New Velocity stacks

[barbagris]

In ether case how would you determine the width apart to benifit from any 'wave' which would also refine plenum shape and volume requirements?

By having the trumpet tuned? - badum-tish!.

 

[Idaho Red Rocket 3]

Did someone say plenum? I know it looks like ass now, but, give it time. This is just the first step, laminate a general shape plug, test fit. Sand and polish the lamination, turn it into a mold, build high volume plenum with ramair provision that can fit a filter for the street.

Inspiration taken from the Ozclaw, but, you can see I definitely didn’t copy anything here. Epoxy is still hardening, can’t do anything further with it for 24 hours.

Rob, How has this intake scoop design progressed ?

 

[Speedy]

When I re-read the above I thought of the trumpet mute as below.

Is this the 3D Parabolic cone shape you where inferring should be on the opposite plenum wall to each intake trumpet?
If so should it be a similar scale to the intake or a much lower profile version?
In ether case how would you determine the width apart to benifit from any 'wave' which would also refine plenum shape and volume requirements?.

Sort of. Imagine the plenum as an enclosed sound chamber with sound waves reflecting from the walls. The trumpet mute is the same but is an extreme case in that the goal is to attenuate the volume by focusing reflected waves back on incoming waves and nearly canceling them. The goal of the plenum is to re-direct not attenuate. Remember the science museum with the large reflective discs on opposing ends of a large room where you could stand in front of one and whisper and your classmate in the same position in front of the other one could hear you but nobody in the middle could hear anything? Parabolic shapes on surfaces opposing the velocity stacks can reflect wave energy back into them. So rather than being a diffuser like a flat wall that reflects at all incident angles, it focuses sound energy to your advantage. And there is a lot of energy to re-direct.

The difficulty is that the plenum and stacks also have to direct actual flows with mass. Thus shapes and angles and spacing must also manage that flow. For example, the back side of the "reflector" if it is free standing can also direct air flow so that it approaches the v-stack from 360 degrees which is optimum for the flow entry into a bell mouth stack. As always, compromises are the order of the day

 

[Claviger]

Have built the plenum itself, haven't gotten around to assembling it with the runners, lots of reasons but I probably won't finish it.

Turns out, even with a good plenum, I'll need longer stacks, and longer stacks aren't an option since my 3d printing service closed down.

With the short nice looking stacks there I lost torque across the entire power curve except peak HP point.

So going with these stacks takes about 8lbft away, adding a good plenum will be only a very small gain over where I'm currently, using longer stacks without a plenum, juice is not worth the squeeze, in this particular case.

 

[Claviger]

The pictured stacks in post #1 vs my longer curved ones, just not a good trade IMHO. The new cams might like the short ones and show more gain after 8000 RPM though. There was a choke point in the build at 8000 RPM, if the intake cam was the choke point, the shorter stacks will now show a meaningful trade of bottom end torque for high end HP, if the choke point is the intake runner in the head, the results Friday are going to be much the same as the chart below, if the choke point was the exhaust cam the gains on Friday will be big with either stack lol.