Mananon wrote:Other than keeping noise down to a legal level, what other function does the can have?

No other function on a 4-stroke (but obviously the engine needs to be tuned for it). have you ever started an nc30 up without a muffler?!

The early 990cc motogp bikes mostly never used mufflers. But a lot of the riders complained about the sound level (as you would!) so mufflers started to appear. My vfr racebike is too loud not to wear ear plugs (ears will ring for a day if you don't - not good!), and it doesn't even come within a mile of how loud the motogp bikes are.

Twin pipes on the v4 obviously make the front and rear cylinder exhausts act independently of each other, so essentially you are designing a front and rear system for cylinders that are firing together (sort of acting as a single cylinder).

I have a full hrc race system on my track bike, and some of the impressions in it are beyond me (they look like big dents, but have seen them on other hrc systems). Exhaust design for optimum horsepower and/or torque is a science. There are many critical factors when it comes to designing exhausts it seems.

If you're serious about building your own, you should read up on some good books. As stated above, John Robinson's 4-stroke engine tuning covers the basics of exhaust design (and some mathematics behind it).

http://www.amazon.co.uk/Motorcycle-Tuni ... 857&sr=1-9" onclick="window.open(this.href);return false;


I've never read it, but I believe A. Graham Bell's 4-stroke tuning book is a reputable source of information also (I want this!).

http://www.amazon.co.uk/Four-stroke-Per ... 1844253147" onclick="window.open(this.href);return false;


I think if you head into your project blind you will do more to harm performance than enhance it. A quick bit of reading might make all the difference.

fastdruid wrote:Bit of an issue on the little V4's!

I loved the micron surpentine systems, pity AIUI the expense of them was one of the things that finished them. :-/

Druid

Serpent systems are pretty cool, Hydrex were using them for a few years berore Micron went up the swanny. There's only 3 area's of welding on mine and that at the joins.

Hi, I would be nice to see if NC30 would respond to tapered headers(like they use on modern race systems and vipers very nice serpent pipe(guessing on ya blade?), as i dont think the old HRC systems had this as i think they were built to long ago, but it would take lots of testing and prob huge amounts of money to make it work any better.
Cheers
Ian

or alot of time making a complete CAD model of the engine on a software like gt engineer that can simulate combustion systems. take a fair bit of time but would save a but load of money and you'd know at the end of it would be the absolute best exhaust for that bike, not just an improvement over the old.

thats how HRC would be doing it now

I want a butterfly valve on my exhaust system that I can open up to make unsilenced roars :) that would be so sick. Who needs a horn?