MotorToad
Well-known member
I can't imagine the thrill of watching a Nighthawk 250 on a dyno. It must be like pulling teeth. With tweezers.
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I just found my most favoritest dyno chart ever!
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I can't imagine the thrill of watching a Nighthawk 250 on a dyno. It must be like pulling teeth. With tweezers.
wfooshee
O, Woe is me!!
That's the funniest thing I've seen all week! Go Ninja!!!
"Proof" that RPM=HP!!
I wonder how accurate the dyno is at that end of the scale???
"Proof" that RPM=HP!!
I wonder how accurate the dyno is at that end of the scale???
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charismaticmegafauna
Well-known member
Thanks for that 'MotorToad'.
CZ Motocross racers of 40 years ago made similar horsepower to the 250 Ninja (each came with its own dyno-chart in the crate). Of course, at about half the revs of the Ninja -- and, being 2-stroke singles, they had a power stroke every stroke (but then, the Ninja, being a 4-stroke parallel twin -- does too).
That was state-of-the-art -- back then. The 250 Ninja would'a been a 'contenda'.
Still, 100hp/liter (250 Ninja) is (now) just about the current standard for an engine of any consequence/desirability -- racers are (now) around 200hp/liter.
The other two, Nighthawk and Virago, are just 'dogs' -- woof woof...
CZ Motocross racers of 40 years ago made similar horsepower to the 250 Ninja (each came with its own dyno-chart in the crate). Of course, at about half the revs of the Ninja -- and, being 2-stroke singles, they had a power stroke every stroke (but then, the Ninja, being a 4-stroke parallel twin -- does too).
That was state-of-the-art -- back then. The 250 Ninja would'a been a 'contenda'.
Still, 100hp/liter (250 Ninja) is (now) just about the current standard for an engine of any consequence/desirability -- racers are (now) around 200hp/liter.
The other two, Nighthawk and Virago, are just 'dogs' -- woof woof...
UselessPickles
Making Grand Canyon replicas from air boxes...
More correctly, RPM = (HP * 5252) / TQ
My brother has one of the newer restyled Ninja 250s that looks like a real motorcycle. You can rev it up to redline through 4 gears and still be within legal surface street speed limits. Combine that with the handling, and it's a lot of fun.
wfooshee
O, Woe is me!!
Or, HP=TQ*RPM/5250. Assuming US units. Blah Blah Blah. Understood. That's why "proof" was in quote marks.More correctly, RPM = (HP * 5252) / TQ
back. It's fun to hear people discovering Formula One say that Formula One engine specs can't be right. How can an engine that barely cranks out 200 lb-ft deliver around 800 HP??!?!? They're used to the numbers in an Amurricen V8, where torque and HP numbers are similar, mostly because the peak is real close to that 5250 RPM. But no Amurricen V8 turns 18,000 RPM!!!!
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W
Wheaton Jr.
Guest
I hope to get a Ninja 250 soon.
I hope to get an Amurricen V8 that turns 18,000 RPM. :dribble:
f1fan
Well-known member
An Amurricen V8 turning at 18,000,...I imagine that would be downright scary. In sight and in sound.
MotorToad
Well-known member
Don't be standing beside it!
Does "shrapnel" mean anything to you?So, here's what you need.
1. Chevy Small block, let's say the new Z06 engine.
2. We need some valve surface area. ... So much for those heads. We build a couple of 4vpc OHV heads.
3. Okay, got air flow. Now for the valve springs. Hrm, I guess we shouldn't have Built OHV heads.
4. I'd like to do the math for what stroke (and resulting displacement) we'd need to get a piston speed that'd be in the ball park of something that'd make a third or fourth revolution under power, but I've lost interest.
charismaticmegafauna
Well-known member
In 1955, Dr., Inginere, Giulio Carcano designed and built a V-8 motorcycle engine for Moto Guzzi that, successfully/reliably, turned 12,000 RPM.
Surely, in the intervening 54 years that could be improved upon...?
Good luck...
Surely, in the intervening 54 years that could be improved upon...?
Good luck...
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wfooshee
O, Woe is me!!
Valve springs?!?!??!! Whatchu talkin' bout? Gotta use high-pressure air to close those valves. No metal spring in the world can work a valve 150 times a second.
OK, I'm bored. Wife's at some function for work, I've DVR'd myself to death, so I'm on the forum.
More numbers you won't get out of your Chevy small-block: Formula One engines are severely oversquare to minimize stroke, to get those revs. They still need really nifty metals, as the piston apparently is subjected to about 10,000 g at TDC. Nobody publishes design specs, but the rules limit bore to 98mm, so guess what they use. . . . Math: 2400 (the displacement limit in cc) divided by 8, then divided by half the bore squared and divided again by pi . . . About 39.7 mm stroke. 98mm bore / 39.7mm stroke is a ratio of just under 2.5. A tad oversquare. So you'll need an "un-stroker" crank for that Chevy.
Leads to all kinds of trouble shaping the combustion chamber, too. It's just too wide to easily get the compression ratio you need and still have the shape you want. The piston's almost 4 inches across, but it only moves about an inch and three quarters. And it moves that inch and three quarters down, then back up, 300 times in a second. In one second at maximum revs, the piston has "travelled" 88 feet! 60 miles per hour mean piston speed! 39.7mm at a time.
Just for fun, similar calculations for the FJR engine:
Bore/Stroke ratio of about 1.2, slightly oversquare. 1 second at 10,500 RPM (who here hasn't done it?) is 175 rotations. Piston "travels" 87.5 feet. Oooooh!! Coincidence? Dunno. We're making 1/8 the HP (give or take) from just over half the displacement, but just over half the revs.
My '89 Grand Marquis, 4-inch bore x 3-inch stroke, 1.3 oversquare. Let's try for 5,000 RPM (it was a good day) and we get 83-1/3 rotations in a second. Piston "travels" not quite 42 feet in that second. Hmm.. Half the above examples. Must be something to that. . . . 1/8 the HP from twice the displacement of an F1, and just over a quarter of the revs. Ow, my head hurts.
OK, I'm bored. Wife's at some function for work, I've DVR'd myself to death, so I'm on the forum.
More numbers you won't get out of your Chevy small-block: Formula One engines are severely oversquare to minimize stroke, to get those revs. They still need really nifty metals, as the piston apparently is subjected to about 10,000 g at TDC. Nobody publishes design specs, but the rules limit bore to 98mm, so guess what they use. . . . Math: 2400 (the displacement limit in cc) divided by 8, then divided by half the bore squared and divided again by pi . . . About 39.7 mm stroke. 98mm bore / 39.7mm stroke is a ratio of just under 2.5. A tad oversquare. So you'll need an "un-stroker" crank for that Chevy.
Leads to all kinds of trouble shaping the combustion chamber, too. It's just too wide to easily get the compression ratio you need and still have the shape you want. The piston's almost 4 inches across, but it only moves about an inch and three quarters. And it moves that inch and three quarters down, then back up, 300 times in a second. In one second at maximum revs, the piston has "travelled" 88 feet! 60 miles per hour mean piston speed! 39.7mm at a time.
Just for fun, similar calculations for the FJR engine:
Bore/Stroke ratio of about 1.2, slightly oversquare. 1 second at 10,500 RPM (who here hasn't done it?) is 175 rotations. Piston "travels" 87.5 feet. Oooooh!! Coincidence? Dunno. We're making 1/8 the HP (give or take) from just over half the displacement, but just over half the revs.
My '89 Grand Marquis, 4-inch bore x 3-inch stroke, 1.3 oversquare. Let's try for 5,000 RPM (it was a good day) and we get 83-1/3 rotations in a second. Piston "travels" not quite 42 feet in that second. Hmm.. Half the above examples. Must be something to that. . . . 1/8 the HP from twice the displacement of an F1, and just over a quarter of the revs. Ow, my head hurts.
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colin
Well-known member
wow, cool.... !
I just raced a '90 CBR250 in a 6 hour endurance race.... red lines around 18000, very fun! Had a spare bike which went up to 22,000, but couldn't get that race-ready in time....
I just raced a '90 CBR250 in a 6 hour endurance race.... red lines around 18000, very fun! Had a spare bike which went up to 22,000, but couldn't get that race-ready in time....
MotorToad
Well-known member
Wow, now I want a CBR250!
I really wish they'd send some more screaming 400s to America, but we fat bastards just don't buy them.
Bustanut joker
Well-known member
Haven't found a good one yet? Well winters coming, I'll bet there's one to be had soon.
They are fun bikes as pickles will attest
:jester:
colin
Well-known member
250s are big here because that is the cut off for not having to do the semi-annual (expensive) inspection.
400s are the cut-off for the mid-bike license. Big bikes require another level of bike license, which is kind of a PITA.
400s are the cut-off for the mid-bike license. Big bikes require another level of bike license, which is kind of a PITA.
colin
Well-known member
Here's my race 250. Started off the morning quite pretty. Got a bit frankenstein getting it back to race-able after a qualifying crash. We had a spare white 250, so used those fairings (and handlebars and footpegs....etc.....)
BEFORE
AFTER
Me in the race....
BEFORE
AFTER
Me in the race....
MotorToad
Well-known member
Wow, that used to be a beautiful bike!
Nice pics.
Nice pics.
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