Velocity Stack

Therealjj91 · Post by **Therealjj91** » Sat Oct 04, 2014 12:45 pm

I must be on the late train hearing about these, I've only read good things about them to be honest but I'm not exactly sure how they work? I know they're meant to improve air flow and throttle response. So my question is do I need to measure my intake tubing and get one the same size or go bigger? And I will also be using a K&n filter, thanks.

YouTube · Post by **Sailor** » Sat Oct 04, 2014 1:12 pm

If I understand correctly what these things are trying to achieve, it's difficult to see how they can improve matters much across the range.

The idea is to reduce turbulence by reducing boundary layer separation at the air intake and smoothing the flow all the way to the inlet manifold. But cars have filters in the way, which can't help but create turbulence, so the smoothing has to take place after that to be of any value. I don't know if you can get a stack to work with a K&N or if you have to get a bellmouth + filter as a whole assembly.

Then there's the issue of length (ooh er missus). Even on cars as old as most of ours, the length of the inlet tract is tuned as a compromise. The longer tubes used when fitting a cold air intake tend to give a bit more torque lower down the range, but don't help much higher up, except to change the noise. Conversely, the short trumpets we used to fit to carbs helped at higher revs.

If you're going to go for it, you should play with the duct length and make sure the whole pipe is smooth on the inside all the way from the filter to the engine.

On the other hand, you could fit a set straight onto throttle bodies ...

Therealjj91 · Post by **Therealjj91** » Sat Oct 04, 2014 1:25 pm

Yeah I've got a carbon fibre intake on there atm which is approx 3" in diameter and attached to a k&n filter and the tubing itself is smooth and the same size until the throttle body, I've seen pictures of people attaching the stack to the filter and then to the piping, so do I need it the same size as my intake piping or go bigger for the stack?

Post by **RattyMcClelland** » Sat Oct 04, 2014 2:11 pm

I run a blox velocity stack intake with 3" tubing to the manifold.

Therealjj91 · Post by **Therealjj91** » Sat Oct 04, 2014 2:12 pm

Ah okay nice, what size stack are you running?

mercutio · Post by **mercutio** » Sat Oct 04, 2014 6:16 pm

The only real way you will feel any difference with velocity stacks is with either carbs or Itb's

Post by **RattyMcClelland** » Sat Oct 04, 2014 6:27 pm

Did you not guess the size from my tubing size?
3".

Therealjj91 · Post by **Therealjj91** » Sat Oct 04, 2014 6:49 pm

Yeah sorry, read it wrong first time round.

Post by **RattyMcClelland** » Sat Oct 04, 2014 8:32 pm

Therealjj91 wrote:Yeah sorry, read it wrong first time round.

I can't say it's has any real benefits as it went on to my supercharger all in one go.

But as merc said. The real benefit would be seen in carb and itb

Therealjj91 · Post by **Therealjj91** » Sat Oct 04, 2014 10:06 pm

Haha yeah that's fair :p and well I ended up buying the blox stack kit and filter cause I thought while I'm doing the engine rebuild I might as well try and squeeze as much out of it as possible lol.