Aero Mods on my Honda VFR800

antrey · #1 02-02-2008, 10:50 PM

The one motorcycle accident I was involved in had me hypermiling on my now sold Ninja 500. A left turner was waiting across an intersection and as I slowly putted across in 2nd gear (instead of quickly accelerating across as I should have) she decided to pull out into my path. I lowsided to avoid getting hit and was not injured but decided certain hypermiling tactics were not worth it on a motorcycle. The rider safety course advises you travel slightly faster than surrounding traffic to keep most hazards ahead of you. On the highway, riding below the speed limit definitely has me checking my mirrors more often than is safe on a bike.

After contemplating how to get better highway mileage on my VFR800 without endangering my life, I've decided to try some aeromods. Motorcycles are known for terrible aero and I suspect turbulence from the rear wheel is quite significant. My VFR800 has a single-sided swingarm and a wonderfully flat stock wheel face which made it a snap to silicone a black Coroplast rear wheel cover in place. Unfortunately the VFR has no fuel economy gauge and a device similar to the scan gauge is not available for bikes as far as I know. I may try increasing the tire pressure a couple of PSI up from stock (stock is 36front, 42rear) but on motorcycles tire wear increases and traction becomes severely compromised at higher pressures.

View of the stock turbulence generator:

3 shots of the rear wheel cover:

lightfoot · #2 02-03-2008, 05:36 AM

You'd probably get more out of mods to the front end. The front wheel and the area just behind it are thought to be the main causes of the dragginess of motorcycles.

The VFR may be slightly better than most in this regard because of its radiator setup. One of the problems with racebikes is that they need more cooling than street bikes, but the air and oil radiators are usually located in turbulent air just behind the front wheel. Putting on a larger radiator increases drag. Though the VFR is not a racebike, it incorporates a racer-like trick of using twin side-mounted radiators, ducting air to them from the area behind the front wheel, and exhausting it out the sides of the fairing. So it may be a bit less draggy than most bikes. The Britten went a step further by ducting air from the nose of the fairing into a radiator mounted under the seat, and exhausting the air into the rear wheel area. This helped reduce its frontal area.

But an even better solution might be a dustbin fairing:

http://www.airtech-streamlining.com/.../MV1751965.htm

These guys sell them, but installation could be a challenge.

southerncannuck · #3 02-03-2008, 07:52 AM

I used to own a VFR800. I don't know the year, but it was yellow. 2001? I never considered MPG with the bike. I had to sell it as it was too fast for me. Let me know if the dish hurts the handling in crosswinds. I had a velodrome bike with a dish and it was unruly on windy days.

MikeN · #4 02-03-2008, 08:40 AM

Your going to absolutely hate that mod on windy days!

phoebeisis · #5 02-03-2008, 10:02 AM

Interesting mod; let us know if it causes problems in crosswinds.
I have ridden since 1973.During the second gasoline crunch-1979-80's-I had a moped,and a series of 400,500,550,600,and 850cc motorcycles.My 1980 SR500-gave the best mpg-60+ around town-when it was in dead stock form.
Riding during rush hour or anytime other than Sunday morning is no fun anymore.It was always dangerous, but with the freakin' cellphones stuck to many drivers ears, it is waaaaay dangerous.
I usually try to stay in another vehicles shadow when I go thru cross streets.If I'm close enough to their left rear fender,I can't be hit by someone crossing from the right.The left turn into a rider is very tricky-you have to suck on the bumper the vehicle in front of you for protection.
Thanks,
Charlie

antrey · #6 02-03-2008, 02:44 PM

I have though about the crosswind issue and will be monitoring it closely. I can currently tolerate crosswinds as high as 35mph. Higher than that and things get a bit sketchy. The wheels are fairly low to the ground, below the center of gravity, and wheel covers should have a smaller effect than adding a taller windscreen for example. Regarding the front wheel, I have an extended fender in mind as shown in the concept pic below. I'd also like to add a side fairing to rear of the bike and that would likely add the greatest sensitivity to crosswinds of the mods I currently envision.

Stock front wheel fender:

Concept front wheel extended fender:

Stock rear sides:

Concept rear side fairings:

MikeN · #7 02-03-2008, 03:58 PM

Good luck on all that.... I'd suggest you get a smaller bike instead

Easier to make more efficient

jcp123 · #8 02-03-2008, 04:56 PM

Good stuff. Yours already puts mine to shame on aerodynamics...but I did notice a helluva gain when I took my saddlebags off. Aerodynamics really kill these things...

psyshack · #9 02-03-2008, 06:18 PM

Just put it in F1 trim and enjoy the ride.

Its a sport bike. So look at droping more weight. Get tucked in and enjoy the ride.

As for the wreck on the Kaw. It wasn't your fault going for mpg or not. Cage drivers don't see us. While its true in some case's it is better to keep the action in front of you on a bike. It can really hurt worse when it all goes wrong. There is a reason for the huge dual disc brakes on your bike and the sexy single sided swing arm. And a engine that makes a cracking whip look like slow motion.

As for over all aero on bikes. Its been my experience that they don't seem to come into play on your ave. sports bike until you get 80 mph or above in normal street use. On the track the magic number seems to be 120 mph.

On a bagger or touring bike. Aero can be a issue. Big fairings and bags can be a issue. And bags on a bike w/o a fairing can act like air brakes.

I once put a full fairing and rear end treatment on my RZ350. It was built to the hilt. In stock trim with my fat arse on it. 160 mph top end. The aero treatment got 164 mph. And the bike was slower to 120 mph. this was not a kind RZ. It was a eco pig.

It didnt leave blue smoke out of the pipes. It just shot 3' blue flames out of the pipes burning all..... LMAO.

antry

You own a bike. I really wanted to buy new at one time. Enjoy your swiss watch quality motorcycle........

jcp123 · #10 02-03-2008, 10:34 PM

Quote:

Originally Posted by psyshack

On a bagger or touring bike. Aero can be a issue. Big fairings and bags can be a issue. And bags on a bike w/o a fairing can act like air brakes.

Exactly what I noticed...mine's just a cruiser, not built as a bagger or a tourer, but ditching those saddlebags instantly re-gained me about 4-6mpg, netting me 50+mpg highway tanks again. Needless to say, they're staying off until such time as I need them again. I wonder if there's crash bars that are angled backwards so that if I covered them to protect my legs from the air they'd still be a little more aero than just the straight-across variety...

Although I really wish I'd kept my Shadow VLX 600. Not all that comfortable aind kind of annoying when it got so hard-revved on the highway but it got better gas mileage, and, as it turns out, these bikes makes a killer platform for a bobber bike.