View Full Version : Restrictors in air intake tubes?
Does anyone know the purpose of the restrictors in the air intake tubes, and the effect of removing them (apart from letting more air in)?
I saw one the other day and its a fairly major restriction, Im planning to remove them unless I hear its a bad idea?
Thanks,
Ben
DJ Tera
27-Aug-2003, 15:27
doesnt noticeably improve power, but throttle response seems A LOT more crisp :D
And it sounds louder too :sing:
It sounds louder with a crisper throttle response... That'll do me..
I wondered if they were primarily some kind of silencer. Not much keeping them when the Termis go on then!
cheers,
Ben
rcgbob44
27-Aug-2003, 15:42
I fitted DP carbon air tubes and a JHP under tank filter system and it definitly feels better than the original tubes.
Fidly to fit but well worth the effort!
DJ Tera
27-Aug-2003, 15:47
i think shazaam was talking about the restrictors being designed to increase airpressure at slower speeds (like putting your finger over the end of a garden hose?) but who rides a 916/998 at slow speeds anyway!!!
I'll take them out this evening, and let you know how many seconds it shaves off the ride to work in the morning :D
The noise alone should be worth a few tenths
cheers,
Ben
They are fitted to cut down noise from the airbox.
It's all to do with sound waves and resonance.
Desmondo
27-Aug-2003, 16:09
...and just think of the weight saving. Worth at least another 3bhp.
Nigel Booker
27-Aug-2003, 20:37
As far as I was told they are just fitted for noise reduction, but the engine seems to respond better without them and the induction noise is great.
Yellow Bip
27-Aug-2003, 22:02
I have also fitted a JHP under tank air filter and removed rubber restrictors and front mesh on the nose cone and it does sound nice.
And i hope this does not sound stupid but if you start it up and put your ear to the front of the intake and rev it it sounds GREAT!!!!!!!!!
Hum ,methinks mine might get accidently lost the next time i oil the filters !!;)
Shazaam!
27-Aug-2003, 22:49
Long answer:
Like sps955 says, the rubber restrictor annulus on the superbike inlet runners are designed to reduce air induction noise to meet US EPA (and Euro?) limits. These are not inlet restrictors designed to limit performance like those used recently on some Japanese bikes to meet maximum speed limits. The superbike blocks merely increase the velocity of the air as it passes through the device but reflect sound waves back to the engine inlet. Said another way, the pressure drop across them is very low as opposed to a high pressure drop created by a dirty air filter. Removing them increases the free air volume between the velocity stacks and the stock air filters which has the added benefit of a better throttle response (but no more power).
Short Answer:
Like weeksy says, if you take out the restrictor blocks you’ll get a nice intake growl.
Well, I removed them last night, rode in this morning. The instantly obvious change was the intake noise - much more of a growl than before. Not sure if I'll still be able to hear it once the stock exhausts are removed and the new ones fitted, but definately worth doing if it helps everything breathe easier.. not to mention the huge weight saving ;)
Bianchi
28-Aug-2003, 10:58
My 2001 996Bp bought new didn't have these rubber restrictors in.
I am informed that bikes destined for the USA market did, for the reasons stated by Shazaam.
Im pretty sure my '02 998 is a UK spec bike. It doesn't have any of the extra emission control equipment that a US destined bike would have and the Ducati delear that I bought it from was the supplying dealer and they confirmed it was a UK spec bike. Apparently some of the recent new 998's that have been turning up are US spec bikes that the dealers are having to modify to UK spec which is apparently quite a bit of work.
.
Anyone mailed JHP/Ducati for the Official version ?
Just pulled mine out today & went for a ride
The throttle response is deffo better , Plus she sure does Growl now !:D
[Edited on 29-8-2003 by Totto]
JHP say its OK to take them out ,won't make much difference & is best done with other mods IE pipes/chip
But the throttle response is improved , well i think it is anyway !
Originally posted by Bianchi
My 2001 996Bp bought new didn't have these rubber restrictors in.
I am informed that bikes destined for the USA market did, for the reasons stated by Shazaam.
Wierd that. My '01 996 Bip did have the restrictors in. UK dealer supplied and UK spec bike.
Fitted some of Ripsnortingvtwins carbon airtubes and a JHP undertank filter a while back and took them out. Couldnt get over the size of them!
My '00 996bp had them in as well. That was a UK bike supplied through an official Ducati dealer.
pguenet
01-Sep-2003, 19:25
Ben
Nobody seems to have picked up on that and sorry if I am stating the obvious - but since you don't have many posts, you might be new to Dukes- better to check than you making a big mistake.
When you removed the filters from the airtubes, I believe that you fitted an under-tank filter (such as ITG / JHP / etc).
Don't let the airflow completely free cos the bike does pick up some crap and this is going straight into the engine if there is no filter on the way.
Just imagine the dammage that a small stone could do to your top end... It did happen to me once on a GoKart (you don't have air filters in Gokart, that would restrict airflow too much) and it was a carnage in there.
Again sorry if there is stating the obvious but better to do so then leaving you with a totalled engine!!
Cheers
p
Thanks for the thought but the OE air filters are still in the intake tubes, they should hopefully stop any rubbish getting in. I dont have any other filters installed.
I'll have a look though and speak to the dealers when I get the bike back - see next post! :(
swiss 998s
02-Sep-2003, 12:40
I guess that removing them also "frees up" volume in the airbox which should have a similar effect to increasing the size of the box by 1l or so. The effects as I understand of a bigger box is to lower the helmholtz resonance and hence boost mid range.
I have heard the counter argument that installing an in tank filter takes up volume, increasing the frequency of resonance, so the opposite should apply when removing the blocks
psychlist
02-Sep-2003, 21:56
how do you remove the restrictors?
:ninja:
Do a search on the old boards.Loads of threads on the subject.
pguenet
03-Sep-2003, 10:12
Dead simple although quite a pain ... You undo all the little screws holding the air tubes and plit them in 2. Then you can remove the filters.
One thing though, be patient and use a good screw driver, those screws are a pain to remove and if you start rounding one up you are buggered!
"if you start rounding one up you are buggered!" technical term that Phillipe??:lol:
John
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