Suggestions for Velocity Stacks?

joel mac · 08-31-2014, 09:22 AM

Quote:

Originally Posted by Jordo!

Minor update: After having NO luck finding a drill attachment that could smoothly bore the inside of the airbox intake tube to 2.625" (i.e., 2 5/8"), I attempted to bore it out manually with my dremmel...

Ehhhh... the short version is that it's too sloppy and needs more honing and, even worse, I cracked the outside of the tube trying to wedge my v-stacks in. D'OH!

So I am now considering a different route. If I just cut out the outer intake tube and cram the v-stack inside the hole, I can then simply use coupler to connect the intake tube to the v-stack, with the end of the v-stack poking through the hole in the airbox.

So long as I cut it right, it should be airtight (or easily fixed to make it so), connect perfectly to the OEM intake tube, take advantage of the OEM heat shielding as planned, and work almost identically to how I had originally envisioned the final version.

Moreover, it will allow me to recess the bellmouth further back, which may allow me to use OEM panel filter frame or at least minimize the likelihood of inadvertently losing part of the effective volume of the box because the v-stack protrudes too far.

More on this soon -- I may need a fresh set of airboxes... anyone willing to sell them to me on the cheap in the name of experimentation and adventure?

you could have mine if you pay for shipping

Jordo! · 08-31-2014, 11:16 PM

Quote:

Originally Posted by SouthArk370Z

Good luck. I've got my fingers crossed.

Thanks!

Just assembled them tonight! Test fit and dyno coming soon. Succeed or fail, I'll report back

Jordo! · 09-02-2014, 04:59 AM

Quote:

Originally Posted by joel mac

you could have mine if you pay for shipping

Thanks -- I'll keep you posted

Jordo! · 09-20-2014, 02:57 AM

Rats.

Finally made it to the dyno and the result is no gains. Nada.

Even datalogging MAF voltage showed no evidence of better flow. No change whatsoever from stock.

Sadly, this project is a bust

If anyone is interested in experimenting where I left off, shoot me a PM and I'll sell you my v-stacks and other odds and ends.

SouthArk370Z · 09-20-2014, 08:07 AM

Quote:

Originally Posted by Jordo!

... Sadly, this project is a bust

...

Not true. We now know that velocity stacks in the air box won't do much good.

Thanks for sharing the experience. It was an interesting journey.

P's_Z · 09-20-2014, 08:43 AM

Sorry to hear that jordo, but just like southark mentioned, thanks for taking the initiative and experimenting with this

Jordo! · 09-20-2014, 04:10 PM

Thanks, guys -- that's much appreciated

Yeah, there was only one way to know, and I'm glad I didn't just throw them on without testing.

Also glad I didn't clog up a thread with all the build pics just to announce the uselessness of it...

SOUTHZZ · 09-20-2014, 04:37 PM

Great idea in priciple.However,think the gains you may think you may get
could be elusive.Velocity stacks work great on carbs like Webers.I've got some on
a Lotus I own.Fabricating and installing on a stock air box is pretty futile.
a air box opening ducted directly through a grille does work.If you are serious about poer gains in the intake system,I'd look at improving yourthrottle body.I had a Mines
throttle body in the 350 I previously owned.There was(after tuning)a substantial
power increase.

shivers · 09-22-2014, 08:40 AM

You ever consider getting the stacks outside the box, say up in the grill where the G3 filters sit? Have some tubing run from the stacks to the front of the box. This was an idea that I wanted to try, but never have had the time to do it.

ANMVQ · 09-22-2014, 10:53 AM

I'm in the middle of that Idea now

ANMVQ · 09-23-2014, 02:01 PM

Just ordered some silicon pipes and aluminum pipes. Hope there here this Friday

SouthArk370Z · 09-23-2014, 02:29 PM

I just don't see velocity stacks doing much good. The longer/bigger the intake/manifold system is, the less good velocity stacks do. If they were mounted mani->TB->MAF->VS, without all the duct work, it might do some good; on a modified factory setup, not so much. While the bell of a VS can give some very small gains, the VS's main function is to tune the intake/manifold. By the time you get from the heads to the air intake, there's not a lot you can do to affect the tuning significantly (without major mods).

Velocity stacks are great for small carbs/TBs with short ducts/plenums/manis but aren't going to do much for a more-or-less stock 370Z setup.

But I'm no Engineer, so YMMV.

1slow370 · 09-23-2014, 02:45 PM

hmm kind of touching on it but kind of not, a velocity stack prevents boundary layer separation which basically reduces restriction at an air (or fluid) inlet, they do not aid in the tunning of an intake manifold but are merely a feature that stabilizes the incoming airflow, the manifold is tuned by adjusting the length, taper, and diameter of the runners(longer velocity stacks are just runner extensions with the same entry profile as a shorter one. The reason that Velocity stacks loose effectiveness in a longer intake system is that they are no longer the primary restriction, the tube wall friction, bends, and pressure loss is.

The other thing to take note is that not all velocity stacks are created equal, I can't remember the name of the text but there was a good book on air velocity that described the differences between the airs density and velocity and the path a of the boundary layer for a tube inlet (a velocity stack is basically designed to follow the path of the air closest to the tube that wants to bend and enter it.

Jordo! · 09-23-2014, 03:56 PM

^^^ I know elliptical bellmouths are supposed to be better than perfect circles. Mine was not elliptical...

I saw a few examples where they made power on the airbox inlet going into the bumper -- that's a good idea! Keep us posted. If you succeed I guess I could try that next.

SouthArk370Z · 09-23-2014, 04:28 PM

Quote:

Originally Posted by 1slow370

hmm kind of touching on it but kind of not, a velocity stack prevents boundary layer separation which basically reduces restriction at an air (or fluid) inlet, they do not aid in the tunning of an intake manifold ...

Yes. In the proper application, vortexes, boundary layers, laminar flow, &c are an important part of what a VS does. But just sticking one on the end of an intake will more than likely not have any appreciable effect, positive or negative - as Jordo! has shown (at least for his setup).

I could be wrong (my personal experience with VSs is, for all intents and purposes, nil but I have a lot of experience with gas/fluid flow measurement), but everything I've read on VSs says they are an important part of tuning the intake system. If I'm wrong, please show me the light - I'm not too old to learn something new.

09-20-2014, 02:57 AM	#64 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 418	Rats. Finally made it to the dyno and the result is no gains. Nada. Even datalogging MAF voltage showed no evidence of better flow. No change whatsoever from stock. Sadly, this project is a bust If anyone is interested in experimenting where I left off, shoot me a PM and I'll sell you my v-stacks and other odds and ends. P's_Z likes this. __________________ Enjoy it. Destroy it.

09-20-2014, 08:43 AM	#66 (permalink)
P's_Z A True Z Fanatic Join Date: Apr 2013 Location: PR Posts: 1,530 Drives: Zeta Rep Power: 469	Sorry to hear that jordo, but just like southark mentioned, thanks for taking the initiative and experimenting with this __________________ Zeta

09-20-2014, 04:10 PM	#67 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 418	Thanks, guys -- that's much appreciated Yeah, there was only one way to know, and I'm glad I didn't just throw them on without testing. Also glad I didn't clog up a thread with all the build pics just to announce the uselessness of it... __________________ Enjoy it. Destroy it.

09-22-2014, 08:40 AM	#69 (permalink)
shivers Base Member Join Date: Aug 2012 Location: Tennessee Posts: 48 Drives: G37S Rep Power: 13	You ever consider getting the stacks outside the box, say up in the grill where the G3 filters sit? Have some tubing run from the stacks to the front of the box. This was an idea that I wanted to try, but never have had the time to do it. ANMVQ likes this.

09-22-2014, 10:53 AM	#70 (permalink)
ANMVQ A True Z Fanatic Join Date: Mar 2011 Location: Framingham MA Posts: 2,732 Drives: 2014 Q50 AWD Rep Power: 19	I'm in the middle of that Idea now shivers likes this. __________________ 14 Q50 AWD, ARK, ECUTEK (SEB), Takda,

09-20-2014, 04:37 PM	#68 (permalink)
SOUTHZZ Enthusiast Member Join Date: Jan 2014 Location: ALABAMA Posts: 305 Drives: 09 NISSAN 370Z CS M6 Rep Power: 3400	Great idea in priciple.However,think the gains you may think you may get could be elusive.Velocity stacks work great on carbs like Webers.I've got some on a Lotus I own.Fabricating and installing on a stock air box is pretty futile. a air box opening ducted directly through a grille does work.If you are serious about poer gains in the intake system,I'd look at improving yourthrottle body.I had a Mines throttle body in the 350 I previously owned.There was(after tuning)a substantial power increase.

09-23-2014, 02:01 PM	#71 (permalink)
ANMVQ A True Z Fanatic Join Date: Mar 2011 Location: Framingham MA Posts: 2,732 Drives: 2014 Q50 AWD Rep Power: 19	Just ordered some silicon pipes and aluminum pipes. Hope there here this Friday __________________ 14 Q50 AWD, ARK, ECUTEK (SEB), Takda,

09-23-2014, 02:29 PM	#72 (permalink)
SouthArk370Z Premium Member Join Date: Nov 2010 Location: South Arkansas Posts: 8,435 Drives: 2014 Challenger Rep Power: 324198	I just don't see velocity stacks doing much good. The longer/bigger the intake/manifold system is, the less good velocity stacks do. If they were mounted mani->TB->MAF->VS, without all the duct work, it might do some good; on a modified factory setup, not so much. While the bell of a VS can give some very small gains, the VS's main function is to tune the intake/manifold. By the time you get from the heads to the air intake, there's not a lot you can do to affect the tuning significantly (without major mods). Velocity stacks are great for small carbs/TBs with short ducts/plenums/manis but aren't going to do much for a more-or-less stock 370Z setup. But I'm no Engineer, so YMMV. __________________ Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

09-23-2014, 02:45 PM	#73 (permalink)
1slow370 A True Z Fanatic Join Date: Aug 2009 Location: In the D Posts: 3,732 Drives: v8 74 260z ;) Rep Power: 7251	hmm kind of touching on it but kind of not, a velocity stack prevents boundary layer separation which basically reduces restriction at an air (or fluid) inlet, they do not aid in the tunning of an intake manifold but are merely a feature that stabilizes the incoming airflow, the manifold is tuned by adjusting the length, taper, and diameter of the runners(longer velocity stacks are just runner extensions with the same entry profile as a shorter one. The reason that Velocity stacks loose effectiveness in a longer intake system is that they are no longer the primary restriction, the tube wall friction, bends, and pressure loss is. The other thing to take note is that not all velocity stacks are created equal, I can't remember the name of the text but there was a good book on air velocity that described the differences between the airs density and velocity and the path a of the boundary layer for a tube inlet (a velocity stack is basically designed to follow the path of the air closest to the tube that wants to bend and enter it. SouthArk370Z likes this. __________________ ANSWER PRICE LIST Answers - - - - - - - - - - - - - - - - $0.75 Answers (requiring thought) - - - - $1.25 Answers (correct) - - - - - - - - - - $12.50 Last edited by 1slow370; 09-23-2014 at 02:53 PM.

09-23-2014, 03:56 PM	#74 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 418	^^^ I know elliptical bellmouths are supposed to be better than perfect circles. Mine was not elliptical... I saw a few examples where they made power on the airbox inlet going into the bumper -- that's a good idea! Keep us posted. If you succeed I guess I could try that next. __________________ Enjoy it. Destroy it.

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