Anyone ever flowed the stock dual carb oil bath air cleaner

[Multi69s]

If you have read my previous posts, the you know that I picked up a set of dual DCNFs to put on my T4 powered Squareback. Putting these carbs on is kind of a long term project for what may seem to be a small amount of work. One of the main concerns that I want to address, is to connect the incoming air to the carbs, to the stock cool air connection on the body.

While going through different carburation configurations, I have noticed a definite pattern. Whenever you are pulling in cool outside air to the carbs, you gain some major benefits. I have noticed better mileage, lower engine temps, and better low-end engine response when pulling in cool air to the carbs. This last one is really important when the engine is connected to an automatic transmission.

What I am thinking about is to build some smallish plenum boxes to mount on top of the carbs to contain any standoff. Then connect the plenum boxes to a stock oil bath air cleaner, and connect the air cleaner to the fresh air inlet. However, I am kind of doubting the ability of the T3 air cleaner to not be too restrictive. Has anyone tried something like this? I also have a T4 oil bath, but it is probably triple the size, which would definitely require some creativity on the carb linkage.
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69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[ataraxia]

Have you read Mark's build thread?

There's a similar topic and his solution:
http://www.thesamba.com/vw/forum/viewtopic.php?t=4...;start=120

[raygreenwood]

As most know....the oil bath air cleaners are probably the best "filtration" units.....but they are restrictive. One of the primary features that make them work is a nearly 180° turn over the oil pool in the bottom.
heavy particles that will be to heavy to be arrested by the oil covered coir material are, dropped out into the oil pool by this turn.
Some industrial oil baths have more thqn one of these turns.

The trick is sizing it right for the engine. Too large to keep restriction down....and velocity drops....filtration then drops. To small and its restrictive.

Most of VWs oil baths, were fairly well, sized for the engines they came with. Its when you modify them or increase displacement that they start to be a problem.

I domont know about type 3....but the type 4 1700 oil bath cleaners were juuuust barely large enough for the 1700. Any substantial improvements including maybe just, changing the cam or exhaust changes this. Ray

[Multi69s]

well poop, that's not the results I wanted to hear. Thanks for the link
_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[Multi69s]

Ray,

What would your opinion be for the T4 oil bath, if it were converted to a dry filter element?
_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[Dodgy]

You could use a Brazilian paper element filter unit, as I did in my Squareback...

This maintains the cold air inlet from outside the engine compartment, as per original.

Best fitting filter element I could find (in UK) was for Rover Mini, there may be other choices in the USA.

_________________
'75 1303 (current project) owned since 1989!
'72 Squareback - full resto completed 2008 - now sold
356 Speedster kit, completed 2005 - now sold

[Nate M.]

I fabricated a center mounted air cleaner w/ 2" individual runners going to each throttle body throat. The center section is from a couple 914 2.0L factory air cleaners grafted together with a large square K&N filter element.

Since this photo was taken, I have completely removed the inlet snout and the entire air cleaner is exposed beneath. Even this is restrictive at WOT. Enough so that I can feel the power difference from the driver's seat. I take it off for racing and run individual filters.
_________________
Regards,

Nate M.

Squarsche build
Heavy Metal Affliction feature

For heaven's sake, put a type4 and a Porsche 5-speed in there. . . It's the right thing to do!!

[raygreenwood]

[W1K1]

I'm re-doing my intake assembly


It seems that the intake needs a lot more space to flow the air than the throat size of the carb, that was what i based my first intake off. I figured the area of one 36mm throat to be 1.417cu/in and two is 2.834cu/in. So I sized the tubes to 2.5" thinking the 4.91cu/in was going to be enough to supply the carbs. It was falling on it's face at around 4500rpm.

The new intake per carb will be around 10 sq/in with an overhang around the carb base like the stock oil bath has.

this is the styrofoam buck carved to shape.
It has come a ways from this.
The biggest thing is for it to fit under the deck and not interfere with the other components.

I also changed to a square filter instead of the round one I had in the oil bath housing. That way I can shape the intake into it and build the box around that.

_________________
http://www.thesamba.com/vw/archives/manuals/jim_martin_engine_build.php

1973 super
1965 squareback 1500E
1971 bay window westy- subi swap

[68vwfasty]

I like where you are going with this.

I really would like to think there is a good solution out there.

My 2110 runs a bit hot and I would love to get cooler air into my carbs.

But is it possible to build a intake plenum that simply goes around the existing CB filter assemblies. Using scoops similar to what you added on the one side. Maybe they would need to be too big to fit. I am thinking one for each carb instead of trying to build something that joins together.

I am just thinking out loud.

Maybe this has already been thought of and discounted.

[Nate M.]

[Clatter]

One thing my little brain was thinking,
Not sure if it's real or not:

The air being drawn into the motor is being acted upon by a vacuum,
Unlike the exhaust, where it is being moved by combustion pressure.

Hence, the intake valves are larger than the exhausts, and a hot motor has big 'ol velocity stacks, but still one relatively small hole at the end of the exhaust pipe.

Therefore, with a bigger/stronger motor,
You are going to want to increase the size of the hole your motor sucks it's fresh air through.

While Nate's is sweet for keeping intake noise down, and getting a large surface area for filter media, it does draw air from the compartment.
W1K1 draws some cool air in from up over the trans, which is supposed to be a good place airflow-wise, if a bit dirty at times.

Seems that doubling up the factory location would be good.
It robs some of the cooling air, but the factory built these splash-guards to help keep things clean/dry.

How on earth to build a box to use both intakes is far beyond me.
A project for my 'golden years' after retirement, I guess.
Always pictured hacking up two OG oil bath filter setups,
Making two small round ones side-by side, one for each carb, yet kind of 'siamesed' together.. If that makes any sense..

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Bus Motor Build

What’s That Noise?!?

[68vwfasty]

Clatter I am with you. I think two separate intakes/filters would work. The more I ponder the more it makes sense to create hats that connect to tubes that connect to a filter box that connects to cool air intake. My concern was where to get the cool air. Your solution is perfect I think. My car is all finished and I didn't want to hack into the metal anywhere. You have the perfect opportunity to add a second inlet. I don't think it's going to rob any significant amount of air from the cooling system.

But I do think the solution that Nate and W1K1 are working on will work the same and could look real cool.

[W1K1]

some pictures just for future reference: my cold air intake is under the car it is a scoop that is 12" X 1" that goes to a 2.5" hose


view from under the car.

scoop, I made from a metal shelf hanging around the garage and exhaust tubing. A walk thru the pick and pull one day after I made it showed lots of small cars have similar intakes, I could have saved a few hours tin bashing

2.5 flex hose bends to connects to the engine rear tin over the starter.

The connection on the tin for the hose fits the indent on the engine tin

made a plate that screws into the hose connection plate to sandwich the ends and keep a solid connection for the hose, and the connection made to the air cleaner

the cold air hole without the air cleaner in the way, same sq/in size as the 2.5" hose.

_________________
http://www.thesamba.com/vw/archives/manuals/jim_martin_engine_build.php

1973 super
1965 squareback 1500E
1971 bay window westy- subi swap

[Clatter]

Once finished, it would be SO cool to do back-to-back dyno runs with and without different filter setups.
Really wonder how a set of tall open stacks would do vs. short filters even..
_________________
Bus Motor Build

What’s That Noise?!?

[Bobnotch]

[68vwfasty]

W1K1 (Mark?),

Thanks for posting more details on your routing for the fresh air. It is very helpful. But as you said this is a 2.5 inch setup and you probably need 3 inch or bigger, right? So will you be modifying your cold air inlet piping?

As Bob says it's pretty tight around the T3 engine. Not much room to run a 3 inch hose. I was looking at where to either run a single 3" hose (if joined system) or maybe two 2.5" hoses if I ran separate intakes for each carb.

I know I can build a hat. It's just making sure each carb has the right hose sizing and how to route it including filter(s).

Anyone smart enough to figure out the size each hose required for each carb. I looked at the calculators and for a 2110 I believe it calculated out to less than 3 inch. But I know it's complicated depending the hose type and other factors (bends, length, ...).

I was thinking you could make a hole through the firewall directly behind each carb. That would make a nice routing. And have an intake scoop and filter for each carb along side the transmission (same spot you put your scoop). I think that would work. I just hate to hack the car and was hoping to avoid that. Not sure how dirty the air would be down there.

Clatter, I think you could make a intake system including a filter and it would fit in the corners of the engine compartment. I would try that if my car is where yours is at. Mock something up and see what you think.

Love all the ideas going around. And some great work done. Got to be a good solution that others can use. And I am pretty sure a lot of people have the CB performance linkage/filter setup or are using Webers or Dellortos.

[raygreenwood]

You guys are thinking well.

But remember...its not just volumes that count....its restriction. Its not only the volume of the spaces you are pulling from that can restrict.

A modern pleated filter uses very high area with low restriction materials. Its not actually that these materials have small holes at all to trap "rocks". they have many layers or labyrinth ....and actually rather large holes.

These keeps that static pressure down from the incoming air.
You also need to be careful of drag and angles. Getting too circuitous creates a lot of drag. Hard angles can create tumbling turbulence and that in itself is a restriction.

Just some thoughts. Ray

[W1K1]

That's what got me rethinking my setup Ray.

The air flow of my first intake has a lot of sharp corners that I think affected the flow. As you can see from the underside the air has to make some sharp corners to get to the carb intakes, which i am trying to correct and smooth out with the new design

_________________
http://www.thesamba.com/vw/archives/manuals/jim_martin_engine_build.php

1973 super
1965 squareback 1500E
1971 bay window westy- subi swap

[W1K1]