| Author | Message | ||
     Moondust |
Hey peeps, Im just thinking out aloud here - Im pretty new to the Buell club - my first bike was a Duc M750 for about 6months then I jumped on the XB9SX. I love it but already after a few months of owning - I've added the Remus pipe & Im now thinking maybe I should get the race kit & K&N to compliment the remus  But then Im wondering maybe I shoulda opted for the XB12S .. as Im clearly trying to up power & am starting to feel 5th gear isn't enough. Im not a speed junkie but wondering how much power the 12S has over the 9SX ? The reason I opted for the 9SX was lower insurance & I wanted a commuter for the city & obviously the City X came to mind. Anybody else had this scenario ? any thoughts ? Cheers (Message edited by moondust on February 28, 2007) | ||
| Bake |
I have ridden a 12 and own a 9, really I didn't notice a ton of difference except the 12 gets it's power a little lower as the 9 revs higher. Mind you I was on a test ride and didn't want to try and torture a new engine in a frame I wasn't familiar with. | ||
| Ghalsey |
According to American Sport Bike's exhaust shootout stats: Buell XB12 Power: 101 (RWHP) Torque: 84.19 lb-ft Buell XB9 Power: 79.61 (I believe its probably around 81 to 83 RWHP; they had noted a premature redline cutoff during testing.) Torque: 65.27 lb-ft Just some numbers to go with people's personal experience... | ||
| Kdan |
Get a Suzuki GSXR. You want to drive faster than a Buell by the sounds of it. As for top end, I really don't think you can notice a significant difference in 5th gear. | ||
| Blackxb9 |
I have both a 9S and a 12R. Both produce equal grin factor. I use the 9 as my commuter and the 12 as my weekend carver. IMO, stick with the 9, it's not worth the extra money and insurance for a few more ponies when Buell's aren't built for top end anyway. Just twist the wrist and lean in and you'll be happy. | ||
| Phantom5oh |
Almost 20 HP and 20 ft/lbs is a pretty significant difference considering the bikes weigh the same. Stock claimed power numbers for the 12 are 103 HP and 84 ft/lbs. Stock claimed power numbers for the 9 are 92 HP and 70 ft/lbs. 11 HP and 14 ft/lbs difference. | ||
| 12r |
I've ridden quite a few 9s and 12s and IMO the difference is significant enough to give them unique characteristics. Stock, the 9 is generally more willing to rev and goes on to a (slightly) higher redline but the 12 has a relentless surge of user-friendly drive right from tickover that's available more-or-less any time, in any gear. It makes for great cut-and-thrust overtaking and smooth progress on unfamiliar, twisty roads. The only drawback is it's inability to capitalise on this massive midrange (chasing revs is a fruitless excercise) and a lumpy delivery when riding slowly. For hacking around town I'd take the 9 every time but for the open road I'd choose the 12. | ||
| Reepicheep |
My 9sx dynoed around 76HP. I would be surprised to see a stock 12 dyno much above 92. An XB9 with a 1250 kit will smoke both a 9 and a 12 for top end. You end up with an oversquare 1200cc engine instead of a stroker 1200cc engine. So I bought a 9, which I knew I would ride a lot. My plan was that if I decided I wanted more power after two or three years riding (which will probably be pushing 30k+ miles) I would just ship the bike to a friend in Colorado and have it rebuilt with a big bore, probably for $$ that is close to the difference between the 9 and 12 to start. So far though, stock rocks for me for the 9sx. It feels faster then my M2 (carb'd 1200cc). | ||
| Metalstorm |
For hacking around town I'd take the 9 every time but for the open road I'd choose the 12 I second that. I love my 12. I prefer my 12. But when I'm putting around in town I wish for a 9. Fortunately I don't spend much time in towns  | ||
| Spatten1 |
The magazine dyno tests are generally in the low 70's for the XB9 and the mid 80's for the XB12. So, about 12 horsepower or so. I like the 9 for revving, "performance feel", but the 12 definitely makes more power. As for the 100hp XB12 dyno results: Any dyno that puts the bikes RWHP at the same level as factory claimed crankshaft hp is obviously way optimistic. | ||
| Isham |
"But when I'm putting around in town I wish for a 9. " Putting around like the 9 is really all that slow. lol. the difference is about + or - 10hp. I've demoed many 9's vs 12's and I still can't really tell that much. I think both bike just have a slightly different personalities. The best gauge for performance are qtr mile times. | ||
| Isham |
These number show that there really isn't much of a difference. http://www.sportrider.com/bikes/146_performance_nu mbers/index2.html | ||
| Metalstorm |
The 12s are a wee bit rough(ish) at low speeds/rpms such as you find in slow town traffic. The 9s are just plain silky smooth everywhere. After 6 years of riding a Sporty I got used to a low reving torque monster so the XB12 felt better to me than the 9. The Sporty had the same problem as the XB12. It didn't like going slow either  | ||
| Cityxslicker |
Pushing 92-95 hp depending on the tester, time of day and the machine that does it. Running the City X with the Buell Race exhaust and air cleaner & ECM. I like the gearing better on the nine, but then I am doing low speed high torque passes down twisty county dirt roads. I will take my 9 up to any Uly (12) only time it beats is on top end on black top, then I will bow to displacement | ||
| Ekass13 |
I have a XB9SX with a race kit. With 8,000 miles put on the bike 1,500 stock. I can tell you its plenty of power. Smooth off the start, levels off around 4000, but once you hit 4650; look out! I’ve hit 132mph. But with speed wobble aka “no steering stabilizers” and the seat position the city x was not meant for top end. Hands down if you’re a good rider you should smoke most people to 100. With the ability to get stroke and bore kits for your H-D engine, the power possibilities are endless. Rock you city X, it’s a sick bike. | ||
| Xbullet |
my city x has indicated just over 130 (131, 132?) and it's bone stock except for a k&n filter. course, i was downhill with a tailwind.... go to americansportbike.com and check out the dyno runs and exhaust tests. it will tell you what the 9 is capable of versus the 12 with the exhaust,etc. that's out there readily available for them. the 9 gets very VERY close with the right equipment. then you can count on the lower weight, as well. | ||
| Mortarmanmike120 |
Hey Reepi, What's the difference in oversquare and stroker. I assume that means the 9 upgrade has shorter stroke but larger diameter cylinders then a stock 1200 engine? What is the advantage to this? Why would oversquare beat the other engine if displacements are the same? Just curious, as you can tell, I'm NOT an engine guy. | ||
| Metalstorm |
The shorter stroke of an over square engine allows higher revs over that of a stroked engine of the same displacement so it can reach a higher overall speed. So with a 9 bored to a 1200 you have a 1200cc bike with a 7500 rev limit Where as the stock 1200 cuts off at 6800. Then factor in the differences in gearing between the 9 & 12, A 9 converted to a 1250 would be mean, wicked, nasty and cool. | ||
| Tunes |
Moondust - I've ridden both the 9 and 12 XB Buells. As everyone has pointed out... the 9 is a freer reving engine, the 12 has more grunt/brute-force type power. I installed the Race Kit on my 12S and there are times when you twist the throttle and that damn thing takes off! Speed-wise, I can ride both the 9 and the 12 quickly. They just get up-to-speed differently. It's all in the type of engine you like: quick reving vs. a big torque engine. Either way, your still riding a Buell, which is always a good thing! | ||
| Mortarmanmike120 |
Thanks Metalstorm that was fast. That's also what I was thinking. Please indulge me one more time, I promise I'm not trying to hijack the thread. I have a couple more questions then I'll shut up for now. 1) If the rev limit (7500rpm in this case) is the same for the oversquare 1200cc versus the standard 984cc, wouldn't the theoretical top speed be the same? 2) Wouldn't the additional displacement just allow you to reach your max speed faster? 3)If that's the case, would an oversquare 1200 reach 7500 rpm faster then the stock 1200 reaches 6800? 4) Is the redline raised on the oversquare 1200cc above 7500 rpm? Isn't piston velocity the limiting factor in max rpm? I guess I just don't see how a higher top end is achieved if max rpm is constant. Acceleration yes but not top end. Sorry guys for the hijack. Thanks for your patience. | ||
| Old_man |
Mortarmanmike120, You are correct, but it would be an easy task to install the final gearing from the 12 - then it should be possible to attain a higher speed with the added revs. | ||
| Reepicheep |
You have it right. Max RPM does not stay constant, you can change the ECM to rev it more if it is short stroke. You can change the ECM to make a long stroke motor rev faster as well... once... right up until it explodes. All I know is what I have read, so people that do real work on these things should feel free to correct me, but here is what I think to be true.. Long stroke engines sweep a smaller diameter piston down then back through a longer stroke. Short stroke engines move a really large diameter piston through a fairly short distance. Total amount of air displaced would be the same in either case, but how it gets displaced is a lot different. I think one of the current major limitations on how fast an engine can spin is film strength of oil. The faster two pieces of metal are moving relative to each other, the more the film strength is stressed. So the main limit on RPM is simply how fast the peak speed of a piston ring will be relative to the cylinder wall. Picture a really short stroke engine. The cylinder ring only has to move 1 inch distance per revolution (half inch down, half inch back up). So if it is spinning 6000 RPM's, the cylinder ring is "moving" at 6000 inches per minute. Now picture a really long stroke engine. The cylinder ring has to move 10 inches distance per revolution (5 inches down, 5 inches back up). So if that engine is spinning at 6000 RPMs, the cylinder ring is moving at 60,000 inches per minute. All for the same RPM and same displacement. So you can make an oversquare engine (piston is wider but sweeps through a short stroke) rev far faster then an undersquare engine (narrow piston moving through a long stroke). Now Horespower is really the only thing that matters. And horsepower is not just torque, it is torque *multiplied* by revolutions per minute. So an engine making 100 foot pounds of torque and spinning at 6000 RPM's will make TWICE as much power as an engine making 100 foot pounds of torque spinning at 3000 RPM's. So why aren't all engines really wide pistons moving through a really short stroke? Well, the higher your RPM goes, the less time you have to fill a cylinder with air and fuel. So higher RPM's have trouble getting good air fuel mixes. Also, the power coming out of a short stroke is a VERY hard push over a fairly short distance. Like lifting 100 pounds 1 foot rather then lifting 1 pound 100 feet. Same amount of work in both cases, but one is gonna need a hell of a lot bigger rope. So back to the topic at hand. Horsepower, which is the *only* thing you feel on a motorcycle, is torque times RPMs. So if you can get your motor to rev to 7800 RPM's, you can make more power even if you have a little less torque. And the way to get to those high RPM's is by moving as wide a piston as you can manage through as small a distance as possible. This approach typically leads to a little less torque, but lets you multiply it by higher RPMS. So you end up ahead at the top end, but at low RPM's your bike is not making quite as much power. So you are trading some low RPM horsepower to be able to rev higher, and ultimately make more peak power (right when you have to shift to the next gear). I think that with the 1250 kits on the shorter XB9 stroke crank, you can keep the 7500 RPM redline. The XB12's have a longer crank, therefore a longer stroke, and I think they redline at 6500 RPM or something. Not sure where, my M2 had no tach  And I am not saying that Buell did the wrong thing, I think they did the right thing. They make less peak power with the longer stroke, but make better low RPM power, and have a really nice grunt that makes them really nice on the street. A short stroke just makes more *peak* power, which hits right at the moment you can no longer use it anymore, and you have to shift. High peak power compromised bikes look good on the dyno, and could do well on the track if you become a slave to your transmission, but generally annoying day to day on the street. Think about it, your bike probably spends 95% of it's life running at less then half of your peak RPMs. Why would you throw away some power there, to get more power up top, that you only use 5% of the time? A 9sx with a good 1250 kit *would* be one heck of a fun bike. Probably about the same low end power as stock, and "wheelie at will and then some" top end. A aircooled pushrod VTwin motor winding it out at close to 8000 RPM's just sounds really cool also... | ||
| Spatten1 |
Great writeup Reap! The only thing I might add is that, as you said, short stroke engines do not have much time to fill the cylinders, especially at high revs. Solution: 4 valves per cylinder and VERY STRAIGHT intakes, and fuel injectors that atomize extremely well through their design and their placement in the intake/intake port. | ||
| Spatten1 |
I also believe that with high revving engines you need a lot of valve overlap. Big overlap timing hurts low-end power. Solution: variable valve timing to keep low end, and feed high RPM efficiently. 1/2 Solution: use an exhaust valve. Can help significantly, but not as effective as the more expensive variable valve timing solution. It seems like the 9 would benefit more from an exhaust valve than the 12, due to higher red-line. Makes me wonder....... (Message edited by spatten1 on March 03, 2007) | ||
| Mortarmanmike120 |
Thanks Reepi and company. Nice write up. A 1250XB9S does sound pretty awesome. This is a pretty interesting discussion (at least for me.) Every answer brings more questions to mind. | ||
| Ulyssesguy |
I think it all comes back to what you want to do with the bike. Are you going to ride it on the street where your spending most of your time in the middle of the rpm range or are you going to be on a track where you can go Wot for long periods? |
