airbox | Moto-Abruzzo

13/02/201703/05/2019

Take a deep breath ……..

Hawker Typhoon air inlet and radiator With plans a-foot to assemble a big-cc motor for the Capo, it was time to cast an inquisitive eye over the airbox snorkel, that ugly rubber protrusion at the front of the airbox, sucking in hot air from on top of the radiator. This one object has been debated far and wide over the years – keep it, or remove it? Yes the questionable snorkelectomy!

Only a couple of ways to find out I guess. Dyno the bike with and without it or draw it up and run a flow analysis on it from the comfort of an armchair. Armchair it is then! With the model complete, here’s a couple of basic facts: Snorkel Inlet area (total) 1,750mm² and outlet area (total) 3,050mm². So the inlet is slightly restricted, the offending area is highlighted in the picture (click to enlarge). In fact, if the restriction were removed, the snorkel would have an inlet nearer to 2,400mm² – about 37% more!

To keep it simple the analysis was run with air at 1013mb and 20C, both with AND without the restriction in place and at RPM’s ranging from 1,300 to 10,250 – well above Caponord max RPM of 8,750.

I think it’s reasonable to say that the OEM snorkel doesn’t really do badly until it hits 9,000RPM+ and lets face it, by then the whole thing is over for the poor old Capo anyway! Based on a days digital twiddling and some airbox datalogging several years ago, I have to say that I’m planting my flag firmly in the ‘leave it alone’ camp when it comes to the OEM Capo snorkel. It isn’t and never will be an RSV so why try to make it like one ….. the standard bits are designed to work well enough together for the style of bike it is. Yes of course remapping will improve things no end, but why screw up the ride by making it noisier and offering the local mice a HUGE entrance through which to set up an epic knocking shop on the air filter!

But what about the big-cc conversion? well running the analysis with the 1,103cc and 1,127cc flow certainly seemed to cast doubt on the suitability of the OEM snorkel as the strong pressure drop is now occurring lower down the rev range. So the snorkel design originally drawn up back in October 2012 was dug out of hibernation, modified and polished up for 3D printing and run through the flow software – the green line on the graph above. Overall it seems to offer a cleaner flow, less pressure drop and maintains a similar airflow velocity into the airbox. Unfortunately the one thing the software can’t tell me is how much extra noise will be generated! The OEM snorkel is made of PVCD (flexible) AND has a foam pad in the roof of each inlet – both presumably are to reduce inlet noise.

With everything looking OK a few test parts were printed to make sure it’s going to fit, then the model was split into two along the mounting plate and both parts printed separately. This was due both to size limitations in the printer and because I didn’t want to use any support material to upset the surface finish. Afterwards both parts were bonded together and the inlet tracts rubbed down with 80/180/400/1200 grit sandpaper to get a reasonable finish.

Aprilia Caponord ETV1000 Rally-Raid acoustic panel AP8117151 With a bead of sealant and 4x M4x12 and 4x M5x12 screws and nyloc-nuts, the snorkel fits into place just fine. Of course only time will tell how well it stands up to the rigours of its new home! The OEM snorkel has a rubber/foam acoustic panel (AP8117151) that fits over it and of course it won’t fit the new one, so I’ve trimmed this one to suit(ish) and placed an order for a similar dual-material sound deadening product to make a new one specifically for this snorkel. However the chopped-about old panel can’t be far off the ball park, as inlet noise just wasn’t noticeable which was a pleasant surprise …… It could well be a different story from the saddle though! 🙄

So what next? Well the plan is to get a day on a dyno when the weather is more amenable. I’d like to run it as standard, standard + new snorkel and Futura throttle bodies, new velocity stacks and new snorkel and see what the numbers say. Any guesses?

07/02/201728/04/2019

Airbox crankcase vent – Mk2

Aprilia Caponord ETV1000 Rally-Raid engine crankcase vent pipe to airbox and throttle body

With the velocity stacks and snorkel measured up and squirreled away in CAD, it was time to rebuild the airbox …… except billy-butter-fingers here, went and knocked the airbox base off a chair onto the floor – not far – but enough for it to land awkward and break the spigot for the crankcase vent. Unfortunately the spare I’d made, I gave away to a friend last year! So there I am trying to remember where I’d bought the bits to make Aprilia Caponord ETV1000 Rally-Raid engine crankcase vent flow analysis another one, when I had a “Stop the bus!” moment …… don’t waste time and fuel going into town, sit down, draw something in CAD and print that puppy! 😀

Here’s the finished article …. it has a slightly larger inlet/outlet cross-section, although the previous one worked just fine and this time the fit for the grey pipe is better. internally there is a chamber to help reduce gas flow and (hopefully) convince some of the oil to condense and run back down into the crankcase, not out into the airbox. That’s the theory anyway, but it’ll probably turn out to be complete bollocks! Either way, it looks neater so that’s a positive step forward ……. now, what else can I break today! 😀

Aprilia Caponord ETV1000 Rallyb-Raid engine crankcase airbox vent 3D print

The MK1 vent did well and lasted almost 2 years (37K miles) and in that time I never had a moments issue with oil in the airbox going where it shouldn’t. Let’s hope this one does as well!

02/02/201703/05/2019

Hybrid velocity stacks

If all goes to plan, later this year the second Rally-Raid that’s currently being rebuilt, will finally get a motor installed. The plan is to use a big-bore motor …. an 1,103cc in place of the standard 998cc. The compression and valve timing will remain bog-standard Caponord (10.5/1 Inlet timing – 25°BTDC/37°ABDC and Exhaust timing – 57°BBDC/5°ATDC). However to accommodate the increase in air-flow, I’ve decided to use Futura 51mm throttle bodies instead of the Caponord 47mm items.

Meanwhile on top of this chunky aluminium marvel sits a pair of velocity stacks. These stacks vary in height (and diameter) depending on the intended tune of the engine. The RSV Mille of course is designed as a race-rep and as such wants high horsepower at high RPM – hence 57mm throttle bodies and very short velocity stacks. On the other hand the Caponord was tuned for improved low-end grunt and so has small throttle bodies (47mm) and tall velocity stacks to maintain good gas flow speed at low RPM. The Futura seems to sit firmly between the two!

Now of course I could simply use the medium height velocity stacks straight off a Futura, but I decided to go a different route and print a new pair of hybrid stacks – Caponord height BUT 51mm diameter to fit the Futura throttle bodies. Unlike ABS, Colorfabb Ngen (Co-Polyester) can’t be vapour polished with Acetone, so I’ll have to sand the venturi down with a variety of grades of wet-and-dry up to 2,000 grit and maybe finish it off with something like Quixx plastic polish – if it works on this stuff! Here’s a couple of pics comparing the original and new version – straight out of the printer!

Unfortunately 3D parts (unless made on high-end machines) don’t typically have the same strength as injection molded or machined parts – but they do make great ‘proof-of-concept’ parts! If these stacks prove to be a positive step forward, but not durable enough for the working environment, I can at least get the drawings to the machine shop and have them made in aluminium … but that’ll be a tad more expensive than 85p each off the printer! 🙁

UPDATE

Just had a spare half-hour to rub some 100/400 & 1200 grit paper down one of the stacks and all I can say is – WOW! This material rubs up lovely and probably a couple more sessions will see it through. All the print-ridges have gone and I can’t feel anything but a nice smooth surface that retains a print pattern that makes it look quite distinctive. 🙂

Aprilia Caponord ETV1000 RST1000 Futura Rally-Raid hybrid velocity stack

25/05/201603/05/2019

Airbox breather update – (almost) a year on

Just gave the Capo motor a service. No drama, everything went according to plan. I just thought I’d share a couple of pics of the inside of the airbox – with the modified breather – straight after the air-filter assembly was lifted. No cleaning, no Photoshop ….. just as it looks after 5,354 miles. The throttle butterflies, velocity stacks and idle air control valve (IACV) are all perfectly clean.

The extended drain tube from the airbox (down below the oil filter casing) held about a spoon full of oil when drained and what can be seen in the photo was only a light coating in the bottom of the airbox. One sheet of kitchen towel had that as clean as a whistle in a few seconds. Since doing this breather modification I’ve ALWAYS run the oil level to the HIGH mark on the tank. So without the tedious job of removing and cleaning out the complete airbox, it was a pleasure to simply replace the Athena air filter and button everything back together.

Aprilia Caponord ETV1000 Rally-Raid airbox breather drain

27/08/2015

Oil in the Airbox …..fixed!

You may (or may not!) have read the post a couple of months ago – Fixing a few Capo niggles. That was where between Continental trips, the original air-box molded connection for the crank-case vent was drilled out and a new 90° bulkhead coupling and Aprilia Caponord ETV1000 Rally-Raid extended airbox drain tube pipe fitted to drain any oil into the front of the airbox, well away from the throttle body and IACV (Idle Air Control Valve).

Now with the Caponord seriously (+1,000 miles) overdue a service, I got stuck in and removed the tank ready for plugs/air filter. I admit to being really pleased to see no oil what so ever in the upper part of the airbox and only a tell-tale smear in the front section. A syringe sucked what oil there was from the drain tube – approx. 5cc @ 3,000 miles WITH the oil tank filled to the HIGH mark.

Previously it didn’t seem to matter where the oil tank level was, oil kept getting thrown into the airbox and sucked down into the throttle body. Look closely at the design of the airbox and you see the ‘fenced’ in area (red) around the velocity stacks – and of course, the two slots in the stacks (arrows) for excess oil to drain through.

Aprilia Caponord ETV1000 Rally-Raid new crankcase drain inside the airbox

It’s pretty obvious then that Aprilia/Rotax EXPECTED regurgitated oil – and tried to ensure it was fed back to the engine and burnt. Unfortunately that isn’t always the case and when some bikes are left on the side-stand oil manages to get over the ‘fence’ and muck up places it shouldn’t!

Of course a little hot oil can spread a long way and look far worse than it really is ….. I guess it just niggled the hell out of me each time I lifted the airbox lid. In hindsight it’s one of those quick jobs I wish I’d done years ago.

08/06/201508/06/2015

Fixing a couple of Capo niggles

One niggle that has wound me up more than anything about the Capo over the years, is its unerring ability to regurgitate oil into the airbox – apparently no matter how much or little I fill the oil tank. In the end, enough is enough, time to do something about it.

So this is it, remove the molded spigot/structure into the airbox and replace with a new low-profile 90° coupling and pipe to dump regurgitated oil into the front section of the airbox, from where it can be drained off via the extended drain-line down by the oil filter. Hopefully no more lumpy idle and intermittent ‘cough’ coming off idle after extended (12Hrs+) runs at motorway speeds from the vented oil draining down into the throttle bodies. A better fix of course would be to build a trap before the airbox that would allow oil to drain back the way it came while still passing vapour into the airbox. That’ll wait until winter, for now I’m hoping this will work good enough.

Aprilia Caponord ETV1000 Rally-Raid clutch oil jets Secondly, and I don’t mind admitting when a change to the Capo doesn’t work – I’ve gone back to the #60 clutch oil jet from the #40. Why? Simply because the benefits were outweighed by the losses …… yes the #40 jet made the initial 1st gear selection go from ‘CLONK’ to ‘clonk’ but it also buggered up all subsequent gear changes, gone was the silky smooth shift that I’d had with the #60 jet. In the end I would say that if your Capo shifts gears smoothly and doesn’t have an issue selecting Neutral, then leave well alone. I’m sure for those with no jet, a blocked jet or a nasty gear shift this may well be a worthwhile modification, for me I’m glad to have the old slick-shift gearbox back again.