 Velocity stacks on a six, Are they needed? |
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| Kerrys914 |
 Nov 27 2004, 09:44 AM
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#1
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Dear, the parts I just sold paid for that part ;)  Group: Members Posts: 1,568 Joined: 26-December 02 From: Williamsburg, VA Member No.: 16  |
I have some Weber 40's for a six and they don't have velocity stacks (air horns or ?) are they needed? I will not be using the air box but will have seperate air filter/ water shields.
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| michel richard |
Nov 27 2004, 10:00 AM
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#2
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Senior Member Group: Members Posts: 1,291 Joined: 22-July 03 From: Longueuil, Québec Member No.: 936 |
Despite the name, with rainshields, I would think that one of the important functions of the airhorns would be to keep rain out of the carbs and cylinders.
Michel Richard |
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| carambola |
Nov 27 2004, 10:42 AM
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#3
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Member Group: Members Posts: 84 Joined: 25-October 04 From: south jersey Member No.: 3,007 |
i always thought the air horns cleaned the intake air and the longer the horn the higher the velocity of the air entering the cylinder. the higher the speed of the air, given the amount of time the intake valve is open and a higher speed of air would mean to me a higher volume of air entering. i may be wrong, but i think i'm on the right track
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| Downunderman |
Nov 27 2004, 10:47 AM
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#4
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Senior Member Group: Members Posts: 852 Joined: 31-May 03 From: Sydney, Australia Member No.: 766 Region Association: Australia and New Zealand |
Yes they are, and while you are about it get set of tall secondary venturis from PMO. They make a world of difference to the mid range.
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| kkelly |
Nov 27 2004, 11:45 AM
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#5
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Newbie Group: Members Posts: 20 Joined: 21-October 03 From: Dallas, TX Member No.: 1,268 |
Not sure about the technical reason for velocity stacks, but they are used for "tuning" the air intake. Similar to changing the length of exhaust headers for better flow.
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| Trekkor |
Nov 27 2004, 12:20 PM
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#6
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I do things... Group: Members Posts: 7,809 Joined: 2-December 03 From: Napa, Ca Member No.: 1,413 Region Association: Northern California |
i just like this...
Attached image(s) 
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| J P Stein |
Nov 27 2004, 09:11 PM
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#7
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Irrelevant old fart Group: Members Posts: 8,797 Joined: 30-December 02 From: Vancouver, WA Member No.: 45 Region Association: None |
No, No...like this (IMG:style_emoticons/default/laugh.gif)
Thanx for helping me slip this pic in ....again (IMG:style_emoticons/default/biggrin.gif) Attached image(s) 
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| krk |
Nov 27 2004, 09:36 PM
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#8
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Senior Member Group: Members Posts: 997 Joined: 27-December 02 From: San Jose Member No.: 22 |
JP -- that's a great pic -- I liked it the first time around as well (IMG:style_emoticons/default/laugh.gif)
kim. |
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| campbellcj |
Nov 27 2004, 10:00 PM
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#9
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I can't Re Member Group: Members Posts: 4,543 Joined: 26-December 02 From: Agoura, CA Member No.: 21 Region Association: Southern California 
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JP's pic is a true classic; I never mind looking at it again (IMG:style_emoticons/default/smilie_pokal.gif)
I recently switched to the tall secondaries and in the (very) limited time I've driven the car since, it seems to be a nice improvement. Just my luck -- today after 9 WEEKS w/o even looking at it, I did a little work on the 914 and put it back to its semi-streetable config. I need to make sure there are no more boogers in the fuel system prior to the next track event. It fired right up after a bit of cranking and warmed up w/o any probs. Then THE EFFIN' RAIN STARTED! Hopefully tomorrow I'll get out for a canyon run and will report on the latest carb and suspension mods. |
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| McMark |
Nov 28 2004, 02:00 AM
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#10
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
Velocity stacks (or air horns) will help you make more power. Where that power comes in on the RPM range depends on the height of the velocity stack. If you don't put them on it's no problem. The engine will run and all will be fine with the world. That said, you could be making more power if you put on stacks. The stacks smooth the incoming air, reducing turbulence. The longer the stack, the less turbulence. But the less turbulence you have the more likely it is that the fuel vapor will condense on the intake walls (bad for power). That's why longer stacks make lower power at lower RPMs. The smooth air is moving slowly without turbulence, giving the fuel lots of opportunity to drop out of the air.
Was that clear? |
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