Exhaust restriction

dookie · Post by **dookie** » Sun Jan 29, 2006 1:39 pm

Just reading on the oz firestorm site about filing out a restrictive bit as the pipe enters the right side can.
Is this the same on uk bikes? and if it is has everyone already done it?

Zer0Zer0 · Post by **Zer0Zer0** » Sun Jan 29, 2006 4:58 pm

it most likley will be dookie m8 . i got link pipes when i fitted my end cans.
and im not sure i saw the[ FLANGE] when i fitted them, and yes i think it would be beneficial to remove ,increasing flow of exhaust gasses ..IMHO of course

Post by **kevg** » Sun Jan 29, 2006 7:24 pm

Yup, i know mine are like that, never really thought about removing it though.

but i'm going to get my pipes ceramic coated to bring back the shine, as they have discoloured badly, poor quality material, might remove it before i send them off to get treated.

anybody know if these guys are still going, the website prices are from 2002.

http://www.camcoat.u-net.com/Exhausts.htm

i'll prolly phone them soon anyway but just wondering.

Stormin Ben · Post by **Stormin Ben** » Sun Jan 29, 2006 10:22 pm

DON'T DO It

Quote from Roger Ditchfield at Revolution racing (VTR GOD!!!)

> > ----- Original Message -----
> > From: "revolution racing" <roger@...>
> > To: <VTR_List@yahoogroups.com>
> > Sent: Thursday, October 06, 2005 9:32 AM
> > Subject: Re: [VTR_List] Stock header clean up
> >
> >
> > The restrictor in the standard headers is there to
> > assist the pulsing which
> > helps to scoure the front cylinder and to create a
> > turbulence vacumn thus
> > accelerating the gas speed at that point above certain
> > revs. If this is
> > removed the left hand exhaust can will discharge a
> > greater proportion of the
> > gas emmisions.as did the first Akropovic and Two
> > Brothers full exhausts did,
> > until they were modified, to the detriment of the
> > engine performance. Later
> > full systems were designed to overcome this effect by
> > changes in their
> > length, merge angles, tapers and taper length.
> > Honda, Moriwaki, Akropovic and others could have
> > saved themselves
> > millions in R&D if they had only listened to some AU
> > guy and cut away the
> > "excess" to improve power output !!!!
> >
> > Regards
> > Roger

My thought on it would be that at high revs removing itt allows more gas to escape therefore more power
However, at lower revs its gas SPEED you're interested in to provide response (how quickly the engine picks up) and a large hole is gonna make the gas speed SLOWER (think of putting your finger over the end of a hosepipe)

Ben

Post by **kevg** » Sun Jan 29, 2006 10:48 pm

Thanks for that, think it'll stay for the foreseeable future then.

Zer0Zer0 · Post by **Zer0Zer0** » Sun Jan 29, 2006 11:34 pm

Ahh the gospel according to roger........
good enuff for me.........................

Pete.L · Post by **Pete.L** » Mon Jan 30, 2006 8:25 am

Del had tried it as well.
He said it made no difference to the proformance.
Personally I think it also adds to the strength of the joint, especially important if you have aftermarket cans cause most only use a single hanger to attach themselves and can shake about a bit over the bumpy stuff.

Pete.l

dookie · Post by **dookie** » Mon Jan 30, 2006 10:23 am

Nice 1 guys , being a 2 stroke nut i understand about exhausts and understand what rodger is on about.
And im also clever enough to not question someone with a million times more experiance with exhausts than myself.
Thanks Stormin Ben i was thinking of getting the dremmal out this afternoon , PHEW
Seems that most of the oz site have buggered ther exhausts up then.

slim_boy_fat · Post by **slim_boy_fat** » Mon Jan 30, 2006 2:04 pm

To be honest it looks to me like its ment to be there, and not a bit Honda just couldnt be bothered removing, so you have to ask why is it there, and even if you dont know the answer, dont go cutting it off before you find out.

I will not be touching mine...

Post by **sirch345** » Mon Jan 30, 2006 2:46 pm

Well done Ben with that info

I think you're wise guy's to listen to that report from Roger

Chris.

Rufion · Post by **Rufion** » Tue Jan 31, 2006 8:48 pm

There is another reason why it may be there...which nobody has mentioned in the UK.

Honda made several mods to get sound down, I have been told by a friend who worked for honda and had a vtr as company bike. These may have included the 16t sprocket, lip on the airfilter and the flange in the pipe. All these mods reduce the sound at 4500rpm, doesnt the vtr have a flat spot on a dyno here? The two noise tests he mentioned were the 60kmph ride by in top gear and the rpm at half peak power noice test. anyway food for thought, I have removed all these base on that understanding, storms going better than ever!

Zer0Zer0 · Post by **Zer0Zer0** » Wed Feb 01, 2006 6:16 pm

Dont think ive' ever experienced a Flat spot on the Storm?

V-Thump · Post by **V-Thump** » Thu Feb 22, 2007 10:28 am

I've just gone to the trouble of joing the OZ Firestorm site to read what all the fuss is about. There are several guys who swear blind that removing this exhaust restriction has improved their bikes in terms of sound and smoothness. Has anybody here got any real life experience to offer?

LotusSevenMan · Post by **LotusSevenMan** » Thu Feb 22, 2007 6:17 pm

Rufion

These may have included the 16t sprocket, lip on the airfilter.

Umm, I have a 15t front and no lip on the airfilter. Well I'll leave the exhaust one though!!!

V-Thump · Post by **V-Thump** » Sat Mar 10, 2007 6:07 pm

Well I did the mod today so here is my two penth for what its worth....

1) Smoother reving
Have to agree with the OZ dudes as the bike is noticeably 'smoother' from idle 1200rpm to 4000rpm. I can't really say if its 'smoother' above 4000rpm as it was always pretty smooth reving from that point to the red line anyways.
2) Less raspy exhaust note (suits my preference)
At idle both Scorpion race cans are pumping out an equal amount of gas with the 'two hand test'. Before the mod I could only ride for 2/3mins with out earplugs (as soon as the pipes were at full operating temp they would get much noiser than from cold) today I road for a full hour with no complaints. Granted the "thump" isn't as strong as before as two cans are absorbing the noise where as before it was 80% RHS and 20% LHS (my guess) Defo better in my opinion.
3) Reduced engine braking
I don't really miss this but the bike has lost a little "character" it still has better engine braking than a CBR600 but i'd say its 1/2 as strong as it used to be.
4) Less backfiring on overun
I'd guess this follows from 3) defo suits my preference as this used too wind me up.
5) Less torque in 4000-5000 ish range
I have a 15t sproket, in 2nd gear at 4000rpm if I give her full throttle to the red line it is definately less agressive. It reminds me of a VFR800 or CBR600 you get a change of engine note when you give it full gas and the pickup comes later. Previously there was no delay, not a sniff

Some dyno time may get back some of the lost torque . I feel pretty sure the restriction was there to boost torque. There are guys in this forum who have gone from two exhausts to one and all state that "torque goes up but you loose top end". Seems to me that with my 80% - 20% anology Honda were balancing the exhaust so that a large porportion is just going through the RH pipe i.e just one exhaust for torque.

All in all I'm happier with the bike now than I was before, it sounds better is easier around town as the engine braking is less severe and I can enjoy the sound with out earplugs!. If you don't mind loosing some power and engine braking then the mod is a no brainer.