| Author | Message | ||
     M1combat |
Why can't the XB crank be balanced well enough to let the engine spin to 10K or higher RPMs? What exactly holds back the valve train? Why has no one designed a COMPLETELY different head to help solve the problem? Why haven't they decided to use a hydraulic valve train? WHY!? WHY?! WHY!? It's not that I'm unhappy with my XB12 at all, it's just that I am a race fan and I HATE to see Buells given SOOOO much via rules to make them competitive. Why do we need 1350cc's to compete with a freakin 750? Even a 750 twin... Does Harley not have any sort of REAL race development program? I think the stock cases should be modifyable to run a hydraulic valvetrain. I suppose the rules wouldn't allow it but the Duck valvetrain is a little exotic... I think HD pairing up with Porsche to make an engine was a bad idea... they don't run F1. | ||
| Mikej |
form follows function. all displacement is not equal. life is not fair. equality is a subjective process. venting clears the head and often dislodges a little earwax in the process too. YMMV. | ||
| 99buellx1 |
The Porsche - Harley colabiration is not a new thing. But I think it is a good thing. Craig | ||
| M1combat |
But isn't that what racing is all about?? Taking your idea and making just as good as someone else's, or at least as close as you can get it? I think a hydraulic valve train would go a LONG way towards making the XB competitive. You could replace the entire cam assembly with the hydraulic pump. Many of the F1 teams do this. They run a MUCH more complex system because they have to actuate 40 valves and they do it to the tune of near 19K RPM's making >900 HP. I think HD has the budget to do this. I think maybe they are just content to rest on their laurels because the rules LET them. Form does follow function, which is exactly why the form should be modified to make the function better. All displacement is not equal.. True, but to me the idea of racing is to try to make it equal or better. Life is SOOO not fair  . equality is a subjective process yes, but it's VERY rare in racing that you get a displacement advantage AND keep the same power/weight ratio. just about the only other place I can think of is motocross with 2 stroke vs. 4 stroke. I'm sure I have plenty of earwax . | ||
| Glitch |
What exactly holds back the valve train? Valve springs I think. Once the engine gets going so fast the valve springs can't keep up, so the valves can't open and close in time with the engine. "Valve Float" | ||
| Oconnor |
Yeah but valve float is a relatively easy thing to fix. well for a few more thousand rpms anyway. M1- you could have the motor balanced and have a cam cut to run higher rpms. You would then need to run a programmable ecu. Like electromotive or something. Its possible and expensive. like at least 5 or six grand just for the labor on parts and the computer. But no building. | ||
| Road_thing |
I've got two words for you: "Piston Speed" r-t | ||
| M1combat |
Yeah, I got the 5317 piston speed thing, but I would de-stroke the engine. Keep in mind, I'm not looking to do this to MY bike, I'm happy with it the way it is for now, and later I may do the big bore thing to it but I was wondering why HD doesn't do this for their race teams. I understand no one has official backing from them, but if it's on the down-low and all. I just think the race bikes would benefit from some race R&D done by Harley is all. | ||
| Mikej |
There has been some development work with overhead cams and chain-drive instead of pushrod accuation. You can see over 10Krpm with a properly set up engine in a Sportster or FL based engine format, you just have to set up everything right, tune it right, have the right upgraded ($$$) components designed to handle the higher stresses and fluctuations, and a whole slew of other little nitpickey things that you can't learn by simply having someone build you an engine and taking notes as they do (at best you'll get a superficial understanding due to them not saying everything happening as they think and work out miniscule issues). Harley engine design does not start with a blank sheet of paper, there are pre-determined parameters they have to adhere to (even with the V-Rod and Porsche). Riddle me this: how much difference is there between a 600cc Honda factory full-race bike and a 1000cc Honda factory full-race bike? And after that is there a comparable appreciable difference in lap times between the two? (I don't have the answer handy so someone else will hopefully chime in.) "I understand no one has official backing from them" Not true. "I just think the race bikes would benefit from some race R&D done by Harley" Some do, and it tends to be a reciprocal (sp?) process with feedback going in both directions. Factory: "try this" Team: "here's what we found, now you try this..." Factory: "Hey, neat, now how about this part here ...." Team: "Great, and here it is back with a little tweak" Factory: "Interesting, probably not for production but if we adjust it a little it could work ...." Back and forth and back and forth and not quite as simple as this but not too far from it. | ||
| Fullpower |
M1 much of the rpm limitation with the XB is due to the mass of the pushrods, and rocker arms. if you ran overhead cams, act ing directly on 5 titanium valves per cylinder, you could spin up 13000 rpm, and make 180 horsepower per liter. this has been done, and machines like this are in production. the limitations you noticed are mostly due to valvetrain dynamics, and also the relatively long stroke. a shorter stroke and bigger bore would leave more room for bigger valves, and more air flow, and a side benefit of lower piston speed. | ||
| Nevco1 |
In as much as this may not make any sense to an aspiring world class racer, I think that HD/BMC has made a credible decision to keep the playing field level for the grassroots home mechanic. Tweak a little here and there and you have a bike that plays well with others, gets attention for a variety of reasons (some good, some bad), sets us apart from the crowd as individualists and perhaps purists, yadda yadda yadda. I liken Buelling more to racing sailing yachts than offshore power boats. More mental and physical coordination/timing required. Kill 'em in the tight stuff and pray the straights are either short or filled with radar! See...nobody ever understands me.  | ||
| Whodom |
The top end of the Buell engine is not the RPM limiter. They already use some things learned from NASCAR, and those engines, with similar valve sizes and pushrods are reliably (relatively) turning ~9,000 RPM. One of the magazine articles specifically stated that the XB12 was RPM limited due to rod bearing reliability issues at higher speeds. They've even incorporated a sophisticated "soft" limiter which allows very specific limited higher RPM bursts, but holds extended RPM at a lower level. Can they make a bottom end that'll handle more continuous RPM? Maybe is my guess. | ||
| M1combat |
So, uhhh, why don't they make this system race worthy? Too spendy? I suppose though, with the knowledge that HD has told the XB teams to use the perimeter brake system maybe they are trying to see what they can do fairly close to stock? I see the point of that, it would allow them to develop parts that can be used on the street version... Mikej - Who is "officially" backed by HD? I have heard of them giving trick parts (or at least paying for them) to Hal's, but isn't that on the down low? Also, I'm not trying to get info for MY bike so money isn't really an issue (unless HD has money issues?) and as far as building them, I was thinking more along the lines of HD building and testing them and then supplying them to the teams who race HD's. | ||
| Joojoo |
M1, What turns your crank? a Cobra 427 block, in a Shelby ragtop roadster, or a VTEC driven Integra that spinns to 9000 RPM with no torque at all? Buell does not compete or try to compete with the high revving Japanese bikes out there. The XB line is doing their own thing, not trying to play in the other bikes parks. Theyre also doing this with an air-cooled twin. The XB motors are not designed to run at high RPM's. They simply do not want to. It physically hurts them to run that way. If HD wanted to, they could (trust me) build a high revving twin, or I4 for that matter. They have the cash and R&D to do it. Thats not what the company wants to do. The VROD motor revs nicely, and it won most every award for design, and reliability is great. So we know they can do it. Right now we are at the beginning of Buell's "Corporate" lifecycle. One line of bikes, one motor....Watch as time goes by. New lines will show up, addressing all of our hopes, and they will do this in a very "Buelly" unique way. I cant wait to see what happens. Id like to end up with a Buell collection, starting with my XB12S and grabbing a new bike everytime they introduce a new motor. FUN FUN!! Jack | ||
| M1combat |
I plan on the same myself, maybe skipping some but I agree, most of them should be classics. As far as not competing or trying to compete, I have to disagree... From what I hear they will make an effort in FX. Honda has also decided to do that, as well as Ducati and possibly aprillia. I just want to see Buell's at the front. Personally, I think I will, but I hate that they need to use so much more displacement to do it. I think you hit the nail on the head with the "wait and see" comment though. I expect good things. Besides, it wouldn't sound like a WWII fighter plane if they changed the engine too much . I only hope that HD doesn't get bored with it. | ||
| Nevco1 |
Where are Blake and Jose when you really need them??? | ||
| Mikej |
See, some believe the top end is the limiting factor, some believe it's the bottom end that's the limiting factor, when in fact both ends get tweaked on race bikes, but then both ends get tweaked on inline-4 race bikes. I don't really follow the race teams but there is a lot of factory sponsorship going on at many levels. There may not be a functional "wrecking crew" like there was back in the board-track days, but there is still factory support. And I kind of went the other direction, started with a 2000 M2 and then went to a 1995 S2 and would like to get a 1988 RR some day. The XB's might be fun bikes, but they don't really tickle my gizzard much. I guess I'm just a caveman riding a dinosaur, but that's okay. I'm still kicking myself for not getting that old ULH prior to moving to Wisconsin, would have been fun. And in the mean time I'm waiting for the 55" wheelbase 1340cc XBRS to be released (purely fictional, but stranger things have happened).  | ||
| Nevco1 |
And in the mean time I'm waiting for the 55" wheelbase 1340cc XBRS to be released (purely fictional, but stranger things have happened). Mike...That's the one with the re-invented wheel, eh? | ||
| Hootowl |
M1Combat, The Buells have hydraulic valves already. The XB uses nascar type springs to push valve float up to 8K. Hydraulic valves limit, not enable, high RPM usage. Or have I completely misunderstood you? | ||
| Mikej |
Nev, You mispelled flywheel.  Otherwise, yes. Hoot, I believe he is talking about pure hydraulic actuators or plunger type valves without the limitations of rockers arms and such. I could be wrong though. Other varieties of valving have been tried including flapper valves. Cams and pushrods and rocker arms are simple and basic and fairly straight forward in design and assembly and application. If you want faster consider leaf/blade shutters, they too have been tried in the development of internal combustion engines. | ||
| Blackhat |
I may be wrong, but...... The Harleys, and Buells, run a single pin crank. Both rods connected to one point on the crankshaft. This, along with the tight cylinder angle, gives the distinctive ka-plop, ka-plop sound to their motors. I've heard that Harley has tried to patent this in order to maintain their individuality in the design and sound. This causes the crank to turn well over half a revolution before the lead piston reaches TDC the next time around. This also causes the heavier vibration, and is tougher to balance throughout the RPM range. The Japanese bikes balance their action by using multi-pin cranks that fire around the full turn of the crank, giving them a smoother turn with less vibration, better balance by design, and power throughout the 360 degree turn of the crank. Top this off with 3, 4 or 5 valves per cylinder and eliminate the valve train by using overhead cams and there you go. I'm not a big fan of the Japanese bikes, but I have to admit that the technology they run commonplace is well ahead of Buell. I ride the Buell because of this exact reason..... And others. I honestly feel that the big American V-Twin has been nearly maxed out as far as output goes. Without changing the design, bigger displacement is one of the few options left for REAL increases in power. Sounds like a very American approach to the issue, and the reason I like these bikes. Blackhat} | ||
| M1combat |
Blackhat - Understood that this engine is a "venerable" design... but I just think it would be both possible to implement and beneficial to the race teams. I don't think I'll see a new streetbike the year after they try this on a reacebike, but maybe a few years. See, I agree with you, I think the V-Twin has nearly maxed out as it goes, and I am asking why don't they change the design, and if they do, why not take it straight from the pinnacle of motorsport? If they have a weakness, they should strengthen it by using the best method available. I think that enough is known about both hydraulics and these engines that it could be done. I think it would be drastic, but why not? Keep in mind that I'm not thinking they should do anything different to say a wideglide, sportster, FX.. Just take the race bike and make it a damn world dominating freakin race bike. IF THEY CAN, but they should try. Hootowl - I am talking about a completely hydraulic valvetrain. You wouldn't even have cams as you know them. Just the Valves and a hydraulic pump running from the output shaft. BTW, the fact that there is as much in this XB12 as there is, and that it should be quite reliable is mostly why I bought it too. edited by m1combat on December 11, 2003 | ||
| Joojoo |
Blackhat, You wrote "I honestly feel that the big American V-Twin has been nearly maxed out as far as output goes" Erik Buell will figure out ways to drive the American Twin for Buell's XB lines for the next decade, while making then 'better' every revision. From everything I have read about this man, and watched him produce, he is one of the most unique thinkers and amazing designers to come to the motorcycle industry. And then, we have to look at the whole picture and wonder, what does 'better' really mean? More power from less size? more moving parts? Depends on how your brain works...Some people go crazy for complexity, some just love simplicity. I myself, am a minimalist. I love to sit and watch these companies try to jam as many computers and springs into their motors in hopes of "being the best". Its a joke. Buell takes the other road.The best to me is the simplest, that feels the best. I get that from the Buell's. Have faith in the American Twin my friend, and have faith in Erik Buell and his team! They wont let us down. Jack | ||
| Blackhat |
JooJoo, I agree. I'm one who rides these bikes. I tried to make it clear that, the current design, (how old?) I feel, is just about maxed out. Yes you can get a little more here, a little there. Holes drilled in airboxes, big bore kits, heads, porting, polishing, race filter, headers, mufflers, ECM etc. These upgrades will only go so far to make the XB9R that I ride faster. With all of these upgrades, will it hold it's own in pure balls against a Gixxer 1000 straight out of the box? An R1? By design, I mean 45 Degree, V-twin, push-rod, 2 valves per... etc. Displacement size is going to be your biggest power gain without changing the design. Not that I give a flip. You never heard me complaining. I'm not on the quest for the next biggest and baddest speed demon. If that was my bag, I would've bought the 'Busa. Instead I ride the Buell. Blackhat | ||
| M1combat |
Good post Joojoo, but I think if the binefit is great enough, then complexity can be added in moderation. I love the simplicity of this engine. I wouldn't want much else in my bike until it's been VERY proven wrt reliability. As far as a hydraulic valvetrain, I think they are reasonably simple... They didn't use them in F1 in the eighties because they couldn't get it to work at a great enough RPM. Now they run >18000 RPM's for hours. I don't think you'll find an HD engine that runs at the temps that F1 engines run either. If research was put into this, I think that a five valve engine would be easy (Compared to how they apparently do it now). Maybe it's been tried and doesn't work... The first thing I can think of is trying to make the pump work consistently while hooked to the output shaft of a V-twin. I'm sure there's others, but if Ferrari can do it at 18K RPMs for race distance making somewhere around 900 bhp it can be done with the HD design. Not quite to the tune of 18K sure, but higher than all that stuff that doesn't wan't to accelerate in the valvetrain will let you go. As I recall, I think these systems eliminate valve float completely. I guess I just look at it a bit differently than most. I like to see car manufacturers take a chassis (good or bad, think Ford GT-40 vs Viper) and do whatever it takes with the engine to make it fast. I suppose though, the Viper does have a huge displacement advantage in GT, but a bit of a weight DISadvantage as well. edited by m1combat on December 11, 2003 | ||
| Rocketman |
This, along with the tight cylinder angle, gives the distinctive ka-plop, ka-plop sound to their motors. Blackhat - POTATO POTATO <grin> Rocket  | ||
| Fullpower |
M1 in regard to hi rpm and balance factor, i took a wild test ride on a v-rod. a most un harley like vtwin: no engine vibration, either on handlebars or footpegs. smooth, but real low on power till you get to 6000 rpm, then it gets real strong. revs out to 9000 rpm in the first 4 gears, ran out of road, so only got 8000 in 5th, but it was still pulling pretty well. again, no perceptible engine vibration, 9000 rpm redline, and yet vtin made in usa. so it can be done, now if they would just scrape 250 lbs of crap, radiator, goofy handlebars, one of the disc brakes, and maybe put it in a more sporting chassis 'sport-rod' maybe i will have to buy one. | ||
| Fullpower |
my only point was that you can make 100 hp per liter with an american vtwin at 9000 rpm, and not have a paint shaker.... dean | ||
| Blackhat |
Got it...... My bad. That's the exact word I was looking for when I came up with Ka-Plop..... Damn. Blackhat | ||
| Wyckedflesh |
to much Monty Python there Blackhat? |
