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they are careful to point out that the difference between a crude radius entry and an optimized bellmouth is only a few percent. But about any kind of radiused entry is better than a flat cut pipe.
Saw a similar experiment somewhere else, simply flaring the tube end at a straight angle (30 total?) To about 1.5D, with flare length equal to D, was within 2-3% of a more developed bellmouth, both being 25%+ superior to a simple straight cut pipe.
basically, a little effort is way better than nothing, and can get you 90-95% of the benefit with much less cost and work.
Playing around with software to machine some ellipse Bellmouth's for an intake.
Pretty simple to do a ruff template...about 20 minutes with a friend. First numbers taken from doc on one file just taken from numbers on the link at top of my thread.
Second numbers of 45mm and 95.85mm more appropriate to the port size on my 2V cylinder heads that I have.
For this set I measured the intake port on the head it’s going to go on.
I am going to use the same 3 inch pipe Refresh951 used...3inch Centre line length.
The first one will of course not be a tapered runner.
Super easy to change ID for people. Just a matter of plugging in different numbers on the machine.
The key here is the ID affects the overall OD fitting the bellmouths to a plenum. It’s a mathematical relationship that is key to maintaining an ellipse profile.
The diameter should be bigger or at least as large as the diameter resulting from calculating the area of the inlet valve minus the valve stem. This is what I call the diameter of the "air column", or the area of how much air flows through.
For instance on a 968 head using a pair of 39/7mm inlet valves we want an ID no smaller than 54mm...
10-16-2018, 10:29 AM
Intake Bellmouth Design Read I found
