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worzella

Weber air flow - valid or hooey

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(edited)

Another rather unnecessary post, but I still have today off :)

 

For you slide rule guys, I have a theory/practice question. In my exciting first day of 2019, I was watching a bunch of carb videos on Youtube (ladies.. please do not message me all at once!) and a guy was installing/explaining a 38/38 installation. He got it screwed down and was about to add air cleaner and started saying how dumb the Weber design was having the air come in the sides of the air cleaner with the top covered by the chrome cap. He showed that the air has to come in the side, slam into the side wall of the barrels climb up and then get sucked into the carb. Kind of made sense.

 

Then his solution was this attachment he called an "air horn" (pix below) that provided a smooth, rolled edge and a foam air filter open on sides and top (other pix below). This was from some CA company called "RamAir". His conjecture (first big word of 2019!) was that this allowed better direct air flow into the carb from top and sides. Again, makes sense.

 

But my question is.. for a stock 02 running a basic 32/36, does this "free flow" upgrade provide much benefit? And if not, does it make more sense in the 38/38 setup where both barrels need to gulp air?

 

Just curious.

 

Randy 

 

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Edited by worzella
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Pierce Manifolds has a three part video about the Weber downdraft carburetors.  It is worth a watch, imho.  He mentions the rounded lip and says it is worthwhile.

 

I believe the stock air cleaner is a superior solution, if you can pull it off without hacking out the beautifully domed base.

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Yup.  The radius helps.   Enuf to MATTER?  Not unless you find yourself

with your foot on the floor, tugging on the wheel, making 'giddyup' noises.

 

I like Tom's solution- lotsa flow, lotsa filtration, period correct.  Cold air intake, too!

 

t

those clever Germans...

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(edited)

It's absolutely not hooey... the OEM domed air filter housing Mint pictures above is far superior for flowing air than the box typically seen on Weber two barrels. What does it get you on a real world, street car? Probably not enough to notice, but it might help the #s a bit.  Folks with access to a dyno could easily test it.

 

Google "velocity stack" for plenty of information about laminar flow, etc...

 

Ed

Edited by zinz

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Agreed - NOT hooey --   We use this setup on our vintage race cars with the 38 two barrel.  VARA has a special class for 2 barrel carbs.  Guys are getting 160+  at the wheels.  Probably only makes a difference at high rpm.

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19 minutes ago, jireland2002 said:

Agreed - NOT hooey --   We use this setup on our vintage race cars with the 38 two barrel.  VARA has a special class for 2 barrel carbs.  Guys are getting 160+  at the wheels.  Probably only makes a difference at high rpm.

 

Hi - "by this setup" I expect you mean my picture posts and not the stock round OEM that came with Solex that Mint shows?

 

OK thanks slide-rulers....

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"Air silencer" they called it.

For good reason.

 

air box design is a hot topic for side drafts, but not so for the lowly downdrafts. 

iirc, there are formulas regarding the volume of the box to engine displacement... and stuff.

 

there are pulses generated and the intake and exhaust systems play-together, as designed, by real scientists.

 

power power power

power power

power

 

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(edited)

Science.  This short article on induction systems design is a simple primer I think's pretty good for explaining this stuff (not 02 specific).

See the sections on Tuned Ports and Helmholz Theory for the details on pulses/pressure waves/resonance...

 

Tom

induction systems tech.pdf

Edited by visionaut
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For inquiring minds.  A slide rule is not needed, but it gets to the finish line quicker.

Entrance Loss.jpg

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This is the same reason why I cringe when people put face-mounted filters on DCOE's with no stack underneath.  You NEED at least a little radius to avoid off-idle stumbling.

 

Air boxes.... that's a topic for another day.

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(edited)

For a street car  I wouldn't lose any sleep over not having one of those "RamAir" devices, or even a nice parabolic velocity stack. Think about how much time your engine is at full throttle...that  downstream butterfly blocking most of  the throat , most of the time, plays serious havoc with those pretty textbook streamlines. Race cars a different story.

Edited by Mike A

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1 hour ago, Mike A said:

For a street car  I wouldn't lose any sleep over not having one of those "RamAir" devices, or even a nice parabolic velocity stack. Think about how much time your engine is at full throttle...that  downstream butterfly blocking most of  the throat , most of the time, plays serious havoc with those pretty textbook streamlines. Race cars a different story.

 

 

I dunno. I bet I have the 2nd barrel open a good half dozen times per day....

 

Cheers,

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11 hours ago, ray_ said:

 

 

I dunno. I bet I have the 2nd barrel open a good half dozen times per day....

 

Cheers,

OK......pedal to the floor for.about 3 to 4 seconds each....times 6 per day.....all of 18 seconds.  That "Ramair" device is sorely needed for sure.

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2 minutes ago, Mike A said:

OK......pedal to the floor for.about 3 to 4 seconds each....times 6 per day.....all of 18 seconds.  That "Ramair" device is sorely needed for sure.

True. I should buy a Kia.

 

?

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