Tale of the Leaf Blower & a Smoke Bomb

phoenixtexoma · 03-10-2009, 06:06 PM

After fitting a super snorkel from SJBMW to go with the full induct, I recently noticed that the front fork looked like it substantially blocked the air path to the snorkel. On a hunch, I got out my 160mph leaf blower and a smoke bomb (the kind you get at a fireworks stand) and began observations. The fork indeed diverts A LOT of air from the snorkel by creating a tornado-type vortex that swirls to the outside, and the higher the air speed, the larger the vortex. I'm assuming it's because of the circular shape of the fork tube. I fabricated an ear as shown in photo to shunt the air back to the snorkel, and it made a VERY noticeable difference. This isn't important for the average S, but it may be important for an induct/snorkel set-up. Anyway, for what it's worth.

YellowRacer · 03-10-2009, 06:11 PM

SJBMW Super Snorkel = Failure

Ha ha, I just had too!

lennie · 03-10-2009, 06:38 PM

pheonix,

you just cannot help yourself can you ?

does it make any on road difference ?

I had given thought to having the InDuct go straight but it meant cutting a hold in the body work.

Not a good option for most.

signit98 · 03-10-2009, 07:14 PM

Lennie, got the sprockets today... I shall try to put them in next weekend but I am waiting for parts for that bike and I do want to do an extensive before/after...

Look sweet, though... the only difference is that little hole?

Thank you, I'll report my findings in depth.

phoenixtexoma · 03-10-2009, 07:22 PM

Lennie: It makes a LOT of difference at high speeds. The ear is a good compromise to deflect the air, pushes the vortex right back into the snorkel. With the smoke bomb, you can see the vortex very clearly. An intriguing phenomenon. I would have thought the air would just slide around the fork tube into the snorkel in a straight line, but it doesn't. My next step is to look at the left side of the tube for possible placement of another ear. I'll post another photo of the side of the bike to show how the ear looks. It's actually pretty unobtrusive visually.

Bigred455 · 03-10-2009, 08:14 PM

Have you tried your smoke trick with the engine running? Could the pull of air from the engine change the air pattern behind the fork tube?

chewie · chewie's Garage

One either side eh? might end up looking like you ran over Micky Mouse and he's stuck upside down up in there somewhere...

interesting though all the same

nice one!

SergioK · 03-10-2009, 09:08 PM

We need a video of said vortex.

lennie · 03-10-2009, 09:36 PM

pheonix,

when I did the InDuct originally it was meant to sit under the fairing to look as stock as possible.

Not sure how they would sell as some people might not to see it like that.

So you noticed a difference at speed on road. Good.

Every little bit heps.

lennie · 03-10-2009, 09:38 PM

signit,

Yes just the little hole for the R1200 for the sensor on the right cylinder.

see how you go and report the findings.

squall_line · 03-11-2009, 05:35 AM

Quote:

Originally Posted by Bigred455

Have you tried your smoke trick with the engine running? Could the pull of air from the engine change the air pattern behind the fork tube?

Or with an air stream as wide or wider than the bike, for that matter... In a dynamic fluid environment, the size of the stream makes a BIG difference. If you're only pushing a 3" wide stream of air at 160 MPH directly at the fork tube, that 3" column of air is going to act a LOT differently than a 30" stream or a 90" stream, never mind the natural turbulence introduced by the tube on the leaf blower itself.

Something quite a bit larger than a leaf blower, such as a 6' diameter industrial fan (with the proper calming mechanisms in place) or, say, a real wind tunnel, would be needed to properly understand the air flow over the bike.

squall_line · 03-11-2009, 05:39 AM

Quote:

Originally Posted by lennie

So you noticed a difference at speed on road. Good.

Every little bit heps.

Actually, he just said "at high speeds", and has only really talked about the leaf blower, but never actually mentioned taking the bike out on the road to test it.

I'm not trying to say, with this post and my previous post, that this is all a bunch of baloney, but there are some pretty serious flaws in methodology that make me skeptical.

JonyRR · 03-11-2009, 06:33 AM

my own version of a big schnorkel has a very venturi-effect snout at the end for just this effect.
I also moved the schnorkel toward the outside of the bike more. I DID have to mod the bodywork a bit but I think it looks just fine..since I don't make and sell replicas I didn't worry about modding the fairing any.

Moybin · 03-11-2009, 07:25 AM

If BMW had been actually thinking instead of just 'designing' the left tupperware panel would have a NACA-style inlet duct that fed directly into the stock snorkel.

phoenixtexoma · 03-11-2009, 08:56 AM

I HAVE tested the bike on the road after installing the mod, and noticed a distinct difference. That said, Squall Line is 100% correct about a more scientific testing scenario. The leaf blower & smoke bomb experiment was just a hunch, and I'm not extrapolating hard-and-set conclusions from it other than that a lot of air was hitting the fork tube, bypassing the snorkel and going around the tupperware. The fork tube is directly in front of the snorkel mouth, and no doubt blocks some of the incoming air. I noticed on an earlier post that SJBMW had also been experimenting with an induct set-up that got the inlet tube more directly into the air stream.

Mad Otter · 03-11-2009, 09:00 AM

I want to see video of Phoenix riding down the interstate at 140mph with a leaf blower and smoke bomb bolted to the front of his S. Curious how the increased air speed at the leaf blower's intake would effect it's output? If it goes in a zero and comes out at 160 what might you create if it goes in at 140??? Is it a straight line increase or is it exponential???
That said, imagine how much more air could get in if BMW had designed the bike as a mono-fork?

JonyRR · 03-11-2009, 10:00 AM

here's my schnorkel. I am contemplating pulling a plug and mold...
The Uber Schnorkel Is Born...

JonyRR · 03-11-2009, 10:00 AM

or maybe THIS is MINE:
uberschnorkel part deux

phoenixtexoma · 03-11-2009, 01:35 PM

Here's an exterior photo to show how it looks. Regardless of the vortex effect, the front fork acts as a substantial barrier to incoming air.

R111S · R111S's Garage

Maybe a few small lengths of bright orange string attached to the fork tube. Then have a friend take a video from the right window of a car while another friend is driving said car on your left side. At highway speed it would give the best evidence of what is really happening.