Exactly what I've been trying to say. Thanks yellow01.

 

I think the Vararam claim is that they are forcing a higher flow rate at higher speeds than a stock setup, thus the hp increase.

The higher velocity probably only helps with the air/fuel mix, maybe, higher velocity, better mix? Also a higher velocity will help the air get past some of the TB and intake restrictions better, improving the flow into the cylinders. Just taking a stab at a guess...

Now that tornado that you can buy, wow, what a great idea, spin the air into a tornado, can't go wrong there!

 

Sign me up for one of those tornadoes too....

 

It "is" increasing velocity. That is one component of generating more HP, jamming more air in faster.

Now I paused at what XTrooper said "A few guys tried these when they first came out and, if I remember correctly, lost 1-2 rwhp and gained about the same amount of torque." I'd like to know his rich friends or see those dyno results.

I can't see ANYONE who spend about fifty bucks on that part, pay the big bucks for a Dyno run to see what effect it had. That's a bit over the top for me to believe. So I gotta take it for what second hand information is worth.

..rickko..

 

But you are NOT JAMMING MORE AIR IN FASTER.

Two requirements:
Material in = material out (conservation of mass)
P+.5(density)*V^2 is constant along the venturi (conservation of energy)

the pressure at the constricted end REDUCES, hence the velocity INCREASES to move the SAME amount of air molecules.

I still don't understand how this increases HP. I'll happily admit I'm wrong if someone can tell me how this increases HP.

 

Ok the error in my points are I am comparing mass flow at points along the nozzle (essentially) and I really should be comparing them with and without the nozzle.

Still not sure how the addition of a nozzle helps since atmospheric pressure is constant and the vacuum generated by the engine (hence the pressures on either side of the nozzle) are fixed.

oh well.

 

I'm curious,.............

No matter how fast or faster you can get the air into the intake manifold, aren't the cylinder's going to suck in only so much air???

No more air can get in unless you force it or compress it in right??? Once the cylinder is full, it's full?? Is this correct??

 

So, what else is true that you left out? The KEY ingredient that assists in boosting HP. The velocity of the air has increased coming into the intake. Its no longer just sucked in, its now getting rammed in.

Velocity stacks have been used on hotrods since the '50s to increase hp. Racing cars have used them. Old Indy cars used them. The list goes on and on, boat racers use 'em.

Its a cheap and easy installation mod. It definitely won't hurt your performance (unless you are one of XTroopers friends. I wish I could get one of them to send me theirs.). If you do notice an improvement what more could you ask for for fifty bucks. But if you don't notice anything then to quote you, "oh well." fifty bucks is like pocket change when you own a vette anyway. Fortunately you get to decide where its spent.

Here's a couple quotes I pulled off the internet related to Velocity stacks in general.

"The performance advantages of velocity stacks and turbo bellmouths have been well known to race engineers and engine builders for decades."

"The rammed air affect of Velocity Stacks and Turbo Bellmouths have been shown to improve airflow into the induction system by around 19%"

But I don't care what they say because I know Bernoulli was correct.
..rickko..

 

The results I alluded to were read on this board a year or more ago. I can't vouch for their authenticity as they weren't conducted by friends of mine, rich or otherwise. Did anyone do a search on this topic? I'm not interested enough to look it up myself.

 

Rickko, well said!

 

Yeah see, I wasn't questioning the principal, I'd like it to be explained to me how it helps.

If I'm reading your explanation correctly, the tapered intake vs. straight increases velocity of the air [we agree] and hence you are saying the mass flow rate increases, i.e. more air [this is the point I'm sticking on] as your buddy Bernoulli's principal dictates that the pressure of the air changes to accomodate this increase in physical velocity in order to maintain the same mass flow.

I guess I'm not asking or saying it right, so I'll let it go.

Velocity stacks (in general) obviously work as they would not be on every carbuerated racing engine around...so it's clearly me just not getting it.

 

If this is such an effective product, why doesn't anyone have dyno proof sheets? A before and after with the only variable being changed being the product is the only real way to test a claim. If manufactures were willing to offer money-back policies if their claims were BS people would line up for the products. However, we all know a lot of these things are snake oil. I am not saying this one is, but most industries are sued for false advertising. Pretty soon we will have to make the aftermarket products part of the "health supliment" industry so they can colaborate their advertising strategy.

 

Dyno's will show a difference of 5HP but will not be accurate. You can do 10 pulls on a dyno and each time you will get slightly different #'s reguardless of variables staying the same.

.....No real way to measure 5HP on a dyno.

 

If there is no real way to measure 5 hp on a dyno then there is no way to measure it in performance feel. If these are the case, then what is the point of the modification?

 

What I'm saying is, the dyno will read out will be different each and everytime you run the car on it.

I did two dyno pulls with a very reputable group, (21st Muscle Cars) and the first dyno showed 296.8RWHP and 315.7RWT, and then 5 minutes later did another pull.....all variables the same, no changes to car or weather condition and the second dyno pull showed 308.6RWHP and 321.1RWT.......that's a big difference, and no changes in anything, just that the drivetrain and parts had heated up which made the difference. I'd bet if I did a 3rd pull, it would have been slightly different from the 2nd one too.

Any tuner knows that dyno's are good to measure major HP changes and obviously tuning a car, all the little stuff under 8-10ishHP and less is not realiable stats. Tuners will all tell you the same thing......you can make a dyno tell you anything if you really want.

The stack is IMO, you can speed up the air all you want into the intake manifold, but the valves will only let in so much at a time unless you compress and force it in which the stacker won't do.

Mabye a real tuner will chime in and set us all straight.

 

Same thing I was thinking. Also, as velocity increases, pressure decreases. I don't know if this has a noticable effect or not. Just thinking that FI cars with more (lots more) pressure makes more HP, I can't help thinking that less would somehow decrease HP.

I guess that Heat transfer & Fluid Flow class wasn't useless after all.

 

Its less pressure against the side walls of the venturi but its ramming through faster.

That means, without the stack, the pressure the air is exerting on the sides of the throttle body (where you'd insert the stack) if it could be measured as it passes into the induction system would be higher than if you could measure it on the sidewall of the stack if it were inserted.

But that ISN'T the reason for buying a velocity stack. Its in the phenomena created by the stack; it increases the velocity of the air moving in/through the induction system (I hate to use this analogy but kind of like a the effect/principal of a turbo charger which crams air into the induction system).

Take a look at that link I suggested in my first post. You can design the stack any way you like and see the effect (the velocity curve) change based on how you shape it. Make it a straight pipe and check the blue velocity curve. Shape it like a venturi stack and note the change (increase) in velocity.

I don't have a clue as to the speed air is normally asperated into the engine but say its at the rate of 100 miles per hour. If the stack increases that 19% or 19 miles per hour, then you are ramming more air in over the same amount of time (ie. valve open) thus 'ramming' more into the cylinder (more to compress), etc. etc.

That's why it works and as Yellow01 said, "Velocity stacks (in general) obviously work as they would not be on every carbuerated racing engine around..."

What I don't know is, when DO THEY affect HP and torque? is it only at the highest RPM or is the effect consistent throughout the RPM range? IOWs, if you rarely push your car into the 4k+ RPM range is the $50 for the easily added on part worth it?

My opinion is, it sure won't hurt! Its cheap, and if it really kicks in only above 4k or 5k RPM then, cool; it'll be there waiting to shine when I want it too, like maybe the day you want to pass an 18-wheeler as quickly as you can because of oncoming traffic and you're running out of passing room.

..rickko..
PS. For the uninformed, dyno runs are expensive and something you don't generally spend your money on casually (ie. to check out a $50 part) unless you are expecting to see large differences between runs. And they aren't fun to watch when its your car on the dyno. They'll make you cringe.