You check for breathing." (Markus Zusak)
Hence it stands to reason if I wanted this thing to not just be alive, but rudely healthy, I needed BIG breaths, yeah?
So another driver for going with the alloy tank was the airbox. This was always going to be problematic if I wanted something of a decent volume, as my self-built cover/sub-tank arrangement had created some awkward under-tank shapes/voids.
I did have something in mind....but the idea worked even better with the alloy tank given it had flat sealing surfaces I could use to make something along the lines of a carbon RS unit that would seal against the underside of the tank. Basically, the bottom of the tank would become the lid of the airbox and the volume outlined below would be assumed into the airbox:
And from my previous post, this is an F0/RS airbox:
Why? Because even if I could find some of the above sexiness, and had the necessary lottery win to fund it, none of it would fit my 1098 throttle bodies, on Jetprime intake adapters, bolted to an RS engine, fitted to a road frame, with a one-off alloy fuel tank.
Now before someone yelps "Heimholtz resonator!" or some other esoteric tuning phrase, the 749/999 range from base 749 to 999R and everything in between, with the various cams, bore/stroke differences yada yada, all have exactly the same airbox and intake runners. So airbox resonance (a means of increasing the filling of each cylinder by timing the pressure pulses within the airbox) obviously took second place to cost of production and simple packaging. Even if resonance was on their radar, most OEM manufacturers use resonance to boost the more usual mid-range hole, not peak power.
As you see up there under the title my intake/throttle body setup is pretty similar to the 999F0/RS version, a classic "racing improves the breed" example with the unobtainium 999RS/F0 intake being "productionised" for the next model 1098 road bike. The Jetprime trumpets are a direct copy of the Corse parts with the addition of the injector standoff as the 1098 has the injectors mounted in the lid of the airbox.
But getting back to the resonance thing, varying the length of the intake tract moves the torque peak up or down the rev range. Shorter stacks don't increase peak torque, they just move the peak further up the rev range. As we know, torque and hp are linked by rpm, so more torque at higher revs equals more hp.
How short? This short:
Bottomline? OEM parts/volumes were absolutely no use to me, not even as a rough guide. So I figured 3 x WSBK championships with the 999 platform, even against the might of the 1000cc IL4's, hinted that Ducati Corse were onto something with their "bigger is better!" policy.
I really, I mean really, wasn't looking forward to this but unless I did away with the airbox altogther and just put a couple of old footy socks over the intake trumpets I had to just suck it up.
Now I'm sure there are smarter ways of doing it, but "smart" is not an adjective that springs to mind when carrying out a self-assessment. So:
- "Corflute" corrugated plastic sheet? Check
- Masking tape? Check
- Cable ties? Check
- Expanding foam/ Check
- Beer...make that lots of beer? Check...check...check...check...check.
....with the plan being to form a rough mold from the Corflute, fill the mould with expanding foam, shape the foam appropriately to form the plug, wet-lay carbon fibre over the plug, then my RS-rivalling airbox would spring forth fully formed in a cloud of butterflies and harp music: "it's a miracle!!!!" OK...ok...that last is complete bullshit, but I needed a reason to start drinking/working on this bloody thing:
The expanding foam I was using to form the plug didn't go quite as far as I thought, barely filling the mold once it stopped expanding...
...only to find the next morning that it hadn't stopped expanding!
Er, yup, I think that'll do it.
Removed from the mold:
I don't know about you but I didn't realise expanding foam cures with exposure to moisture, not air. So with a reasonably large volume you end up with a sort of skinning/skull effect where the interior hasn't been exposed to moisture and remains mushy, until opened to atmospheric humidity and it all finally cures.
Craniotomy performed, as I begin roughing out:
It sits a bit lower now that it's snugged down in the right position, so it's obvious I need to make some minor adjustments. Trialling some spare intake air-ducts against it informs me I also need to puff out/add to the front for the duct flanges to mate up properly. But hey, it's only foam and refreshingly easy to work with, so I think things are moving in the right direction.....
....and eventually I arrive at this, using epoxy filler to smooth/adjust the shape as necessary:
I actually don't mind faffing around with carbon fibre....in theory. But in practice the complex shapes involved with bikes, always crammed into small areas/volumes, give me bloody conniptions! I tell you, a car bonnet or such-like would be a delightful exercise after this malarkey. It's about having the right tools for the job, and vacuum bagging equipment would be ideal in persuading fibre to follow form, but I just don't have the kit.
Now I know you'll be surprised, but the airbox did not "spring forth fully formed", there were no butterflies and the harp "music" may have been the beans from last night. Instead there was some medieval carnage as I dug out the remains of the plug, but the gods weren't entirely displeased with the sacrifice, releasing something I could actually work with:
You'll notice nowhere above have I talked of aesthetics (forget about the footy socks for the moment). I had no expectations of professional quality and so it turned out, but it'll do the job, and will be hidden behind the fairings anyway:
Oh yeah, before I cut the holes for the TB's I did a rough volume measurement: approx 12L. Add in another rough measure of the undertank volume: 3L. So total: 15L. I haven't measured a 749/999 OEM airbox (note to self) but I would suspect it's around half that volume.
And we're pretty much done:
I've since fitted a "pinchweld" edge-seal and some aluminium heatshield tape to the underside but you'll have to take my word for it until I take a pic (added to the list....):
All the above would make a good "spot the difference" game, with a few give-aways that this took a crazy amount of time (running out of beer was a rookie mistake!), not helped by big complications both inside and outside the shed. Apologies, my head hurts trying to keep track of what happened when, and I was there (!), but hopefully your WTF-O-Meter isn't too far into the redline.
