| Author | Message | ||
     Highscore |
Here the net stock timing numbers, measured at 1mm valveŽlift: Intake overall duration 252°, 10,4mm lift Intake opens at 20° before tdc Intake closes at 53° after bdc Exhaust overall duration 259°, 10,6mm lift Exhaust opens at 66° before bdc Exhaust closes at 13° after tdc These are strange numbers for a stock valve timing, designated for an emission controlled vehicle. An overlap of 33° together with such an early intake opening at 20° before tdc is nice for peak power, cleaning any residuals out of the combustion chamber. But is also creates some direct blow -thru of fresh mixture directly into the exhaust. Such timing is therefore really unusual for a modern engine, commonly the intake opens rather lately, not seldom at tdc or even some degrees later. This numbers are from a reliable source, but I have not had the time to proof them. So are these figures true? | ||
| Dannybuell |
I don't know anything, but I can imagine that Erik Buell Racing wanted a cam that would release the engines full potential knowing that the rest could be controlled via ECM. What would Highscore do??? (Message edited by dannybuell on July 07, 2010) | ||
| S21125r |
After looking at the stock exhaust design it is obvious that the Buell engineer carefully selected parameters such as primary/secondary diameter and lengths, expansion chambers placements, etc. I speculate that the whole intake/exhast track from TB to muffler were all selected this way to work as complementing system with the end goal of a torque curve as flat and fat as possible. We all know that every part of engine has compromises (generally speaking) - sort of a rob peter to pay paul when it comes to performance. And we all know that all out HP was not the goal for this engine. Me thinks the cam timing was selected not with peak HP in mind but a "what is good for the entire RPM band" approach. For example, maybe those cam numbers work well with the intake port exhaust design and was the magic combination that got the torque curve that EB was looking for. BTW - For reference I found cam timing on the internet for a 916 - I cant vouch for it's validity nor what lift the measurements were taken... "916 with cam timing specs of 11/70 inlet, 62/18 exhaust" Durations and overlap are close to being the same but looks the like the 916 opens and closes both intake and exhaust later - power higher in the RPM band maybe?? I haven't seen the inside the Helicon up close to know, but wouldn't be unreasonable to think that an adjustable cam sprocket could be developed to retard both cams a little. Might be robbing peter to pay paul though... | ||
| Highscore |
What would Highscore do? Before I do anything with an engine I try to gain as much information as possible about it to get a coherent picture of its operation. The cam timing is here crucial. And may be this is the reason, where there are so many secrets about this information, anybody could gather, who takes the effort to install a timing wheel to the crank and and add a dial gauge onto the valves. My intention to start this thread was to verify that timing figure, I have received from the "source" of this engine in Upper Austria, simply because I have not the time to do this job by myself. Regarding this intention, I am a little bit disappointed by the replies. Does this mean, nobody here has measured the cam timing yet or, who has done it, handles this information also as a hidden secret? Regarding "engineering": Each tune and set up of an engine is always a compromise. The stock set up too, even in a pronounced manner, because it has to satisfy so many and "average" needs. From that point of view, aftermarket tuning is nothing else but redefinition of that compromise for a different goal. And if things run happy, this new tune and set up does not mean some gain here for the expense of some loss there, but a "win-win" over the whole range. In the case of the Helicon-engine, the changes are real good to achieve this goal. For me it looks like, as the Buell (or HD) executive board became afraid, when the received that engine from Austria about its potential. So they tried its "best", to de-tune it to make it "manageable" and controllable for the "average" costumer. The stock exhaust system with its tiny headers is a perfect proof for that "design-thesis" of me: It is a choke, cutting the peak out of the engine. Of course it makes a flat power band, that is its only advantage, if it is any. At least me I want to change this on my private 1125. Call it patriotic fever, I am an Austrian, so it is my personal mission to release the full internal potential of that beautiful engine. So again my question: Has anybody measured the stock cam timing of the Helicon engine yet? Easyrider, not even you? (Message edited by highscore on July 07, 2010) (Message edited by highscore on July 07, 2010) | ||
| Zac4mac |
Dris showed this ... about a year ago? http://www.twinmotorcycles.nl/artikelen.asp?aid=62 This bike is starting to follow another lead from the TLs. the first year may well be the best... Thanks Highscore and Easy for the deeper insights. Z | ||
| Highscore |
Thank you, Zac, for this link. So there is at least one guy around here, who should be able to give me an answer to my question: Easyrider. A simple "yes", this timing numbers are valid, or "no" should not mean much, since you. Esay, reads carefully, what is going on here on this board. So obviously you do not want to answer, what means to me, cam timing belongs for you to your "secrets" and "hidden know how". It is also obviously that you, Easy, tries your best, to become the "tuning guru" for Buell here at this board. But I have problems with "gurus" in the field of engineering. And to this field belongs "tuning" as a subsidiary too: A "guru" gets his inspiration from a privileged source, preferably directly from God, and his rule is to explain this message to us less inspired and average people. But in the field of engineering the "holy grail" is no secret, is is the physic around us, controlled by laws and thereby by formulas and numbers. Therefore I really can not understand, why you, Easy, make such a secret of the timing numbers of the engine. I am not here to become and present myself as the "new" and "better" guru, I am only here to find people, to discuss and gain new ideas. For what? For our common subject: To improve our Buell to make it for the best motorcycle around. In that way, Easy, to not handle it as pure criticism, but as a contribute of a brother in mind, when I comment the pics, Zac has send my by this link: Regarding porting: O.k, the exhaust valve could be smoothed. But for my self, I would never cut the valve guides down without "careful" research. Regarding the intake ports, there is a machined step visible, forming the joint to the valve seats. Is there anybody believing here, Rotax, like all other manufacturers, is not able do design the proper core for the die cast, to avoid that "need" for this visible mechanical re-manufacturing? This step here is no "imperfection", because someone decided to install larger valves in the moment, the tooling for the die cast was finished. This step at the "outer" wall of the intake runners is intentionally: It is an "aerodynamic" device which guides the intake stream in the ports to avoid the cylinder liner and other "walls" inside of the combustion chamber. Remember: The 1125 features extremely large valves, so large, that they are masked by the pore dimension of the bore diameter. A "turbulator" at the right distance of the port (or valve) may therefore help to stabilize the flow at the intake. In my opinion the time of "shaving the ports" is over in the 21. century. The chance to make thing worse is larger than to make an improvement. To go this way you need a flow bench an painstaking testing there. From my point of view, the intake pates and valves are so large at the Helicon engine, that at least for "mild" tuning, there is no need for any porting. What limits the gas exchange here, is only the valve timing (to come back to my essential question). Regarding your header-design, Easy: Looking at the pics, it is obviously that your headers start with thick primaries joint into a common down pipe for each cylinder, whose cross section is obviously considerably smaller than the sum of the streaming area of the primaries streaming upwards. This is an essential failure for an exhaust design. The best performing exhaust is someone, which tells "inside" a story of continuous expansion, offering of the exhaust path an continuous increase of area for the expansion of the exhaust gases. When the exhaust valves opens, the is still a residual pressure of approx. 10 bar or 150 psi inside of the cylinder. This is the pressure of a truck tire. You know, what happens, of such a tire explodes? It blows the windows out in a short distance. This real violate potential energy within the exhaust gas transforms a "well balanced" exhaust system into a sucking effect, helping the engine to discharge the burned gases to grasp new and fresh one. And what is the principle of this transformation of the internal pressure inside of the exhaust gas into "suction"? It is expansion. When the exhaust gas expands, it transforms its internal and potential pressure energy into kinetic energy or gas speed. And for this reason an efficient exhaust necessarily never starts large and continues its path with an smaller diameter. The perfect pipe is a megaphone, which open its the streaming area in the pipe over its whole length. The megaphone has been invented in the late 40th of the last century. So do I have any problems to give you this information. Is this any "secret know how? That just my 2 cents. The "high art" regarding megaphones starts with the question, where, at which distance of the port the "angle enlarges". Or where, within a combined exhaust lay out, the primary headers are merged into a common down pipe. When designed carefully a 2-1 may act like an open megaphone regarding its efficiency to transform the internal pressure energy of the exhaust gas into a better charge and efficiency of engine operation. (Message edited by highscore on July 10, 2010) | ||
| Buellishness |
"The mental features discoursed of as the analytical, are, in themselves, but little susceptible of analysis. We appreciate them only in their effects. We know of them, among other things, that they are always to their possessor, when inordinately possessed, a source of the liveliest enjoyment. As the strong man exults in his physical ability, delighting in such exercises as call his muscles into action, so glories the analyst in that moral activity which disentangles. He derives pleasure from even the most trivial occupations bringing his talents into play. He is fond of enigmas, of conundrums, of hieroglyphics; exhibiting in his solutions of each a degree of acumen which appears to the ordinary apprehension preternatural. His results, brought about by the very soul and essence of method, have, in truth, the whole air of intuition." -edgar allen Poe like reading your threads | ||
| Dannybuell |
Buellishness - I can barely read and write English let alone German/Austrian or Dutch. Nice EAP quote, fits well right here right now. | ||
| Battyone |
I've just spent a couple of days trying to measure valve timings. I say trying because they are a pain to get consistency and even when you do,as there is nothing to compare them to,you doubt the readings. But I'm reasonably happy with what I've got recorded and it gives me a base to work from. I don't get as much duration or lift as Highscore suggests though. all measured at 40thou lift(1mm)and lash set to minimum service values(in 0.006" ex 0.010") inlet:- opens at 15btdc,valve centre 107atdc,closes 41adb. 236duration exhaust:-57bdb,centre 112btdc,closes 11atdc. 248duration. Now the kicker! after trying 3 sets of cams and trying to carefully dial them in,the rear exhaust is advanced 4degrees, giving 61,116 and 7. You can move things about as much as you like but the only way to match the front cylinder would be to move the drive gear relative to the cam. Getting 9.4mm inlet and 9.5mm exhaust lift,but that might not be 100% as it was a little difficult to get dial gauge exactly inline with valve travel. One thing you need to do to get some repeatability in readings is lock down the chain tensioners.Otherwise the cams start moving themselves...try it you'll see what I mean! No wonder they make so much noise. At times I thought I was going mad and was going to check on my 09 motor-but not so easy as there's no thread in stator side of crank to attach timing wheel..doh!So I just removed cams and refit to the race motor. | ||
| Blownharley |
Battyone, have you tried using softer springs during your attempts to measure the timing of the cams? It makes the life easier since there is less spring force that wants to turn the engine around when you want it to stay still.... |
