Venturi Port by David Vizard

General engine tech -- Drag Racing to Circle Track

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LotusElise
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Re: Venturi Port by David Vizard

Post by LotusElise »

modok wrote: Sat Oct 01, 2022 4:10 am Earland Cox years ago did a clean sheet kind of study on ports with slices of tubing, and one thing he found that I thought was very clever was that 'the flow should be aimed at the valve". ok sounds dead simple right? But all real ports are always angled and curved so that can't be maintained at all lifts. The only way for the flow to always be centered on the valve at all lifts was if the port was perfectly straight of course :shock: So depending on how things are, sometimes you can use a smaller area just upstream of the valve to aim the flow at it ideally, and other times you can't, with some designs it becomes impractical. Venturis don't really work around curves.
Yeap, a centered flow would utilize the complete available curtain valve area. But how would the kinematic to control the valve lift looks like. A port has always system immanently a bended part to implement the valve stem axis into the outer side of the port itself to connect a proper valvetrain kinematic to it. Motorcycle heads try to mimic that best, steep ports, narrowed inclined valve angles and low bend angles, giving an easy short turn angle. There is an aftermarket V8 head company called Trick Flow, they introduce exactly this into their wedge head designs.

Regarding Venturi flow regimes don't work at short turns. They do, but the point of view has to be individual to each section. The short turn flow can support a Venturi flow regime. But that said, it means, except to the seat cut the other cuts or radii are section-wise individual to adapt that flow regime. Honda K-series heads go easy into the 0.5 Mach area, despite their flat port angle of 15° and 50° short turn bend angle. These are one of the best stock port heads in the automotive area. But they lose a lot of low lift flow when you reduce the Venturi flow regime by increasing the throat.
DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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