Faster Top Speed Fairing or Naked?

[Suzuki Stevo]

If all things are equal other than an F style fairing or being naked?

[The Buddha]

I've done some runs on the same bike (sen7ty7's 89) with and without fairing but some of the observations are seat of the pants ,not exactly timed etc ...
Naked bike is definitely faster to 60-65. To 80 or so it may be a tie. However the fairinged bike will pull a far higher, maybe as much as 10mph higher indicated top speed as well as get there faster. If the naked and fairinged bike take off side by side, the naked will get to 80 with the faired one lagging as much as 10 mph and maybe 1/8th mile behind, then it will reel the naked one in, and scoot away.
Naked will essentially run into a wall of wind by the time it shows a 100 indicated, fairing will let it get to 110 or even more, I didn't twist its tail and hold on any further than that. Cos I also didn't want the thing to grenade itself.
Cool.
Buddha.

[Watcher]

{snip}
Cool.
Buddha.

Makes sense.  The fairing's weight would impact low speed acceleration negatively, but the aerodynamics come into play at higher speeds for a greater advantage there.


How much does the fairing kit weigh?

[gregjet]

Pretty much ALL of your limitation to top speed is aerodynamic. Weight has close to zero effect on the flat on top speed, only on acc.
You find nakeds sexy but they MUST use more fuel and have a lower top speed all things else equal. A naked bike is a whole bunch of parachutes and vortex producers. A properly faired bike has much less drag. Even above 40kph it makes a difference. At 80kph there is 4 times as much drag. At 120kph 9 times as much drag and at 160 ( 100mph) 16times as much drag.

[Suzuki Stevo]

Yeah... I was thinking about the thread "Power Mods" - Worthwhile or Waste of Time? and thought that the "Naked" trend might be a good way to slow a bike down and that if you really want to improve your bikes performance, jet it correctly and leave the fairing on it. 

[twocool]

To increase top speed....drag reduction is a far better game plan than horsepower increase.

Drag goes up with the square of the speed...so drag reduction pays off big time.  In theory it is "cheaper" to...just use the right shape...no expensive engine mods..

Horsepower required goes up with the "cube" (third power)..so you have to throw tremendous HP at the problem to get significant results.

But....I look at the fairings on my GS500F...I'm not so sure they are really aerodynamically that "slick" ...lots of edges, sharp corners, blunt trailing edges, and weird scoops and pockets.  I don't think there was wind tunnel testing on this...

BTW  with piston engines, one of the biggest forms of drag is "cooling drag"   that is the air which must be ducted thru scoops, over the cylinders, or in water cooled, into the radiator..

I think the fairings on the GS are more for show and less for go, although some say a slight top speed increase.

Cookie

Pretty much ALL of your limitation to top speed is aerodynamic. Weight has close to zero effect on the flat on top speed, only on acc.
You find nakeds sexy but they MUST use more fuel and have a lower top speed all things else equal. A naked bike is a whole bunch of parachutes and vortex producers. A properly faired bike has much less drag. Even above 40kph it makes a difference. At 80kph there is 4 times as much drag. At 120kph 9 times as much drag and at 160 ( 100mph) 16times as much drag.

[The Buddha]

To add to twocool's point - The GS fairing is also huge, its almost the same size as a busa from that 04 vintage.
When I slapped the fairing n the 89, my welder remarked, "man that's a huge a$$ fairing on a little a$$ bike"
Cool.
Buddha.

[qcbaker]

I don't know how much this counts for anything, but there is very noticeable decrease in wind that hits the rider on my faired bike than there is on my naked bike. Riding my Buell Blast in the cold I feel much more wind on my body than I do when riding my GS (F model). I think maybe the GS's fairing is meant more for aesthetics and comfort/wind deflection than it is for actual aero performance. It may increase top speed a bit due to slightly better aero, but I sort of doubt that that is what it was designed for.

[Endopotential]

http://www.motorcyclespecs.co.za/model/suzu/suzuki_gs500e%2095.htm
They have the naked GS listed at 373lb dry; the faired one at 384lb.

Do you guys agree that the fairings add 11lbs?  Doesn't seem like that would be enough to weigh the bike down significantly, and well pays for the difference in aerodynamics.

BTW, QCBaker I agree on the Buell.  Have been riding my Lightning more, and it's full body buffetting.  Still sounds awesome though 

[gregjet]

Remember the fairing is not just fairing the bike, but the rider as well. The bike may be "small" displacement , but it is a full sized bike physically. The rider is full sized also so the fairing will be the size and shape required by that combination, NOT the displacement of the engine.
Now it's true that the shape required will change with speed but the max width and height will pretty much stay the same.
The actual shape of the GS fairing is obviously a compromise by virtue of the need to cool an air colled motor although that drag is very complicated ( it has very complex shape that both increases and decreases drag). The fact that it is designed for a more upright rider also increases the height (max) of the streams ( though not necessarily the pyhsical height).
Compared with a lot of current bikes the fairing both front and rear is not too bad. Modern Jap bikes have manga looking fairings to SLOW their top speed. The Japanese industary tried all sorts of engine things to limit the top speed on bikes and rider immediately faound a way around them. So they used psychology and technology. Most sport riders now are obscessed with looks as much as performance and don't want their bikes to look uncool or mod the fairings ( the old factory knows what it is doing). Yes they do know what they are doing.
Current street sports bikes have fairings specifically designed to massively increase drag as the speed increases. That's the point of all the pointy bits and folds. Have a look at a Hayabusha or MotoGP bikes( especially now the moto2 and 3 bikes where downforce is not such an isssue) . The fairings are smooth curves , except the current wave of downforce generators. The MotoGP engineers and riders will tell you that these INCREASE drag and LIMIT top speed as a trade off to downforce and anti-wheelie.
The other one is the rear. It is common for the rear drag to be greater than the frontal component. The back should fair the rear and smoothly reattach the streamlines. See those tiny rear duck tails on a MotoGP bikes. They are mandated by the regs to INCREASE drag and limit top speed on purpose. The size and width and height is regulated to ensure that rear flow is messy. Again look at a Hyabusha. That was designed to reduce drag. Everyone hates it because the industary has established the tiny rear as a style icon. They produce more drag and a Les Girls show.
One practical way to decrease drag ( and as such increase top speed) is to make a rear top box that fairs the rider. Sounds wierd doesn't it. Well in the late 70's I went on a big ride ( 7000km) and decided to make a top box for my CX500. Interesting bike in that with wasn't really faired but the engine config and seating position dropped the rider down and inside the bike. With a large tank bag and the top box designed to fair me in my top speed was increased by...17kph. NO OTHER CHANGES!

Looks dorky and ponderous but was 17kph faster

[Sandgroper57]

I'll bet you were the designated beer carrier with that setup. Or was it the entire rallies supply of Stones Green Ginger? 

[gregjet]

Don't think beer bottles would have lasted long in there on Aussie roads in 1979... Plus I don't drink beer...