| Author | Message | ||
     M1combat |
Nascar engines are bigger bore and longer stroke than an XB and they run 9-10K RPM's for hours... What can be done to an XB12 to make more RPM's? Does anyone make high dollar conrods? What about a good crank? I won't be even opening it for two years and a 351 Cleveland rebuild but I like to research early  . | ||
| Bykergeek |
NASCAR engines only have to live for 500 miles. I'm sure an XB12 motor could spin faster but would it work reliably for X number of years if it did? | ||
| Bykergeek |
Another difference is the V8 is a 90 degree motor which can be naturally balanced. The 45 degree engine with a common crank pin never sees one piston at the bottom while the other is at the top and can only be artificially balanced. Excess vibration at high rpm can shake an engine apart. | ||
| Steelshoe |
Its the 45deg cyl design that restricks hi rpm. They fire to soon after one another, then a long trip around to the next cycle. Thats what gives HD,s the sound the world is attracted to. Can't think of any other manuf. that use a 45deg eng, all 90deg. | ||
| Mikej |
There are aftermarket connecting rods. Contact HalsPA for help. Or any competent shop with a bonafide long term race prep experience should be able to help as well. Long engine life comes down to components and experience in assembly. If you want a motor that lasts go to the pros. There are lots of shops who say they know what they're doing, and they may even be doing some racing of sorts to point to, but there are probably less than a dozen shops open to us non-pros in the US that really know their beans from their bolts. | ||
| M2cyclone00 |
They were designed for a long life (think 100,000 miles), not high revs. Bykergeek is correct. Erik & his staff didn't design it for a 500 mile race. Look at the other post about the XB completing the 8hr race. With the 3 13/16" stroke, if you want long, long, ring & piston life you need to keep the revs down. They can safely rev to probably 7500rpm as configured with an ecm change. But, you're not going to have long ring life at those or higher piston speeds. | ||
| M1combat |
I understand the drawback of high R's... I also understand the benefit. I'm not complaining about the capabilities of the XB (Heck, I'm buying one soon, I'm looking for ways to make RPM's once my warranty runs out. RPM is king on a racetrack. So, I'll go take a look at halspa and see where I can go. Thanks for the info Mikej. | ||
| Mikej |
No problem, you might also see how close you are to the Buell TorqueFest down in Arizona this weekend to maybe get a chance to talk with some other Buell owners. http://www.buell.com/en_us/brag/adventures/torque_fest_main.asp Mapquest.com says it's a little over 200 miles from Prescott to ShowLow, but you probably know a shortcut or two over the hills out there.  | ||
| M1combat |
That's in Show-Low??? Why yes, I do know a few shortcuts over the hills and through the woods . I even know a few guys who grew up over there and are headed over there on a 66 Triumph TR-6 and a 76 Sporty this weekend to see some old friends... I might just have to tag along on my CB750F-SS. I doubt I'll be able to out torque a Buell, but I CAN roast the tire on command . Neat . Thanks for the heads up Mike . | ||
| Mikej |
Again, no problem, glad to have helped in some small way. Have fun. Also, you might want to print out the BadweB logo and tape it on your bike someplace. At the very least it will open up some conversation.  | ||
| M1combat |
Good call... I'll do that. It may even keep me from getting my ass kicked for riding a Honda . | ||
| Mikej |
Buell riders/owners tend to be cut from a slightly different cloth for the most part, so no worry about the ass-kickin', most likely anyway. At the recent Buell 20th Celebration there were a few bikes of non-Buell brand, and I don't think any of them were even run wide into a ditch, not even on the original house/barn/factory site's gravel driveway, not even an accidental tip-over. Since it's a factory sponsored event there may be some restrictions on riding with the group ride, but as far as showing up and doing independant rides there should be no problem. Show up, say howdy, and enjoy the day. | ||
| Leeaw |
M1, tell them your Firebolt is in the shop for a broken belt, so you had to ride the Honda. I am sure that will fly. If you feel like making the 6,000 mile round trip to NY, you can borrow my M2. | ||
| Bads1 |
edited by bads1 on September 30, 2003 | ||
| M1combat |
uhh, yeah don't tempt me Leeaw . | ||
| Steelshoe |
Back to the RPM's that harleys can't make, think of a guy racing in a wheel chair, he can only push that short distance from the top, thats how an HD engine fires. If he had long arms and handles on the wheel he would get going much faster, like an I4, always has relentless push on the crank. This is the biggest reason HD are called antiques by many. They are not capable of much more than 8 grand. | ||
| M1combat |
Well, they don't compress at the same time like an old Triumph right? The crank journals are on the opposite side of the crank as well? If so, there shouldn't be anything but balancing holding them back from 10K... What do the Buell race bikes run for RPM's? | ||
| Reepicheep |
It's a question of bore, stroke, and reciprocating (ummm... bouncing) mass. An inline four will always out "rpm" a twin, as it has four smaller masses moving through a shorter distance, not two larger masses moving through a longer distance. Sure, you could make the twin WAY oversquare (a dinner plate moving through a half inch stroke), but then your torque curve sucks. And whatever oversquare tricks you play with the twin, you can also play the exact same ones with the four, so the four will always win for high RPM (and therefor peak power for a given displacement). How streetable a motor is will be an entirely different question though. Fours make better race bikes. Deal with it. Twins make better street bikes. Deal with it. That's not to say you can't make a great twin race bike or a great inline four street bike, it's just to say that you are fighting an uphill battle. IMHO | ||
| Blake |
Steelshoe, "Its the 45deg cyl design that restricts hi rpm. They fire to soon after one another, then a long trip around to the next cycle." They fire 315o apart not 45o apart. Not much different than a parallel twin that fires at 360o intervals. You might want to rethink your analysis on the speed limitations of the Buell engines. | ||
| Dynarider |
I believe the Mid USA 114" v-twin has a 9000 or 9500 rpm limit. Course that motor also costs over $14,000. The V-twins can be made to rev pretty damn high...just gonna cost you more. | ||
| Crusty |
XR 750 Harleys red line at 9400 RPM. It's a pretty damned good racebike, too. There's a direct relationship between RPM and engine life. XR's get rebuilt every 3 races. How long do you want your motor to live? | ||
| M1combat |
I understand the reliability thing, the reciprocating mass thing, and that an inline 4 will make more RPM on the extreme limit. There are some inline 4's out there that turn 16000 RPM's that you can buy off a showroom floor. I'm not looking for 16000 RPM's, just a mere 10K or so. That's all, just 10K RPM's. Lightweight pistons, STRONG conrods, STRONG wristpins, a VERY balanced crank and some high dollar bearings should get you there. Well, with some cams, maybe a little different intake and such but the main parts I think can be designed to make it work all the rest is down to experience and design iterations... I guess the main problem I see is flow rates. Anyone know how much air a stage3 nallin head will flow at .500 lift? For that matter, anyone know how much lift you can get out of one with something shaped like a stock piston? For what it's worth... Don't worry about reliability yet. What I'm somewhat interested in is a rotating assembly that can TAKE 10K, then cam it for about 8500-9000 or so. | ||
| M1combat |
BTW mikej... I'll be at the torque fest . | ||
| Blake |
Ducati's L-Twin Superbike racing machines are claimed to turn upwards of 15,000 rpm. I have a Japanese IL4 engine that redlines at around 6,000 rpm. It ain't the number of cylinders, it's the stroke and valvetrain that will limit peak rpm. | ||
| Bucknut |
I don't believe anybody has mentioned our pushrod valve train and hydraulic lifters...all serious limitations when it comes to rpm's. Valve float and collapsed lifters are common when you get over 6500 rpms in a hydraulic pushrod setup in V8's. The weight of our stock valve trains would have to be addressed as well...lots of titanium and beefy valve springs, with some type of adjustable rocker. Ducati's have an edge in the rpm department, as they use a Desmodromic valve setup....basically, there is no valve spring to close the valve, so valve flow is not an issue, but adjusting the valves is necessary periodically. Most 4's that rip in the rpm department have overhead cams (no pushrods)...which means less reciprocating mass and multiple valves. | ||
| Adamz |
Hmmm, not sure bout the need for the extra rpm. If higher speed is required then surely there must be an method of changing the final gearing. On most bikes this could be done by changing the sprockets - don't know how it is done on a Buell. | ||
| Hootowl |
more RPM = more power, as long as the torque doesn't drop off. Putting shorter gears in will not necessarily equate to a higher top speed. | ||
| Aaron |
What Hoot said. Power is torque times rpm. 'Course, that little detail about the torque not dropping off, that's the kicker. As things happen faster and faster you have less and less time to fill the cylinder and when you can't fill the cylinder, torque drops. When torque is dropping faster than rpm is rising, you're done. The heads aren't always what constrains it. | ||
| M1combat |
Yeah, intake manifolds and exhaust ports/manifolds play a large part in the breathing game but there's usually plenty you can do there, just depends on your machine shop . I don't want more top speed as such... I want more peak power at the RPM range I want it (7000-9000). If this is attainable, each gear becomes more effective basically. I also think a 6-speed may need to be added. My guess is that's a large expense... As far as just changing the sprockets... Yes, that would go faster, but it needs to be quick AND fast. I am thinking by the time I get done (a while) I will have 130-135HP, 9500 red line, 6 gears. Can the stock block take that much power on an XB12? | ||
| Steveshakeshaft |
Hi M1combat, you need an SP2 not an XB12. My 2 cents. Steve www.ukbeg.com steve_s@ukbeg.com |
