Hello... still waiting on ideas for a new post. Call, email, or leave a message. Thank you for your input.
Thank you to everyone who has contacted me or done business with me in the past. Hopefully I was helpful and the cam profiles are working well for you. If not, be sure to let me know and I will fix that. Have a prosperous new year.
I am sure I will not have many racers agree with me on this post. We would joke around about asking the customer what he was doing when a component failed. The customer would reply "racing" and we would answer “well, there’s your problem”. Not that funny to the customer with broken parts, I guess. My point is racing is hard on parts. Most would agree on that.
Years ago, racing valve train components had many problems. Valve springs were manufactured with inferior steel and camshafts were bad copies of other camshafts. Some cam profiles had been copied many times, so the errors just added up. The combination of these camshafts and springs in a racing engine was a problem waiting to happen. The quality of flat tappet lifters was inconsistent. The crown and edge chamfer on the lifter face was the problem. This would sometimes cause the camshaft lobe to wear and of course the camshaft grinder was blamed. Roller lifters also had their problems. Especially when used on small base circle camshafts. This creates too high of a pressure angle. Unfortunately, it is still a problem today. Pushrods were tubes with ball ends welded on. Not very strong. Roller rocker arms were fairly decent, but still had their share of problems.
Today, the quality of components is the best they have ever been. There is junk out there and that is what you must avoid. If you are going racing, any racing, you better buy the best parts that are available. Many racers do not do this. Racing is an addiction, just like drugs. Many do it even though they can not afford it. This causes them to buy the junk parts or parts that are not as strong as they need to be for the application. The results are obvious, broken parts.
Sometimes a particular rule will force the racer to use components not up to the task. Unless you ignore the rule, the results are broken parts. All components wear out and break. They must be replaced before this happens. This can get expensive, so many do not do it. The results are broken parts. If components are continually failing, there is more than likely a problem on your end, not the components.
If you want to get in to this sport, realize it will take all your money and may not give you anything in return. Just as bad or worse than that pretty girl at the mall. There should be some kind of agreement to sign in order to be a racer. That may stop some of the whining. If money is a problem, do not get in this sport. If you do anyway, accept the consequences. As the saying goes “the truth hurts”.
In summary, parts are high quality today. If they are used correctly and in the environment they were designed for, the chances of having a failure are low. They must also be replaced on some type of schedule. Always analyze what you are doing before immediately blaming the part.
If you send me an email or leave a voice mail and do not receive a response, there is a problem some where. I will always reply. I will usually reply within a few hours or certainly the next day. There is no telling what the problem might be, so please try again. Make sure your email address is correct. Make sure your phone number is correct. My phone does not receive or send text messages. Do not send me a text message. Please use email or voice phone. Thank you.
The dynamic compression ratio is calculated based on the intake valve closing point. I use 0.020 tappet height as the closing point. Some people use 0.000, 0.001, 0.005, 0.010, 0.050, or 0.053 for Harley-Davidson camshafts. As long as you are consistent and become familiar with the results, I do not think the exact height matters.
The dynamic compression ratio is calculated the same way as the static compression ratio. The volume in the cylinder when the intake valve closes is used instead of the full volume of the cylinder when the piston is at bottom dead center (BDC) is the difference. To find the location of the piston in the cylinder when the intake valve closes will take some involved math if done by hand. Like everything else done today that involves calculations, software and a computer is used. The location of the piston is determined by the stroke of the crankshaft and the connecting rod length. A profile report of the camshaft or a degree wheel and dial indicator will be necessary to find the degree of crankshaft rotation for the particular tappet height you have chosen. A program on the internet can probably be found to do the calculations for you.
Once you have the piston location (actually it will be the center of the small end of the connecting rod) the volume of the cylinder can be calculated. The compression height of the piston will need to be added in for the actual top of the piston location. Any dish or humps on the piston top will also need to be added in just like static compression ratio calculations. The dynamic compression ratio will obviously be less than the static ratio. How much less will have a large impact on the performance of your engine.
The dynamic compression ratio will be a more realistic number to use when choosing a camshaft. The importance of the intake valve closing point can now be seen. Use this next time you are changing camshafts. It could make a big difference in a good way.
Don't forget, keep sending suggestions for more topics.
I will be increasing my cam profile design cost for the first time. Not much, $8 increase for each standard cam profile design. It will help cover my increasing costs. This should be good for the next ten years. Thank you to everyone who has trusted me to design your cam profiles. Have a prosperous new year.
revised 12-22-2017... Hopefully I have some dedicated readers that follow these posts. I am going to leave it up to you to pick the subject matter for the next several entries. I am honestly running out of topics and this will assure me that the subject matter will be of interest. I do not want to write about topics that are of no interest and I do not want to repeat the same information that has already been posted. I spend a lot of time on these posts with the purpose of helping those interested in this stuff. Please speak up and leave a comment, send an email, or call me. I look forward to your suggestions.
A better title would be non-camshaft technology. I believe this is the future of camshaft technology. The technology appears to be there but like anything new, the costs are high. Like most modern advances in the internal combustion engine, efficiency is the driving factor. This technology will be standard for passenger cars long before it is common in racing engines. The same as the electronic fuel injection and engine management technology. Today, the production car technology filters down to the racing industry. Funny how things change. https://www.youtube.com/watch?v=FJXgKY2O4po
If you are someone that has just acquired a camshaft grinder, you might be thinking about what to do next. I will leave it up to you how to run the business end. After that part is figured out, making a camshaft usually comes next.
I will use a small one-person shop with a manually operated Berco or Van Norman camshaft grinder for my example. I will also assume there are no finished master plates with the latest cam profiles. It does not take long to realize that your camshaft grinder is a nice conversation piece, but has no ability to make a camshaft.
Making some master plates is the first priority. Copying profiles from other camshafts is one route to take. Having your own cam profile designs is a better and more professional choice. I would guess that every cam grinder has copied other cam profiles at some point. It is the easiest way to get started grinding camshafts. After awhile you will want to have your own designs.
Unless you just want to design cam profiles, paying someone else for this service will be more practical. Cam design software is not cheap and neither is your time. After buying the software, you will need to spend time learning how to use it. It will also take years to become proficient with it. Being able to talk with someone that can design cam profiles and then actually having some designed at a decent price can be frustrating. I am probably one of the most affordable and easiest to deal with, of the designers out there.
Once you have a cam profile design, the next step is to make a master plate. There are a couple of options here. You can send the necessary design data to someone with a CNC cam grinder and have them make the master for you. This usually produces the best quality master and is also the most expensive. Having just a few masters made can add up quickly. The other option is to make your masters with your own camshaft grinder. To do this will require that you make a cam profile model first. The model can be made in a vertical milling machine with a horizontal rotary indexing table. Using a CNC milling machine is the best way, but a manual machine works fine also. A used CNC mill is very affordable today and can be useful in making index plates, which you are also going to need. The lift table from the cam profile design data is used to whittle out the model. The cam profile model is then put into the camshaft grinding machine and the master is made in the same way as if you were copying another camshaft. This was the best method available before CNC cam grinders came along. It is still a viable method for those on a small shop budget. There is some more information about this in previous posts, so be sure to read all of them. I have generated many models and master plates and will be glad to give you more detail about this method or anything about camshaft grinding, just ask. Good luck on your new adventure.
I can always use your help coming up with new topics. Just send me an email with your suggestions.
In my entries about cam profile designs, I intentionally try to make it simple and easy to understand. The information is intended for readers that have little or no experience with cam profile designs. It was very frustrating to me when looking for information, that everything written was mostly about mathematical equations. Most of the information is written by mathematicians and not people that actually design cam profiles used in real engines. Most people are not looking for that type of information, thus one of the reasons for this blog.
Software programs and computers do all the math when designing cam profiles. I have no desire designing cam profiles by hand without a computer. I do understand the complex mathematical equations and calculations that are involved, but I do not want to read or write about that stuff. Again, that is what the computer is for. The design software cannot tell the difference between a good profile and a bad one. That is the type of information I like to read and write about.
Now on to the topic of this entry. Here is a simple example to help you understand. Mark off two points in the street. One point is where you are standing and the other point is some distance away. The distance between the two points will be the lift. The duration will be the time you have to go from one point to the other and back. Lets say the distance is 50-yards and the duration is 1-minute (60-seconds). To go the distance (lift) in the allowed time (duration) will be a slow speed walk (low velocity). If you run (higher velocity), the time (duration) it takes you will be much less than the 60-seconds. Your average speed (velocity) is determined by the distance (lift) and the time (duration) you have to go the distance. You cannot go faster or slower or the time will change. Simple physics determines this. You could run in spurts combined with slower walking periods and still complete this in the 60-seconds time frame. That would create large swings in velocity (high acceleration) and be harder on you than the slow, smooth, easy walk. By the way, you are the valve train.
Let’s change the duration from 60-seconds to 30-seconds. The lift stays the same at 50-yards. What will this do to the velocity? The velocity will naturally have to increase since you now have less time to go the same distance. Your original slow, smooth, easy walk will now be a run. Cut the duration in half again. The duration is now 15-seconds. You must run even faster. You can see the pattern. At some point, the velocity and acceleration will be too much for the runner to maintain. The same physics applies to cam profiles.
Keep the original duration at 60-seconds but increase the lift to 75-yards. That will create the same situation as above. The velocity will naturally have to increase also. You now have to go a longer distance in the same amount of time. You can see the same pattern here. This also applies to cam profiles.
Normally in cam profile design, the lift is chosen first based on the physical layout of the valve train or because of some racing class rule. The duration is chosen next based on the engine size and the rpm wanted for peak power. The lift and duration along with the ramp designs will determine what the designer and the software can do with the lift, velocity, acceleration, and jerk curves.
It is not really a big deal that the duration and lift is off by a small amount from the original design. A larger or smaller profile can be chosen easy enough. It is just not acceptable today like it was years ago. Even though the duration and lift numbers were slightly off, the velocity, acceleration, jerk, pressure angle, and radius of curvature values were still close to the original design. Today, the duration and lift numbers may match what is published, but other numbers that are more important are not even considered. Most customers do not look at this part of the cam profile. Since the customer does not care, the camshaft grinder does not care either. That is why cam profiles are still copied and used in the wrong applications.
As long as the camshaft numbers match the specification card, everything is good… right? No, everything is not good. When cam profiles are chosen based on duration and lift alone, much of the cam profile potential is ignored. I have talked about this in previous post, so I will try not to over repeat myself. When base circle diameters and roller wheel diameters are changed from the original design, other important parameters also change, not just the duration. Opening and closing ramps may not be correct for the application. Problems in the valve train can be created including premature wear of the tappets and the valve springs. This can come from excessive values of acceleration, velocity, jerk, pressure angles, and small radius of curvature in the profile flanks or the nose. Unless these parameters are also analyzed, you are just hoping for the best and so is your camshaft grinder. There is much more to a cam profile than just duration and lift.
Camshaft consumers have been getting more sophisticated over the years. Engine builders and even some individuals are checking their camshafts with a computerized cam profiler before installing them. Those not using computers are checking their camshafts with a dial indicator and degree wheel. This has caused the camshaft grinder to profile each camshaft on his own cam profiler before sending it to his customer. The camshaft grinder uses the actual data retrieved to create the camshaft specification card. This prevents having to explain later why the camshaft specifications do not agree with the card.
Years ago when computer designed cam profiles were becoming common, a model lobe was created from the design data in a milling machine and a cam profile master plate was then created from the model in the camshaft grinding machine. This was before CNC machines were used to make the master plate from the design data. The master plate is used in manually operated camshaft grinding machines to make the camshaft. The most popular machines are the Van Norman and Berco camshaft grinders. There are many of these machines used today to make camshafts. The machine uses a follow wheel to trace the master plate shape onto the camshaft. There are many videos on the internet showing the operation of these machines. Check them out if you are not familiar with how a camshaft grinding machine works.
Between the cam profile design, the making of the model lobe, the making of the master plate, and the making of the camshaft, many errors are accumulated. I am not sure but I may have just let out a big secret. I always say, there are three different cam profiles for each design. The original design (1), the actual lobe on the camshaft (2), and the profile that is created in a running engine (3). Obviously, you want all three to be the same, but in reality, they are not. Today’s technology is allowing them to become closer. Making master plates directly from the profile design data using CNC machines has removed many of the errors experienced years ago. A well maintained Berco camshaft grinder and CNC produced masters, along with a skilled operator, will produce a wonderful camshaft.
Back to the years ago. There was usually a big difference between the original cam profile design and the finished camshaft lobe. A decrease of around 2-3 degrees in duration and 0.003 in lift were common discrepancies. This was from the major camshaft grinders of the time. If the camshaft grinder created the specification card from the original design, and most did, the actual camshaft specifications did not mach. Most people did not analyze their camshaft at the time and the small differences in specifications were usually accepted. It was just considered the normal tolerance. Today, the consumer expects to receive a camshaft with all the lobes matching the specifications exactly. Unless the camshafts are being ground on CNC machines, it is very hard to deliver that kind of quality. Profiling the camshaft and using that data for the specifications, is the only way to make them match and please the customer.
My last three entries were linked to articles that I thought were interesting. Together, they sort of created a camshaft time line. We learned a little about the early American development of the performance camshaft and the people and companies involved. We now know in today’s world, there is not a magic formula that can pick the perfect camshaft for the application. It seems the people that market these formulas do not have any reputation for being engine builders or have much experience running engine dynamometers (just thinking out loud). We also got a glimpse into the future where the mechanical camshaft and valve train will be non-existent. All this spans about 130-year period.
Cam profiles were initially shaped by hand with grinders, files, and abrasive materials. Models were created on paper with compasses, protractors, scales, and straight edges. The modern cam profile is designed using computers and software to run sophisticated mathematical equations until the desired valve motion is created. We now look at the early cam profile designs as crude and ridiculous compared to modern designs. The future valve actuated systems will make our modern cam profile designs also look crude and ridiculous.
The mechanical camshaft and valve train, as we know it, has reached its peak. We have squeezed out all of the performance that is going to be possible. Stronger, lighter, wear resistant, CNC machined components, larger base circle diameter lobes, larger follow wheel diameters, the best valve springs and systems without valve springs, multiple OHC systems, finger follower systems, variable cam timing systems, the best cam design software, and so on. It has all been done. If you think you are doing something new, you are probably only catching up with technology.
Even though the technology is here, many are not using it. The OEM world seems to be the most advanced. Look at the automobiles that can be bought today. Simply amazing! Power, efficiency, suspension, brakes, aerodynamics, electronics, and air conditioned. Much of the racing world is far behind in the available technology. That has not always been the case. It is all about money, I understand. It will be a very long time before the mechanical camshaft becomes obsolete. Until then, please keep me in mind for today’s modern cam profile designs.
I enjoy reading about the history and development of things. Here is a good article on the beginnings of the automotive performance camshaft in America. It basically starts with Ed Winfield and the Ford Model T. In the beginning, Winfield and others modified existing stock camshafts. My question has always been…Who designed and ground the stock camshafts of the day? We never hear about those individuals.
I look forward to this engine being perfected. I think it will bring a whole new perspective to the cam profile design world.
These two phrases are sometimes used to mean the same thing. In reality, they are two separate processes, but both are important to produce a properly performing camshaft.
Cam profile design is my main focus. This is the actual designing process of the cam lobe. Most of the information in this blog section describes what is involved in designing a cam profile. Hopefully, you have read all of the posts so far, and have a good understanding about cam profile designs.
Camshaft design is different from cam profile design. Once the cam profiles are designed, the next step is to make the camshaft. Obviously, making the camshaft is much more involved. There are many stages in the camshaft manufacturing process. From the material to make the camshaft, heat-treating, indexing the lobes, gear cutting, machining and grinding equipment used, quality control, all the way through to the packaging to ship the finished camshaft. I’m sure you will be glad to hear, that I have no desire to describe in detail, the manufacturing process. It is easy enough to imagine all that is involved.
The part of camshaft design that most of you are interested in is, what camshaft do I need for my application? That will involve the choosing of the correct camshaft core, the proper profiles, lobe separation angle, and the camshaft indexing in relation to the crankshaft. All of these choices have to be correct, or the camshaft will not perform as well as it could. No doubt, a big task for the person picking the camshaft. If you find someone that can routinely choose the correct camshaft for the application, stick with that person. There are also software programs written to do this. From my experience, the programs that really work are expensive. They are marketed more towards a company than an individual.
As you can see, cam profile design and the camshaft design, must work together. You can have the best cam profiles, but if the camshaft design is poor, the camshaft does not perform well. The cam profile designs are blamed along with the camshaft and the manufacturer. You can also have cam profiles that are not correct for the application, but the camshaft design is good. The camshaft will generally perform ok, but not as well as it would with the proper cam profiles. This is the most common problem with camshafts today.
If you are new to my blog page, please start at the beginning and read all of my posts. You will have a better understanding of cam profiles and my approach to cam profile designs.
If the cam profile lift table is the same on the opening and closing side, the profile is symmetrical. If the lift table is not the same, the profile is asymmetrical. Simple enough…right? You must study and graph the lift table of any cam profile to truly understand the profile. The lift table is the blueprint of a cam profile.
Most of the early modern cam profile designs were symmetrical. When I speak of modern cam profiles, I mean a computer was used in the design process. Symmetrical profiles were easier to design and the knowledge available, at the time, was just in the beginning stages. Asymmetrical profiles were created when the opening and closing ramps became different. This is because the valve can be opened faster than it can be closed. Most cam profiles today are asymmetrical.
In most conventional cam profiles, the opening and closing ramps are what make the profile asymmetrical. This causes some of the main profile to also be asymmetrical. Usually from the end of the ramp to around .050 tappet lift, the profile will be asymmetrical. As you move up the lift table to maximum lift, the profile will become less asymmetrical. On either side of maximum lift, the profile will actually be symmetrical for many degrees. The major asymmetry is in the low lift areas of the profile. The higher lift areas may be asymmetrical, but not by very much. Again, the only reason the profile is asymmetrical, is that the opening and closing ramps are designed differently. There is no magic going on here to try and manipulate the air flow.
For an unconventional cam profile, the entire opening and closing side of the profile is intentionally designed different. This is because the rocker ratio is not consistent (as in a conventional profile) throughout the valve movement. Usually, you can see the different shape of the opening and closing side of the lobe. This type of profile is highly asymmetrical and must be designed that way for a smooth valve motion.
Conventional symmetrical cam profiles are still designed today. There is nothing wrong with them. Just because a cam profile is symmetrical, doesn’t mean that it is a poor design or inferior.
If you haven’t noticed, the website has a new domain name (web address).
This is a registered address that belongs to me. Having a registered address is more professional and it makes the website easier to find in search engines. It is just another ongoing development in the website. I created this website and constantly update and develop it myself. I am certainly not a professional website builder, but if you are someone wanting to build your own website, I would be glad to offer any help to you.
Be sure to update your bookmark to this new address. The system will automatically forward you from the old address until you change.
Check back, I will have a new technical post soon.
It seems like each person has their own way of adjusting valve lash. As with hydraulic lifters, talked about in the previous post, there is nothing mysterious or complicated about adjusting the valve lash. The valve being adjusted must be fully closed. That is the only rule that matters. Whatever procedure you want to use is up to you. The content of this post will be about the lash itself and not the adjusting procedure.
Since the solid lifter does not have the ability to take-up the clearance created in the valve train, there will always be some running clearance in a hot engine. Most engines will gain clearance in the valve train from a cold to a hot engine. I’m sure there are exceptions, but I have not come across one. This gain in clearance is taken into consideration when designing the cam profile ramps for a particular engine combination. A cast iron push rod engine will not gain as much clearance as an all aluminum push rod engine. The ramps should be designed differently for each application. Many times a cam profile is used without any thought given to what the actual running lash was designed to be. The more lash, the less area the cam profile has. The opening and closing valve velocity points will also increase which could cause mechanical damage to the valve train. Less lash will increase the seat-to-seat duration, which may bleed-off cylinder pressure. Changing the rocker arm ratio also changes the lash setting. There is more to choosing the correct cam profile than just lift and duration numbers.
The valve lash settings come from the cam profile design. It is not just some number that is made up. The material of the engine block and heads, the rocker arm ratio that will be used, and the application, are all considered when designing the cam profile ramps. Older cam profiles were mostly designed for cast iron engines with 1.5 or 1.6 rocker ratios. Many engines today are all aluminum or have aluminum heads and higher rocker arm ratios. Again, the best performing cam profiles will be the ones that are designed specifically for your combination and application.
I will finish this post the same as the previous post. I know all kinds of combinations and lash adjustments are used for camshafts and lifters. I have already stated many times the disadvantages and dangers of mismatching cam profiles and lifters. I will just continue to shake my head and be amazed at why this is done.
Standard hydraulic lifters are designed to automatically compensate for any clearance that is created in the valve train from a cold engine to a hot operating engine. They will also compensate for any clearance that is created from wear or unintentional conditions. The lifter not following the cam profile is the most common unintentional condition. Lifter float or valve float is the more common term. This can be caused from not enough valve spring pressure, over revving the engine, or the wrong cam profile design. When this happens, the hydraulic lifter will “pump-up” to take up the temporary clearance created. Since the initial hydraulic lifter adjustment was set to operate at zero clearance, this extra “pump-up” of the lifter will keep the valve from fully closing until the lifter “bleeds-down” to its original setting. Until the lifter “bleeds-down”, that cylinder will obviously loose compression and power.
Special “anti-pump-up” hydraulic lifters are designed to keep the lifter from “pumping-up” during this condition. There is a strong snap ring retainer in the top of the lifter that stops the lifter plunger travel. The standard hydraulic lifter also has a retainer, but it is usually a weak round wire type. It is not designed to resist the plunger movement. The “anti-pump-up” lifters are adjusted differently than the standard lifters. Standard hydraulic lifters have around a 0.200 total plunger travel. I still do not understand why they are designed with that much travel. Certainly much more then will ever be necessary. Probably to compensate for the “stacking” tolerances (engine, head, pushrod, etc.) in production. The preload adjustment can be set anywhere in this travel range. Normally, the plunger preload adjustment is less than 0.050 when done by hand. All that is needed, is enough preload to compensate for any clearance that is created in the valve train from a cold engine to a hot operating engine and from any wear. In reality, on a cast iron stock engine, this would be less than 0.010. An all aluminum engine may require more. It always amazes me how some mystery is created when adjusting hydraulic lifters. Take a hydraulic lifter apart and analyze it. Look closely at the oil holes, oil channels, check valve, and envision how the oil flows. Make sure you understand how it works. Simple… right? Certainly, no mystery involved. I am referring to a stock OEM lifter here. Special “anti-pump-up” lifters operate the same way as stock ones. The plunger travel is only around 0.050 and they have that strong snap ring retainer. Adjustment is a little different. The idea is to preload the lifter so the plunger will just be touching the retaining ring during hot engine operation. This will prevent the lifter from “pumping-up” any further if valve float was to happen.
The retainer in the standard hydraulic lifter is not designed to resist the plunger travel, so the lifter should be preloaded enough to keep the plunger from touching the retainer during hot engine operation. The preload can be set anywhere within the plunger travel range. I guess this is where the mystery comes in. Usually you hear “quarter turn”, “half a turn” or “one full turn” on the rocker arm nut used to describe the preload adjustment. The plunger can also be adjusted where it is bottomed-out in the lifter. For engines without adjustable rocker arms, the pushrod length should preload the lifter at the midpoint of the plunger travel. All of these will work fine. Take your pick.
Cam profiles are designed a specific way to use a hydraulic lifter. I know all kinds of combinations and lash adjustments are used for camshafts and lifters. I have already stated in previous posts, the disadvantages and dangers of mismatching cam profiles and lifters. I will just continue to shake my head and be amazed at why this is done.
This is the new website for Ingram Engineering Cam Profile Designs. The old website service is being discontinued and that website will no longer be updated and will eventually be deleted. Be sure to change your bookmark to this new website address. The new service is much easier to use and has more features. Hopefully, everyone will like the results. Please leave a comment.
The majority of my cam profile designs are for conventional valve trains. Meaning the valve lift is a constant ratio compared to the cam profile lift. An example would be if the rocker arm ratio were 1.5 to 1, the valve lift would be the cam lobe lift multiplied by 1.5 at any point. Push rod engines with a rocker arm and overhead cam engines with a direct acting tappet are examples of a conventional valve train. Unconventional valve trains have a ratio that will vary through the valve movement or a cam lobe shape that is not typical. Overhead cam engines with finger followers are an example of a ratio that will vary. A Desmodromic valve train is also unconventional and very interesting. I would recommend studying this valve train. There are a few other older valve trains that are unconventional, but are not used in modern engines. They are still worth studying. You cannot fully understand something without knowing the history and its evolvement. Early internal combustion engines did not have an intake cam lobe and only used an exhaust lobe that opened at the bottom of the exhaust stroke and closed at the top. The intake valve used atmospheric pressure and a valve spring to open and close. To go from no intake cam to what we have today, is an interesting and educational journey.
Different cam profile design programs are written for the different valve train designs. Each program is costly and has to be justified based on the demand for certain profile designs. Much of the input data for these unconventional cam profile designs consists of angles and dimensions for that particular valve train. This data is usually not known and is not easily measured. Having the program only solves part of the problem. Usually a blueprint of that valve train is also necessary. Good luck getting that! Many times, if the customer can plot a ratio table of cam lift to valve lift in 1-degree increments, I can design a cam profile.
Like all of the posts, be sure to read the previous ones first.
I hope some of you participated and drew the lift curve in the previous post. For those that did, you will be further along in understanding cam profiles. If you haven’t already, play around with creating your own lift curves. There are many important observations that can be made by creating different lift curves.
An increase in the slope of the straight-line segment will increase the area of the profile. Once the lobe lift and the duration at 0.050 are chosen, the slope of this line will be the main difference between profiles with the same lift and 0.050 duration numbers. Would you intentionally design a cam profile with less area than what is possible? If you want less area, would it not be better to just design a cam profile that is smaller at 0.050 and/or less lift, but still with as much area as possible. Common sense will give you the answer. This is where you have to watch out for the marketing gimmicks.
Another observation is the length of the ramp area. The ramp area will be from 0.000 to 0.020. The valve contact point will fall somewhere in this range. This 0.020 can be divided-up into as many degrees as you would like, but after a certain length, it is just senseless to keep going. Around 20-degrees or less is plenty of room for any type of ramp design.
You will notice how the duration spread between 0.020 and 0.050 will set-up the slope for the lift curve. The terms high intensity and low intensity cam profiles are more of a marketing term, but relates to this spread. The closer the spread, the steeper the slope will be and more area will be created. This gives you more of a practical explanation without the marketing.
The top of the lift curve coming from maximum lift should be a nice, gentle curve. There should be no dwell at maximum lift and no corners blending into the straight-line segment of the lift curve. The lift curve from 0.050 to 0.020 to 0.000 should also be a nice, gentle curve. After you draw a few lift curves free handed, you will be able to see them in your mind and do it with your eyes closed. I know that cam profiles are sometimes designed with a dwell at maximum lift. These are special application profiles only and are not considered a good design.
Being able to look at a lift curve and seeing this information will be a big advantage when comparing cam profiles or analyzing a particular cam profile. It also takes something that seems very complicated and breaks it down into something simple and easy to understand.
Here is a simple exercise to start with. We are going to create a cam profile in the form of a lift curve chart. Draw a horizontal and a vertical line. These will be the “x” and “y” axis of the chart. The vertical line is the cam profile lift and the horizontal line is the degrees of rotation (duration). Zero is the point where both axis meet. This chart represents only the opening side of the cam profile. Next, plot the maximum lift of the profile. Now, plot the duration points at the following lifts: 0.020, 0.050, 0.100, 0.200, and 0.300. In the example, the maximum lift is 0.400. The plotted duration points are 68 (0.020), 60 (0.050), 52 (0.100), 39 (0.200), 26 (0.300). Remember, this is camshaft duration, not crankshaft. This is also only half of the cam profile, so the duration points are ¼ of the crankshaft duration. If this doesn’t make sense, think about it until it does. It will help to go back and study the posts on lift tables. From 0.020 to 0.000 will be the ramp area. The beginning of the ramp at 0.000 is 90-degrees. The chart should look like the one below. The plotted points show up as the red dots.
Now, with a smooth, gentle curve starting at 0.400, connect the plotted points down to 0.000 at 90-degrees. If you have been drawing along with your own chart, guess what? You have basically just created a cam profile and you didn’t even have to use any mathematical equations. Obviously, there is more to designing a cam profile then just this, but this is a legitimate profile with good area that would perform well if manufactured. If you haven't been playing along, you can take a short cut and print the chart.
Now, let’s analyze the lift chart closer. Notice the curve you drew connecting the plotted points is straight between 0.300 and 0.100. Depending on the profile lift, this straight segment will be shorter or longer in length. There will always be a straight segment in a good profile design. This straight segment has a slope to it, right? Maybe around 50-degrees with the horizontal axis. As the slope of this line increases, the area will also increase. The velocity and acceleration numbers will also increase. At some point, the slope of this line will be at maximum for the profile. When this maximum slope is reached, the cam profile is what I call “maxed out”. Basically, all of the area has been designed into the profile, within the limitations. It would be difficult to “better” this type of profile. Trying to make the profile smoother would be the only possible outcome.
I create a lift chart many times, as the first step in designing a cam profile. Especially, if a customer is giving me durations at different tappet heights. I will know right away, by the slope of the straight-line segment, if the cam profile will even be possible. I will usually plot duration points at 0.020, 0.050, and then at every 0.100 lift interval. From 0.020 down to 0.000 is the ramp area. The length of the ramp is usually around 20-degrees. In the example, the ramp length is actually 22-degrees. A good modern solid or hydraulic ramp can be designed with 20-degrees or less of length. You can see in the chart, a longer ramp will serve no purpose. It only keeps the valve separated from its seat for a longer period of time. No advantage. There is no significant airflow in this area. The area under the lift curve is that area inside the curve drawn to connect the plotted points. It is easy to see how changing the curve, changes the area. The area to increase for better performance is that above 0.050. Not below.
Usually, a cam profile concept starts with a maximum lift and the duration at 0.050. From there, the duration at 0.020 is around 30-degrees bigger than at 0.050. That spread determines the high and low intensity profiles that you hear talked about. You can see on the chart how the 0.020 and 0.050 durations will setup the slope for the straight-line segment.
Much can be learned from the cam profile lift chart. Whether from an existing profile or the design of a new one. The lift chart is essentially the cam profile.