I was looking at the new 2010's today (more like drooling over them) and I noticed that under the back of the seat, the exhaust pipe makes a complete loop before going to the silencer. I asked the guy at the shop, but he had no idea why it did that.

What is this for?

You have to have a certain length for backpressure and for exhaust to function properly. if it went straight out you would make no power. even drag cars have a certain length header required. Did you notice the little Hermoldz chamber too

May help with maintaining velocity to the end of the pipe, may also help with cutting noise. I say "may", I'm not claiming to know.

Dud you're all about the "Hermoldz chamber"! First you noticed mine, now you're asking this guy if he saw one!

well after you get your education on them. its pretty trick the factory is making some trick stuff.

What is the Hermoldz Chamber for?

from what I learned from it, was originally design for W.W. planes for short runways. making the engine's build torque bottom end but at the same time help with top end horsepower. it also works well in adding sound repression.

interesting... can you add them to your existing exhaust or do you have to buy a new one?

you can add to an exisiting exhaust but its not just bolt on and go. it had to be positioned correctly. if not your wasting your money.

hmm, I might try to find someone with one next time I'm riding (both the 2010 and just a bike with a chamber) and see if I can test it out

This is exactly right. FMF powerbomb headers use the hermoldz concept. It's a similiar concept to an expansion chamber on a two stroke though the properties are different. The cylinder is flipped with the intake coming in straight from the front and the exhaust routing out the back on the 2010 YZ450F which is why the need for spaghetti bend trickery.

^ ^ ^ ^ is the coolest part of the 2010.

the new 450F is bad effin arse, plain and simple!!

I would've thought it's a seat heater.