| Author | Message | ||
     Gonen60 |
As far as Mechanics go, I can easily admit I am a mere mortal, Novice, Layman. I think you get the idea. Considering the Size of the XB9s Motor (and 12s) Why does it seem the HP output is fairly Low. It seems every review I have ever read always touches on this point. V twin, air cooled, water cooled, inline 4s, there are so many different engines and sizes and combinations. You have your Ducati 999, water cooled 998cc making 120+ Horse power. You have your Honda 600RR, 599cc water cooled making 100 true HP, of course not the torque the XB makes, But thats almost 400cc less than the Mighty (isn't it) XB motor. almost all of us love our V Twin Motor, But truth be told we would all like 20-25 more Horses. Why does the XB not come from the factory like that? Is it because it would take away from reliability? would it cost the factory a lot more money, that would be passed on to the buyer? Is it simple as Buell just wants to keep something up it's sleeve, so they can grow better and better each year, slowly? Can the V Twin motor we have not make the 20 more HP? Sure the XB is fantastic, and I love every ride. But like all of us, more HP would be a major plus. I don't subscribe to the notion that, Sure the 600 Honda will whip the XB on the straights, but the XB will catch up in the corners. If possible I would like both. Top end and flickability. the answer is not as simple as buying a different bike. That is not in the choices. Just wondering if the motor the XBs use at the end of it's Cycle? and if not, when and what is left to come? | ||
| M1combat |
It's a pushrod 2 valve engine... It would make more power if there were four valves and overhead cams would certainly make more RPM's thereby producing a good deal more power. Of course, water cooling allows you to run higher piston velocities as well adding even more RPM and power. I belive that four valves and over head cams could be done but I like the air cooling. I think the XB's could have come in at 110 RWHP but I do believe they would cost a bit more as there would be more warranty issues. The other thing is that I think Harley sees cruiser types hopping on a 110HP monster and getting hurt badly. I think Buell will work up to it over the next few years. | ||
| Dyna |
Of course, water cooling allows you to run higher piston velocities as well adding even more RPM and power. Hows that? | ||
| Johncr250 |
Its all about rpm`s. If an XB 12 could spin to 10,000 or 12,000 rpms you could make a ton of more power. If you compare dyno runs of other bikes (v-twin or inline) the XB 12 motor is better or atleast equal to many bikes up until 6500rpm where it hits it rev limits. | ||
| Johncr250 |
I think if i could get 20 more HP from my XB12 it would be one the best bike on the market. In all aspects (acceleration, handling, and fun factor. But i still love her because of the way it sounds, looks, and handles. | ||
| Static |
The major reason ( and I think the point has been partly made) that the xb motor does not make more Hp than it does, is that it can't rev as high. Hp is a mathematical function of torque. The equation to find Hp is Hp= torque multiplied by RPM divided by 5252. So the faster you can spin a motor the higher the Hp. This is why a 600cc sportbike can make fairly high Hp near 13,000 rpm or more. The major limiting factors of the buell design is the valvetrain. Lifters can actually launch off the top of the cam lobes, pushrods vibrate and flex, and valvespring pressures are so great just to keep everything under control that they would cause premature failure ( in a street application) if moved much higher to get those extra revs. Though overhead cams and pent-roof four-valve heads (the same type of design that virtually all other bikes use) would make a great change in the operating range of the motor, I doubt that will happen anytime soon. | ||
| Johncr250 |
Well stated Static!!! | ||
| M1combat |
"Of course, water cooling allows you to run higher piston velocities as well adding even more RPM and power. Hows that?" By keeping the cylinder cooler... I agree with Static, I don't think Buell will go water cooled for quite some time if ever, and I'm down with that  . | ||
| Smitty |
Higher compression, water cooling will help keeping temps in check ,stroke and bore are limiting piston speed (component mass). edited by smitty on March 28, 2004 | ||
| Gearhead |
How does the 90 degree vs 45 degree configuration figure into this? | ||
| Dyna |
You could water cool the rpesent v-twin & you still wouldnt be able to rev it any higher. I still fail to see where water cooling would help with the hp. Water cooling helps with noise emmisions from the motor itself, water cooling will help a motor that already is capable of reving high, but it wouldnt add any hp to the preent v-twins at all. | ||
| Static |
first off gearhead, 90 degree vs 45 degree v-twin- the angle between the two cylinders really has little affect on power output of a motor, but it does change the way the rotating assembly ( crankshaft ) is balanced, and how the engine feels ( vibration) to the rider. second dyna, though water cooling wouldn't help the current engine rev any higher ( valvetrain already the issue) it could help hp in that with greater control of both combustion chamber and cylinder temps a cooler more controlled environment would be present in the combustion chamber and the piston to cylinder wall clearance could be lessened without worry of excessive piston scuffing. This would help reduce blow-by due to less rocking motion of the piston and the smaller ring end-gaps necessary. Likely leading to higher torque output and therefore higher horsepower | ||
| M1combat |
Yes it would. You could rev the engine higher because it can dissipate heat faster. Have you looked at the power curve on an XB? (yes that's a rhetorical question) It goes up all the way until the rev limiter. It's quite obvious that if you were to raise/remove the rev limiter and rev the engine farther the power curve would continue to rise. I don't think the boreXstroke of the 12 is enough to yank a conrod at 6800 RPM's. I think with a good deal of extra cooling you could pull 7800(7200 yellow) just as reliably (with maybe a little work to the valve-train as well). I don't think that conrod strength is the issue at 3-13/16" stroke at 6800. I think it's heat and valvetrain deformation. edited by m1combat on March 28, 2004 | ||
| Static |
m1, what is the conrod length on say and xb12? And though strength isn't an issue, what about piston sideloading at increased rpm? I know it's not likely a problem but I'm just curious. | ||
| M1combat |
I'm not sure static, but I can check my manual... As far as side loading... well, I would suspect it to be more of a problem than at 6800 but I think that heat and the valvetrain are the bottlenecks you would run into first. | ||
| Static |
that's what I figured, just my curiosity getting in the way. Thanks m1 for the help | ||
| Johncr250 |
I think the only thing liquid cooling would allow, is for you to run higher compression and maybe alittle more timing. As far as RPM`s you could probably spin a XB12 to 7500 max. Higher than that you`d just be floating the valves and tappets. The bottom end could probably go to 8000rpms in short spurts (with your fingers crossed and couple of Hail Mary`s thrown in) I don`t think the issue is heat at higher RPM`s, it`s the valve train. | ||
| Blake |
Please explain how hot water cools better than cool air. That's rhetorical. The answer is that it doesn't. Take a look at the air ducting on an XB sometime. Why add an intermediary fluid to cool two cylinders that are not touching and are sticking out in the air already? Think about the difference between an IL4 and a V-Tsin. Why might an IL4 do better with liquid cooling versus air cooling? Answer... modern IL4's benefit from liquid cooling because their cylinders are so darn close together that there little to no room for finning or adequate cooling airflow. Ducted forced air cooling ss more efficient than liquid cooling. No water pump, no extra weight from radiator and fluid. Simple, more efficient, and better looking too. Water cooling does help attenuate the noise though, and that is a big factor affecting how powerful Buell can make the stock engines.  Friggin EPA noise nazis!!! | ||
| Johncr250 |
I`m not an engineer, but i think liquid cools much better than air. Thats not to say that air can`t cool very well, it can. And aircooled/oilcooled Buells run very well. The only comparision i can think of is that if i was on fire, i would want someone to throw water on me, not blow on me. | ||
| Unibear12r |
Not that I can argue from personal experience. But- In the time I've been around Sportsters the Conventional Wisdom is (that I've heard) that yes you are pushing the valvetrain but it IS the rods that limit rpm most. The engine can make a lot more power but not much more rpm. Esp. the longer stroke 1200s. There have been a couple of interviews with EB about the reason for the soft limit on the 12s and he flat out says its there to save the bottom ends from those who would live at 6800. Check out FUELL a few issues back if you can. | ||
| M1combat |
"The bottom end could probably go to 8000rpms in short spurts (with your fingers crossed and couple of Hail Mary`s thrown in)" That's why I was thinking 7200RPM for the soft limit and 7800 for the hard limit. "As far as RPM`s you could probably spin a XB12 to 7500 max. Higher than that you`d just be floating the valves and tappets." Which is why I think you would need a bit of valvetrain attention. Carbon-Fiber rods and better rockers would go a long way, as would some springs. Maybe even Ti valves. As far as water cooling a harley style engine, I would probably leave as much fin as I could just because every little bit helps. You really think that water cooling a Harley style engine would be less effective than the air cooling you see on a Buell? Just curious. Now I need to look up the rod length on a 12 so I can figure out the l/d ratio. Does anyone know what a "pretty safe" ratio is when using slipper pistons? | ||
| Johncr250 |
Unibear, I never figured that about the bottom end. I thought it was pretty strong. I learn soo much from you guys!! | ||
| Static |
"Please explain how hot water cools better than cool air." Blake, I think you are misunderstanding something. In and internal combustion engine there is a lot of heat trying to make its way out. shortly after ignition the combustion chamber reaches in excess of 2300 degrees. Mind you that the aluminum your pistons are made out of melts at about 1800 degrees. So cooling is pretty important. Yes, an air-cooled engine does seem to skip a step (compared to a water-cooled) and exchange heat directly to the air surrounding the heads and cylinders, but that rate of heat exchange varies greatly depending on the temp of the ambient air. If you live in a consistently cool environment that's great, but if temps in your area vary too much this makes the control of the temps inside the engine difficult. So the designers had keep specs on the motor wide to accept a broad range of ambient temps. Water is much more controllable and has a faster heat transfer rate. So water at a temp between 180 to 195 will actually transfer heat away from the combustion chamber more rapidly as well as keep it a more predictable controlled environment. Plus around these parts 180 degrees is only 60-65 degrees hotter than a typical August day | ||
| Johncr250 |
Static is 100% right | ||
| Alex |
If YouŽd rev the engine much higher You will be limited by head breathing ability. ThereŽs a lot of power hidden in the heads. We produced 100hp @crank on a XB9 and 115hp @crank on a XB12 with a mild head job, a less restrictive intake and exhaust system and a slight increase in compression leaving all other things stock. With the older Thunderstorm engines we gained around 10 to 13 hp rear wheel with a head job using stock valves and reworking combustion chamber thereby even reducing CR to about 9.7:1 ending in the 95 to 100 hp rear wheel range. So the heads are a real power source. BTW have You ever tried to port 10 horses out of a Hayabusa head? Have fun. | ||
| Unibear12r |
If fact if I read one of his interviews right you wont be seeing a watercool from BUELL for awhile. Startup/warmup on a watercool is waaaay to dirty for Euro2, Cali 2008-USA 2010 so ALL the watercools are going to cats & air pumps & etc to pass EPA nearly world wide. Current Buell passes. Chatted with a guy that sat on CARB ( Cali. Air Resources Board or EPA) once. Funny thing he was pro motorcycle. They didn't make motorcycles smog test before because the full fairing bikes were too hard to access. Gotta make money! CARB is supposed to be requiring all makers to provide access with 2008. Smog testing for bikes is on the way. At least out here. edited by unibear12r on March 29, 2004 | ||
| Unibear12r |
Sorry guys when I said bottom ends I was thinking bottom end caps. Good stuff Alex. edited by unibear12r on March 29, 2004 edited by unibear12r on March 29, 2004 | ||
| Rocketman |
BTW have You ever tried to port 10 horses out of a Hayabusa head? Ah, not to split hairs dude but didn't Suzuki do that to start with, which I think is exactly the point of this thread, no?  Rocket | ||
| Gonen60 |
It seems every sort of engine seems to ring a little more HP out of it every year. Automobiles, motorcycles, race cars and race bikes. case and point the ford 4.6 motor. 240, 260, 280, 310 HP, the factory changing heads, 2V or 4V, intake...etc The XB seems to be praised for it's design, style, frame, cornering ability..etc then the Motor, "performance bike" magazine states why was it saddled with a "wheazzy old Lump" (brits have away with words"... again I like the V Twin, I just believe the factory could bump the HP up..Can't they, and if so, why don't they. If E Buell came and scanned this site, He would see we are grasping for one, two or three HP where ever we can find it. (XB12 airbox mod) And Yes I know if the XB came stock with 120 HP, We would all still be scavenging for more. But at least we would be starting on a more level playing field. | ||
| Hootowl |
"It would make more power if there were four valves and overhead cams would certainly make more RPM's thereby producing a good deal more power." How does using 4 valves allow the engine to spin faster? It's all about piston speed. I see where you're going, valve train limitations etc, but the valves in the Buell work just fine all the way up to max safe piston speed. The 9's got the beehive treatment to push valve float up to 8K, but they have a shorter stroke than the 12's. Also, rod length does not affect piston speed, stroke does. The 12's have more stroke than a Chevy 350. Would you spin your daily driver to 7.5K? Fuel made 4 valve heads a while back (maybe they still do?) but from what I understand, they didn't make a big difference. Never seen a dyno sheet for them though. Rocket. Yup, it's getting pretty hard to improve on the factory stuff these days. |
