| Author | Message | ||
     Theshinenz |
So had my sx for a month or two now, and am wondering if anybody is having similar thoughts. I have been back riding my Cr, which has showa rear shock, Tm stage one kit and a bunch of other mods. So after riding the Cr again I actually think it's a more enjoyable ride. Which brings me to ask why I prefer it for Street riding. I think firstly the belt drive is better as much smoother and way less vibration through the frame. Secondly it handles low revs riding better even though I have an ids ecm and tips on the sx. The TH2 exhaust also has a great sound so that adds to the character. The sx is more stable and more powerful but I think the main thing I'm finding is Im not really into the chain drive vibrations. Anyone else have similar ideas? | ||
| Ebrfan |
Sounds like it is a first love thing... | ||
| Terrys1980 |
To me the low RPM driveability on my RX is better on the CR. When traveling 25 mph streets the RX does not buck like my CR did. I would never go back. I prefer the raw power of the RX. | ||
| Theshinenz |
My CR doesnt buck at all, but then it has an aftermarket ECM etc.... Maybe its just what you get used to, but the CR is definately a LOT less vibey... smooth like butter :-) | ||
| Cmmagnussen |
Put the CR back on its stock computer and exhaust.... that will bring back some memories | ||
| Terrys1980 |
My CR had Barkers and ECM for it. My RX has tips and IDS ECM. | ||
| Theshinenz |
But have you gone back and forth between the two bikes to compare? Naturally if you now own the 1190 and no longer own the CR you are going to say the 1190 is better anyway, I own both and was just an observation. Due to chain drive you get chain vibration and rattle is the motor labours at low revs, basically anything below 4000 revs on the 1190 its common to get that engine labouring sound, on the CR it will happily run at 3500 revs without labouring. | ||
| Stevel |
The basic motorcycle is essentially the same between the 1125 and the 1190. There have been some improvements, like the cooling. No longer does waste heat cook the fuel tank. Another improvement is the cosmetics. I think the RX is what the 1125R should have been cosmetically. I absolutely hate the radiator pods on the 1125. They neither work well or look good. In fact they are just plain ugly. The use of a chain in place of a belt is a mixed blessing. In my mind the chain is much better for tire choice and efficiency especially as a sport bike. The belt however, is much better in the maintenance and commuter application. I think the handling of both is superb, where one is no better than the other. The engine in both could be much better than it is. I've written quite a bit in past posts about the issues and in my opinion none have been resolved with the changes made with the exception of adding two extra injectors. The shower injectors really help in the creation of a more homogenous charge, although, I would have placed the second injector under the throttle plate rather than above it. | ||
| Sprintst |
Interesting, since my 08 and 09 1125R's both had the race ecm (factory exhaust and k&n filters) and both bucked at partial throttle, low speed To do 25 mph in a neighborhood, it's bucking in 2nd or revving up in 1st Steve - how does a chain drive help with tire choice?? (Message edited by sprintst on June 16, 2016) | ||
| Stevel |
A chain allows the choice of a lower profile, wider tire without interference. The belt, being significantly wider is often the limiting factor. The bucking you notice is a first class pain. It is caused by the excessively long cam timing. Intake and exhaust gases do not travel in one direction, they oscillate in their respective pipes. Long duration valve timing is an advantage, if you can maintain adequate gas column inertia, but with this engine and its large column diameters, the gas column speed is too low at low engine speeds, so you have to contend with a very high level of gas column reversion. The reversion allows some of the fresh inlet charge to escape into the exhaust system during valve overlap, leaning out the air/fuel mixture, as well as exhaust gas pollution of the fresh air/fuel charge causing erratic combustion. Adding extra fuel will make these effects less noticeable, but the condition will not disappear with just ECM changes. Tuning is the art of optimization, balancing, if you will, of all the engine parameters. The factory really got this wrong from the beginning and only band aids have been used since the original design. The existing cam timing only adds value at engine speeds far higher than this engine can operate at without self destructing. It is possible to shorten valve timing by 10 degrees on both intake and exhaust and gain both power and tractability within the speed range this engine runs at. | ||
| Stevel |
Theshinenz, You are misinterpreting your observations. Contrary to common belief, all engines and motors do not maintain an even angular velocity when running at a steady speed. The engine/motor output shaft will accelerate and decelerate several times during a single revolution. The severity of these velocity changes depend on the number and severity of both the power pulse and the load resistance. It is called velocity modulation. Drive chains absorb far less power than belts. They are simply more efficient in coupling power than a belt. They also couple drive vibrations more efficiently as well. This is why cushioning devices are used in the drive line. However, none of these devices are perfect. They will reduce, but not eliminate the vibrations. Add this simple fact to the erratic combustion of the engine at low speeds, as explained above and you have the real cause of your observations. | ||
| Dannybuell |
Stevel makes an interesting point "It is possible to shorten valve timing by 10 degrees on both intake and exhaust and gain both power and tractability within the speed range". Detune the bike for tractability. What would all of that entail besides different camshafts for this optimum cruiser? what else? :-) | ||
| Stevel |
Dan, I think detune is the wrong word. correctly tuning is more correct. The valve timing used on this engine is very similar to what is used on a F1 engine that runs around 18,000 rpm. Correct valve timing should deliver maximum gas flow past the valve during the most optimum period during the intake cycle. This period theoretically is between TDC and BDC. Now depending on the gas column inertia using the fact that a gas column at speed cannot stop or start instantaneously, allow us to cheat a bit and open a little before TDC and stop a little later than BDC. This works like free supercharging. To take advantage of this, port length and port volume comes into play and the amount we cheat must be optimized for the individual engine. Similar considerations must also be used on the exhaust side where opening the exhaust valve too early causes huge unnecessary valve gear loading when trying to open the valve under cylinder pressure. I once used an early opening exhaust cam on a HD EVO motor and completely crushed the Crane aluminum pushrods in short order. I must emphasize that these optimum timing points are different for every engine and small changes can make very big differences. That said, optimization is usually achieved through making a best guess and then testing. Then with lessons learned, you do it again and repeat until you get it right. Unfortunately, nobody has made different cams for this engine. It is an expensive exercise and the demand just isn't there to justify the investment. The cost is not just cams either. Changing the closure point of the intake valve has very significant effects on the compression cylinder pressure, which often results in a piston design change. It is very important to have a big picture overview when designing changes to an existing design. I am in the middle of this exercise at the moment. I have designed what I hope to be a very good guess on new cams and am having a very difficult time getting them made, but it will happen. | ||
| Hughlysses |
Drive chains absorb far less power than belts. The belt may absorb power during a portion of each sprocket revolution, but they return most of it within that revolution. That's why they do a good job of smoothing out the power pulses of the V-twin without the need for a separate compensator. Any power truly lost in the belt will appear as heat. If this was a significant loss, the heat build-up would quickly destroy the belt. | ||
| Sprintst |
a 530 chain is within 1mm of the belt on the Buell, I measured my Sprint ST vs my Buell. As I recall, the 530 was actually wider, though I may be mis-remembering that. Are the EBR's running a 520? (Message edited by sprintst on June 17, 2016) | ||
| Snacktoast |
Are the EBR's running a 520? Yes | ||
| Stevel |
Hugh, There is measurable power loss with a belt over a chain, typically 3 to 5 HP. I think that's why you never see belts on racing motorcycles. Please also note that the larger the chain, the greater their frictional losses are. In the old days 530 chains were very common, but with the development of high speed chains and their increase in both strength and durability, most bikes today now use 520 chain. You are correct that lost power translates to heat and belts do get warm, but they are also cooled by the air movement around them. There are also air pumping losses, as the tooth enters the groove in the pulley. Interestingly, this was one of the many teething problems encountered in the development of the Hovercraft. Those huge fans are tooth belt driven and the air blast from the large pulleys made a very loud howling noise during operation. Their solution was to drill air venting holes in the pulley grooves. | ||
| Snacktoast |
You wont see belts on race bikes, especially road race, because as rubber comes off the tires, it can get caught between the belt and sprocket and break the belt. This happened with the first 1125s that hit the track before a chain drive conversion was available. | ||
| Nobuell |
Not to mention ratio changes are not possible with the belt | ||
| Hughlysses |
There is measurable power loss with a belt over a chain, typically 3 to 5 HP. Steve- I can believe 3 to 5 HP loss. I've just seen some claims of "10% power loss" and similar which would be crazy. ~15 HP being lost in the belt would fry it. |
