| Author | Message | ||
     Lenb |
Guys, maybe this may help explain the difference between torque and power (sorry it's a bit long but I posted this as an article on another site): Torque is a measure of the twisting force an engine can generate. Essentially torque is what you feel when you open the throttle on your bike and accelerate. Trouble is, the published torque of an engine (whether measured at the crankshaft or the rear wheel) is really quite meaningless unless you take gearing into consideration. For example, many bikes have enough torque to power wheelie in 1st gear but few can power wheelie in 6th gear. Put simply, we can either have a lot of torque at the rear wheel or a lot of rpm — but not both. Every time we change up a gear, we are trading torque for rpm. (thus the fact that a Buell has more torque than a I4 600 means nothing - sorry). This is where power comes in. Power is a combination of torque and rpm. An engine can produce little torque at the crankshaft but if it revs high enough can still produce a lot of power. Conversly, an engine might not rev very high but if it has a lot of torque it can produce a lot of power. This may be easier to understand if we compare a 1200cc Buell XB12 and a 600cc Yamaha R6. The 1203cc XB12 engine produces 111Nm crankshaft torque at 6,000rpm and the 599cc R6 engine, 66Nm crankshaft torque at 12,000rpm. Despite the fact that XB12 produces nearly double the torque of the R6, due to gearing differences, driving force at the rear wheel and thus maximum acceleration in top gear at the bikes’ respective torque peaks is roughly the same. The big difference however is that the Buell only revs to 7000rpm whereas the R6 redlines at 16,000rpm (the marked redline of 17,500 is a little optimistic apparently!). High rpm equates to high horsepower, consequently, the Buell only makes 74.6kW, while the R6 makes an amazing (for a 600) 93.4kW. Hence while the Buell runs out of puff at 230kmh in top gear the R6 will pull to around 265kmh. One thing that is worth bearing in mind is that with the R6, as with many other bikes that claim high max hp ratings, unless you are riding above 11,000 rpm, you will never get to experience most of that power. This is because even in 1st gear 11,000rpm on bikes like the R6 equates to about 100kph. So if you regularly experience life above 11,000 on city streets, it is only a matter of time before you get arrested! Truth be known, a low revving, high torque bike has much more accessible power for the street and is therefore a lot more practical in the real world than a highly strung, high revving 600cc race-replica. But then again, who ever said motorcycles had to be practical?! Hope the above helped. (btw - I am a degree mechanical engineer). As an aside: a 1000cc sportbike has the best of both worlds - plenty of punch at low rpm and eye-watering top-end. Personally, I find that when I ride open class I4s I can't even come close to using all that power - so a XB12 suits me fine. I like to be able to use all of the available revs most of the time. | ||
| Badbuell82 |
A long time ago, I learned from riding 2 strokes, that RPM range is irrelevant. You simply keep the bike IN the power band, no matter what you are riding. Just like you wouldn’t lug your Honda Civic in 5th gear at 10 MPH. Yes, I too feel my XB12 is a more “practical” street bike, especially for riding in Florida, where every thing is straight & flat. Not that the XB doesn’t handle well, it does! I know it might be a Sacrilege to say so here, But, when I want a real “high performance” thrill, I’ll take my RSV Factory over any other bike I currently own. | ||
| Eexb |
Bad Buell "the tweaked RSVR Factory is certainly the most exciting bike I've EVER owned, and there've been more than 30." Just curious - have you been here before under SEVERAL different names ??? E | ||
| Lenb |
A long time ago, I learned from riding 2 strokes, that RPM range is irrelevant. You simply keep the bike IN the power band, no matter what you are riding. Trouble is, as I said earlier, to keep something like an R6 in the powerband you have to be doing a highly illegal speed even if you stay in 1st gear. With a Buell however, you're in the powerband at ANY speed. (btw - there is a world of difference between a 2 stroke bike and a modern high revving inline 4 sportbike.) | ||
| Spike |
Yep. He's been banned two or three times already. | ||
| Spatten1 |
"Talk to drag racers and they will tell ya that may be true, But Torque is what gets the work done..." No offense, but not knowledgable or good drag racers. Drag bikes leave at high rpm and burn the clutch because there is more power at high rpm. I've never seen a pro drag racer leave the line at 2500 RPM. It is easier to launch a bike that makes high torque at low rpm, but a skilled rider will leave you in the dust with a higher horsepower bike by using the clutch and the power band, where ever the powerband may be on that bike. | ||
| Kurosawa |
Ya know what's really cool? Those who rant about their bike du jour, the brand-new whatever I4--next year it's just another has-been. Worse than if it had never tried to be fastest, because now something else is faster. That's the kind of loyalty these trolls have to their bikes and each other, unlike this board where tubers and XB riders alike hang like family. And of the umpty-zillion that will be sold on the basis of being the fastest, just how many will *ever* get within 15% of their vaunted top speed? What a freakin' joke. Street bikes are made for street riding, day in, day out, rain or shine, road ragers, potholes, decreasing-radius corners, car doors opening suddenly, not for polishing and profiling and trading in every year. Choose for numbers and your happiness is hosed as soon as the year's up and the new ones come out. Choose for the real world and the long haul, and you can be happy enough with your choice to ride it year after year until you've ridden it into the ground. | ||
| Spatten1 |
"That's the kind of loyalty these trolls have to their bikes and each other" You'd be right about me. I look at bikes like tools, and get the one that works best for me. No real brand loyalty at all, just want the best tool, or the one that fits my current needs best. I'd still say that I have strong commeraderie with other motorcyclist friends, it's just not based on brand loyalty. | ||
| Lenb |
Drag bikes leave at high rpm and burn the clutch because there is more power at high rpm. I've never seen a pro drag racer leave the line at 2500 RPM. That's because drag bikes make their maximum torque at high rpm. Maximum driving force at the rear wheel always occurs at the torque peak. If you were drag racing a tractor which made peak torque at 2500rpm you probably would want to leave the line at 2500rpm. | ||
| Curtyd |
I think someone who cites lap times and 1/4 mile times as a reference point for buying a streetbike is living in a Moto-magazine fantasy world. Is it your daily street-rider or a trackbike? You have to know that at least. The idea of "staying in the rev range" is a good concept for the track and absolutely a poor one for the street. I've said it before, how long to you expect to keep a valid DL running around at 10 to 14K RPM all the time? Or doing stoplight to stoplight 1/4 mile launches? Just ridiculous really. I love technology as much as anyone, but I live on the street. Street and Track, two completely DIFFERENT and OPPOSITE venues. The explanation for HP being the ability to carry torque by revs and doing more work with higher revs makes good sense and I understand that more now. Given that the rev range I ride in most days is in the 4 to 8K range on most bikes. It would serve me best to have the lightest weight bike that delivers the highest and flattest torque (twisting) power in that range. Means I could use another 1K to 2K in revs on my BUELL, but I am hopeful that is coming soon. | ||
| Rafartist |
A V-twin makes a whole lot more attention getting noise between 4k and 8k than a I-4 IMO. It is about keeping the bike in the rev range where it makes power. To have a Buell sitting on the edge, it requires a bit of noise too. | ||
| Hattori_hanzo |
"That's the kind of loyalty these trolls have to their bikes and each other, unlike this board where tubers and XB riders alike hang like family." I consider myself a loyal Bueller and a motorcyclist. But, I am not going to ignore the other wonderful machines being produced, whether it's Italian, Japanese, or British. I would hardly call any of the guys defending IL4 sports bikes (in this thread anyways) a troll because they can see benefits from that type of configuration. Brand loyalty is fine, as long as it's not blind loyalty. If you're blind, you'll be missing out on a LOT of great motorcycles! | ||
| Curtyd |
"A V-twin makes a whole lot more attention getting noise between 4k and 8k than a I-4 IMO." Not with the stock exhaust, it doesn't. Let me see 10 to 12K RPM, vs. 4 to 6K, who do you think the cops think are streetracing? | ||
| Spike |
Exactly what I was thinking. Stock exhaust on an XB below 4-5k rpm is like stealth mode, and reasonably fast. Even with a drummer my XB12 is loud but not nearly as frenzied as even a stock piped 600 at 10k+ rpm. | ||
| Rafartist |
I would have to see a db meter to believe that. And who runs a stock exhaust? | ||
| Spatten1 |
I kept a stock exhaust on my last I4 Japanese bike for that exact reason. I shimmed the jet needles and kept everything else stock for a smooth and stealthy quiet 125hp at the rear wheel. | ||
| Slaughter |
I have been told that the sound of the HD-type motor at lower RPM for a given speed doesn't attract as much attention as an I-4 wound out at higher revs at the same speed... kind of "urban stealth" I keep that in mind in the canyons when I don't need a lot of pull - just running the canyons at a comfy steady pace - I've passed up parked police on the Crest going 5-10 over the limit and hadn't been pulled over (keep in mind, it's a double fine zone and you can get written up for a measured 57 in a 55 zone!) (Message edited by slaughter on June 05, 2006) | ||
| Curtyd |
"And who runs a stock exhaust?" All of us who have had our windows and ourselves shaken awake in the night by some IDIOT with his straight pipe HD!! No bigger noise nuisance in this world, as bad as the Ghetto Blasters, at least they carry some kind of perverted resemblance to music . | ||
| Spatten1 |
"All of us who have had our windows and ourselves shaken awake in the night by some IDIOT with his straight pipe HD!!" LOL | ||
| Kowpow225 |
I think that whatever rpm your engine is spinning at whether it an I-4 or V-Twin will always attract attention from LEOs if it is high in its RPM range and under heavy load. Think about it this way. Say Jane is sitting on her 600 gixxer and I'm on my XB, both with aftermarket exhausts. We take off from a stopsign 1/4 of a mile from where you are sitting in your squadcar and run 'em both like we're racing and shut em down before we reach you. Who was going faster? It doesn't matter. We're both guilty. Theres no need to differentiate between who ran at higher rpms both sounded hurried. A higher decibel level only means you would be able hear us further away. See you in court, officer. | ||
| Sinatra |
my D&D is so loud, i get tickets just letting it idle at a stop light. it is also quite a bit louder on the highway at speed than a buddys stock gxr600. (Message edited by sinatra on June 05, 2006) | ||
| Spike |
I don't think it's as much a volume issue as it is a tone/type of sound issue. The I4s have more of a "busy" sound that makes them seem like they are having their necks wrung even when going through the midrange. On the last 600 I rode ('03 636) I got to put in some highway miles while cruising at ~80mph. This had the bike at over 7k rpm just to cruise down the highway. The engine isn't stressed in the least at that rpm (isn't making much power either), but it sounds like it's screaming. | ||
| M2nc |
I run stock exhaust on the Uly and it is quiet. The Uly goes by at 75mph in 55mph unnoticed by LEO. As a matter of fact the last license check I rode the Uly through the State Trooper said, "Oh, you ride one of those expensive bikes." Okay, I don't think so but it tells me that the LEO is not confusing me for a Squid on Repli-Racer and that is a good thing for my license and insurance rates. The M2 on the other hand has the V&H slip on and is notice by everyone, everywhere. It really gets more attention for bystanders than the Uly. It really gets allot of good comments even if I have to correct some that confuse it for a Ducati Monster. As far as for torque, horsepower and torque are mathematically connected. The higher the torque the higher the HP within the engine's RPM range. Torque is the base measure that through a mathematical formula including rpm, expresses horsepower. This is why liter bikes make more horsepower than the 600cc bikes even though the 600cc engine has a greater rpm range. The 600cc bikes do not have enough of a rpm advantage to counter the liter bike's torque. That is why I pointed out that at 5000rpm, the XB12R had almost twice the HP of the Aprilia. The Aprilia make that awesome HP because it can get those fantastic revs (I love the Aprilia so I am not putting it down, just making a point) but you have to twist it to get it and you are breaking just about every speed limit out on the street in first gear. Torque is a measure of the work the engine can do. Horsepower is a calculated figure that expresses how fast the engine can do the work. An engine with more torque will be able to do more work and so it can push more weight. Thus, if you are riding two up, a bike with more torque will be less affected than a bike with less torque, even if it has more horsepower. When I am riding with my wife, I am just cruising the bike, and the Buell pull so hard down low that I barely have to crack the throttle to get to 70mph. When I had my Honda CB750 with all its 47ftlbs of torque, I had to keep the rev up to get the bike moving. So torque does matter. The trick is getting more torque down low out of an engine that can rev north of 10,000rpm. | ||
| Lenb |
Thus, if you are riding two up, a bike with more torque will be less affected than a bike with less torque, even if it has more horsepower Sorry to be pedantic but as I wrote before, it's not just about how much torque a bike has - gearing plays a big part. Whether one bike has more torque than another is really quite irrelevant. A 600 with half the torque of a 1200 will perform exactly the same as the 1200 when you open the throttle (even when 2-up) if the gearing is half as tall (eg. the 600 may be doing 6000rpm and the 1200 3000rpm at the same road speed). What Buell's trump card is is that an XB12 produces a fairly FLAT torque curve compared to a I4 600. ie. 90% of peak torque at 3000rpm. Thus, re-phrasing the above, if you are riding two up, a bike with a flatter torque curve will be less affected than a bike with a peakier torque curve. If you really want to compare 2 bikes engine performance you need to graph either torque or power (either will do just as well) against road speed - not against rpm. | ||
| Curtyd |
"Sorry to be pedantic but as I wrote before, it's not just about how much torque a bike has - gearing plays a big part." I would hazard a guess that there is only minimal difference is stock gear ratios from one bike to another in an equivalent motor size and power range. Change the ratios too much and one bike would just fall on it's face, while the other drove away nicely. Wouldn't it probably be all pretty uniform? I would think within a small range of variation. Might work in industrial machinery, but when you have a certain mass that has to move from stop to driving speeds with a set torque/hp figure there probably is a very limited set of gear ratios that can get that work done effectively, wouldn't you think? | ||
| M2nc |
Thus, re-phrasing the above, if you are riding two up, a bike with a flatter torque curve will be less affected than a bike with a peakier torque curve. Agreed, only if the peak torque of both engines are the same like the Aprilia and the Buell. The flatter torque curve means that the engine can do more work through the rpm range of the engine. If both engines are kept at a constant rpm where peak torque for the engines are, then they will do equal work. Now with a 1200cc bike having twice the torque of the 600cc bike at both bike's peak torque, it will do twice the work(Work being defined as the displacement of mass, not the acceleration of that mass) So the 1200cc engine can displace more mass than the 600cc engine no matter the RPM so less affected by more mass. It is true that gearing with have a lever effect on the work the engine can do, but twice the gear ratio will not counter half the torque. It will help the 600cc engine get to its peak torque quicker and will allow the engine to displace the affected mass with more force, but the lever action will not be able to level the playing field though it will help. (Message edited by M2nc on June 06, 2006) | ||
| M1combat |
Ummm... We're talking rear wheel right? | ||
| Lenb |
Now with a 1200cc bike having twice the torque of the 600cc bike at both bike's peak torque, it will do twice the work(Work being defined as the displacement of mass, not the acceleration of that mass) So the 1200cc engine can displace more mass than the 600cc engine no matter the RPM so less affected by more mass. Huh? Are you saying the 1200cc has more mass to shift? Sorry, I don't understand your reasoning. It is true that gearing with have a lever effect on the work the engine can do, but twice the gear ratio will not counter half the torque. It will help the 600cc engine get to its peak torque quicker and will allow the engine to displace the affected mass with more force, but the lever action will not be able to level the playing field though it will help. Sorry, but half the torque at twice the revs EXACTLY matches twice the torque at half the revs. Power (the rate at which work is performed) is directly proportional to torque and rpm. | ||
| Duc_htr |
hey lion hows that finger?  --badbuell82-- when are you coming to TWO? off hwy60 suches GA, its only a couple of hours from ya... and on a 600 it could be less than that with all that HP you got... ohhh but its mountain roads... well anyways, we are usually there on sunday mornings... would love to ride with yall sometime... leave your titles at home, we ride for BRAGin rights...  that maybe an inside joke but then again you own a Buell... I was thinking we could ride over 180 to blood mountain... that way you could show us how well that 600 handles... now I don't want to race Im really really slow actually... but I would be willing to take some video of you and send it to ya... well let us know when you are on your way down... bring your buddies we can all have dinner at turners corner and maybe find a case a beer to drink... | ||
| M2nc |
LenB - Do not confuse HP with Torque, they are not the same thing. Yes an engine with half the torque at twice the RPM will have similar horsepower, but the torque (peak torque I mean) does not change. It's a differential equation. Position - Velocity - Acceleration. Horsepower is the rate that the work can be done, but does not mean the amount of work that can be done. At its limits an engine with half the torque gets to a point that it can not displace mass when an engine with more torque can, no matter the rev. Example: The original 1991c Cummins Turbo Diesel in the Dodge Ram versus a modern R1 The Yamaha = 160hp & 95ftlbs (may not be current) Cummins = 160hp & 400ftlbs Now, removed the Cummins from the 5500lb pickup and replaced it with the R1 motor, add a CVT transmission so you can keep the RPMS at peak torque. Do you think that the engine can pull a 18,000lb camper up a 7° incline at 70mph? No way. The little engine will rev until it blows but it will no pull that much weight with only 95ftlbs of torque. Heck a 318ci V-8 with 285ftlbs of torque will probably not be able to do it, but the Cummins will. Capacity of work it can do (torque) versus the rate the engine is doing the work (Horsepower). Twice the capacity at half the rate = Half the capacity at twice the rate. This is what you are saying and in a vacuum it is accurate. But when you start to reach the limits of the engine with half the capacity, it will not be able to maintain the rate it is doing the work. It will go slower. While the engine that can do twice the work will not be as affected because by percentage, it still has plenty of capacity to do the work. At some point the engine with less torque will not be able to displace a mass large enough and add in the forces of friction and gravity. It will not move at all. But the engine with more torque still will be able to. So if you draw a line representing the rate of work as you add mass and other countering forces, at some point the rate the two motor can do the work will meet. Past this point the motor with more capacity will also be able to do it faster. Make sense? |
