Hi All I keep seeing references to the "usual air box mod" but can't remember what the mod actually entails. I have a '94 600SS and a '93 900SS so both carbies. I did run the 600 to work once with the the top of the airbox removed, but it just made a horrible droning noise - no change in grunt as far as I could tell. So, pray tell - what is the mod.............? Glen.
Most people drill holes in the lid and fit a K+N or similar filter. You can also cut the whole lid away, but make sure you leave the front intact so water doesn't run off the front of the tank into the airbox. Either way, make sure you re-jet to suit.
Some people think the horrible droning noise is good as it supposedly makes the bike louder............Personally, I don't think it makes much difference to what other road users and pedestrians hear, but it is certainly more noisy for the rider. My airbox has just got the rubber trumpets removed and straight through zorsts are fitted........so I have a Stage 2 Dynojet kit fitted. Unless you are thinking of Dynojetting your bikes (and who knows, they may have already been done) then I wouldn't bother to piddle around with your airboxes because it will make sod all difference. AL
If you're not racing it I'd just add performance filter and jet kit. You may get a hp or two from modding airbox but tbh the cost of setting it up after probably outweighs any benefit
The usual air box mod = cutting the top out of it. I am led to believe that drilling holes, or removing the trumpets, is usually detrimental to performance (reducing midrange torque) rather than making an improvement. It's apparently got not much to do with overall air flow and a lot to do with something called pulse resonance. The theory is that, as the inlet valves close, the momentum of air down the inlet tracts suddenly hitting the stop of the closed valve causes a "pressure pulse" to travel back into the air box, which, if the air box lid is removed, pretty much dissipates and disappears other than some weak reflections off the underside of the tank. The standard air box lid is carefully designed ('tuned"?) so that reflections from this pulse off the airbox lid travel back down the inlet to the valves and hit as the valves are open again, thus aiding airflow into the cylinder. Mucking about with the air box lid design can result in a delay in the timing of this reflected pulse, so it meets the upcoming pulse from the next power stroke and stalls the airflow momentarily in the intake tubes, thus reducing airflow into the cylinder. A bit like the exhaust system, which also requires tuning of pipe lengths and diameters to avoid pulses from each cylinder meeting in the exhaust headers and upsetting exhaust gas flow - incidentally, some have attacked the crucifix in the exhaust headers and removed the gas porting in the crucifix with the intention of aiding exhaust gas flow, this we proved on a dyno also had a detrimental effect and reduced midrange torque with no corresponding increase in top end power. As others have advised, don't do this unless you are also changing the fuel metering, open air box + open pipes will need a Dynojet stage 2 kit fitting otherwise the bike will run lean. With the fuelling set up correctly for the extra air flow, more power and torque is available, probably about 3BHP on the 600. Running with an open air box lid on standard fuelling will not increase performance as the air fuel mixture will be lean.
right here is what I did with my M600 removed airbox lid stage 2 K&N filter matching dynojet kit std headers, Termi slipons 44hp to 51hp with a shagged tyre & chain but most was top end
Its a lid, its a lid they found that fits, like the carbs, they fit. I don't think any of these parts had any more thought from Ducati apart from how cheap they could buy them. I agree with al here, remove trumpets, jet up and ride it.
The carbs are off the shelf items, but the air box, and lid, aren't - they are designed specifically for the bike model they are to be installed on. Airbox design isn't a matter of accident, there's a lot of science involved there are massive performance differences associated with a good or bad air box design.
HOORAH! Someone with a little insight has joined the thread. the airbox was the same shite that was on the 851 and 888, it was too small for those as well. An addition to the 916 statement, that airbox was not particularly great!
I replaced my "cut" airbox with standard and noticed an immediate increase in power on the road. Lifted front wheel for the first time ever and shat myself! This led me to research why this should be. My findings would suggest that the "standard" cutting mod is completely wrong. I have seen comments that Ducati just fitted any airbox they could find , and whilst this may be true of electrical and comfort items it is not true of engine design. Ducati invented the desmo system which mechanically opens AND closes the valves, without relying a a spring for closure. This is an extreme departure from the accepted norm, but has proved over many decades to be the best design. I hardly think they would have gone to that much trouble without considering airflow into their engines! So I have a pal who has a masters in aerodynamics have a look at the bike. I am also a pilot so have a pretty good understanding of the subject..in fact I in the process of dealing with an engine cooling problem associated with the dynamic airflow set out below... The fairing has large air scoops facing forward in the airflow. These direct air up under the tank and create a high pressure chamber. The trumpets on the airbox are directed forwards into this high pressure airflow effectively pushing air into the intakes like a turbo. (these scoops also force HP air over the rear cylinder for cooling) Cutting the top off the box has 2 effects. 1 Takes away the forced air above. 2 Creates a low pressure at the intake. Air flowing across any aperture creates a vaccuum, it's called the venturi effect and is how all carburettors work. So with the cut airbox you now have a MASSIVE venturi, which creates a LOW pressure area effectively sucking air back out of the intake. Exactly the opposite of what you want! Of course tests on a dyno are static, ie no airflow, so the trumpets and fairing are having no effect, other than slowing the airflow, so removing the airbox will show an increase in power. However in the real world on the road it is a very different story. It is also likely that the airbox is tuned to the resonant frequency of pressure pulses caused by the cyclical intake, but I have not researched this in detail. On a final note, Ducati stuck foam sound-deadening all over the inside of the fairings. In time this degrades and I found large quantities of black powder inside my airbox, and clogging the filter on every service, until I discovered the source. Get inside your fairings and scrape all this crap out! Stay safe
I need to politely correct you, as desmodromic valve gear was a Daimler-Benz invention long before Taglioni developed it at Ducati. Also, if air is redirected by the fairing scoops it would generally be at a higher speed and thus at a lower, not a higher pressure (ref Bernoulli). Inlet-air Helmholtz resonator techniques were, I believe, only developed in the 916 era. Only the designers know the work that did or didn't happen, and as the air-filter trumpets are forward facing but not in clear air, it could be that they are sucking air from a region of diliberate stagnation It's been a while since I fiddled about with a 900SS-style airbox lid so please take this with a pinch of salt... Just because someone states something on the internet.....
my 750 ss ie runs great the air box lid has had extra holes of a large diameter cut into it at some point for the extra air flow but at some point in its life has had them covered over now i believe at some point it has been a track bike so possibly the thought was more air more power but maybe they found it didnt work hence blocked back up
A ram-air intake is any intake design which uses the dynamic air pressure created by vehicle motion, or ram pressure, to increase the static air pressure inside of the intake manifold on an internal combustion engine, thus allowing a greater massflow through the engine and hence increasing engine power.[1] Design features Ram air intakes on a 1973 Mustang Mach 1 Motorcycle with gooseneck mounted hypercharger air intake Ram air intake on Kawazaki ZX12R The ram-air intake works by reducing the intake air velocity by increasing the cross-sectional area of the intake ducting. When gas velocity goes down the dynamic pressure is reduced, while the static pressure is increased. The increased static pressure in the plenum chamber has a positive effect on engine power, both because of the pressure itself and the increased air density that this higher pressure gives. Ram-air systems are used on high-performance vehicles, most often on motorcycles and performance cars. The 1990 Kawasaki Ninja ZX-11 C1 model used a ram-air intake, the very first on any production motorcycle.[2][3] Ram-air was a feature on some cars in the sixties. It fell out of favor in the seventies, but recently made a comeback. While ram-air intakes may increase the volumetric efficiency of an engine, they can be difficult to combine with carburetors, which rely on a venturi-engineered pressure drop to draw fuel through the main jet. As the pressurised ram-air may kill this venturi effect, the carburetor needs to be designed to take this into account, or, alternatively, the engine may need fuel-injection. https://en.wikipedia.org/wiki/Ram-air_intake Is Wikipedia man on internet?
Hmm, let's re-visit the "I got it wrong" concept.. Seems we were both wrong.. mercedes-benz came to the party 58 years after the original design...! Andnow I'm going to ride my Ducati instead of wasting time arguing the toss on here. I just thought i'd share my personal experience but everyone is too busy trying to outsmart each other... As I said, buy a standard airbox and try it, forget dynos because they give a false reading as no airflow. Much nicer sound too IMHO! Design and history Desmodromic poppet valve example. Fully controlled valve movement was conceived during the earliest days of engine development, but devising a system that worked reliably and was not overly complex took a long time. Desmodromic valve systems are first mentioned in patents in 1896 by Gustav Mees.[citation needed] Austin's marine engine of 1910 produced 300 bhp and was installed in a speedboat called "Irene I"; its all-aluminium, twin-overhead-valve engine had twin magnetos, twin carburettors and desmodromic valves.[3] The 1914 Grand Prix Delage and Nagant (see Pomeroy "Grand Prix Car") used a desmodromic valve system (quite unlike the present day Ducati system).[4] Azzariti, a short-lived Italian manufacturer from 1933 to 1934, produced 173 cc and 348 cc twin-cylinder engines, some of which had desmodromic valve gear, with the valve being closed by a separate camshaft.[5] The Mercedes-Benz W196 Formula One racing car of 1954–1955, and the Mercedes-Benz 300SLR sports racing car of 1955 both had desmodromic valve actuation. In 1956, Fabio Taglioni, a Ducati engineer, developed a desmodromic valve system for the Ducati 125 Grand Prix, creating the Ducati 125 Desmo. He was quoted: The specific purpose of the desmodromic system is to force the valves to comply with the timing diagram as consistently as possible. In this way, any lost energy is negligible, the performance curves are more uniform and dependability is better. The engineers that came after him continued that development, and Ducati held a number of patents relating to desmodromics. Desmodromic valve actuation has been applied to top-of-the-range production Ducati motorcycles since 1968, with the introduction of the "widecase" Mark 3 single cylinders. In 1959 the Maserati brothers introduced one of their final designs: a desmodromic four-cylinder, 2000cc engine for their last O.S.C.A. Barchetta.
