|
|
| Author |
Message |
| colin1 |
This post is not being displayed .
|
 colin1 Captain Safety
Joined: 17 Feb 2005 Karma :  
|
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
| Huambo81a |
This post is not being displayed .
|
 Huambo81a Brolly Dolly

Joined: 16 Apr 2005 Karma :  
|
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
| colin1 |
This post is not being displayed .
|
 colin1 Captain Safety
Joined: 17 Feb 2005 Karma :  
|
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
| mchaggis |
This post is not being displayed .
|
 mchaggis World Chat Champion

Joined: 09 May 2004 Karma :    
|
 Posted: 17:47 - 28 Aug 2005 Post subject: |
 |
|
I'll just point out that the Transalp has a V-twin lump. I can tell you that an inline four is very smooth, and has a linear power increase, which jumps when it gets to high rpm and the engine starts to howl.
A single (my single pot bike anyway) has plenty of go to start with and in the mid-range, but just dies away at the top end. ____________________ I must not be a troll...
Mmmm, Guinness
Discovering the delights of Hammerite and a 3/4" brush.  |
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
| knockout_bar |
This post is not being displayed .
|
 knockout_bar Scooby Slapper
Joined: 06 Jul 2005 Karma :  
|
 Posted: 22:02 - 28 Aug 2005 Post subject: |
 |
|
V-Twins have shit loads of low-end torque but they don't do much at high rpm (as far as I know).
I THINK 4 valves per cylinder produces more top end power that 2 valves per cylinder.
The big 400cc enduros (4 strokes) tend to have loads of low-end and mid range grunt, while the motorcrossers have it mainly at the top end (for over-revving), they need the power up high.
Not sure about this tho. ____________________ 125 trail bike, custom bars, handguards etc. - ?500.
"egg flied lice" - R6jonny (inspired by McGee)  |
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
| craigs23 |
This post is not being displayed .
|
 craigs23 Mr Muscle

Joined: 08 Jun 2005 Karma :    
|
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
| MADDOG |
This post is not being displayed .
|
 MADDOG Borekit Bruiser
Joined: 26 Jan 2005 Karma :     
|
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
| G |
This post is not being displayed .
|
 G The Voice of Reason
Joined: 02 Feb 2002 Karma :     
|
 Posted: 13:50 - 30 Aug 2005 Post subject: |
 |
|
In the end, engine characteristics are going to be more based on exactly what the engine is designed to do, however specific engine types are much more likely to be used for specific purposes.
Sorry, I was intending this to be a structured post, but it's degenerated into a bit of a ramble.
The main difference between a v-twin and a parrelel twin is the firing order / balancers (apart from the obvious layout issues).
The V naturally has a 'big bang' firing order. This means that the two cylinders fire (and thus produce power) relatively close to each other, followed by a longer period with no power being produced.
This can give you better grip, as the tyre is given some time to recover, if it is starting to lose grip.
However, I'm not convinced this is at all useful outside a race track, when ridden by very fast riders.
Also, it is possible to use a different crank to replicate this on a parrellel engined bike, whether twin or four cylinders (my trx has a 270 degree crank to do this, so that it appears to be more like the duke it is copying).
Generally the sportier twins are v's, though cruisers also are, which are the opposite.
Note that I'm not aware of anything that suggests a V should make more midrange power than a parrellel cylindered bike - this, as far as I know, is a myth, partly based on (what is to some degree also a myth) twins making more midrange than fours - and twins are often in the v configuration.
The charaacteristics of a twin, as with all, do depend a lot on the type of bike - so a my Aprilia rs250's engine is nothing like that of the Honda VTX1300 I had for a testride.
A cruiser will have a fair bit of low down torque, but you will soon have to change up if you want to make progress. However, providing you're not in too high a gear, at any speed the low down torque should let you just turn the throttle and get some half decent go. Don't expect anywhere near the go of a relatively much smaller sports bike though.
An unduro bike (usually a single) will normally have a very broad range of torque - so that you get about the same torque at any point in the rev range - you still get more power higher up though, so it's still worth revving usually.
A motorcross bike (Again usually a single) will probably have a bit more of a powerband than it's trail cousins - though on a 4 stroke this now seems to more be an extension of the revrange to last longer, than one section that makes significantly more power.
Commuter bike tend to have a fatter middle range, with the power tailing off as you get to the top end. These tend to have relatively flat torque graphs - allowing for useable go anywhere in the revrange.
4 cylinder commuter style bikes are sometimes based on sports bikes with engines changed to produce a flatter power and torque graph from thier peaky sports bike doners.
Sports bikes tend to have relatively less lowdown and midrange power, with a top end rush, where significantly more power is produced as you reach the top of the rev range.
However some 'sports' twins don't seem to do this so much, often leaving me with the feeling that the powerband is just about to kick in, when infact the power's about to die out.
There has been many arguments on twin vs four cylinder engine design debate. I don't think anyone's suggesting that the twins produce less power, but many do say that they have more low down and midrange torque.
The below graph is an sp1/2 vs an R1 from a similar year. The blue shaded area is where the four makes more torque, while the red shaded bit is where the twin makes more torque.
https://www.bikechatforums.com/download.php?id=1937
As you can see, it's only at the very bottom of the twin's shorter revrange that it actually makes more torue.
You can also see that while the 4 manages to sustain it's peak power, on the twin you are changing up just after you touch upon it.
For 'fun' riding I like to have this top end rush - and with a 4 of a similar capacity you also get a similar midrange.
While 4s may be slightly lacking low down, I generally find that sports twins do feel very 'lumpy' lown down as well, only smoothing out when they reach higher revs, where you get better response from the 4 as well. |
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
| colin1 |
This post is not being displayed .
|
 colin1 Captain Safety
Joined: 17 Feb 2005 Karma :  
|
|
| Back to top |
|
You must be logged in to rate posts |
|
 |
Old Thread Alert!
The last post was made 20 years, 177 days ago. Instead of replying here, would creating a new thread be more useful? |
 |
|
|