cam manufacturer will have recommendations for the proper compression ratio for any given cam.
I'll try to keep my remarks brief. Your starting mechanical compression and cam selection must be considered as a system. You're starting with a fixed static compression, which is (roughly) the amount of air that your cylinder holds compressed into your combustion chamber. Your static compression starting point along with your cam's design will determine what your dynamic compression will be. Your cam has four main valve timing points: Intake valve open and close, and Exhaust open and close.
Lets start with the piston on it's intake stroke. In a performance cam, your intake valve opens before top dead center, and towards the end of the exhaust stroke. This period of time when both intake and exhaust valves are open is called overlap, and the exiting exhaust gasses help pull in the fresh charge in a siphon type effect. Stock cams eliminate the overlap period, because the EPA doesn't want any unburned fuel escaping with the exhaust gasses. The stock cams open the intake just after TDC.
Your cam's intake valve closing point determines the rpm band your best performance occurs. Because your camshaft intake valve closes after bottom dead center, you don't start compressing the fuel charge until sometime after the piston starts upwards on it's compression stroke. A early intake close results in greater cranking pressure, which builds early torque. Higher rpm motors need a cam with a later intake close to insure all the fuel possible makes it into the combustion chamber. The faster the motor spins, the quicker the valve opens and closes, so a longer duration is needed for high rpm power. Ideally, you want the intake valve to close exactly at the point where air stops flowing into the chamber, but that point changes with rpm, so a cam has to strike a balance. Shorter duration cams are designed for low rpm and early torque, long duration cams are designed for high rpm motors and peak horsepower. An early closing cam would generally be considered as closing at 38 ABDC or earlier. A mid closing cam at 38-45 or so would shift the torque curve up the band by a few hundred rpms, and peak horsepower would also increase. Unless static compression is increased, response off-idle will decrease somewhat. Also, later closing, longer duration cams are more effected by exhaust design.
Back to intake opening, briefly. All cam design componants are a balancing act. Open early and the exiting exhaust gasses can pull the incoming charge into the combustion chamber. Open too early, and some of the exhaust gasses can back into the intake manifold, slowing the intake pulse velocity, and contaminating the fresh charge. It also hurts fuel economy if more unburned fuel escapes with the exiting gasses. A late opening intake will result in smooth operation at low rpms, and better throttle response off idle. Early means more overlap, less throttle response at low rpms, rougher idle, and poorer fuel economy. You want your intake valve to open early enough to where the valve is open far enough to flow max CFM at the same time the piston is traveling at max velocity.
Exhaust opening. Probably has the least effect on performance of the four open/close points. However, if you open too early, you decrease torque by bleeding off cylinder pressure that's still pushing the piston down. It does have to open early enough to provide enough time to scavenge the cylinder. Late opening helps low rpm performance by maximizing burn time and keeping pressure on the piston. Too late and you suffer pumping losses because the piston has to work harder to push out the spend charge. Too early, and you hurt the bottom end, but help the top end. Most cams split the difference, with stock cams tending towards a later open.
Exhaust closing: close too late and you hurt the bottom end. Closing late increases overlap, and is similar to opening the intake too soon which can cause reversion up the intake manifold. Close too early, and you might not evacuate all the spent gasses, and the residual burnt fuel will dilute the fresh charge.
As a motor spins faster, all the opening and closing points need to be pushed out to allow sufficient time for the various functions to occur.
Most street engines benefit the most by a cam with moderate specs. Not too early, not too late, not too much.
Three more things, quickly. Lobe seperation angle (LSA) is the angle between the middpoint of the intake and the exhaust lobes on the camshaft. Generally, a tight LSA (98-103) produces a narrow, early torque curve, and a wider LSA (104-108) broadens the powerband, and develops more power late. Lift: more is better generally. As long as your valve springs can handle the amount of lift, and you don't bang the valves into the pistons, opening the valves as much as possible is a good thing. The primary downside is increased wear because of the higher stresses put on the valvetrain. Even though your heads only flow up to a certain amount, opening the valves beyond that generally increases the amount of time they are open during the max flow period. Finally, duration. The faster the motor spins, the longer the valves need to be open. Short duration cams (under 220*) tend to build torque early. They can usually be bolted in as a stock replacement and will return moderate gains across the entire rpm band. Mid duration (220-240 or so) start moving into the mild performance arena, but will still work with stock compression and exhaust. Move up past 240 or so, and the cams will generally work better with other induction, compression, and exhaust modifications.
The good news though, is that a simple cam and header swap will boost performance in a big way, more so than with the earlier 88 motors. The 88's had better cams and no cats, but less displacement and a less effective head design.
Guys get hung up over one cam spec or another. When I was a young hot rodder, we were all about duration. It's human nature to want the biggest bang for your buck, and it's tempting to push a bigger cam in your motor than it needs. Adding too much cam is one of the most effective ways to make a fast bike slow. Generally, too much of anything in a cam will hurt low end power. Your cam manufacturer will have recommendations for the proper compression ratio for any given cam.
I'll try to keep my remarks brief. Your starting mechanical compression and cam selection must be considered as a system. You're starting with a fixed static compression, which is (roughly) the amount of air that your cylinder holds compressed into your combustion chamber. Your static compression starting point along with your cam's design will determine what your dynamic compression will be. Your cam has four main valve timing points: Intake valve open and close, and Exhaust open and close.
Lets start with the piston on it's intake stroke. In a performance cam, your intake valve opens before top dead center, and towards the end of the exhaust stroke. This period of time when both intake and exhaust valves are open is called overlap, and the exiting exhaust gasses help pull in the fresh charge in a siphon type effect. Stock cams eliminate the overlap period, because the EPA doesn't want any unburned fuel escaping with the exhaust gasses. The stock cams open the intake just after TDC.
Your cam's intake valve closing point determines the rpm band your best performance occurs. Because your camshaft intake valve closes after bottom dead center, you don't start compressing the fuel charge until sometime after the piston starts upwards on it's compression stroke. A early intake close results in greater cranking pressure, which builds early torque. Higher rpm motors need a cam with a later intake close to insure all the fuel possible makes it into the combustion chamber. The faster the motor spins, the quicker the valve opens and closes, so a longer duration is needed for high rpm power. Ideally, you want the intake valve to close exactly at the point where air stops flowing into the chamber, but that point changes with rpm, so a cam has to strike a balance. Shorter duration cams are designed for low rpm and early torque, long duration cams are designed for high rpm motors and peak horsepower. An early closing cam would generally be considered as closing at 38 ABDC or earlier. A mid closing cam at 38-45 or so would shift the torque curve up the band by a few hundred rpms, and peak horsepower would also increase. Unless static compression is increased, response off-idle will decrease somewhat. Also, later closing, longer duration cams are more effected by exhaust design.
Back to intake opening, briefly. All cam design componants are a balancing act. Open early and the exiting exhaust gasses can pull the incoming charge into the combustion chamber. Open too early, and some of the exhaust gasses can back into the intake manifold, slowing the intake pulse velocity, and contaminating the fresh charge. It also hurts fuel economy if more unburned fuel escapes with the exiting gasses. A late opening intake will result in smooth operation at low rpms, and better throttle response off idle. Early means more overlap, less throttle response at low rpms, rougher idle, and poorer fuel economy. You want your intake valve to open early enough to where the valve is open far enough to flow max CFM at the same time the piston is traveling at max velocity.
Exhaust opening. Probably has the least effect on performance of the four open/close points. However, if you open too early, you decrease torque by bleeding off cylinder pressure that's still pushing the piston down. It does have to open early enough to provide enough time to scavenge the cylinder. Late opening helps low rpm performance by maximizing burn time and keeping pressure on the piston. Too late and you suffer pumping losses because the piston has to work harder to push out the spend charge. Too early, and you hurt the bottom end, but help the top end. Most cams split the difference, with stock cams tending towards a later open.
Exhaust closing: close too late and you hurt the bottom end. Closing late increases overlap, and is similar to opening the intake too soon which can cause reversion up the intake manifold. Close too early, and you might not evacuate all the spent gasses, and the residual burnt fuel will dilute the fresh charge.
As a motor spins faster, all the opening and closing points need to be pushed out to allow sufficient time for the various functions to occur.
Most street engines benefit the most by a cam with moderate specs. Not too early, not too late, not too much.
Three more things, quickly. Lobe seperation angle (LSA) is the angle between the middpoint of the intake and the exhaust lobes on the camshaft. Generally, a tight LSA (98-103) produces a narrow, early torque curve, and a wider LSA (104-108) broadens the powerband, and develops more power late. Lift: more is better generally. As long as your valve springs can handle the amount of lift, and you don't bang the valves into the pistons, opening the valves as much as possible is a good thing. The primary downside is increased wear because of the higher stresses put on the valvetrain. Even though your heads only flow up to a certain amount, opening the valves beyond that generally increases the amount of time they are open during the max flow period. Finally, duration. The faster the motor spins, the longer the valves need to be open. Short duration cams (under 220*) tend to build torque early. They can usually be bolted in as a stock replacement and will return moderate gains across the entire rpm band. Mid duration (220-240 or so) start moving into the mild performance arena, but will still work with stock compression and exhaust. Move up past 240 or so, and the cams will generally work better with other induction, compression, and exhaust modifications.
Last edited by Mike; 12-21-2010 at 03:03 PM.
#6
12-21-2010, 01:24 PM
Hmmm....After reading your responses and the above info link, I'm thinking it may be best for me to hold off on this type of mod until after the manufacturers warranty expires. I'm sure the added power of the 103 engine with V&H mods will be fine for now for the wife (130 lbs) and I (200 lbs). I will still have my 1000cc sport bike for those days when I have a need for speed.
#7
12-21-2010, 01:53 PM
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#8
12-21-2010, 02:03 PM
Ultimate HDF Member
Your riding style and what rpmyou want your motor to have the sweet spot in is key to choosing the right cams and of course you know your bike is a heavy one, which also is a big factor in the equation.
As far a warranty concerns, you can probably get your dealer to do the install on certain HD cams and not have any issues with warranty but you need to go over that with you dealer.
As far a warranty concerns, you can probably get your dealer to do the install on certain HD cams and not have any issues with warranty but you need to go over that with you dealer.
#9
12-21-2010, 02:55 PM
Probably a wise decision. When/if you decide to change cams in the future my advice would be to pick a cam package that keeps your compression below 10. High compression makes for high power but also leads to detonation unless you always have access to good gas. A lot of the "fringe" gas stations still only carry 89 (91 if you're lucky) octane. Those high compression engines run like crap on the lower octane gas.
#10
12-21-2010, 03:19 PM
The good news is, that it's a lot easier and cheaper to build a 90hp motor than it was even a few years ago. Back when we were riding Evos, it would cost upwards of 4K to get that kind of power. Now, a simple cam swap and stage I upgrades and you can get that out of a 96. There are lots of cams to pick from: Woods 6, Andrews 26 or 37, SE255 or 204, any of these bolt-in cams will boost your performance with no real downside. Pick a moderate cam that will set your corrected compression at about 9.2:1 and it will be easily tuned, and have a huge jump up in performance as compared to stock.
Last edited by Mike; 12-21-2010 at 03:25 PM.