Please explain exhaust theory to me

[Colapop]

Ok, so you get a new bike. One of the things people talk about doing to improve it's performance is to change the exhaust - Akrapovic, Two Brothers, Yoshimura... etc. That's great. A new exhaust looks good, sounds good and makes your wallet lighter. But what does it actually do? What difference does an exhaust pipe make? If it's about 'breathing' better (apart from the sound law) wouldn't it be better to leave the exhaust pipe off? Is there a reason for the length of exhaust pipe? Anyone care to give me a reason for varying types of exhausts?

[nodrog:Me]

have a read here, you are pretty brainy so it should answer some of your questions.

http://www.burnsstainless.com/TechAr...ry/theory.html

[vifferman]

Oh nodrog - what a party pooper you are.
If only you hadn't posted that link, you would've left room for the KB X-spurts to post all kinds of interesting, convoluted and misinformed bollocks about zorsts.

[NighthawkNZ:Me]

Please explain exhaust theory to me

Petrol goes in the tank comes out the exhaust...

[nodrog:Me]

Oh nodrog - what a party pooper you are.
If only you hadn't posted that link, you would've left room for the KB X-spurts to post all kinds of interesting, convoluted and misinformed bollocks about zorsts.

im doing my best to save server space, go planet!

[Morcs]

Looks faster and sounds faster - therefore - makes bike faster.

[Winston001]

have a read here, you are pretty brainy so it should answer some of your questions.

http://www.burnsstainless.com/TechAr...ry/theory.html

Take no notice of that site, its all Intelligent Design type stuff.

The truth is, when you put petrol in your tank, very small imps take it and deposit tiny bucketloads in a magic furnace. This is called an " Impulse". The furnace is there to keep the dragon happy and its task in life is to try and fly out of the cavern it is trapped in.

The dragon pushes against the front of the cavern and attacks it with gusto (another magical element made from oil). This force is transmitted through the engine which is just a fancy cover for the cavern, to the frame of your bike, and pushes the bike forward. The rear wheel follows giving the illusion that it is doing the work.

The exhaust is nothing more than a fancy chimney for the furnace. However dragons are noisy creatures and have been known to escape so the exhaust is designed to make this as difficult as possible.

Straight pipes are great for the furnace but sometimes dragons can get through them and the motorcycle stops. This incidentally is why you see Harley Davidsons stopped quite often.......

[Pwalo]

It keeps the after market exhaust makers in business.

[koba]

While having a natter this morning a mate and I also noted that a fancy super exhaust on a sportsbike is much better value for money than the titanium fancy one he can get for his turbo sports car.

We thought this because the bikes 'zorst represents a far greater proportion of the bikes total mass and with an engine tuned for top end power like a sportsbike is probably going to make far greater use of removing noise and gas emmision limiters.

We also noted the main reason that a sportsbike owner seems (to us at least) more likley to shell out big $$ for an exhaust is you can SEE it (and the brand on the side of it) alot better than on a sports car, although it may give performance gain that really doesn't mean shit all in real world road riding.

[MSTRS:Me]

I have noticed in recent years that manufacturers have started to grab hold of quantum technology and put it (in the form of Black Holes) into their exhausts.
This, of course, means that fuck all escapes in the form of detectable gas and sound emissions.
It is every biker's task to ensure that this emasculating modern technology is resisted at any cost. To which end, we need to be grateful that there are still manufacturing types out there who recognise that not all that is new is good. Fail to support these wonderful philostines at your (and my)...oh, and his...peril.

[The Stranger:Me]

Looks faster and sounds faster - therefore - makes bike faster.

Everybody knows that more niose = more power.

[nodrog:Me]

Everybody knows that more niose = more power.

not always

http://www.kiwibiker.co.nz/forums/pi...pictureid=7746

[AllanB]

The most interesting recent change in after-market mufflers for bikes is the db killer insert - designed to shut the muffler up to legal levels. What is interesting about this is that most of the major makers also claim that the db killer will not reduce the performance of their muffler (when bolted onto a stock bike).

I also notice that 95% of these mufflers have the db killer removed. This leads to the conclusion that a aftermarket muffler is all about noise.

(an estimate for you wankers who will demand documented proof of my posted %)

More noise - and bloody rightly so

Now there will be some who will state that the weight difference between a stock (heavy) and slip-on muffler (light) gives a performance gain - this is in theory very true however I doubt you can actually notice it unless you are on the track being timed to the 100th second. And I conclude if this weight loss was so important to them then why do they not go on a diet and lose 20kg - this would make the greatest performance gain to their bike.

In addition to all this HONDAS RULE. Period.

[AllanB]

not always

http://www.kiwibiker.co.nz/forums/pi...pictureid=7746

Now that's not true - everyone knows that a 1600cc Harley with open pipes will go from 67 to 69 hp.

[The Stranger:Me]

Ok, enough of the bullshit.

First mod to the Fazer was a PC only, that yeilded +4.5hp peak with gains in the top half of the rev range only.
Next was an air filter and Yoshi can (this removed one cat) that yeilded +9hp peak but healthy gains from 4k up.

The XT is a whopping 41hp std and with pipe and air filter only was pulling 45hp. Gains were only available in the top half of the rev range.
With the PC we have gains through the entire rev range, and surprisingly quite an increase in fuel economy to go with it - despite tipping a lot of additional fuel, go figure.

All measurements are on the same dyno.

Draw your own conclusions.