muffler power loss *with Pics*

[Funkenfresh]

well i got a hotdog put on my cbr954 fighter today (pics tomorrow)... looking reallllll nice!!!
but theres now a flat spot while riding.. and a prity noticable one at that...
the setup is 4-2-1-hotdog... and the hotdog inner pipe diameter is 2"..
will this effect RWHP figures or not????

[zx12argh]

probably not top end stuff - the scavenging effect ain't quite so effective at high rpm (me thinks)
But who cares - you've got a flat spot in your rideable rev range... you gotta fix that or you'll get shit off with it very quickly... try a bit of baffling in the hot dog... you don't need it THAT loud do you? :D

[Funkenfresh]

baffling.. hell no !!!
you remember the straight through pipes a had with only baffles a few weeks ago...
the hot dog was done to queiten my bike down... you could hear me up to 3 kms away with the straight through on.....
and everyday riding was doing my ears and every other civilion damage..

[zx12argh]

yeah well i'm one to talk - the 12r has straight through pipes - i'd rock up to a mates place and his garage door would already be open to let me in. They reckon they could hear me 5 minutes before I got there... Bullshit I reckon but they are fucken loud :D

[Funkenfresh]

so will reducing the diameter of a exhaust by almost half decease RWHP even after a tune up??

[Hillsy]

The standard muffler on my ZX9 had an internal diameter of around 50MM, so your hotdog shouldn't be too restrictive on the motor. I think your problem is going to be the lengths of your headers (they tune them to specific lengths).

Hopefully a good dyno operator can tune out the flat spots......but WE NEED PICS.....

[Funkenfresh]

yep pics will come after work

[Slain]

i had similar problem with my 954,
threw on a cbr600rr can (chopped down to 25cm) in a custom undertail setup. it wasnt too bad until i chopped my can down and now she picks up around 5/6 grand very hard as if its got turbo lag. im using 2 1/4" piping from the 4 to 2 to 1 bend under the rearset up under the tail. problem was made worse too when i ripped out the htev valve and airbox flapper, picked up a crapload more top end but the bike badly needs a power commander and custom map to rectify the problem. so yeh i would suggest getting yours remapped (if you have a non standard ecu) to suit the change to your state of tune.

[Funkenfresh]

close up of hotdogg
http://www.streetfighters.com.au/forum/upload/1062418284206846.JPG


Tanto the dog, and my un-named bike
http://www.streetfighters.com.au/forum/upload/1062418284119390.JPG

[latheboy]

My tuner at work says the you need 12-13 inch's from the collecter pipe to the start of the can to get the best power and torque , and by changing the dia of the can you will have either got more or less back pressure .. more in your case so its gotta get some air speedup to push it all out. ..... its like a head of air just sitting there trying to get out but doesnt have the force behind it to move , ala flat spot .. you need a better flowing system or less restrictions in the line ...
Bike looks good and i do like the hot dwag .....

[cutcat]

Hi Latheboy, they are some interesting points you made. So if I run an in tail muffler and have a really long collector pipe like 600mm or 24", does this mean to achieve max power and torque I need to decrease back-pressure by running a bigger can?
Or would I never recover the lost power of the long collector pipe and be better off sticking with a side mount can?

[HueyonaBlade]

I have also noticed a bit of a drop in power when I went to the under tail exhaust for my Blade aswell , I think we need to hook up and you can explain it to me so I can fix it Ivan

[latheboy]

No matter what you do ie: side or under tail .. you gotta get it on a dyno and see whats happened to the AFR .. As soon as you change anything on the exhaust side it will change to either rich or lean .. what i said before is just a rough comment on the goings on with an engine not to be taken as finnal .. but having said that when i changed my can i had it on the dyno for a couple of days (cause i can :) and had the carbs on and off 4 times to get the jetting right .. and all i did was change the lenght of the can .. same Ø in and out of the can .. them put pods on and got to do it all again ..
as a guess an under tail can with a long collecter pipe will run richer than the side pipe cause it will have more air to push out so there will be less air going though the carbs .. hope this makes cents ...
Im trying to get a dyno day set up at work but will see how that goes ..
Sure thing Huey ..