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Old 10-26-2012, 04:36 AM   #17596
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Originally Posted by UnsureFooting View Post
And what's wrong with a low rpm engine? Lots of very practical uses. They develop power earlier and get better gas mileage.
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=...9QEwBQ&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.

Quote:
Originally Posted by Jim Moore View Post
Power = Torque x RPM. The "x RPM" part is the problem with low rpm engines.
divided by 5250 ...but yes.

This is also why Harley religiously prints torque figures and never publishes horsepower.
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Old 10-26-2012, 04:40 AM   #17597
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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.
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Old 10-26-2012, 04:40 AM   #17598
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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.

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=Tiger...98&tx=77&ty=51

That is prerty farking flat lol
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Old 10-26-2012, 04:42 AM   #17599
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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.
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Old 10-26-2012, 04:43 AM   #17600
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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.

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.
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Old 10-26-2012, 05:03 AM   #17601
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Quote:
Originally Posted by UnsureFooting View Post
If you don't believe long stroke twins have a flatter torque curve than short stroke fours, you don't know much about engines.
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.
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Old 10-26-2012, 05:05 AM   #17602
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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.
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Old 10-26-2012, 05:12 AM   #17603
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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.
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Old 10-26-2012, 05:19 AM   #17604
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Long stroke engines must be respected, they won World War 1 for us.
They have a place. Not everybody wants zip around at 6k rpm.
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Old 10-26-2012, 05:28 AM   #17605
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I prefer long strokes over short strokes ....
















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Old 10-26-2012, 05:29 AM   #17606
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Clearly, you have never been in a long line of Harleys...
I usually pass em!!!



On my Harley
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Old 10-26-2012, 05:33 AM   #17607
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But the important question is, what is the airspeed velocity of an unladen swallow?

Ah yes, pictures--

Old pfarts with attitudes:



Apropos, no?

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Old 10-26-2012, 05:38 AM   #17608
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Originally Posted by Tripped1 View Post
divided by 5250 ...but yes.
Power = torque x rpm

Horsepower = torque x rpm / 5252.
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Old 10-26-2012, 06:26 AM   #17609
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Quote:
Originally Posted by Jim Moore View Post
Power = torque x rpm

Horsepower = torque x rpm / 5252.
Fair enough.
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Show folks something with a clutch and carburetor, and it's like teaching a baboon to use a Macbook.
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Old 10-26-2012, 06:29 AM   #17610
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Quote:
Originally Posted by UnsureFooting View Post
They have a place. Not everybody wants zip around at 6k rpm.

If 6000 is the speed limit its not zipping now is it?

Quote:
Originally Posted by UnsureFooting View Post
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.
......and where did I bash anything. I stated that long strokes tear themselves apart at high rpm regardless of configuration YOU are the one inferring that I have an issue with this.

The reason that I don't like Harleys is the air cooling, I don't like airheads. That 1050 I noted is a pretty long stroke for a sport application.
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Tripped1 screwed with this post 10-26-2012 at 06:34 AM
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