Manifold restrictors
Thread Starter
Junior Member
Squid
Joined: May 2007
Posts: 18
Manifold restrictors
Can anybody give me an explanation for the restrictors on the inlet manifolds. I realise most people have them removed under the impression that this will allow a better/more air flow giving better power/torque/response. But the Honda engineers are not fools. These things are there for a reason. I feel the restrictors have a lot to do with low speed idling smootness and midrange response. They must also have a big impact on the turbulance of the a/f mixture at WOT therefore being very important for efficient combustion. Any opinions/advice gratefully received.
Cheers, Reb.
Cheers, Reb.
Banned
MotoGP
Joined: Aug 2007
Posts: 5,942
From: Lake View Terrace, CA
Can anybody give me an explanation for the restrictors on the inlet manifolds. I realise most people have them removed under the impression that this will allow a better/more air flow giving better power/torque/response. But the Honda engineers are not fools. These things are there for a reason. I feel the restrictors have a lot to do with low speed idling smootness and midrange response. They must also have a big impact on the turbulance of the a/f mixture at WOT therefore being very important for efficient combustion. Any opinions/advice gratefully received.
Cheers, Reb.
Cheers, Reb.
Thread Starter
Junior Member
Squid
Joined: May 2007
Posts: 18
This is the Australian bike. Dont know if its the same as the Euro version, but as far as I know our bikes dont have a lot of the pollution crap the US bikes came out with. In standard form the Firestorm sold in Australia had approx 100hp. The restrictors on my bike would cover about 10% on the intake manifold area.
Cheers, Reb.
Cheers, Reb.
Moderator
MotoGP
Joined: Dec 2004
Posts: 2,553
From: South Texas
Are you referring to items 6 & 7? Or number 8?
http://www.ronayers.com/fiche/200_03...ir_cleaner.bmp
http://www.ronayers.com/fiche/200_03...ir_cleaner.bmp
Senior Member
Superstock
Joined: Jul 2007
Posts: 387
Indeed...be precise. I removed the center divider in #8 and took out #9 completely. I run a K&N from PO and "Factory" jet kit/2Bros carbon cans, and I put long intake funnels on both front and rear. Great idle...at 900 or so. Wonderful midrange torque and response, and more OOOPH all the way up. I DO have a lot of intake noise now though....especially on decel....BAHWWWAAAAUUUUGGHHHHH. I then slapped in a 4 degree timing advancer (mine's a 98) and get even MORE grunt and response from the bottom up. TPS is at 485.
YMMV
YMMV
Banned
MotoGP
Joined: Aug 2007
Posts: 5,942
From: Lake View Terrace, CA
Are you referring to items 6 & 7? Or number 8?
http://www.ronayers.com/fiche/200_03...ir_cleaner.bmp
http://www.ronayers.com/fiche/200_03...ir_cleaner.bmp
Banned
MotoGP
Joined: Aug 2007
Posts: 5,942
From: Lake View Terrace, CA
This is the Australian bike. Dont know if its the same as the Euro version, but as far as I know our bikes dont have a lot of the pollution crap the US bikes came out with. In standard form the Firestorm sold in Australia had approx 100hp. The restrictors on my bike would cover about 10% on the intake manifold area.
Cheers, Reb.
Cheers, Reb.
Out of my mind, back in 5
MotoGP
Joined: Nov 2006
Posts: 6,109
From: Skurup, Sweden
Yup, Euro bikes commonly have a metal plate with a "D" shaped hole instead of the metal band, to keep them at 100 hp...
And yes... removing that plate completely screws up the carb setup royaly... This has been tested extensively on the Swedish forum... much smarter to replace the rubbers with unrestricted ones or to file the plate...
And yes... removing that plate completely screws up the carb setup royaly... This has been tested extensively on the Swedish forum... much smarter to replace the rubbers with unrestricted ones or to file the plate...
Last edited by Tweety; Nov 3, 2007 at 02:22 PM.
Thread Starter
Junior Member
Squid
Joined: May 2007
Posts: 18
Thanks for the info. I had replaced mine with a home made version when I was playing around with the jetting just to see what would happen. Did'nt notice any difference in top end, but idling was smoother and I felt the motor was a little slower in coming on when cracked wide open in 4th, 5th, 6th. Still had good power, just a fraction slower in making it.
I will be looking for an unrestricted set of rubbers on ebay.
Cheers, Reb.
I will be looking for an unrestricted set of rubbers on ebay.
Cheers, Reb.
Its A fire, Its A Storm!
Squid
Joined: Oct 2009
Posts: 36
From: Sydney, Australia
I have an Aus bike and have seem them in there and have thaught of fileing the D out.. Has any1 done this to a stock bike. And i mean stock, no pipes, no jet, no filters nothing? What results did everyone get?
Member
Squid
Joined: Apr 2013
Posts: 42
From: Canberra ACT Australia
Indeed...be precise. I removed the center divider in #8 and took out #9 completely. I run a K&N from PO and "Factory" jet kit/2Bros carbon cans, and I put long intake funnels on both front and rear. Great idle...at 900 or so. Wonderful midrange torque and response, and more OOOPH all the way up. I DO have a lot of intake noise now though....especially on decel....BAHWWWAAAAUUUUGGHHHHH. I then slapped in a 4 degree timing advancer (mine's a 98) and get even MORE grunt and response from the bottom up. TPS is at 485.
YMMV
YMMV
Senior Member
Superstock
Joined: May 2012
Posts: 397
From: UK
In the UK those D shape restrictors where not introduced until 2001 when the upgraded models with the 19L tank, different dash and some other upgrades came out. As part of the, for want of a better word, upgrades. The PAIR system and those restrictors where introduced.
(:-})
(:-})
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