Posted by Curly on June 25, 2008, 8:38 am
Today I looked at a 900 Vulcan Kawasaki cruiser. Long story short the
salesman said that the donk on the Kwakka ..900 V twin .. is equivalent in
power to a 400 cc 4 cylinder. Is that True ????????????
Thanx
Curly
Posted by ~ on June 25, 2008, 10:42 am
> �Today I looked at a 900 Vulcan Kawasaki cruiser. Long story short the
> salesman said that the donk on the Kwakka ..900 V twin .. is equivalent in
> power to a 400 cc 4 cylinder. Is that True ????????????
Horsepower is a measure of the *rate* at which work is done.
You can take an engine that produces 50 horsepower at a certain RPM,
and double the RPM and get twice the horsepower.
OTOH, you can compare a 400 cc engine that turns twice as fast as an
engine twice the displacement, and the smaller engine will equal the
larger engine's horsepower.
Posted by Timberwoof on June 25, 2008, 11:40 am
In article
> > ?Today I looked at a 900 Vulcan Kawasaki cruiser. Long story short the
> > salesman said that the donk on the Kwakka ..900 V twin .. is equivalent in
> > power to a 400 cc 4 cylinder. Is that True ????????????
>
> Horsepower is a measure of the *rate* at which work is done.
>
> You can take an engine that produces 50 horsepower at a certain RPM,
> and double the RPM and get twice the horsepower.
Uh... Let's clarify that a bit.
If you use a gearbox to change the rate at which the shaft spins, then
you also change the torque, but the power remains constant (minus, of
course, losses to friction.)
As long as the engine's torque curve (that is, the function of maximum
torque output for a range of RPMs) is flat, then what you say is true.
However, it rarely is.
> OTOH, you can compare a 400 cc engine that turns twice as fast as an
> engine twice the displacement, and the smaller engine will equal the
> larger engine's horsepower.
Well, not necessarily either. It all has to do with how much torque the
engine puts out. My little Honda CB-1 had a 400cc engine; it typically
ran at about twice the speed of my big R1100GS engine. However, at any
engine speed, the R1100 would put out about twice the maximum torque and
thus about twice the power over its range as the CB-1.
Curly, it really ultimately comes down to the power-to-weight ratio.
--
Timberwoof <me at timberwoof dot com>
faq: http://www.timberwoof.com/motorcycle/faq.shtml
Ten Steps to Fascism: http://www.guardian.co.uk/usa/story/0,,2064157,00.html
Posted by Curly on June 25, 2008, 11:35 pm
Thanx for the quick response guys.
I think that I am beginning to understand the torque/hp thingy and I am
making my way through your excellent faq's Timberwoof.
It's good that I can come here and ask dumb questions as I didn't want to
reveal my embarrassing lack of knowledge of all things mechanical to the
salesman .
cheers
Curly
Posted by Timberwoof on June 26, 2008, 2:36 am
> Thanx for the quick response guys.
> I think that I am beginning to understand the torque/hp thingy and I am
> making my way through your excellent faq's Timberwoof.
> It's good that I can come here and ask dumb questions as I didn't want to
> reveal my embarrassing lack of knowledge of all things mechanical to the
> salesman .
> cheers
> Curly
Neaah. Questions are only dumb when you don't ask them. (Okay, and if
you continue asking the same ones. But most sane people don't do that.
:-)
--
Timberwoof <me at timberwoof dot com>
faq: http://www.timberwoof.com/motorcycle/faq.shtml
Ten Steps to Fascism: http://www.guardian.co.uk/usa/story/0,,2064157,00.html
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> salesman said that the donk on the Kwakka ..900 V twin .. is equivalent in
> power to a 400 cc 4 cylinder. Is that True ????????????