2.25" Exhaust Question

[.:Dave:.]

Desperatly needing a new muffler and was looking into a 2.25" system.

i am looking to replace it from the Cat back with the bigger bore but am not sure if this is going to benefit the performace of the engine.


Everyone says (on forums) that the 2.25" is the go, but i havnt been able to work out if they mean cat back or engine back.

If anybody could provide some insite to this, it would be greatly appreciated.



--

Also does $350 sound reasonable for the 2.25" with a more open muffler


Thanks, Dave

[Miyagi]

AVOID THE OPEN SYSTEM!!!!!!!!!!!

seriousley, i've got extractors and 2.5 system and ended up burning an exhaust valve. the open systen dosent give enough back pressure which in time can lead to nasty problems. i ended up getting a hotdog (resonator) installed and had an oval tip put on (but the tip was pure bling factor, which only lasted to the first time i went wheeling and sat the rear down on it.)

going from the engine (as in get extractors) i've been told that the paj exhause manafold has been known to crack easily.

Sounds awesome and has Made a difference in performance

[klrevo]

dave i dont ahve the exhaust done, butim presumignt hate everyone is talking about a cat back system. iv previously had catback systems on cars with great improvements, and from what iv heard fitting extractors to the 3L is a bitch...but yeh any increase in diameter will free up the exhaust considerably if u go on a small to big principle. some try to fit extractors with the stock exhaust but it does not work because it is free flowing and then restricted, so whatever you do make it go all the same size right through or small to big and you should see an improvement, and 2.25" sounds about right, 2.5" maybe, no bigger, there needs to be some backpressure

thats about all i can add

dean

[Hekta]

Hey Dave... this is off topic, but do you have pics of that tube bar in your avatar ?

[.:Dave:.]

Thanks for the help guys,

I will definitly be going for the 2.25 cat back now that you have cleared some things up for me.

Thanks agian,




Hey Hekta

Got Some Pics for ya

http://members.optushome.com.au/davedale/


Can also take some more recent ones that show the color fading and the surface rust,

Tell us what parts you want and ill give ya closeups

(Not Sure if i like that look of the body behind the bar but cant think of a way to fix it up)

Cheers,

Dave

[Bitsamissin]

Yep I've got Genie extractors, high flow V8 Guppydore cat, high flow muffler and 2.25" exhaust. It made a noticeable difference.
You need some backpressure so a 2.5" is too large.
Just doing the 2.25" exhaust ain't really going to release more power but will give it a nice note.

[.:Dave:.]

Well i went to carline in seven hills and booked her in straight away


Picked it up disarvo and pretty happy with the sound.

It might be all in my head but seams to go a bit better, (probly just because the old muffler with 6 holes in it has been replaced).


Sofar i am happy with the outcome

[klrevo]

hey dave,

from the photo in your avitar i thought you had a little stinger bar ont he front, but from the photos i take it not, nice bar, but i understand what you mean about all the 'body' behind it, looks the goods anyways. WTF is what the bike in your pics but, that thing is just screaming death

what did you end up having done and how much cost??? 2.25" from the cat back with a new muffler? new cat? hiflow cat? let us all know and the pricing

dean

[.:Dave:.]

Klrevo,



Not sure what a stinger bar is but yeah the bar is alright from different angles.

Bar: cost $800 from Overkill Engineering, it was sorta an experiment.

Exhaust: $350 from the Cat back With a new muffler. Got it done at carline in seven hills (station rd).

If you guys are interested ill get some pics of the work and post them up.


He also said a new cat would be between 2 and 300 for a high flow.



The sound of the 2.25 is interesting, it seems to have a few peaks (i think the sound resonating). i can hear it at 1500 rpm then quiet then loudest at 3000 then quiet then can hear it a bit more at 4000 rpm.


The first time it happened i felt like the clutch was slipping or something: ie like it reved all of a sudden.


You can hear the sound here, (i dont think mine ended up this deep)

http://www.carline.com.au/default.asp?p ... D&catid=53

(look under growl sounds)




Yeah the bike is crazy to ride, felt like an old skool penny farthing or something. I had to get rid of it, Everytime i rode it i was taking my life in my own hands. Like you said before Klrevo, "Its called uni". Never give an engineering student 2 old bikes and free time

[Hekta]

It made a noticeable difference.
You need some backpressure so a 2.5" is too large.

2.25" sounds about right, 2.5" maybe, no bigger, there needs to be some backpressure

What do you guys mean by needing backpressure ?

AVOID THE OPEN SYSTEM!!!!!!!!!!!

seriousley, i've got extractors and 2.5 system and ended up burning an exhaust valve. the open systen dosent give enough back pressure which in time can lead to nasty problems.

Is this what happens if the exhaust is too big ?
Mine is RS and will be replaced real soon.

Yep I've got Genie extractors, high flow V8 Guppydore cat, high flow muffler and 2.25" exhaust. It made a noticeable difference.

Frank, you got good results from your setup didn't you, after you had it tuned ?

[Bitsamissin]

Yeah if the exhaust diameter is too big you can actually loose performance and risk burning out exhaust valves as mentioned above.
Yep mine was dynoed at 76Kw and after the extractors/exhaust and some "EFI" tuning it was cranking out 92Kw.
From memory he advanced everything until it started to ping then backed it off a tad.
I noticed a definite "seat of the pants" improvement after the extractors/exhaust were fitted (had it for a few days before it was re-dynoed and EFI tweeked).
After the re-dyno and EFI mods it definitely felt even more peppier.
Mine had a real bark to it at full noise and sounded way faster than what it actually was.
Noisey & Scott have DVD's of mine revving it's tits of in some sloppy stuff so they can tell you. I can send you a copy if you want.

[-Scott-]

Dave (pickle) used to have a link from his web page which explained the importance of back pressure. It may still be there?

Essentially, reducing back pressure improves the flow out of the cylinder, which effectively increases the valve overlap - sort of like a "larger cam." This increased overlap helps the engine produce power at high revs, but can detract from low end torque.

NFI how it burns valves.

[Hekta]

Noisey & Scott have DVD's of mine revving it's tits of in some sloppy stuff so they can tell you. I can send you a copy if you want.

I would like that. I'll send you a PM.

So it sounds like the 2.25" is the go. I'll go with that and see what they come up with. Did you pick Genie Extractors for any particular reason, over other brands ? or were they just the ones you got ?

[its fishi]

I had a 2.25" cat back system and foam panel filter put on the shorty last year. Definitely made a difference as I can go up one of the larger hills near home in 5th, where it was back to 4th previously.

Chris at Artarmon Automotive did the work, can recommend them.

It sounds great and makes a really nice burble when crawling around.

[Leeo D]

I read an article on backpressure and cracked exhaust valves. It stated that low restriction and high velocity was a good thing because it actually causes a vaccum behind the exhaust valve which lowers the exhaust valve temp.On the other hand, if you go too big a diameter then you lose the velocity and this is what helps crack exhaust valves because the hot gas hangs around the exhaust valve for too long. A 3.0 Ltr engine rule of thumb would be 2.5 inch system.This applies to normally aspirated engines as turbo/supercharged engines have a different set of rules.