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in this link you can see what the author calls a Velocity Intake, this is much like a Velocity Stack, but it has an Airfoil machined into it that speed up the air flow into the Carb, the higher air flow helps pull more fuel out of the Fuel Jetts at lower Throttle Settings,,

to add, I have a few Walbro carbs here that have this Airfoil designed into them, such as the WT481D

Buzz Buzz Buzz

11-24-2016 04:11 AM

Elite Veteran

Killeen, Texas - USA

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Ive proven that velocity stacks actually hurt high rpm power... work good at lower rpms and acceleration (like for gasser trucks, buggies or planks). but increasing rpm range, any length that is added to the intake tract hinders and slows air acceleration during the extremely short intake duration offsetting the "velocity" gained just before the intake window is closed. It also allows fuel to puddle up around the stack (yes the intake burps fuel back out) causing instability in the mixture ratio...

Anyone that has truly studied "the" 2 stroke tuners handbook will understand why.

every modification that enabled me to double the HP at higher rpms on my engine has come from the information in that book specifically

just take off the choke lever butterfly on a 20 and see for yourself... you'll gain 100 rpms... but put a velocity stack on and you'll see around 100 peak rpms lost.

showing a preference will only get you into trouble, 90% of everything is crap...

11-24-2016 07:15 AM

Senior Heliman

Holliston, MA - USA

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^^^^ Yes, the intake length can be "tuned" to optimize for different RPMs. Intake tuning is a big deal in high performance car engines, and a number of manufacturers make variable length designs that change length as you accelerate.

Helix 700G
T-Rex 450 fbl conversion
alot of planks

11-24-2016 01:35 PM
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