Super V.E. for diesels

[freebeard]

Thanks -- best explanation of vena contracta I've seen. The high fractional Mach number extends further down the throat.

[Logic]

Originally Posted by freebeard

Thanks -- best explanation of vena contracta I've seen.

No-no! Thou may not utter the phrase 'vena contracta' and 'understanding' in the same sentence!
That goes against the ecomodder law which states: Only aerohead may utter 'vena contracta', with the utter conviction of knowing that only he will ever 'know' and NOT to even try explain it to mere mortals, thereby dethroning himself!

Originally Posted by freebeard

The high fractional Mach number extends further down the throat.

It does more than that:
The number is higher, by 30%.
Air weighs ~1.225 kilograms per cubic meter (at sea level and 15°C; 59°F).
So you get a BIG increase in air kinetic energy (1/2 * mv²), that can be captured in the chamber as increased pressure, with clever valve timing.
(square 30%...)

Also NB the thickness of the slow to dead air on the the tract's surface.
That means you have 'lost' what? ~20% of your intake tract diameter in the pic..?
So if it's say 40mm; pipe area is 1257 mm².
Minus 20% = 32mm; pipe area is down to 804mm²..!

It's 'just weird' that many people are all 'aero the outside of the car!'
but 'too hell with (even thinking about) the inside'...

[Logic]

Straight:


vs plain rounded:


vs Elliptical:


The maths works out..? It seemed to, to me.

A look online points to (some?) tuners preferring plain rounded..??
Why?

Staring at it: It seems to me that there may a wider but lower-power, effective 'rev range' with the ellipse? But perhaps a narrower rev range (more suited?) with the rounded..?
Or something??


Perhaps 'The Ellipse' is best, both into and out of, the filter box, where all cylinders are 'sucking' on the same pipe in turn..?

Also interesting is static pressure recovery.
You want that, into the filter box and probably into the manifold too.
A 7 degree cone or diverging sides? is used in HVAC. But that's more 'simple curves' to make, than optimal compound curves IMHO?

[freebeard]

Perhaps it's easier to fabricate what is essentially a half-torus?