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Thread: Tech Discussion on Camshafts *LONG*

  1. #1

    Default Tech Discussion on Camshafts *LONG*

    what you need to know before you buy cams and what they do.

    Power Tech: Camshafts

    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 toits 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, thepiston 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. Â*







  2. #2

    Default Re: Tech Discussion on Camshafts *LONG*

    all you ever wanted to know about these guys... i'm going to start a serious compilation of information. please keep comments to a minimum this is for reading everything you want to read in one place.

    Quote Originally Posted by Blak94GSX
    A multi-volume library could be written about cam timing, and several are available if you would like to purchase some...

    Without getting into extremely boring engineering equations, which have limited practicality anyway, here are the basics as they apply to the 4G63 DOHC setup and the commonly used types of cams:

    There are basically 2 reasons to mess with cam timing, one being to move the powerband around to match the mods in an effort to maximize the usable powerband, and the other is to "fix" cams that are a poor match for the mods in the first place.

    Next, there are 2 basic concepts related to cam timing, which are the relationship of the cam to the crank, and the relationship of the cams to each other since we have a twin cam motor.

    The relationship of the cams to each other are commonly referred to as "overlap", and the relationship of the cam timing to the crank timing is referred to as "lobe center".

    Here is an excellent write-up, which I won't bother to recreate since it covers what is important: http://www.starracing.com/Cam%20Lobe...0Explained.htm

    So, back to EVO specific stuff...

    Do you have crappy cams, or do you have good cams? If you have crappy cams, cam timing will be very important since you need to correct for a poor cam design. If you have good cams, you can use the stock cam gears...

    If you have good cams but want to move the powerband around a bit, here are some rules of thumb.

    -Retarding both cams will move the powerband up a few hundred RPM. On the EVO with the HKS 272 cams, a popular setup is to use 2 degrees retarded for both cams. Since both cams are moved evenly, the overlap doesn't change, only the lobe centers change, causing the valves to open and close later. In this case, the cams spin half as fast as the crank, so 2 degrees at the cam is 4 degrees at the crank. The crank will be an additional 4 degrees through its rotation before the valves open/close.

    -Advancing the Intake cam, and Retarding the Exhaust cam will open up the overlap a bit. This allows the cylinder to fill sooner due to the intake valve opening sooner, which can sometimes be advantageous in a turbocharged engine. This also helps to improve the idle quality since the Intake cam has a larger impact on the idle than the Exhaust cam does. Or, the exhaust cam can be retarded more than the intake cam, as in a -1 -4 setup. Both cams are retarded in this situation, but the exhaust cam is moved more, increasing the overlap.

    Ultimately this is one of those cases where a dyno comes in real handy. You move the cams around until you find the right combination. Unfortunately theory only gets you so far, and practice makes perfect...
    http://www.socalevo.net/gallery/albu.../camshafts.pdf



    http://www.starracing.com/Cam%20Lobe...0Explained.htm

    One of the least understood topics and regarding engine tuning and building continues to be the concept of cam timing and “lobe centers”. The opening and closing process of an inlet or exhaust valve as controlled by a cam lobe constitutes a complete “event” in the cycle of the engine. Like any event, it has a beginning and an end. Naturally, then it also has a middle or center. The location of this center in relation to the rotational position of the crankshaft is known as the lobe center.
    The process of “degreeing” cams allows the engine builder to place the lobe center of a cam in the correct orientation with reference to the crankshaft. The opening and closing points and resultant figures of the cam, although important, are very difficult to reference to set cam timing and are, after all, the result of where the lobe center is placed. Therefore the lobe center is used to reference cam timing. The difficulty in measuring the opening and closing points is the result of the very shallow and gradual starting and stopping of the valve motion. How do you tell just when the valve motion starts and stops? If you pick a specific amount of lift at some height beyond the initial gradual motion and always use that amount as a marker for the beginning and end of the motion, the center will always be halfway between these points. Therefore, the lobe center is computed from a timing number derived at a specific valve lift. Any lift could be used to compute this, but in the Japanese motorcycle industry 1mm or .040” is traditional. U.S. (automotive) cam grinders have used .050”. This “checking height” must be used to minimize the effect of the shallow opening and closing ramps on the cam lobe. Without this, each builder’s subjective notion of when movement starts would be the defining factor of timing. One picture is worth a few thousand of my words so now refer to my crudely drawn diagram for clarification. The diagram graphically shows how these points lie in relation to the degrees of crankshaft rotation. The usable range of lobe center values for just about all commonly used engines is only about 15 degrees wide from about 98 to 112 degrees and for the engines we use, the right spread is even smaller than that. Small changes of one degree can have considerable effect on the power delivery characteristics of an engine.

    Very generally speaking, the effect of moving lobe centers is as follows:
    Advancing the intake and retarding the exhaust (“closing up the centers”) increases overlap and should move the power up in the RPM range, usually at the sacrifice of bottom end power. The result would be lower numerical values on both intake and exhaust lobe centers.
    Retarding the intake and advancing the exhaust (“spreading the centers”) decreases overlap and should result in a wider power band at the sacrifice of some top end power. This condition would be indicated by higher numerical values on both intake and exhaust lobe centers. By moving only one cam the results are less predictable, but usually it is the intake that is moved to change power characteristics since small changes here seem to have a greater effect. With twin cam engines we have the luxury of moving the cams independently.

    With a single cam engines you must advance or retard the intake and exhaust together, usually using the intake lobe center as the reference and only the cam grinder can spread or close up the centers when the cam is ground.
    Basically, here’s how it’s done in the real world. I’m not going to tell you what lobe centers to use, as this varies from engine to engine, just how to determine them.
    Many engine builders take lobe center measurements with zero valve lash (clearance) so that all movement can be detected. In fact, the valve lash can actually be slightly negative, that is the valve can be held slightly open by the cam with the valve in the closed position. You may also do the calculation with the running clearance at the valve. The amount of pre-load or clearance on the valve has no effect on the lobe center number but will effect the opening and closing numbers. What IS important is that, for future comparison purposes, you always do it the same way with the same lash value. It is also very important that an accurate top dead center “TDC” reference be used when degreeing cams.
    Therefore, this should be checked carefully and the degree wheel and pointer set accordingly. Take a great deal of care when setting up your degree wheel, pointer, method of turning the engine, and dial indicator. A change of one degree can be significant, so accuracy is very important. A dial indicator is used to measure the valve motion in hundredths of a millimeter or thousandths of an inch. Set your dial indicator so that the plunger pushes on the retainer or tappet and moves as nearly parallel to the valve travel as possible. It is not necessary to use any particular valve, use one that allows the easiest indicator set-up and that you can easily see from the same side as the degree wheel.
    I recommend that you begin with the intake cam, since the intake is the most likely to be damaged by an insufficient amount of valve to piston clearance or incorrect timing. Always start with the cam sprockets closest to the stock position.
    Begin with the valve fully closed and with the dial indicator zeroed.
    Double check the plunger movement to see that it moves freely, does not interfere with the cam lobe, rocker, or any other moving parts, and returns to zero when moved and released.
    Rotate the engine in the correct direction while watching the dial indicator. Stop when the pointer shows 1mm of movement. Note this number.
    On an intake cam, this will be a value before top dead center (BTDC). Continue rotating the engine, watching the dial indicator as the valve opens, then begins closing again. By counting the revolutions of the pointer and watching
    it return towards zero, you can stop when the valve lift is still 1mm before fully seated, noting the degree wheel value at this point. On the intake cam this will be a value after bottom dead center (ABDC). It is important to stop at the correct point because you should avoid turning the engine backwards as this unloads the cam chain and can result in an erroneous reading.


    To compute the lobe center, you:
    A. Add the two opening and closing numbers noted
    B. Add 180 to this sum
    C. Divide this sum by 2
    D. Subtract the smaller number of the two opening and closing numbers from this quotient.

    The result is the lobe center. For Example:
    Intake opens (at 1mm lift) 38 BTDC
    Intake closes (at 1mm lift) 68 ABDC

    38+68+180=286, divide by 2 =143, subtract 38 from 143 = 105
    The lobe center on this cam is 105 degrees.

    The method is the same on the exhaust except the opening number will be a value before bottom dead center (BBDC), the closing value will be after top dead center (ATDC) and again, subtract the smaller number.
    For Example:
    Exhaust opens (at 1mm lift) 60 BBDC
    Exhaust closes (at 1mm lift) 40 ATDC

    60+40+180=280, divide by 2=140, subtract 40 from 140 =100
    The lobe center on this cam is 100 degrees.

    Note that in both cases, it is the smaller of the two numbers that is subtracted.
    Also note that the 286 and 280 degree values are similar to what may be the advertised duration of the cam. This number is called the “checking duration” as it is dependent upon the checking height used (in this case 1mm).

    Remember, the opening and closing values (and duration) are dependent on the checking clearance and will vary based on this amount. The lobe center number will not. This is why published numbers are not a good way to compare cams. You must always know the checking height that was used to derive those numbers.

    To change the lobe center, loosen the sprocket attach bolts and move the crankshaft slightly to alter it’s relationship to the cam. Retighten the bolts and re-check. When the selected value is finally reached, tighten and loctite the bolts, then re-check one more time. With a little experience you will know which way to go to advance or retard a cam to achieve the desired lobe center.

    Caution:
    Moving lobe centers can drastically alter valve to piston clearance. And remember, the closest point is rarely at TDC. The most critical is the intake and usually occurs somewhere after TDC. Make all adjustments in small increments and NEVER force the engine past any resistance until you know the cause.
    Changes to the power output are can be subtle, hard to predict, and frankly, most of this has been explored to death so it’s unlikely you will find some “new power”. But each engine is different and cam timing must be part of any fully prepared engine. Be careful with following “we always did it that way” thinking.
    The advent of electronic fuel injection and four valve heads has changed the cam requirements of engines. Increased valve area means less “cam” gives you more flow. On an injected engine you no longer need to create a strong vacuum signal through a carburetor throat for good fuel atomization. The injector is going to get the fuel in there instead of flow across a jet. The only way to optimize cam lobe centers is through extensive and careful dyno or performance testing.

    I <3 Nisei Engineering

  3. #3

    Default Re: Tech Discussion on Camshafts *LONG*

    this is a hairy subject that i wasn't gonna tackle for some time... but since it's here i'll start compiling info. i'll sort through this crap later i have something to do atm.

    Quote Originally Posted by Ted B
    My 280s set at +2/0 (don't try this without expert tuning) spool as quickly as my 272s did at -3/-3, both configurations reaching full boost by 3500rpm with a TME 16G Ti/Al turbo.

    - However -

    With the 280s I made 30 ft/lbs greater torque than with the 272s, reached peak torque ~200rpm quicker, with no change in boost pressure. This is probably more reflective of the cam timing than the cams, but the point is I definitely didn't lose any torque by going to the 280s, so the notion that one loses torque with the 280s is baseless and is dependent upon tuning accuracy and other factors.

    Despite the advanced cam timing with the 280s, I reached peak power at 6400 rpm, just as I did with the 272s set at -3/-3. The difference is I made 16whp more with the 280s, again with no change in boost pressure.

    Note: This was all done with a Dyno Dynamics dyno, so tack on another 12-15% to those differences for Dynojet numbers.

    I did however install a new IC at the same time as the HKS 280s, so maybe there is some difference there, but from what I've seen, most of the observed difference is due to the cams, the timing thereof, the capability of the tuning hardware, and the skill of the tuner.
    Quote Originally Posted by Ted B
    HKS 272s, set at -3/-3, stock IC and 93 oct (black) vs. -4/-1 setting (red):


    Quote Originally Posted by Ted B
    HKS 280s set at +2/0 with Nisei IC and 93 oct:

    Quote Originally Posted by Ted B
    HKS 280s set at +2/0 with Nisei IC and 93oct + 100% METHANOL

    Quote Originally Posted by Ted B
    The Cossie M2s give a 110 deg LSA, like the HKS cams. However, the LCs for the Cossie cams show that if installed straight up, the Cossies are like HKS cams installed at +1.5 Int / +1.5 Exh. So, if one wanted to run the equivalent of HKS 280s at +2/0, he'd install the Cossie cams at +0.5 / -1.5. If he wanted to run the Cossies at the equivalent of HKS at -3/-1 (more top end), he'd set the Cossies at -4.5/-2.5.

    The nice graph you pointed to at norcalevo.net shows what one gets with the HKS 272s, when set to +1/-1, which is a setting that I always recommend for the HKS 272s for best all-around street performance. In that graph, the longer valve timing of the HKS 272s is what gives the broader hp/tq bands vs. the factory cams. Where cam timing is concerned, the tighter LSA of the +1/-1 setting he used for the HKS 272s vs. the factory cams at 0/0 (106 deg vs. 110) is why the larger HKS cams spooled ~250rpm quicker than the factory cams.

    More hp, more tq, larger power bands and faster spool. It's definitely like having your cake and eating it too.
    Quote Originally Posted by Ted B
    If it were up to me, I would probably (at least initially) set the Cossies to the equivalent of the HKS 272s at +1/-1. For the Cossies, this would be a setting of -0.5/-2.5.

    Quote Originally Posted by Ted B
    For autocross, if the revs will drop to less than 4000rpm anywhere on the course, I wouldn't touch a retarded timing configuration, such as -2/-2. That improves peak power slightly, but at the expense of midrange torque and spool time.

    For 264s and even 272s, I would opt for +1/-1, or possibly even +2/0. The result is quicker spool, fast transient response, and a significant bump in the midrange torque peak. If getting in and out of corners is what you're after, this is what you want.

    this thread is just an exercise to see if you can do the math and visualization. it's got some pretty good info in it.

    http://forums.evolutionm.net/showthr...highlight=cams

    http://forums.evolutionm.net/showthr...highlight=cams


    this is ams's test of the juns vs the hks cams. beware of the aggressive ramp characteristics of such cams.

    http://forums.evolutionm.net/showthr...highlight=cams


    this is a long winded debate about long durations cams

    http://forums.evolutionm.net/showthr...highlight=cams


    here's a way to lose a lot of low end power to gain top end power.

    http://forums.evolutionm.net/showthr...highlight=cams
    I <3 Nisei Engineering

  4. #4

    Default Re: Tech Discussion on Camshafts *LONG*

    Quote Originally Posted by Ludikraut
    And last, but certainly not least ... cam timing.

    When I first got the car to break it in, the HKS 280 cams were installed straight up (0/0) and spool up was ... well ... less than optimal. The turbo would begin spooling around 3800 rpms, with full boost by maybe 4100, if not later. Needless to say, I wasn't very enthused or amused.

    At this point a HUGE THANKS goes out to AMS, because they spent an inordinate amount of time troubleshooting the slow spool issue and were more than fair in what they charged me for labor.

    Ultimately we finally got a decent baseline tune on the car, which would be Run 038. We did not adjust boost at all between runs, only timing. So, to summarize the runs (SAE correction):

    Run 038: 344 whp, 300 tq - 0/0 - Baseline tune, 2nd worst spoolup, worst topend
    Run 042: 358 whp, 303 tq - -2/-2 - didn't lose spoolup, much better topend
    Run 043: 361 whp, 302 tq - -4/-4 - worst spoolup by far, best topend
    Run 048: 356 whp, 314 tq - +2/+2 - slightly better spoolup, good topend, good torque
    Run 054: 360 whp, 317 tq - +2/0 - Best spoolup, Best Torque, Best topend (just look at the curve)

    I've also attached a second graph, comparing just the torque curves (uncorrected) ... IMO it's easier to see the differences.

    So it looks like Ted B was 100% on the money when he decided on the +2/0 settings for his HKS 280s (running a TME turbo). Even with a bigger turbo (GT3071), there is no appreciable topend to be gained by retarding the HKS 280 cams. The gain in spoolup was significant, to the point where the car now spools up at 3500 rpms and hits full boost before 4000rpms.

    l8r)




    Quote Originally Posted by Ted B
    Good job!

    The cam timing results are interesting, but expected. Given the similarity of results posted sometime previously by another individual, I too am sold on the +2/0 arrangement for the HKS 280s, which seems to work in good harmony with the engine's flow characteristics.

    Those who've been led to believe that cam gears aren't worth the trouble should take note of the extra 16whp, 17 ft lbs, and quicker spool time.
    I <3 Nisei Engineering

  5. #5

    Default Re: Tech Discussion on Camshafts *LONG*

    Quote Originally Posted by earlyapex

    I don't have comparison charts for the different types of aftermarket cams but I do have this for the difference between stock cams/gears and HKS 272/272 with HKS cam gears and properly tuned for it, no loss anywhere, gains everywhere.

    Look at the curves not the numbers since the ECU+ dyno is 10 HP off the mustang dyno I was on when I made this log

    I <3 Nisei Engineering

  6. #6

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