Custom exhaust

[Stephan]

Or these

probably I´ve missed something, what are these? Looks quality made.

[mik_str]

Or these

Funking looking unit? May I ask what it is?

[lloydie]

Or these

Funking looking unit? May I ask what it is?

Titanium big bore exhaust !! No branding but custom made

[Stephan]

lloydie: looks like the pipes have the same diameter everywhere, how is bigbore made then?

[lloydie]

The pipe diameter is bigger than standard

[bigtwinthing]

Or these

holy shite there lovely!!! its a good job they haven't got fir round them

[Stephan]

ok, I ask becase my understanding is that big bore benefits from conical shape of pipe from the inlet, as initial diameter is given by hole in the cylinder.

Like new ducati have

[lloydie]

I don't know I'm just a lube tester !!

[Stephan]

I don't know I'm just a lube tester !!

oh, than I understand initial diameter is the same

[lloydie]

They ain't mine so can't measure them to find out sorry

[bigtwinthing]

ok, I ask becase my understanding is that big bore benefits from conical shape of pipe from the inlet, as initial diameter is given by hole in the cylinder.

Like new ducati have

is it me or does that look like a keep fit cycle machine?

[lloydie]

or one of carls bongs

[VTRDark]

ok, I ask becase my understanding is that big bore benefits from conical shape of pipe from the inlet, as initial diameter is given by hole in the cylinder.

Well yeh almost. Big bore is just a fashionable term used for anything larger than standard diameter exhaust. In an ideal world one would want a taper coming out of the Exhaust ports. how long the taper should be is questionable depending on the total length of exhaust, and then tapers off to whatever diameter the main pipe is and then should taper back up to where the end can starts. But this is exhaust theory, a black art and every system should be custom made, tuned according to the engine modifications if any and to whichever end cans are used. The tapers are supposed to help with the exhaust pulses as they go from positive to negative, so smooths out that transition point at each end.



The following I have copied from an old post of mine:

Exhaust tuning Is all very complicated stuff as it involves maths and most likely an understanding of fluid dynamics. Way over my head!!! It's not quite as easy as bigger gives better flow because that is not always true. Make it bigger and you loose velocity. The smallest changes can have huge effects. For example...when I was riding around on the fazer I bought some after market headers which did not have the two balance pipes up front (close to ports roughly 6inches away/along the pipe) these linked between one downpipe to the other and basically merged two cylinders to each other. I had an instant very noticeable seat of the pants loss of bottom end grunt. Put the standard ones back on with the balance pipes and the bottom end grunt was back.

Then there is the exhaust length. Does one make the length shorter to compensate for the bigger bore keeping the same total mass in the system. How does the speed effect this. How does the change in temps affect the speed. Should it be longer or shorter depending on if there is more or less velocity. One could even go as far as thinking about the aerodynamics as well. The angle of the exhaust and speed/distance of exhaust pulses/flow out the back of cans to reduce drag. No simple task without the right tools and testing equipment.

Some links.
Exhaust and intake tuning

How To Calculate Muffler Size and Exhaust Pipe Diameter

Exhaust System Theory 101

Exhaust System Technology

This is worth a read as well.
http://www.rc51.org/exhaust.htm

http://speedtalk.com/forum/viewtopic.php?f=1&t=1435

All very interesting reading.

(:-})

[tony.mon]

Of course you can always remachine the heads so that the port exit is slightly larger at the point where the header joins it. I would have thought that as long as there is a regular taper along the port and into the full pipe diameter it should be ok.

It's steps that are to be avoided.

[mik_str]

Or these

Funking looking unit? May I ask what it is?

Titanium big bore exhaust !! No branding but custom made

Nice! Care to share the builder's name? I like the design of the collector (not that I am in any way qualified to judge its technical merits)....