What constitutes a good exhaust system?

[viper_biker]

Well all Iv learnt thats relevant so far on my engineering degree (first term over) about fluid dynamics is that bends are bad (create big head losses create turbulant flows) so you want to route the exhaust so that their are minimal bends, theirs no point getting the length right if their is majour losses in the system, its a compromise between the two

Certainly makes sense, but look at the RC211V GP bikes and the bends in their exhausts. I'm sure they weren't designed just for looks. The pipe under the seat does a full 360 before exiting out the seat.

[Spike16]

yeh but that's to get the front and rear pipe length equal, and being one constant radius bend it creates much lower head losses, I knew someone would bring that up, the truth is I haven't learnt enough to explain stuff like that but I know for instance that a constant 180 degree bend creates almost half the head losses a pair of 90 degree elbows do.

some pic's of the rc211v crazy pipe work, LOVE IT!

http://www.motorcycle-usa.com/photogall ... 211V_C.jpg" onclick="window.open(this.href);return false;
http://www.speedzilla.com/forums/attach ... ust-v5.jpg" onclick="window.open(this.href);return false;

[viper_biker]

Oh I love bikes that have been stripped down.

[rcv4]

how many welds and bends are in the gp systems??? no gimmics like serpent headers,wrapping etc unless you are running a full blown race engine with many of hours dyno time stick to std lengths and dia'....if its good enough for hrc

[fastdruid]

In a rather older and similar note



You can clearly see that the length is more important than the bends. If it's good enough for HRC...

Druid

[Neosophist]

In a rather older and similar note



You can clearly see that the length is more important than the bends. If it's good enough for HRC...

Druid

Omg thats some serious sex :D

As for the exhaust system, it's a black-art and requires at least 2 wizards and some type of shamen.

If you construct something of similar size / length and have the same dia tubing I don't think it's going to be too far out, nothing a good dyno won't be able to tune up.

It's when you start making werid routings that alter the lengths dramatically that things might need more work. Since Honda designed a pretty good system already i shouldn't have thought any slight variations would be too damaging.

Afterall the bikes were designed to produce 60hp (by law not engine size), so providing you provide aditional fuel, a freer flowing system might help with some power gains!

[fastdruid]

Omg thats some serious sex :D

It's pure HRC that bike, virtually nothing std from the donor bike, only made 4 and crushed two. There's 20k's worth of Magnesium carbs, back in 1986....

The more I look at the pictures the more I notice the little details.

Druid

[rcv4]

the art is to make the system fit and look good when you have the correct lengths.

[Neosophist]

Omg thats some serious sex :D

It's pure HRC that bike, virtually nothing std from the donor bike, only made 4 and crushed two. There's 20k's worth of Magnesium carbs, back in 1986....

The more I look at the pictures the more I notice the little details.

Druid

Indeed! Personally I think 1985 - 1995 was probably the best season for motogp / bike racing... To ride a beast like that and do well took some serious skills!

Have you watched

http://www.youtube.com/watch?v=bVZl3DSeo18" onclick="window.open(this.href);return false;

That? :)

[Mananon]

Right, fewer constant rad bends instead of lots of small bends. Try to get the pipe lengths as near the same as possible. I'll go same or very similar diameter and maybe a tad thinner wall.
Now, does anyone have any idea about the relationship of length between the four into two into one? Other than keeping noise down to a legal level, what other function does the can have?
I believe that four into one gives better peak but four into two into one gives better midrange.
How about two into one into can? IE twin can systems? Is there an advantage that makes up for the weight gain?
Some lovely photos Neo and Spike. Saved to my drool folder.
Now, where's my tig gear...