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Velocity Stack

14944 Views 91 Replies 21 Participants Last post by  TargaTop
Well I was searching around for random parts when I came upon a velocity stack. I thought to myself that the 350z's get big gains so I searched some more and found out that most cars do get a nice bump from a velocity stack, I mean it only makes sense because of the direction of the air flow increasing the speed. Then I searched on here and realized that no one has ever used a velocity stack on a 3G. Im sure we would get some what of a bump in hp/tq throughout the power band and coupled with a Diamante Plenum/TB I see a lot better airflow and better results out of those upgrades. What do you guys think?
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This is how I would see it setup best. Velocity Stack is 3" so get a 3" MAF adapter, then it would go through the 2.75" short ram intake piping (AEM or whatever), then through the Diamante TB which is 65mm (2.55"). That way velocity should still increase without changing too drastically between different sized piping and create a smoother flow. That setup would also still have a velocity effect of bottling down from 3" to 2.5" throuought the whole system to the trottle body which should mean it would even pick up more speed for more results.
I don't see this bringing too much of a benefit. Plus where would you mount the air filter?
I don't see this bringing too much of a benefit. Plus where would you mount the air filter?
You can mount it in the same location as you normally would. The velocity stack would mount onto the MAF adapter then the filter would mount over the velocity stack, you wouldnt even be able to tell its there. For the most gains though youd have to convert to a SRI instead of a CAI. People have seen up to 15hp on a 350z and when I was searching little Honda 4 cylinders were getting arounf 5hp and 8tq all over the powerband.
There's really no point to doing this. Beyond the small boost achieved by replacing the stock intake and it's associated resonators with a CAI/SRI, you'll never see much change in altering the intake piping, especially on naturally aspirated engines. A pipe is a pipe. Piston goes down, air gets sucked in. That's all there is to it. There's no magic going on here. Even a CAI is more of a cosmetic mod than a performance one.
There's really no point to doing this. Beyond the small boost achieved by replacing the stock intake and it's associated resonators with a CAI/SRI, you'll never see much change in altering the intake piping, especially on naturally aspirated engines. A pipe is a pipe. Piston goes down, air gets sucked in. That's all there is to it. There's no magic going on here. Even a CAI is more of a cosmetic mod than a performance one.
Then why do people upgrade to the Diamante Intake plenum, SMIM, bigger TB, etc.? To increase air flow and volumetric effeciency which can be tuned to see noticeable gains. Even untuned, you'll see the car pulling harder all around the power band. Oh and for you saying you'd never see a change in altering the intake piping, especially on a NA engine, go look up the history of velocity stacks. They have been used for YEARS on NA engines and have proof of improvements. Just go ahead and look at the 350z Jim Wolf Popcharger. Here read up why we even do any upgrades to our intake system.

Volumetric Effeciency (VE) - This is a term that measure how effeciently your motor injest air through the intake and expells the exhaust gases out the exhaust side. I put this first for a reason. This is a very important term to understand, because most engine modifications effectively change the VE of your motor, and hince why you decreases or increases in torque and power at various rpms. Mathimatically, VE is the percentage of air that the motor injests and expells vs the total volume of air the motor could potentially injest and expell. First the easy part. How much can your motor injest. Lets use the 2.0L FS motor as an example. Its total displacement is 2.0L's, and it has four cylinders, so each cylinder displaces approximately 0.5L's. Now if the motor were 100% effecient at all rpms it would injest 0.5L's of fresh air each cycle then expell it. Unfortunately, a 100% effecient motor is impossible. How effecient your motor actually is unknown, but as a general rule of thumb most dual overhead cam engines have maximum VE's around 85-90%. This actual numbers are not important though. What is important is the VE curve, or a chart of VE vs RPM. You VE curve will have the same trend as your torque curve, as measured on an engine dyno or a wheel dyno. So your peak VE will occur at peak torque. Without changing the displacement of the motor you cannot injest any more air, but you can change the VE of the existing motor. This takes on infinate degrees of modifications, from something as simply as changing the air filter or as complex as reworking the cylinder head with larger valves and ported runners. So we want to change the VE of the motor? Almost all performance modicafications will increase high rpm VE while sacrificing some low rpm VE. Recalling earlier statements, this means that the high rpm torque will increase and low rpm torque will decrease, and where torque increase, so does power. Learn this and understand it, as you will hear this again and again.
Then why do people upgrade to the Diamante Intake plenum, SMIM, bigger TB, etc.?
Personally I did it in preparation of installing my SDS. I did notice a shift in the power band and slightly better throttle response but nothing major. I also feel I lost a bit of torque in the lower RPMs... but I expect that will change once I am FI.

Do you have a pic of this velocity stack? I don't think I have ever seen one.
I guess it depends on what you consider noticeable. Going to all that effort for an extra 5 or so hp/ft-lbs is a waste as far as I'm concerned.

The blurb you quoted doesn't really tell the whole story, either. Increasing the peak VE isn't necessarily an improvement. It's the area under the curve that matters. An increase at peak coupled with a decrease in the low range and end up with no real net gain, other than bragging rights amongst those that are only interested in peak horsepower.

At WOT, every N/A engine is going to be pretty close to that 85-90% VE figure. That leaves very little room for any improvement. At anything less than WOT, it doesn't even matter, because any potential flow restrictions are meaningless when you have that big butterfly valve in the throttle body blocking the flow.
Have you looked at these
http://tearstone.com/shop/RPW-Induction/Performer-Series-Intake-Manifold-6G72/74-1996+.html

It is 6 little velocity stacks, one for each runner.
You can have your stacks and big intake all in one.

With an intake like this you will also, as mentioned above, sacrafice some low end torque and shift the power band up in the rpm range some what. Doesn't bother me. I have stage II cams and an alum flywheel. The top end is where all my power already is so why not. I still have plenty enough torque to bust the tires loose from a roll in first gear if I stomp it.
Do you have a pic of this velocity stack? I don't think I have ever seen one.
http://www.inlinefour.com/blvest.html

I guess it depends on what you consider noticeable. Going to all that effort for an extra 5 or so hp/ft-lbs is a waste as far as I'm concerned.
It cost about $100 total and you get 5 WHP/TQ, which is probably around 12-13hp/tq to the crank from something so simple. Theres no effort except undoing a clamp and installing the velocity stack.
Ohhhh. Thanks for the link! Looks like it just reduces the turbulence of the incoming air. I'm sure it would "help" but I doubt you would really feel anything in the butt dyno :dunno:
Ohhhh. Thanks for the link! Looks like it just reduces the turbulence of the incoming air. I'm sure it would "help" but I doubt you would really feel anything in the butt dyno :dunno:
Yea you get a straighter flow and at an increased speed because of how smooth the flow is. For everyone whose doubting it just search around. Heres a dyno chart of a RSX.


heres one on my wifes rsx type s.

green line is the aem v2 short ram

red line is an 3" short ram intake with the velocity stack
You did a before and after dyno run with NO changes other than installing the VS? If so, impressive :cool2:
You did a before and after dyno run with NO changes other than installing the VS? If so, impressive :cool2:
Not me, the owner of hte car lol, heres the link to the thread. http://www.honda-tech.com/zerothread/1864717.

Yea thats all he did was add a VS. Im telling you since our engines have bigger displacement we even have more room for better results.
This is why its recommended to switch to a SRI when installing a VS. The only difference between the two are the fact that one is in SRI with the VS and then CAI with the VS.

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It cost about $100 total and you get 5 WHP/TQ, which is probably around 12-13hp/tq to the crank from something so simple.
That's some pretty sweet math there. Care to explain how 5hp/tq at the wheels magically grows 2.5x at the crank? :confused:
Not me, the owner of hte car lol, heres the link to the thread. http://www.honda-tech.com/zerothread/1864717.

Yea thats all he did was add a VS. Im telling you since our engines have bigger displacement we even have more room for better results.
im sold. look at the dyno results of the b18 on page 2. he gained 6whp with the VS on a cai. since those motors generally dyno in the same area as the our V6s do then 6-8 whp would be expected imo. torque would probably double that of the honda though. those honda-tech guys sure do have their shit together
also look at any vehicles running ITBs or any performance motorcycles. they all mostly run velocity stacks directly into the carb. they must do something
im sold. look at the dyno results of the b18 on page 2. he gained 6whp with the VS on a cai. since those motors generally dyno in the same area as the our V6s do then 6-8 whp would be expected imo. torque would probably double that of the honda though. those honda-tech guys sure do have their shit together
Exactly, atleast someone is thinking the same way I am. I think someone is going to have to do a before and after dyno with a 3G, I cant find a dyno near me otherwise Id do it since at the moment I have no engine mods done to my car.
A before/after dyno on an SDS equipped 3G would be a big help for me...
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