Gains from a velocity stack on a turbo Honda
 

blox 4" velocity stack gains - Honda-Tech

He was using no filter and the stack (Blox 4") was directly mounted to the turbo.

It'd be interesting to see gains/losses w/ an arm/stack/filter.

so you get like 5whp over 2000rpm from lets say $300 in fab work? Awesome.

took the words right out of my mouth

I cant zoom the graph to actually see wtf is going on, but it looks like there are only gain from 7.5-9K, doesn't help me much.

Quoted from the thread
:facepalm: Clearly not an engineer.

Not sure why the guy had to spend $300 on it. With some creativity it should have been possible to do it for less.

I don't think it's a function of the RPM but the stock piping diameter and the peak power.

Yeah it has more to do with air flow rate and less to do with RPM. But for a given engine and tune, at WOT those two are tied closely together of course.

The Blox 4" stack is $30 on ebay.

so, the fab work on the bells is free?

What fab work? It seems he just bolted the stack to the turbo inlet.

Something about seeing the acronym Vtec, even if legitimate, makes my skin crawl.

so are these idiots taking of the air filter and replacing it with the bell? In for "lol".

Yeah I would not use one unless I put a large air filter on the inlet of the nozzle aka 'velocity stack'. They work, no doubt about it, but I am not about to rearrange my entire CAI setup for that small of a gain.

there is merit to the bell inlet. air doesn't turn sharp corners.

but

no filter = dragster

and filter = reduced bell function

so ... draw your own conclusions.

What you really have to do is make sure that the filter is atleast 1 Diameter away from the edge of the bell, and your surface area of filter media to inlet area is rediculously large. So a proper setup would be around 10 inches in diamater, and maybe 4 inches deep. Like a big carb filter. Maybe one of those extreme flows withe the filter media on top as well. Then imagine ducting?

^^ Yeah exactly. No thanks, at least not on a street car.

There is no real magic to these bells. They are basically just nozzles with tapered reduction sections. The decrease in head loss (pressure drop loosely speaking) is well understood in the world of fluid mechanics and can be calculated.

I had considered one of these Turbohoses AirRam & Velocity Stacks, Velocity Stack, Air Ram, Intake, Airram Intake, Turbohoses Intake because I "think" my current filter may be a restriction. I haven't hooked a vacuum gauge up between the filter and throttle body yet to see though.

I've always thought you could run an airbox with filter and that bell doo-dad on the inlet to the airbox and get more benefits.. never tested this theory though.

I don't know on that, but if your trying to increase the discharge coefficient you can't choke the edge of your bell with flat edges, or your not going to accomplish anything. The purpose of the bell is to dramatically decrease pressure gradient DX,DY,DZ spherically away from the entry so that entrance velocity is decreased, and smaller eddys form around the neck point of the flow in the front of the pipe..

WTF? Can we get that in English please?