Ram-air Cooling Ducts

[Floating VW]

[Lingwendil]

I would be more worried about debris than rain, thousands of bajas have dealt with rain
_________________
73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!

Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884

Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087!

[Floating VW]

Good point.
_________________
"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[petrol punk]

This is such a cool idea. I'd love to try it but I have a feeling that the big all terrains on my lifted bug would cut the duct size down to the point of being a little bottle neck.
_________________
36hp '56 European DeLuxe oval, '70 bug 1835cc dual 36DRLA, and a '98 4x4 5spd single cab Tacoma

[mark tucker]

also when building thing that you may think may be hard to get to relaeae, you can use air nozzel to spary air in between. or on some things Ive molded in a hose so you can use a water hose to to split the parts appart almost effortsley, start off with low pressure/volume and slowley increase the volume as it separates. too fast and you may crack it... keep up the great work!!!

[Floating VW]

Thanks, Mark. That's an interesting idea using water pressure to split the molds. If I ever do anything big, I might try that. I've used compressed air with varying levels of success, but usually what I end up doing is making the flanges of the mold extra thick so I can get in there with some wedges and a decent pry bar.

It ain't fancy, but it gets the job done!
_________________
"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[Floating VW]

I've now got several hundred miles of testing under my belt. I'm happy to say there is very little debris in the engine compartment, even after driving down a couple dirt lanes and through several dust clouds from the farmers combining their fields. There's a thin layer of dust on the engine, but nothing more than I would consider normal, even on a completely stock Bug. It hasn't really rained around here for weeks, so that is still an unknown, unfortunately.

I managed to do a long blast down the freeway at 70+ mph with ambient temps in the low 80's, and the oil held steady at just under 180 degrees F, so that's one of my main objectives achieved.

However. . .

With the end of summer and the arrival of cooler ambient air, the ducts are starting to have a dramatic effect on the Darla twins. Last week, the temperature dipped into the mid 60's, and all that cold, dense air blasting into and around the carburetors and manifolds played merry hob with the air/fuel ratios. At light cruise, EGT's were consistently over 1400 degrees F and a giant lean hole opened up in the transition. After some more testing, I managed to close up the hole and bring the EGT's down by about 250 degrees, but only after going up a full size on both the idles and the mains, and two full sizes on the air corrections. And the hole is still not 100% closed, but it's close enough that I can live with it for now. I might even have to try some different emulsion tubes if I want to make it perfect, though.

I don't know yet what effect this will have on fuel consumption, but I can say that power output has become, for lack of a better word (and a nod to all you Spaceballs fans out there), ludicrous. I got on the throttle a little too hard last weekend and it broke the tires loose in second gear. I'm sure some of that was due to cold, poor quality asphalt, but it sure never did this before. And while doing a WOT pull up a hill in fourth gear, I actually thought I had mistakenly put it in third, or even second gear, it pulled so hard. I even found myself subconsciously grabbing the shift lever to confirm it really was in fourth!

But the problem is that it's not consistent. After sitting in stop-and-go traffic, which basically nullifies the air ducts, this power increase is pretty much absent. And even at WOT, unless I've already been cruising for a while and the manifolds haven't had a chance to get hot again, it still feels pretty normal until about 60 mph, and then all of a sudden- WHAM!- it takes off like a DeLorean with a flux capacitor full of plutonium! So in real-world driving, it's actually more annoying than it is useful.

What that tells me is my ram-air ducts are a step in the right direction, but will require a bit more testing and modification to perfect them. I'm sure switching from carburetion to fuel injection would be an easy way to remedy some of the air/fuel problems, but I'm a die-hard Dellorto man, so EFI is not an option! My current plan is to fabricate a type of heat shield (or cold shield, as it were) to protect the manifolds and the Darla twins from all that cold air. I'll see what I can come up with, but with fall and winter just around the corner, I'll probably be closing off the air ducts until next summer anyway, so it might be a while.
_________________
"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[kpf]

Sounds like you need thermostatically controlled cooling & heating of your intake manifold. This is basically what VW did with the stove pipe and pre-heat hose. They tuned the carburetor for about 90° inlet temperature, and then regulated the temperature of the intake air with a thermostat (different years used different implementations, but the goal was the same).
_________________
1971 Super Beetle

[Floating VW]

Well, just as I predicted, it took me until this summer to address some of the problems I was having with my cooling ducts- namely the intake manifolds becoming too cold at higher velocities and cooler ambient temps. This is what I came up with:

As you can see here, the carburetor and manifold are directly in the path of all that cool air being rammed in:

What I obviously needed was some sort of "cold" shield to protect them. It just so happened that the lid on my neighbor's grill was not only made of good quality stainless steel, but also had the exact contours I was looking for. I hope he doesn't mind that I borrowed a couple of chunks!

The shields bolt on at the base of the carburetors like this:

Now, when the cool air enters the engine compartment, the first thing it hits is this:

The back sides of the shields are very reflective, which should help send a portion of the radiating heat back into the manifolds. And for good measure, I removed the gaskets between the manifolds and the cylinder heads to get as much heat transfer as possible (a thin film of PTFE paste was used to seal the mating surfaces). As an added bonus, this may even help cool the heads, if only slightly.

The result? Problem solved!

Even though the Darla twins are still being cooled, the manifolds stay warm enough that it no longer plays hob with my jetting. And with the carburetors nice and cool, I don't really get that nasty "raw" gasoline smell after shutdown, when all that cylinder head heat travels up the manifolds and cooks off the gas in the bowls.

P.S. I only cut up my neighbor's grill after he bought a new one and threw the old one in the dumpster, so it's all good.

P.S.S. The stainless steel they use to make those lids is really high quality stuff. I highly recommend it if you don't mind extracting it (and your neighbor doesn't catch you!)
_________________
"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[bw65vw]

Really cool idea with all of this! Glad you gave an update or I probably would never have seen it.

[Floating VW]

So, after I got the cooling ducts working flawlessly, I decided to find out just how much air was being rammed into the engine compartment. To do this, I installed a flow meter inside one of the ducts and went for a spin. My flow meter is a neat little device that can be used remotely with an app on my i-phone:

The cross-sectional area of the narrowest part of the cooling ducts (minus the flow meter), is 135 cm². Measuring the velocity of the air flowing through this area, I was able the calculate the flow rate:

The first measurement I took was with the car stopped (0 MPH), and the engine at idle, with the deck lid closed and the louvers covered. So basically I measured how much air was being pulled in by just the cooling fan and the Darla twins. I got an average wind speed of 3.5 MPH, for a flow rate of 44.01 CFM (74.77 m3/hr):

Keep in mind that I was only measuring the air flow through one cooling duct at a time, so these values only represent half of the total air flow being delivered to the engine compartment.

The next measurements were at 40, 50, 60 and 70 MPH.

At 40 MPH, average air flow was 221.28 CFM (375.96 m3/hr) per duct:

At 50 MPH, average air flow was 290.43 CFM (493.45 m3/hr) per duct:

At 60 MPH, average air flow was 340.73 CFM (578.90 m3/hr) per duct:

At 70 MPH, average air flow was 388.50 CFM (660.07 m3/hr) per duct:

At 70 MPH, those air ducts are ramming about 780 cubic feet of air per minute into the engine. That's a lot of air! I stopped at 70 MPH, but now I'm curious what the flow rate is at 100 MPH. Can you imagine the possibilities if all that air could be forced down the intake manifolds?

But for now, I'm satisfied with just using it to cool the engine.
_________________
"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[Floating VW]

[oprn]

Very interesting that intake manifold heat is required on dual carbs too!
_________________
We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[slayer61]

This is outstanding work. Kudos to you Sir.

Thinking so far "outside the box" that the box can't even be seen from where you stand!

[j-dub]

[Floating VW]

Thanks guys.

It's definitely been a fun project!

For the sealant, I just used a common PTFE paste, like what you would find in the plumbing section at your average hardware store. It's rated from -50 to 500+ degrees F, and withstands exposure to most gases, oils and fuels, including steam and most diluted acids. Just be careful you don't apply too thick of a bead, as you don't want it squishing out into the intake ports.
_________________
"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[sled]

I love this thread!


I was recommended loctite 518 flange sealant by Brian_e (type E motorsports) and have had great success with it. I recently pulled my intake manifolds and it was very easy to clean off the old sealant and re-apply. A very thin bead is plenty.
_________________
drive your split.

[Floating VW]

Yeah, loctite 518 and Curil K2 are my go-to sealants for just about everything. The Teflon paste is kind of a new thing I'm trying.
_________________
"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[Floating VW]

One potential problem I thought I might have with these cooling ducts, was the possibility of road debris and rain water entering the engine compartment and causing problems.

For this reason, I designed some expansion chambers at the ends of the ducts where the air is forced to make a 90 degree turn before it enters the engine compartment. You can see the expansion chamber here:

I haven't noticed hardly any dust or debris getting in, but I wasn't sure about the rain water. And then last Friday I finally found a decent storm to drive in. I'm happy to report that, even though the entire insides of the ducts were completely soaked, only a half dozen drops of rain water (and one tiny, little leaf) made it into the engine compartment, and they were all stopped by the air deflectors on the manifolds.

This was a huge relief to me, since I wasn't sure I'd made the expansion chambers big enough. But, it seems to have worked out fine.
_________________
"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[craigman]

Very cool results!
I wonder what would happen if someone were to remove the front (flywheel side) tin to let in fresh air. It would a lot of fresh air into the fan and carbs.
Just a thought...