jaas technique: noviembre 2013

lunes, 25 de noviembre de 2013

homemade velocity stacks

tonight i tried my first attempt to build my own velocity stacks in a lathe.
not to bad for the first try, need to work more in the visual aspect of the stack, but lets see
how it perform in a prb test intake manifold.....

there is a neat gain of 30CFM,before and after the velocity stack. the rsp intake manifold comes with
some velocity stacks, but they lack of any bellmouth...

the idea behind this is to build some velocity stack for a fn2 intake manifold, which i tried earlier but failed. jenvey velocity stacks are too big to weld them inside an oem intake plenum, they have too much bell for an oem manifold. secod goal is to be able to tune the length of the runner to play with harmonic resonance.

sábado, 23 de noviembre de 2013

harmonic resonance and volumetric efficiency

how is possible to obtain 2.5L of air from a 2L engine?

plenum and runner section

All motors will make the most torque at a specific rpm. This is due mainly to the length of the runners in the intake manifold. When the valves are open the air is flowing through the runners. When the valves close, that flow is backed up and a pressure wave reverses back up the intake runner into the plenum. Then the pressure in the runner is lower than in the plenum and a wave is sent back down the intake runner. This oscillation happens multiple times. By changing the length of the runner, you change the distance the pressure wave travels and how frequently the oscillation happens.

This is optimized to have a pressure wave moving down the runner just when the valves are opening
again to have the air rush into the cylinder. By doing this you can for example get 2.5L of air into a 2L of cylinder volume, This is why engines have more than 100% volumetric efficiency. This is why torque will peak at one certain rpm for car engines.