Velocity stack vs spiral

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
The spiral style or "vortex" or "tornado" style has only been proven by the company's making them. Third party testing normally doesn't seem to favor any real world gains. V stacks have been proven for years. Think about this the spiral in our set up is more likely offered as a v stack replacement, meaning it goes before the carb, giving you at least 1 butterfly to straighten out the air to normal flow patterns. With a choked carb you now have 2 butterfly's to change the spiral flow pattern into a normal air flow pattern, not to mention (and this is just a thought) the back and forth pulses generated by the piston would create more air turbulence back up the air tract negating and vortex effect. So imo don't waste your money on it.
 
Nice info. I seem to have the spiral working well but very very tricky to tune . The plus side to the spiral I think is the 2 powerband's it produces but again extremely hard to tune . .. the velocity stack doesn't produce any powerband you can visually see the effect off. ?
 
The spiral is effecting the venturi signal, hence why it's so hard to tune, the power band of a well built engine had a steep, but flat torque curve lasting over most of the usable rpm range. what your describing would be undesirable for most, as were the old dirt bikes back in the 70s. They hit hard mid to high rpm, so hard you had to learn to ride around the power band, subsequently these small engines behaving the same way isnt a fun thing to have to deal with. Same as peaky engines that only produce at high rpm, or very torquey engines that Peter out after mid rpm. A nice balance between the two will give the best results, weather racing or bashing.
 
Back
Top