RotorMotorDriver

iTrader: (1)

Ok, I have seen these on all the side drafts (down drafts too)...Usually in different lengths. Some long, som short, some in between. Are these the "velocity stacks" Ive heard of? Why are they different sizes? Most Racing Beat Dellortos that Ive seen have fairly short ones, yet this is a reacing beat intake manifold, but it has long ones...Is this not a "true" Racing Beat carb? Or can you tune these like you would the jets? Someone wanna help me out? Thanks guys .

~T.J.

Rx7carl

Yes they are velocity stacks.

metalliman

Yup again, they are velocity stacks. Generally speaking, longer one produce more low end torque, shorter ones produce more high end horsepower, much the same with intake manifolds. And they're usually parbolically shaped, to create the least amount of turbulence for incoming air.

RotorMotorDriver

iTrader: (1)

So...The Racing Beat carbs came with little short ones, which should result in high end power according to that logic. Racing beat claims 53.6% increase in power on a stock port 12A with their Dellorto intake and single pipe exhaust (header, pre-silencer, muffler). This means roughly 150 HP. Now, hes using the longer ones, and he was dynoed at 147 HP. Shouldnt there be a bigger difference in HP than that? I mean, if its only a 3 HP loss yet hes got better low end, Im all about that. Someone wanna help me understand more?

~T.J.

85RX7GS

iTrader: (1)

What's with all these tiny velocity stacks?

RotorMotorDriver

iTrader: (1)

Thats what Im trying to figure out...

~T.J.

85RX7GS

iTrader: (1)

I've seen a pair on a BBC and each is about as big as a melon.

RotorMotorDriver

iTrader: (1)

Haha, cool. Thats some serious air flow .

You know, now that I think aobut it, 3 HP is a lot of difference for just changing such a little thing ya know? Maybe thats about right...150 with the shorter ones, 147 with the longer ones...I dont know...Someone help? Please?

~T.J.

Rx7carl

Remember though, its not peak hp numbers that count. It hp through the range that you operate the engine. An engine that makes ungodly top end hp is no good if you need power in the middle range rpms.

851stgen12a

Yea I think where the power is, is ultimately more important than peak horsepower. I would like more Mid range power for the street but when I am at the auto-x or on a road course I would definetly prefer killer top end....

RotorMotorDriver

iTrader: (1)

I couldnt agree more Carl. I wouldnt care if someone had a 300 HP car that had a huge turbo that took all day to spool. By the time they hit 60, I would be gone.

I was just trying to get to the bottom of these velocity stacks .

~T.J.