Commercial Door Repair & Door Replacement. Vortex Doors is your industry expert for commercial and industrial door repair services. Family- owned since 1. Customer Service. Our services include: Vortex has same- day service available so we will be there when you need us when you have an immediate safety or security issue! We operate 3. 5 self- performing Service Centers and over 3. Service Trucks for the fastest response time in the industry. With over 8. 0 years of experience, you can be confident that Vortex will exceed your expectations, and provide you with the most experienced Team of exclusively trained technicians in the industry. Service. Reliability. For your door, dock and gate needs, experience the Vortex difference. Job Interview Practice Test Why Do You Want This Job? Answer this job interview question to determine if you are prepared for a successful job interview. For each lobe there is an opening and closing point. Let’s say you are measuring an intake lobe on a camshaft in the engine using a dial indicator and a degree wheel. We Deliver Power! Quality, Price and Availability are key factors whenever you purchase a product. But why stop there? GB Industrial Battery unites those. Camshaft 1. 01 - Hot Rod Network. Performance may always lay heavy odds on power, but you also need the brains to go with it. The four- stroke internal combustion engine has been around for over a century, but we’re still learning incredible things about using camshafts to make more power. That elliptical lobe may look simple, but it represents the brains for your engine’s brawn. Let’s take a look at what makes this simple eccentric device so powerful. Lift. We’ll start with the easiest concept involved with the camshaft–lift. A cam lobe starts off from a simple circle, called the base circle of the cam. From that circle, the designer creates additional lift using a ramp so that as the circle rotates, it converts rotation into a linear or vertical motion by using a follower or tappet. This lift eventually rises to its highest point beyond the basic radius of the circle. The difference in height between the top of the lobe and the radius of the circle is the lift component of a cam lobe. For most street- type cams, this will be roughly between 0. This is called the lobe lift of the camshaft. But we don’t generate this lift all at once–it’s created by gradually moving the tappet from the base circle to maximum lobe lift. This is where duration comes in. Duration. Ideally, you could slam a valve open, hold it open, and then slam it closed, and many drag race camshafts attempt to perform this feat, but this harsh action is incredibly abusive on valvetrain parts, especially valves and springs. To make these parts live over hundreds of thousands of miles, the cam lobe lift curve must be gentler. The easiest way to measure the amount of time the lobe is creating lift is with degrees of duration. A long time ago, our cam- building forefathers decided to use crankshaft degrees to measure cam lobe duration. So a typical performance camshaft may have a duration of 2. Keep in mind that a camshaft actually spins at half engine speed. But this created confusion because all the different cam companies measured the beginning of the lift curve at different points a few thousandths of an inch above the cam’s base circle. 4 Wheel Parts carries a vast selection of truck parts at discount prices. Browse our online truck parts catalog when you know what your truck needs, or when you’re. Strictly platonic; women seek women; women seeking men; men seeking women; men seeking men; misc romance; casual encounters; missed connections; rants and raves. SENT TO DEALERSHIP. Mossy Nissan CHULA VISTA; Mossy Nissan EL CAJON; Mossy Nissan ESCONDIDO; Mossy Nissan KEARNY MESA; Mossy Nissan NATIONAL CITY; Mossy Nissan. Forklift Sales, Rentals and Warehousing Solutions. Yale/Chase is the leading provider of new and used material handlingproducts in Southern Californiacities, such as. This is called advertised duration and it can get complicated because, for example, Comp Cams begins measuring its advertised duration for hydraulic lifter cams when the lifter rises 0. Crane uses 0. 0. 04 inch, which would make the same lobe “appear” a few degrees longer in duration because the duration would be measured over a 0. This difference between companies eventually led to the selection of 0. So now we have both advertised duration and duration at the 0. Now that you have the basics, we can dive into a few more items that make camshafts complex, but also fun. For each lobe there is an opening and closing point. Let’s say you are measuring an intake lobe on a camshaft in the engine using a dial indicator and a degree wheel. Once the lifter rises off the base circle 0. BTDC) and closes 9. ABDC), then you can add those two numbers together along with 1. This same formula can also be used to determine duration at 0. Duration is a major contributor to the torque curve and where it occurs in the engine’s rpm band. Generally speaking, as you increase the amount of intake lobe duration, this makes for an earlier- opening and later- closing intake valve. This additional duration also extends the rpm point where peak torque occurs. This tends to increase peak hp (depending upon the other components used on the engine) while sacrificing low- and mid- range torque. Conversely, a very short duration camshaft opens the intake valve later and closes it sooner, reducing the potential for high- rpm horsepower but increasing torque at a lower engine speed. Intake Centerline. Now that you have lift and duration mastered, we can move on to more of the measurement values in camshaft design. Imagine looking at a lobe with a vertical line running right down the middle as viewed from the end. This line would represent the centerline of the lobe. If this were an intake valve, this would be the intake centerline of the lobe. Cam designers and engine builders use this centerline to establish where the lobe is located relative to the piston. For example, a Comp Cams 2. Xtreme Energy cam has an intake centerline of 1. ATDC. This means that the midpoint of the lobe (which may or may not be maximum lift, since some cams are asymmetrical in design), will occur when the Number One piston is positioned at 1. When installing a camshaft in an engine, performance engine builders and the blueprinting process demand that you measure or “degree” the camshaft to ensure that it is installed where the engine builder desires. It’s not enough to merely line up the dots on the cam and the crank gear. This way, if the engine builder would like to change the phasing of the camshaft, he can use that installed point as a reference. It’s tough to know where to go if you don’t know where you are. This phasing of the camshaft is important because when the valves open and close has a serious effect on engine performance. This is where we get into advancing or retarding the position of the camshaft relative to the Number One piston. All references to positioning a cam are always around the intake lobe for the Number One cylinder. So if we wanted to advance the previously mentioned 2. XE cam with its 1. It would place the intake centerline at 1. ATDC). Conversely, if we wanted to retard the camshaft by 2 degrees, this would move the original 1. ATDC. This is an important point that many people get backwards, so take a minute or so to study why these numbers are correct by looking at the cam timing graph. Advancing the camshaft means that you are starting the opening and closing process sooner in the cycle. It generally improves low- speed torque and mid- range power while sacrificing top- end hp. Conversely, retarding the cam detracts from low- and mid- range power in order to help top- end power. Generally, moving a camshaft a couple of degrees will not make dramatic changes to the engine’s power curve. Lobe Separation Angle. Here’s where we get into some meaty stuff, so stay with us. If you look at the lobe graph, you can see the relationship of the intake and exhaust lobes. One of the variables that make cam designing such a challenge is the relationship of the intake to the exhaust lobe. The number of degrees between the intake and exhaust lobe centerlines establishes what is called the lobe separation angle. As an example, many Crane street camshafts are built using a 1. This means there are 1. This can be determined from a cam card by adding the exhaust and intake centerline numbers together and then dividing by 2. So if you add a 1. Keep in mind that often the intake centerline and the lobe separation angle will be the same number, but they represent completely different functions. Valve overlap is a function of both duration and lobe separation angle. If the lobe separation angle remains the same but you increase the duration, the amount of overlap will also increase. Overlap is the time, measured in crankshaft degrees, when the exhaust valve and intake valves are both open. Overlap helps improve engine performance by starting the intake cycle before the exhaust cycle has ended. As overlap increases, this tends to make the idle quality more erratic, or lumpy, while improving midrange and top- end power. This is a very complex subject that we’ll just touch on here, but even slight changes in overlap and intake opening and closing points can make a big difference in engine performance. Single- and Dual- Pattern Cams. As we learn more about camshafts, you find that the early cams tended to be relatively simple devices that have become increasingly complex, yet far better in terms of increasing engine performance. In the early days, intake and exhaust lobes were almost always the same. These were called single- pattern cams. But it didn’t take the race- engine builders long to realize that often the engine’s exhaust port was not as efficient as the intake and needed more duration to help scavenge all the exhaust gas out of the cylinder, especially at higher engine speeds. This demanded a longer- duration lobe on the exhaust side of the camshaft. These cams became known as dual- pattern cams. Dual- pattern cams are now commonplace in even mild street engine camshafts. Ironically, as performance cylinder heads continue to improve, their exhaust ports are also achieving parity with the intake side of the heads, so the single pattern cam is again becoming popular, especially when combined with the better aftermarket small- and big- block cylinder heads. Cam Selection Now that you have a general understanding of these concepts, you can employ them to help you in selecting your next camshaft. Of course, there are libraries full of additional material when it comes to camshafts, and we haven’t even touched ideas such as adding higher- ratio rocker arms and how important valvesprings are to making power. Perhaps the most important point to make when getting into the cam selection process is that you need to focus on how the engine will be used. Camshafts have a major impact on where the torque curve begins and ends, and it seems like everyone always wants to use the biggest cam they can physically squeeze into the engine. This “bigger hammer” approach rarely is successful and usually results in a sluggish engine that doesn’t make power anywhere. Taking a conservative approach to cam selection may not always make the most power, but it will offer an engine that can make respectable power over a broader rpm band, which is always useful for street engines expected to run well between idle and 6,5. In other words, that killer lumpy cam may sound nasty, but it rarely works well in a daily driven street machine.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
August 2017
Categories |