Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Larger Airbox for 998

[spinoli1]

Hi DSC folk,

I read recently that the 748R has a larger airbox, and I know that large airboxes are good things.

So I have a few questions for the cognicenti -

1. What size is the 998 (basic) airbox, and is the 748R airbox larger?
2. If yes to 1., can it be installed on the 998?
3. If yes to 1. and 2., where can I get one? How many wongas?
4. Also, are any other specific mods (apart from FI set-up) needed?
5. Finally, has anyone else done this mod, and how fantastic were the results?

Looking forward to any information that comes forward.

Spinoli

PS: Already doing the S cams, S ECU and 50mm pipes thing, so this seems like a logical next step

[Edited on 2-3-2005 by spinoli1]

[neil748r]

1. Can't remember exactly but 7L vs 14L springs to mind. The 748R airbox is huge by comparison to anything else bar a factory Corse one.
2. Yes, but it's a fair bit of work. You either have to cut the airbox to fit over the "X" section of the frame between the cylinders and then fabricate some sort of tunnel that'll seal the airbox again, or, chop out the 998 "X" section of the frame and replace with 748R style "X" section.
3. They appear on eBay very occasionally but remember that the 748R airbox is in 2 pieces and generally it's only the top half that comes up for sale. A carbon upper airbox from Ducati is circa £400 and you'll also need the bottom half, not sure of price but not cheap!
4. Yes, you'll need to make up some brackets to secure the lower part of the airbox to the engine.
5. Not done it to a 998, but the principle is the same.

You're best bet would be to source either a genuine 998 Corse airbox (you'd need to do other mods to fit it though) or buy one of these.

Hope that helps!

Neil.

[spinoli1]

Hi Neil,

Excellent answer. Many thanks.

I guess I'll start the long, slow search for one of the suggestions above. I'm not in a hurry and I'm not bothered about having to make modifications to fit the 998 x-section - I do quite a lot of GRP fabrication.

The EVR kit is very nice - Euros 800 isn't cheap, but we are talking Ducatis so I guess I should suck it up.

One thing, since the dawn of time, I have read that the carbon airboxes on various SP/SPS/R models made a large contribution to the stiffness of the chassis.

Is this a worthwhile consideration? I spend most of my time on the road with about 8 to 10 days spent on track per year. Middle of the fast group and happy to stay there, so I'm not trying to build a super-dooper track or race bike. Just looking to develop the bike and get more oomph as I go along.

Do the non-DP carbon airboxes offer the same structural function?

Obviously hacking into a 748R airbox to make it fit is going to wreck its structural strength.

Spinoli

[neil748r]

No problem matey!

First off, the EVR airboxes are a really nice bit of kit and not actually that expensive for what you get - and they're certainly the "easy" option.

From my understanding, the only airboxes that add any real structural strength are the genuine Corse ones. The main difference is the section under the fuel pump is fully closed, just with a couple of holes for fuel lines etc. By comparison, the "stock" airboxes are really just a perimiter frame so although they may add a certain degree of frame bracing, they won't offer anywhere near the same amount as the Corse version. To be honest, I don't really think that you would notice a difference unless you're capable of running with the rest of the BSB field. Another point to bear in mind is that the 748R airbox is the same part as the 748RS airbox. If increasing chassis stiffness was really such a major issue, wouldn't Ducati Corse have used a "stiffer" airbox in the 748RS? Obviously the 748RS had to comply with FIM rules for Supersport racing but I think that they could have stiffened the airbox without breaking the rules (I'd have to check the FIM rulebook to give you the definitive answer on that though).

Modding the lower part of a 748R airbox will have zero overall structural effect. It just bolts onto the engine and then the top half (which bolts on the same as any other airbox) literally just sits on top of it with a rubber seal between the 2 halves. You'd obviously have to make sure that after you modded the lower part that it was strong enough to retain it's shape and keep the seal between the 2 halves doing what it should.

Another point to consider is that if you fit any larger airbox you're going to need to spend some time on a dyno and use a Power Commander or similar to get it running right. Overall, it's going to be a pretty costly mod and I'm not convinced that you would notice any difference. For my money, I'd be setting squish, dialling the cams, setting valve clearances properly and use a PCIIIUSB to independantly map each cylinder - that you would notice!

Cheers, Neil.

[Shazaam!]

There’s a lot of anecdotal information about the benefits of a larger airbox being passed-around so maybe this would be a good time to summarize.


Chassis Stiffness

The airbox on a Ducati superbike bridges the upper tubular space-frame members so (if it’s properly mounted) it adds rigidity to the frame, particularly in torsion. Less flexing of the frame means smaller geometry changes at the steering head and swingarm attachment points.

The trend in motorcycle chassis design has been a progression toward stiffer frames, but you can actually go too far when there’s so little flex in the fork tubes, swingarm, steering head etc. that small bumps cause problems hooking-up the tires.

So, changing to a carbon fiber airbox will offer a chassis stiffness improvement and a small weight reduction because the material properties of carbon fiber material is better than the stock plastic. To give you an idea of the effect, it was reported that a carbon airbox on a 916 increased the torsional stiffness of the chassis by 20%.

Increasing the volume of the airbox has a tendency to make it less-stiff, as does segmenting-it for ease of installation/removal.


Intake Tract Tuning

The basic constraint to more engine power is the amount of air that you can pass through the engine. Once you’ve got more air, adding more fuel is trivial. A common way to improve air flow is to pressurize the incoming air using a supercharger or turbocharger.

Another way is to increase the size of the valves, throttle bodies and use higher-lift cams to allow more air in and larger exhausts to move air out.

You can also pressurize the intake charge at high bike speeds using air runners coupled to an airbox, but at 160mph you’ll only get a small 3psi increase. Further, larger volume airbox doesn’t offer any ram-air pressurization improvement.

There’s also another way.

You can use the intake air pulses (and the exhaust gas pulses) from the other cylinders to pull (and push) more air through the engine.

The first step is to enclose the air intakes of all the cylinders so they can send pressure pulse to each other. If the timing is just right, the pressure pulse from one cylinder will push air into an adjacent cylinder.

This timing is controlled by the size of the airbox.

An easy way to remember this is, if you blow air across the mouth of a bottle you’ll get a tone. Actually, a tone is a sound of a given frequency with a bunch of harmonics thrown-in. If you fill a portion of the bottle with liquid such that you decrease the volume of air it contains, the pitch (frequency) of the sound will increase.

BTW, if you fill the bottle with foam from an old air filter - you’ll get NO tone - which is the primary reason not to use any after-market air filter that take up space in the airbox.

When you change the size of the airbox, you change airbox resonant frequency (and its harmonics), just like you do with the bottle.

Further, the frequency that the air inside the airbox vibrates and the frequency of the pressure pulses of the other cylinder’s intakes can be paired-up for improved air flow and power - but only for a selected engine rpm range.

If you add a larger airbox, be prepared to do some dyno development work. You’ll change the amount of air going into the engine at every rpm, so the fuel map will need to increased or decreased to optimize the air-fuel ratio at each point.

On stock bikes, the chosen airbox volume is used to minimize mid range rpm dips in the torque curve, but on performance-version bikes a larger airbox is added to enhance red-line power.

So, if you decide to put a larger airbox on a stock bike that’s used primarily on the street, you’re likely degrading power in a more frequently-used rpm range to gain somewhat higher maximum power (if, and only if, you do the dyno development work.)

A larger airbox is a good trade-off on a race bike that lives at high rpm, but a questionable choice for a street bike.

[skidlids]

Just came across this and thought it was interesting

http://www.foxperformanceengines.com/

I like to have control of the bike and what its doing, so I had to chuck the 5.9 computer and harness, and run the bike with a corse 748 RS harness, which uses the 1.6 computer. I can make chips right at the track. I use a Wideband O2 sensor with a data logger that I switch on and off with a handlebar mounted switch. When I am practicing, I will switch on the unit and record the O2 band while running down the front straight. Back in the pits I'll review the data on a laptop and adjust the fueling accordingly as to how rich or lean the bike is running at WOT. There's some power to be found there I have noticed that tuning on the dyno does vary some to being on the track. It's an inexpensive Bosch wideband O2 sensor system that I am now selling. It records the data and comes with laptop software and a gauge that can be mounted on the bike to view in real time if desired. Give me a call and I can get you more details on the system. It really lights the way to proper tuning for anyone from amatuer to expert tuner.

I have been racing with the MRA going on 10 years now, and have tried so many combinations of Ducati motors it's kinda silly, 748,853,890,916,955,984,996 and now 998 which really is the best to date. I also have a 748R right now that I am running in the small twins class. Its a fun bike but I think this winter I am going to put a 749 motor in it, just for the fact that the testa motors are just so much better than the old ones.

Now that Guy Martin at MBP has redesigned his collets, they are a real breeze to install. I am using them in the 998 and have not had to do any adjusting at all. I almost feel guilty about not having to adjust the valves every 3-4 race weekends.

Well I am going to start and update this site with more tech stuff that I have to offer, which I do have alot of info to share, there's just not enough hours in the day to do it all. I have had such great opportunitys to work on a lot of rare machinery, like 748RS's and 998RS's (Gobert's bike from two seasons ago, got dyno runs and some really cool pics inside the engine of this one). and the list goes on. I really wish it was easier for me to share all this stuff with everyone, because no one person should hord such stuff, or it just goes to waste.

http://www.foxperformanceengines.com/

[spinoli1]

Zounds - I've been Shazaamed again!

My woeful grasp of tuning has been exposed.

So, the way I understand it now:

The gains to be had from the larger airbox are only relevant for a highly tuned motor which compromises mid-range and driveability for ultimate top-end. Don't want that, no Sir. I like my bike to be gutsy but friendly.

The increase chassis stiffness is of questionable benefit, and even then only relevant to racing gods. Also, if the RCV211 and M1 like increased chassis flex, then so do I dammit! I shall loosen my swing-arm pivot bolt and triple clamps accordingly.

Thanks Shazaam for another clear and complete answer to my questions.

Guess I'll have to spend the my cash on some diamonte bar-end covers and illuminating tyre-valve caps. Hmmm - a velour seat cover you say?

Thanks for including that excerpt Skidlids - that level of precision is so far beyond me I'd need to catch 3 buses even to check it out.

All the best,

Spinoli

[Felix]

I know everybody always says, ooh don't do this or don't do that, you'll loose midrange power. I don't really buy that. It seems to me that if get a bike tuned properly, that is not just bolt stuff on, but get it sorted, you're much more likely to gain power everywhere. If you don't you need a different tuner!

Having said that, I am a firm believer to get the best out of what you have. Often, that is enough of a difference. And lastly, remember the best money spent on Dukes is to get the suspension setup properly by the likes of K-Tech, etc.

[spinoli1]

By the way, and taking into account Shazaam's comments which I do not disagree with in any way, I ran a Suz### (system crash) TL1000S for over 5 years, which I gradually developed into a really fine bike.

One of the last mods I did to it was to comprehensively modify the airbox and induction path.

The TL's ram air is not direct and the flow turns through 90 degrees twice before reaching the filter. Also, the left and right air flows meet head on and the entry into the (fairly large) airfilter is partially obscured. Finally, there is a quaint flapper valve mechanism in the induction path, which is there to make your coffee frothy or something like that.

My mods introduced smooth curves in place of the right angles, removed restrictions into the airbox and air filter and installed the flapper valve correctly in the rubbish bin.

I didn't get a chance to dyno the bike before I sold it to join the World of Ducati, but my arse-dyno was very aware of a serious improvement in torque in the 3 to 5,000 rpm region. The TL was never lacking in that area before, but after these mods it became a bit stupid. It also started to make a proper honking noise at large throttle openings.

Top-end was more difficult to judge as the bike had always dived for the rev-limiter.

I guess the Frappachino valve may have restricted air intake in order to pass noise emmisions tests, but the extra air getting in after the mod was very effective.

In case anyone is interested, with a full Akro Ti-conical system, PC, K&N and a few little twiddly bits it made 119 rwhp and 72 lb/ft.

I now own a proper bike and hope I will not be judged too harshly for the confessions above.

Spinoli

[skidlids]

Also did my TL1000S airbox, which was all to do with removing the restrictions, along with the Full Scorpion race Exhaust, BMC filter and a TFi injection modifier it was dynoed at 116 rwhp, which is why it was faster than my 916 Strada at some of the race tracks. I would have liked to have tried fitting the fuel injection system off a Cagiva Raptor on to it as it would then have been possible to get a FIM chip sorted for it.