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Discussion in 'The Perfect Line and Other Riding Myths' started by SCQTT, Apr 16, 2009.
no wonder they are so slow....it only fires once per second!
Wasn't there supposed to be a photo thread around here somewhere??
Try this one: http://www.advrider.com/forums/showthread.php?t=830971
That's Larry, he's a hoot
Hell my antique 1997 Bandit does 85 in first gear at redline
And lowend torque? I can go 25 mph in high gear
I believe the Harley "low end torque" to be a myth based on the fact that they lack power at any RPM range.
And I'm not a "hater" I've ridden Harleys I enjoy them for what they're good at which is IMHO cruising at a leisurely pace. Just don't try to sell me on their "performance"
but where are the potatoes?
25 in high gear? So? I can pull away from a stop in fourth. If you don't believe long stroke twins have a flatter torque curve than short stroke fours, you don't know much about engines.
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Any engine can have a flat torque curve. That is more of a function of intake runner length and valve events than actual engine configuration. The issue with long stroke ANYTHING is that torque is all its good for because if you really spin them piston accelleration tears them apart. Go look up a 1050cc Triumph Triple or the the 1300cc I-4 in a Busa or 1400cc in a ZX-14. Flat as the day is long.
For reference I can pull my Speed Triple off a light in 3rd gear two up and not really have to slip the clutch. You can pull any bike off of a light in any gear if you don't mind heating your clutch up a tad.
And what's wrong with a low rpm engine? Lots of very practical uses. They develop power earlier and get better gas mileage.
Clearly, you have never been in a long line of Harleys...
I looked em up, like you asked. They're flat for sport bikes, but not nearly as flat as a sportster or a vstar 1100.
Power = Torque x RPM. The "x RPM" part is the problem with low rpm engines.
Depends on what you call low RPM.
Power earlier only matters if you have a hard time getting it moving.
The fact is ALL of those motors that I lists make big twin torque, and most of them do it by 4-5000rpm. Again using one of my bikes as an example it hits its toque curve at 4,500rpm, that is 15mph in first its actually harder to GO that slow in first. I usually only bother with first for stops if the wheels are rolling there is no real reason to kick it all the way down.
Example the hyper-sports from Kawasaki and Suzuki http://www.google.com/imgres?imgurl=http://images.motorcycle-usa.com/PhotoGallerys/2008_zx14_busa_dyno.jpg&imgrefurl=http://www.motorcycle-usa.com/156/486/Motorcycle-Article/2008-Kawasaki-Ninja-ZX-14-Comparison.aspx&h=602&w=802&sz=75&tbnid=8NSGr8Wx30FtiM:&tbnh=90&tbnw=120&prev=/search%3Fq%3Dzx-14%2Bdyno%26tbm%3Disch%26tbo%3Du&zoom=1&q=zx-14+dyno&usg=__n45OikB2vXLNyCLUUtE7OPx1unM=&docid=xUCWFY8w8JMt9M&sa=X&ei=33SKUP_TI6jn0QHn2YCIDg&ved=0CD8Q9QEwBQ&dur=374
Both go most of 100mph (pretty sure the 14 actually hits 96 or so in first) and are at +85% of torque peak at 4,000rpm.
When you look at super sports its a different thing, but those are spec'd for a totally different purpose, a "slow" corner on a track is like 50mph and you come all the way down to first for that, so sub-6000rpm performance doesn't really matter a bit.
divided by 5250 ...but yes.
This is also why Harley religiously prints torque figures and never publishes horsepower.
Uh-huh. I know. Low rpm is definitely not 4k. If you have to wait until 4k for power, that's not a low rpm engine. The big twins are excellent for riding in situations that require lots of speed changes, because you don't have to shift constantly to stay in the power band. They're not road racing super stars, no. They're for practical riding at a practical pace.
Can you really tell a 10ft/lbs difference across 7,000RPM? Particularly on the ZX-14 and Busa where you have over 100ft/lbs on tap.
...but for the 1050 http://www.google.com/imgres?q=Tige...0&ndsp=26&ved=1t:429,r:9,s:0,i:98&tx=77&ty=51
That is prerty farking flat lol
And that torque curve you showed me isn't all that flat. There's a 40 ft-lb difference between those lines. The graphic is being squashed by the scaling.
When 4,000 is less then a 1/3 of you tach it certainly is.
...and I just showed dynos for THREE bikes that you don't have to shift much at all. Even on "peaky" bikes like an R6 you run the bike at 9,000-10,000 and pick the gear for the road you are on and you don't have to shift bloody much. That R6 has a 17,600rpm redline.
Like I said its a matter of extreme.
Four grand is a lot if you can only turn 5,500, its nothing if your redline is 5 figures. On my 675 I rarely come out of 2nd gear below highway speeds, and I mean interstate highway speeds.
Short stroke engines have two huge advantages over long stroke ones. Tripped1 has already identified one of them. The other is that larger valve sizes are possible.
The only advantage a long stroker has is narrowness.
There's a difference between low rpm engines (which is what I said) and low rpm for a particular engine. Bash away all you want on the long stroke twins, it just makes you look like an idiot.
Long stroke engines must be respected, they won World War 1 for us.