| Author | Message | ||
     Xl1200r |
Also, keep in mind - an XB12 has a longer stroke than ANY factory-offered Chevy big block engine with the exception of the 454 and 502 engines, which had a 4" stroke - less than two tenths of an inch longer than the XB. Keep in mind that the XB12, if were an eight cylinder, would only be something like 292 cubic inches. That should lend to just how drastically undersquare these engines are. | ||
| Hughlysses |
Spatten - RPM limits on the XB aren't limited by bearings or even valvtrain, but piston speed. They've got a loooong stroke (even a 9 is undersquare), so those pistons have to cover a lot of ground during each rotation. While I'm sure piston speed is the ultimate limit for the 12 as far as maximum RPM, up to the 2008 models Buell said the roller bearing/crank pin was the limiting feature. The larger crank pin and new oiling system introduced in 2008 allowed the RPM limit to be upped as a result. After that, the limit may well be piston speed. Not sure exactly how that manifests though- stress on pistons leading to eventual failure? The acceleration at each end of the stroke must be beyond belief . BTW- the XB9 is oversquare- from buell.com: Bore 3.5 in. (88.9 mm) Stroke 3.125 in. (79.38 mm) It may be good for some additional RPM yet. | ||
| Xl1200r |
Hugh - I stand corrected on the XB9. The beefed-up bearings and crank pin are to try and mitigate the piston speed issue. When you have that mass starting, stopping and changing direction that fastm especially in a powerplant as unbalanced as a common-pin 45 degree twin, it just beats the living hell out of the crank. | ||
| Spatten1 |
I read a Kevin Cameron article a while back where he explained that with more power the roller bearings distort and eventually fail. He indicated that plain bearings are necessary at some point to progress with a higher horsepower engine. I don't remember if the limitations relate to longer stroke with more mass and higher rpm, or if it relates to the power stroke. Either way, the roller bearing bottom end apparently limits performance. | ||
| Spike |
2007 BMW R1200R:  2007 Buell XB12SS:  From the dyno charts I found, it appears that the average R1200R/RT/S/GS is putting 100hp or more to the rear wheel, which puts it a solid 10hp up from the average XB12. The big difference isn't the peak power though- it's the way the BMW motor revs. I haven't ridden the 1200 version, but I have ridden the 1150. I was quite surprised to find out how quick the engine revved and how happy it was to spin to redline. It responds much quicker to throttle inputs and feels like it has much less rotating mass. It didn't have as much low end torque, but the throttle response and willingness to rev made it feel stronger in 1st gear than my XB12. I don't particularly care for the boxer sound or the overall character of that engine, but I really liked the way it delivered power in a rev-happy-but-not-rev-needy manner. | ||
| Fast1075 |
The XB engine is a very, very good engine for what it is...it is not the basis for a high rpm monster powerhouse (THAT IS LONG TERM RELIABLE)...it is possible to build a very high output XB engine...ask people like Terry Paisley, Fireman Jim or Wes Brown for example...all it takes is a hp adder like nitrous, or a blower, or turbo, or even nitro. (I like nitrous..it is cheap, simple and effective). The problem is the physics and mechanical limitations of the design..the engine will simply not hold up...it will wear out rapidly or fail mechanically. The big advantage of the plain bearing crank is the huge surface area of the bearing compared to a needle bearing..the softer bearing material will not brinnell the crank and rod like the needles do..and support a far higher load..one of my favorite V-Twin engines is the McClure Overkill top fuel engine...iirc the crank throw and rods are very similar  to a big block chevy...the components are massive and designed to handle 900 to 1000 horsepower...way cool motor indeed. Of course the coolest motor is the 70hp Blast motor that Terry is taking to Bub's  | ||
| Macbuell |
I never said it would be easy ... I'm no engineer. I just don't see how it could be that hard to build a lighter, more powerful air-cooled v-twin for the XB. That engine is big and heavy and surely, with today's technology, there has to be a way to build a lighter, more powerful, air cooled engine that will fit into the XB and still keep the same character that I love about the bike. If 120RWHP is out of the question, 110 would still rock, IMO. Is that out of the question too? If so, I'll probably be looking elsewhere for my next bike. | ||
| Rubberdown |
The BMW Hexhead 1200 is dramatically better than the Oilhead 1150; in performance and maintenance. It's a great engine and can be built to produce more without stressing it. Revs to 8k and does it quick for a flat twin. The R1200 runs cooler, had excellent mapping, and still gets great mpg. I've got a few racing and general riding miles on these bikes.  | ||
| Lemonchili_x1 |
Does anybody have a dyno chart of an '08 or later XB12 and/or XB9? I'm curious what an XB12 does in those extra 300rpm compared to an earlier model. When they did the changes to the bottom end for '08 I'm assuming there were no changes to the breathing - ie cams, valve sizes, ports, manifolds, compression ratio. Is that right? | ||
| Xl1200r |
I just don't see how it could be that hard to build a lighter, more powerful air-cooled v-twin for the XB. That engine is big and heavy and surely, with today's technology, there has to be a way to build a lighter, more powerful, air cooled engine that will fit into the XB and still keep the same character that I love about the bike. If 120RWHP is out of the question, 110 would still rock, IMO. Is that out of the question too? If so, I'll probably be looking elsewhere for my next bike. Still missing the point. Yes, they could build a more powerful, in the 110rwhp range air-cooled vtwin with little issue. But it will have to forgo many of the design elements that give the XB engine the character it has. Long stroke. Commone crank pin. 45 degree cylinders. 2 valve heads. Common intake tract. These all add to formula that makes an XB an XB. Change one and the character starts to waiver. | ||
| Spatten1 |
Yes, they could build a more powerful, in the 110rwhp range air-cooled vtwin with little issue. But it will have to forgo many of the design elements that give the XB engine the character it has. Long stroke. Commone crank pin. 45 degree cylinders. 2 valve heads. Common intake tract. These all add to formula that makes an XB an XB. Change one and the character starts to waiver. Exactly. It's cool because it has some Harley character to it. Start smoothing it out and shorten the stroke and it feels too much like a Beemer or Triumph or some other bike. Anyways so what if you re-design it and get an extra 10 HP, which seems to be all you are going to get from an air cooled twin that is reliable and passes emissions. Not really that dramatic anyway, might as well just give up a little power for the character, to me. | ||
| Blake |
Steve, Not sure who said it would be easy, however an engine exists from which to start, the XBRR mill. Mark, Why not simply derate the XBRR from 150+ to 120 RWHP. Drop the rev limit from 8.5K back down to 7K. Inertial stresses on engine parts increase with engine speed squared, so by dropping the rev limit by 7/8.5, you reduced the stresses by over 32% (almost a third). The XBRR engine suffered some issues with rod bearings from what I'm told, but the thing ran very well and won endurance races. I'd think that it is fine for street duty at the aforementioned significantly derated level. For Scott: 120-90=30 110-90=20 The XB9 is short stroke, as short as (thanks Steve) the XBRR. Does it not retain the Buell character? Who is talking about smoothing it out? Hey, I'd be happy with a very small factory integrated supercharger. Anyone see what Mr. Roehrich was able to do along that line of thinking. Very cool! http://www.roehrmotorcycles.com/TheBike.html Only $49K! Really not a bad price for an exotic. Put a smaller supercharger on da Buell? 120 RWHP? Easy? Maybe we should ask Walter to do it for us? (Message edited by blake on August 18, 2009) (Message edited by blake on August 19, 2009) | ||
| Blake |
http://www.rotrex.com/index1.htm | ||
| Johnnymceldoo |
Id pick turbo over supercharger. Lots of plumbing though. | ||
| Slaughter |
XB9 (984cc) and XBRR (1340cc) have the SAME stroke: 3.125 I really think the XBRR motor with attention to building for long life could make an interesting motor when de-tuned to maybe 115 HP. MUCH sweeter throttle than the XB12 - but not a motor that would be comfy "loping" along. You CAN get flywheel cranksets to go in - instead of the porkchop cranks too. Be a helluva project (in any state but CA) You'd maybe be able to run a variation of DDFI-3 to have 2 oxy sensors running in closed loop. Hmmmm. | ||
| Blake |
Steve, I like your thinking. 1340cc/1203cc * 90HP = 101 RWHP just from increased bore. Another 10% from improved VE (cyl heads, dual throttle bodies)... Okay, then let the thing rev to 7.5K for another 10% There we go, 120 RWHP! See how easy!  | ||
| Lemonchili_x1 |
Now your speakin' my language, and it seems to me, as purely an armchair speculator, a logical evolution. So, how hard would it be to either "production-ize" XBRR cases and heads (from the pics I've seen they have that sand cast look), or retool to enlarge the current cases? Slaughter is running a short-stroke 1170cc on the track and Jakecheez has one on the street, they sound like very interesting motors... See here. Combine that with an '08 onwards bottom end would be even stronger, and potentially higher redline. Did Buell have the future in mind with the '08 redesign, or just improving production and reliability?  Can you buy XBRR cases, cylinders and heads? | ||
| Strato9r |
Or, how about this: Since the Helicon powered bike is already in production, and with it, a couple of years of refinement in the frame and the rest of the platform, why not introduce an air cooled version of the Helicon? (Rotax has built serious air cooled engines) Hot spots in the cylinder head (between exhaust seats and around the spark plugs) could be cooled by engine oil, like Oilhead BMW's and new Sportys, and it wouldn't be a stretch to match horsepower numbers with the BMW HP2, around 120. Without the cooling system, the new bike would be even lighter than the current 1125r, giving it a great power to weight ratio, and a tuned for torque version of the engine could have an impressive range with the Helicon bike's much larger fuel capacity; just the thing for a new generation Uly. | ||
| Xl1200r |
Blake, I think the idea has merit, but all I can think about (in terms of turning a race engine into a street engine) is the Harley Revolution motor, and how flat-out TAME the street version was. I'm not an expert on the XBRR, but I would have to guess that lowering the rev limit and beefing up the rods and mains would not be all that is needed to street-ize the motor. I'm sure the cams are very aggressive and would also need to be dialed back into a streetable profile, if not for a usable power curve than to avoid extra wear and tear on the valvetrain. Not to mention, this was a race engine, designed to rebuilt after hours - not tens of thousands of miles (or more). I know you're an engineer, so you must understand the effort needed just to completely re-engineer the engine to fit all this criteria. | ||
| Blake |
Mark, Actually, the design intent of the XBRR was for it to run an entire season with minimal maintenance/teardown, a point that Buell proudly advertised. Unfortunately the best laid plans... It is a very good start. If that engine isn't then what is? But I like the Rotrex supercharger idea too. | ||
| Hughlysses |
Mark- wouldn't you think that chopping the rev limit from 8500 (I think that's what it was) to something more sane like 7500 would be sufficient as far as making it street reliable? I think the stresses would be dramatically less with a 1000 RPM reduction. My gut feel is that not much would be required to make this engine long-lived and street reliable IF the power and RPM limits are dialed down accordingly. That extra 1000 RPM and 25 RWHP probably doubled the stress and wear on the engine. No doubt milder cams would be a necessity, and for that matter smaller valves, ports, and throttle bodies might be required to give it a usable street power band. Would stock XB12 heads negate the displacement/RPM advantage? I suspect a head somewhere between the two extremes would be the best. | ||
| Lemonchili_x1 |
I know it was a long time ago, and emissions laws were nowhere near as tough back then, but remember combining a race engine and a street engine has been done before...   | ||
| Slaughter |
I wonder WHERE the remaining XBRR "stuff" is...? Supposedly there is a container of all the leftovers. Don't know if us mortals could even find out IF anything's still available - race license or no. I can't help but think that if some 3rd party got to produce an "RR-like" set of cases, they'd just not have much of a market out here. It'd still be a very cool motor. Wonder about tranny part commonality... stuff like that. There are a couple ex-racers still out there which could be bought but it'd be kinda difficult as a project. But hey, it IS a cool fantasy. Lemonchili - could one POSSIBLY be registered there in OZ? | ||
| Macbuell |
Now we're talking. I knew you smart guys could get it all worked out. A special issue XB13R with 110+ RWHP would have me sprinting to the dealership. | ||
| Fast1075 |
There is a XBRR on display at my local dealership... | ||
| Buellinachinashop |
"I wonder WHERE the remaining XBRR "stuff" is...?" Alot of it still sits in the Screamin Eagle lab at the PDC. | ||
| Xl1200r |
Mark- wouldn't you think that chopping the rev limit from 8500 (I think that's what it was) to something more sane like 7500 would be sufficient as far as making it street reliable? I'm not trying to claim to be an expert on any of this, but no - I don't think it would be sufficient. Again, I go back to the VR1000 engine. It was making 135hp, in full race trim at 10,000 rpm 15 years ago. The current V-ROD engine is posting up around 125hp, so it only lost ten. But add in the fact that it's had 15 years worth of new tech AND and extra 250cc, I think you can extrapolate that the difference is really much greater. 135hp in 1994 is likely equal to around 170 in 2009 (possibly more). Now the current V-Rod is down on power by 20% already. Now set the displacememnt to 1000cc (because I don't think an XB-based engine can be made with a bore much larger, if at all, than the XBRR) for the current V-Rod and the power drops to 109hp. A 35% reduction. The 150hp of the XBRR reduced by 35% is 96 hp. Now, obviously I think the street-ized XBRR mill would do plenty more than 96hp since the standard XB motors are past this as is, but I think the point rings loudly that you'll see significant drops in power from a full-out race engine to a street engine. Again, just my opinion. And if all that still rings of BS in your ears, consider that the Revolution engine is around 110hp at the wheel with 1250cc - and it again took overhead cam, multi-valve heads, short stroke and liquid cooling. | ||
| Lemonchili_x1 |
Mark could well be right... by the time you lower the compression and strangle it with emissions laws the hp gain over a stock XB12 may not seem to make it worth it... as a mass production engine... but Buell have been pretty good at coming up with solutions to noise laws. ..."But hey, it IS a cool fantasy."  Oh, yes it is! As well as big displacement and high compression/racing fuel, I would have thought a lot of the (relatively!) high rpm horsepower of the XBRR would come from the big valves and separate manifolds/throttle bodies. To me heads with separate throttle bodies would seem to be one of the next evolutionary steps for the XB. "Lemonchili - could one POSSIBLY be registered there in OZ?" Well, I know this guy, who know's this guy...  Register a racetrack refugee XBRR? Technically no, it's a 2007(?) bike with no ADR compliance plate... but if it was a "re-engined XB12R" that had been previously registered, I think I could find a way... Insurance could be tricky though. (I still regret not buying an ex-Honda Racing Australia VF1000F superbike back in 1990. It was *loaded* with VF1000R and HRC goodies, and I could have put lights on it and got it registered easily back then. Hindsight has 20-20 vision!) | ||
| Buellinachinashop |
"The current V-ROD engine is posting up around 125hp." Noooo. That's a HD Marketing hp number. At the crank its closer to 112-115. | ||
| Xl1200r |
BCS - That's for the 1250cc variants? |
