Velocity Stacks make me excited in deeply confusing ways

"71MGBGT Likes Subarus of Unusual Colors" (adamprotter) 07/30/2014 at 01:58 • Filed to: None

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Good night oppo, stay weird

EL_ULY > 71MGBGT Likes Subarus of Unusual Colors 07/30/2014 at 02:01

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i always felt like more exposed velocity stacks wouldn't work because as speed increases, it would creat a venturi effect around the stacks essentially sucking fuel out. A dude I know had performance issues at the track because he didn't have fender liners and it was sucking fuel out of the carb

71MGBGT Likes Subarus of Unusual Colors > EL_ULY 07/30/2014 at 02:05

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That makes sense, but just look at it

When something looks this cool, IDGAF how it preforms.

Squid > EL_ULY 07/30/2014 at 02:08

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On a modern setup it wouldn't matter because of EFI, but I am not sure with carburetors. That is an interesting question that someone should answer. I'll still give a guess as to why it probably doesn't matter, generally the motor is pumping air through with a greater velocity that the air creating the venturi effect would not create enough negative pressure to effect the fuel delivery. Plus the stacks going out of the hood are generally a long way away from the fuel delivery source.

EL_ULY > 71MGBGT Likes Subarus of Unusual Colors 07/30/2014 at 02:08

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ooohhh man that is bitchin! Dayum!

EL_ULY > Squid 07/30/2014 at 02:14

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see that's what i figured as well. On EFI ITB's i doubt it would matter like you said because of the way higher pressure. And yes the pressure going in shouldn't counter the venturi, if any, on the outside. Yet, once that dude put the fender liners on, it made huuuuge difference engine performance wise. That was on a non velocity Victor Jr. Hmmm questions queations...

Squid > EL_ULY 07/30/2014 at 02:30

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Well that makes sense with just the carb because the distance to the fuel venturi is much much much shorter than with stacks. But then by the exposed stacks idea you present kinda puts the "ram air" scoops at a huge disadvantage. I think that most exposed stacks are long enough to prevent any vacuum from effecting the fuel delivery. Also the old indy cars had stacks and an exposed engine with out any ill effects on power.

kanadanmajava1 > EL_ULY 07/30/2014 at 05:42

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Here's a mechanical injection intake manifold (for BBC) with really long stacks. I think that fuel going to wrong direction is only an issue with some carburetors as some are very sensitive for pressure differences.

The Ferrari's scoop has a flow deflector inside which is probably limiting the air flow so the first carburetors aren't getting too much air and rear ones too little.

McMike > 71MGBGT Likes Subarus of Unusual Colors 07/30/2014 at 05:46

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Brace yourself.

kanadanmajava1 > McMike 07/30/2014 at 06:07

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Nice pile of stack intake manifolds. I bought one nice used intake from eBay but it happened to be only suitable for some very rare Brodix heads that are quite hard to find.

Pixel > 71MGBGT Likes Subarus of Unusual Colors 07/30/2014 at 09:04

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For maximum madness, try unequal length velocity stacks.

EL_ULY > kanadanmajava1 07/30/2014 at 09:19

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oh wow nice! Yeah that is some tricky stuff for getting that flow rate. Plus, I just bet they sound goood

EL_ULY > Squid 07/30/2014 at 09:23

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yeah that was what i'm thinking now. Tho, maybe Indy had a small end piece or wind deflector right before the stacks. At speed, it maybe made a difference moving the air around the area like the suuuper tiny windshield on the latest Ariel Atom? IDK lol :] Look awesome, sound awesome, good stuff all the way.

kanadanmajava1 > EL_ULY 07/30/2014 at 09:40

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An interesting company (Speedmaster) seems to be offering velocity stack intakes for interesting engines. Here's one for LS7. There's even mounting point for second set of injectors. That might sound pretty neat.

uofime > EL_ULY 07/30/2014 at 10:15

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the (T)MAP and or lambda sensors for an EFI system would let it compensate so the engine would run correctly, that's not to say the performance would be optimal if the intake is drawing air from a low pressure area since the engine is having to "work harder" to get it's intake air charge.

uofime > Squid 07/30/2014 at 10:18

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and you can bet they did some work tuning those systems so they did work right, you'll also notice modern F1/indy cars all have air scoops on their air boxes