New PR4s

[dnktng]

That figures out to require 20hp to go 70mph and 29hp to go 80mph. And that figures out to be a 45% increase in power requirement. Your method produced an estimate of 48% increase in power to go from 70mph to 80mph. Amazingly close I think. Maybe I'll remove my windscreen and go try it - or not. No wonder the gas mileage plumits at high speeds.

I had an old Honda 175 rated at 20HP. I'm always reminded of that 1968 CL175 at 20HP that would do 75mph easily on a flat road, and over 80mph with some tail wind or any down hill. Most motorcycles are probably using the same range of 20-25 HP when travelling at 70mph. All that extra HP is just for passing, speeding, and showing off. The performance of that 1968 Honda CL175 was pretty impressive for such an old little engine. She wasn't that pretty, but I got it running well, and then sold it and it's donor CL175 carcass.

I should have put PR4's on it.

 

[Warren]

That's one of the rare sloper models before they went to the upright CL175's. I had one of the CB160's that had 16hp and you could hit 75 if you weighed a buck 25 and got into a tuck.

 

[banjoboy]

Dan, that's damned impressive, but sounds about right.

Terry

 

[Coyote Chris]

That sounded high to me. So . . . ... ... .

I worked it backwards by assuming the NT's top speed of about 120mph requires all of the NT's 65hp. That figures out to require 20hp to go 70mph and 29hp to go 80mph. And that figures out to be a 45% increase in power requirement. Your method produced an estimate of 48% increase in power to go from 70mph to 80mph. Amazingly close I think. Maybe I'll remove my windscreen and go try it - or not. No wonder the gas mileage plumits at high speeds.

And what does this have to do with PR4s anyway?

I think you and Dan are pretty close, knowing what little I know about aircraft/bikes, fuel consumption, aerodynamics, etc. What all this has to do with PR4s is that with more horsepower to put down on the ground by the rear wheel and the hotter the tires run at higher speeds, tire milage may suffer greatly at 80 over 70, as well as fuel consumption, certain parts wear, etc. When I removed my PR3s, I would have felt very comfortable keeping the front tire on longer but just wanted to change both out at once. Running down the road on the FJR, it is interesting to watch the MPG meter as I raise and lower the windscreen. But the most interesting fact is that Frosty (when we travel together) gets better millage than I do every check on his lowered bike with the lowered windscreen and his body which is more aerodynamic than mine. (My baggage is less aerodynamic than his too).

 

[Frosty]

... But the most interesting fact is that Frosty (when we travel together) gets better millage than I do every check ... and his body which is more aerodynamic than mine ...

HEY! Does this infer that my golf ball shape is more aerodynamic? Let's see ... Reynolds number, surface area, velocity, density altitude ...
Hmmm ... Dimpled riding jackets and pants ... I wonder if Aerostitch has thought of this?

 

[junglejim]

HEY! Does this infer that my golf ball shape is more aerodynamic? Let's see ... Reynolds number, surface area, velocity, density altitude ...
Hmmm ... Dimpled riding jackets and pants ... I wonder if Aerostitch has thought of this?

When I traveled with Phil I always used less fuel than he did. We attributed that to his higher windscreen (both screen and position) and his bike was carrying more weight (rider and gear).

I'm not a golfer so I think more in terms of ballistic coefficient. So, Joe, I don't think a round shape would do it. It is more related to sectional density and diameter. So that's why I beat Phil on gas mileage - cause of the rocks in my head and lead in my butt.

 

[Coyote Chris]

When I traveled with Phil I always used less fuel than he did. We attributed that to his higher windscreen (both screen and position) and his bike was carrying more weight (rider and gear).

I'm not a golfer so I think more in terms of ballistic coefficient. So, Joe, I don't think a round shape would do it. It is more related to sectional density and diameter. So that's why I beat Phil on gas mileage - cause of the rocks in my head and lead in my butt.

Frosty has a much better ballistic coeffieient and sectional desinty than I do...

 

[Phil Tarman]

I'm trying to think of some witty repartee to add to this thread in response to Jim's completely analytical statements analyzing our differences in MPG.

I'm totally blank.

 

[Coyote Chris]

I'm trying to think of some witty repartee to add to this thread in response to Jim's completely analytical statements analyzing our differences in MPG.

I'm totally blank.

Just do what Frosty tells me to do..."dont poke the bear!"

 

[junglejim]

I'm trying to think of some witty repartee to add to this thread in response to Jim's completely analytical statements analyzing our differences in MPG.

I'm totally blank.

Aw, come on Phil. No one here is going to believe that!!!!!

 

[Phil Tarman]

Duh.......................

Still blank.

 

[Coyote Chris]

We have to be easy on Phil....he isnt having a good month....he has a right to be speachless.