Graves latest "hot" product

[canute]

Any one using/considering this - any opinions? What does ADSD stand for?

Graves have officially introduced the newest Graves ADSD™ systems.

The average ADSD™ sound reduction over a conventional-style exhaust is 2.5db, while maintaining horsepower increases of 12-20%. ?

2007 - 2009 Yamaha YZ450F 98 DB @ 4000 RPM

2008 - 2009 Yamaha YZ250F 98 DB @ 5000 RPM

2008 - 2009 Yamaha WR250R 95 DB @ 5000 RPM

2008 - 2009 Yamaha WR250X 95 DB @ 5000 RPM

http://gravesport.com/_cms/news.php?xnewsaction=fullnews&newsarch=112008&newsid=2

[grayracer513]

Yet another take on the same basic principle of the Power Bomb and the Akropovic pipes.

[MX926]

With a muffler that long its no wonder it lowers sound levels, regardless of the tricked out header pipe.

[gbalias]

burkhart's had that on his bike for a while now.

havent heard it in person though.

[grayracer513]

98 db is not particularly impressive, anyway. Note that the 95 db numbers are for the new WR250R/X four valve dual sport engine. Cam and compression make a difference.

[NortonMoto]

Nice, Chuck wants too much money for his products.

[gbalias]

jardine's been doing it too......

[qwik12beat]

Is the akrapovic header that stewart runs with the evap can for sale?? I havent seen one for sale yet.

[KJ790]

Is the akrapovic header that stewart runs with the evap can for sale?? I havent seen one for sale yet.

Akro has had that for sale for a few years now.

[qwik12beat]

Akro has had that for sale for a few years now.

Hahaha. guess i havent been looking hard enough:lol: Thanks man:) Do you have a link by chance? It is the factory one your talking about correct?

[grayracer513]

That's not an evap can, BTW.

[KJ790]

Hahaha. guess i havent been looking hard enough:lol: Thanks man:) Do you have a link by chance? It is the factory one your talking about correct?

If this is the one you are talking about:

Then it is right on their website: http://www.akrapovic.com/motorcycle-exhaust/products/yamaha/model/yz-450-f-2008/racing-84/

[spc mike]

jardine's been doing it too......

Is it just me or does someone else get the itch to get the TIG welder out and play with a stock stainless header pipe.

[grayracer513]

The stock header is Ti, and only about .040" thick.

[spc mike]

I got a spare stainless 450 header.

[qwik12beat]

That's not an evap can, BTW.

Well can you clarify then. maybe i can learn something

Thats not the one KJ. Its similar, but different.

[grayracer513]

With all of these header types, the can, bomb, external tube, or whatever is grafted on is simply added air volume, usually connected to the main header tube by perforations of one kind or other in the main tube. There are several variations, but in principle, they all strive to work by damping the pressure waves that occur in the header.

When the exhaust valve opens a pressure wave begins traveling out the pipe. These waves have been used for years to "tune" the exhaust. As the pressure wave exits the system in a single diameter open pipe, a wave of negative pressure (vacuum) is "reflected" back toward the exhaust valve, and if it arrives at the port at the right time, it can aid in extracting the remains of the exhaust charge, and help optimize the intake charge. This is most simply done by adjusting the length of the pipe. Things like stepped headers, diametric changes, and muffler design all affect this wave behavior, and the resulting efficiency of the exhaust system in many complicated ways, but the result is still usually a pipe that is most efficient within a fairly narrow rpm range.

This type of modification to the head pipe tends to cause the engine to behave as if the header has no particular fixed length, and while it quite often actually causes a loss of power at the very peak versus the best non-chambered pipes, this scheme usually results in a noticeably wider power curve adding significant gains on either side of peak.

[qwik12beat]

Nice words. Thanks gray.?

[KJ790]

Well can you clarify then. maybe i can learn something

Thats not the one KJ. Its similar, but different.

You can't buy the exact pipe that Stewart runs, just like how you can't buy the exact bike any factory pro runs, nor would you want to since they probably don't perform as well on a stock engine. You can buy similar pipes though. I was just saying that Akro has been selling a pipe with the expansion chamber like Stewart runs for a few years.