Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) result of air intake "research" Sigma 4/4

I will give a short intake system a try.
But why should air in a longer tube have a higher resistance? What kind of resistance? friction? amount of mass? What you may get in a longer tube are unwanted turbulances because a longer tube could have more "traps" and edges if not well designed.
Don't forget the importance of the right resonance point.

Quoted from Wiki:
Designers exploit a property of air cavities known as Helmholtz resonance. Flow through the airbox is optimal at its resonance frequency, which depends on airbox volume and the inlet area and length of the snorkel. The resonance is typically chosen to be at a medium speed where torque otherwise drops, caused by valve timing overlap."

http://www.calsci.com/motorcycleinfo/Airboxes.html

Regarding the heat, my new system does not run any longer in parallel to the metal water tube which indeed warms up the standard air tube a lot.

this sounds very interesting! Pictures would be great!

Beneviro, if you like and you have not already seen this thread, here are presented some interesting solutions by forum members.

http://www.talkmorgan.com/ubbthreads.php/topics/339575/Airbox_-_Help_needed_to_identi#Post339575

In my opinion the tuned length of the system is important in achieving the torque results that you want at certain engine speeds. The same applies to the exhaust system. Tuning the two together can no doubt be done by skilled engineers with mathematics but us mere mortals have to do it by common sense and trial and error.

From what you say Heinz you have used good logic and experimentation to arrive at the point you wanted. I suspect a shorter tube may produce good results at higher revs whereas the longer tube that you have used has a more "broadband" effect. The long tube would cause a build up of momentum of the mass of air that would cause an increase in pressure, a ram effect, when the intake valve closed and generally increase the charge in the cylinder when the valves opened.

Just my guess.

Interesting reading Heinz, many thanks for sharing.

Maybe an interesting observation: before the era of turbo systems, engines for racing purposes always had very short intake ducts (trumpet shaped without genuine filter systems); the maximum amount of available air with the lowest resistance or obstruction to aspirate at the intake side is crucial imho.

A good story, well researched and with a good ending. I and others spent hours trying to improve the inlet and exhausts of the Triumph "new" 790cc Bonneville's engine, before coming to the conclusion that if I wanted more power I'd buy a bike with a bigger engine.. Why? Because I wanted a bike that ran equally as well at all throttle openings and that involves compromises. The sort of modifications that could be made easily certainly improved aspects of the bikes performance, but not all.

As Peter G says, tuning an engine for road use requires a properly matched inlet and exhaust so that the motor performs well at both normal traffic speed and at higher revs. Whilst there is good science that describes the way air flows down a tube in a stable system the movement of air in an inlet system is more complex as the velocity id constantly changing and is influenced by valves opening and closing. So it is as much logic as art.

Consider the manufacture of a wind instrument, such as a saxophone. The difference between one that can sound divine and one that sounds "OK", when played by the same person, is almost impossible to measure. But it is real. It is so with inlet systems, and exhausts.

The short racing inlet trumpets were also paired with very short exhausts, the system optimized for wide open throttle performance and often difficult and part throttle...

Final comment: the polished stainless tubing over the engine looks wonderful, there is something about large bore polished tubes that appeals to me!!

Top tinkering.

Well done Heinz

Very interesting solution Heinz. Thanks for sharing.