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cliveawn
Samba Member
Joined: December 07, 2010
Posts: 481
Location: Southern Sweden
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 Posted: Mon Jun 20, 2016 2:06 am Post subject: Re: Velocity stacks and filter heights |
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I love the sound actually but the wife and kids complain! Haha,im thinking of a central airbox to quieten it down just a touch.
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''Funny thing about common sense is that its not very common''
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ps2375
Samba Member
Joined: April 24, 2014
Posts: 2471
Location: Meridian,ID
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| Posted: Mon Jun 20, 2016 8:08 am Post subject: Re: Velocity stacks and filter heights |
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| Frankysfree wrote: |
| Is there a big disadvantage to only running filters without velocity stacks? When i got mine it had 40 IDF's with no stacks, only filters. I understand the reason to run the stacks just wondering if it will lose a significant amount of power or tq by not running them or will it be slight. Are there any dyno sheets to show the power difference? |
I found this in a thread about velocity stacks on another forum. Might help you decide if a VS is better or worse. Basically a comparison of flow to a bare carb, but does not address my question of room above the VS.
[url][/url] |
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mark tucker
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Joined: April 08, 2009
Posts: 23937
Location: SHALIMAR ,FLORIDA
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| Posted: Mon Jun 20, 2016 8:42 am Post subject: Re: Velocity stacks and filter heights |
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| cliveawn wrote: |
Interesting thread,do running stacks reduce induction roar?
My motor roars a bit and it does get annoying on long trips. |
just make some covers for the carb's/air filters . I made rain covers for mine out of marine vynel about 1.5" biger than the airfilter and hangs down about 2-3" lower than the filter base. (with a slot for the linkage and velcro tabs to close it around the linkage. it quiets it down a lot. with no ill affects. the thick marine vynel is a little stiff so it dosent suck up to the filter. but I added a few tubes inside just incase(rolled vynel sowen virtlcy to keep the outer portion from sucken inward.2 per cover and they can also pull air through them.) those were very nicley done and looked great.....till one dissapeared  I then made some out of some other stuff that looked ok at forst but didnt hold up and were very soft vynel still no colapsing issues ,those were rectangle with a plastic basket inside the top so they held shape.I need to make some new ones some day. the dollar store has some baskets that are the perfect size for these oval aircleaners. it realy does quieten them down a lot. there soft and dont amplify the sound like a "bucket"put over the carbs would .
going back to the ops product.....K&N used to make plastic stacks to increase cfm of many carbs,they just slid down over the carb horn & it blended everything and took out turblance of all the crap,bump's, sharp edges, screws,linkage&such a lot of racers used them for spec carb classes and also sterry cars wantig a little more. and moroso made a aircleaner with the right shape to the bottom and the top with inverted cone shape that gently directed the incoming upward then gently redirected it downward into the carb, they increased the flow& hp .combine them and you have a nice performance gain. I wish K&N made them for these carbs. that would also make jet changes so fast& eazy without the steel stud strap in the middle....for those of us whoo have that style AC. |
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tattooed_pariah
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Joined: April 24, 2006
Posts: 2047
Location: El Cajon, CA
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| Posted: Mon Jun 20, 2016 11:08 am Post subject: Re: Velocity stacks and filter heights |
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| ps2375 wrote: |
I found this in a thread about velocity stacks on another forum. Might help you decide if a VS is better or worse. Basically a comparison of flow to a bare carb, but does not address my question of room above the VS.
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At an eyeball measurement, I think my stacks are closest to #9 here (these are what i bought.. http://vwparts.aircooled.net/OEM-Weber-IDF-Velocity-Stack-44-48-IDF-52845-014-p/52845.014.htm)
If I'm reading it right.. they increase airflow by 5.5%, which, and bear with me, i was never good at science (or school really).. means I would need less jetting because of increased airflow? or would 5.5% really not impact the jetting enough to make a difference?
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ps2375
Samba Member
Joined: April 24, 2014
Posts: 2471
Location: Meridian,ID
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| Posted: Mon Jun 20, 2016 11:17 am Post subject: Re: Velocity stacks and filter heights |
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| tattooed_pariah wrote: |
| If I'm reading it right.. they increase airflow by 5.5%, which, and bear with me, i was never good at science (or school really).. means I would need less jetting because of increased airflow? or would 5.5% really not impact the jetting enough to make a difference? |
If your jetting is correct, the carb should compensate for the added flow, after all, that air is still going thru the carb and thus it is still "metered air", I suppose it would depend upon how much turbulence you had prior at the venturies that could disrupt the metering of fuel. |
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[email protected]
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Joined: August 03, 2002
Posts: 12785
Location: Salt Lake City, Utah
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| Posted: Mon Jun 20, 2016 11:27 am Post subject: Re: Velocity stacks and filter heights |
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flow wise, you need 1/2 the stack diameter room, from top of stack to filter top.
But you'll also have a 2nd reverse wave, bouncing off the filter top. There is already one from the top of the stack.
So the top there can change the jetting and power characteristics of the engine, AND change it's sound (sometimes a lot).
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ps2375
Samba Member
Joined: April 24, 2014
Posts: 2471
Location: Meridian,ID
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| Posted: Wed Jun 22, 2016 9:41 pm Post subject: Re: Velocity stacks and filter heights |
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I had the powder coating done today and drove it some, sound seems to be a little throatier and might drive a little better, or it could all be my imagination.
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mark tucker
Samba Member
Joined: April 08, 2009
Posts: 23937
Location: SHALIMAR ,FLORIDA
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| Posted: Thu Jun 23, 2016 8:38 am Post subject: Re: Velocity stacks and filter heights |
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I hate to tell you but it looks like your wifes vega has been mounting your bug  and distributing some spark to the bug........  |
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ps2375
Samba Member
Joined: April 24, 2014
Posts: 2471
Location: Meridian,ID
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| Posted: Fri Jun 24, 2016 8:53 am Post subject: Re: Velocity stacks and filter heights |
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| mark tucker wrote: |
| I hate to tell you but it looks like your wifes vega has been mounting your bug and distributing some spark to the bug........ |
That change was made back when there still might have been a Vega or two still on the road... |
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mark tucker
Samba Member
Joined: April 08, 2009
Posts: 23937
Location: SHALIMAR ,FLORIDA
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| Posted: Fri Jun 24, 2016 9:42 am Post subject: Re: Velocity stacks and filter heights |
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| Ive been tempted to do it for eaze of tunability(gm dist, not vega mounting my bug) instead I got the msd style dist that has the same innards.....but this 009 works so good, idles so smooth, never misses a lick.....the new distr&new box with rev limiter is sitten on the shelf for....many many years now. the gm is a good dist, just dont run more than about .040 plug gap or it will kill the coil in the cap.as will dead or dying plug wires. bosch platinums work well with them& .060 gaps work.(Ive changes somany dead gm coils it's skeery) |
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obieoberstar
Samba Member
Joined: March 07, 2002
Posts: 1126
Location: Tucson
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| Posted: Mon Nov 06, 2023 7:13 pm Post subject: Re: Velocity stacks and filter heights |
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| [email protected] wrote: |
flow wise, you need 1/2 the stack diameter room, from top of stack to filter top.
But you'll also have a 2nd reverse wave, bouncing off the filter top. There is already one from the top of the stack.
So the top there can change the jetting and power characteristics of the engine, AND change it's sound (sometimes a lot). |
Thank you for this post from years ago John.
I am starting to wrap my mind around reversion waves and the intake tract dynamics. |
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