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Next Generation Lightweight Cooling Fan - Part 3

What everyone has been waiting for!

If you haven't read "Part 1" and "Part 2" of this blog post series, that's okay, as you can understand the performance results without them, but they give a great deal of context to what I am about to describe, and it's useful in understanding how these results were achieved. Before we get straight to results, I am going to do a short description of the testing method.

Testing Method

To test the OEM fan versus the "Next Generation" lightweight fan, you need a method of testing that creates reproducible results that no matter the barometric pressure and temperature, you get the same results. You also need a method of measurement that doesn't change the results based on doing the measurement. Finally, you need a representative environment that doesn't simulate the static pressure present, but actually provides it in the exact manor that will happen on a running engine. So, with all that let's talk about reproducible results and a measurement that doesn't change the results.

The ASTM created a standard for measuring airflow in ducted systems, like the air cooling system of the VW Type 1 engine. In that standard, they specify the tubing diameter and length necessary to create reproducible results that the measurement itself will not effect the results. With that data in hand, what I did was create a 3D printed tube that was long enough and large enough in diameter to meet the standard, and I put a small hole in that tube that allowed me to slide my pitot tube into the tube and center it to measure pressure in inches of water, and subsequently measure the airflow in CFM, adjusted for barometric pressure and temperature. You can see my YouTube video showing the system here: The tube also has a velocity stack on it to prevent excess pressure at the tube inlet to skew the results. The pitot tube is then connected to a manometer that communicates with software on a phone or tablet, and calculates the measurements in real time. The software side of it is configured with the diameter of the shroud inlet (and different shrouds have different inlet diameters), the temperature and barometric pressure. I have a small weather station and app that does temperature and barometric pressure readings, and I use those for each measurement as they fluctuate.

The other critical component is the tube that leads to the air inlet on the fan shroud has to be sealed against the fan shroud so no air enters the fan shroud inlet except the air that is coming through the measurement tube. I used closed cell foam, cut and shaped to follow the contours of the fan shroud to seal the tube, and I could always tell if I didn't get it sealed, because the measurements would just drop suddenly if there was a leak. After a few iterations, I had my setup so that it was very easy to change the setup, and get a leak free test environment. Finally, how to turn the fan?

To turn the fan, and to turn it at a constant speed so the tests are completely reproducible, I used an electric motor. Electric motors are great for this application, because they turn at a constant speed, and besides turning at a constant speed they will draw a different number of amps depending on how hard they have to work to turn that speed. This gives you the added ability to measure horsepower draw of the fan, because you can calculate the kilowatts from the voltage and amperage (you have to have an amp measurement device), and than turn kilowatts into horsepower. The electric motor sits on top of a stand that aligns it with the height of the alternator, and I made an adapter out of steel that slides on to the shaft of the electric motor, and has a 12 mm threaded part that can just screw onto the end of the alternator. It works perfectly, and is very easy to put on and remove. Besides all this, the next important thing is what the fan shroud is attached too.

To get the same static pressure of a running engine, you need to have a full mockup engine. So, I created just that, starting with an empty crankcase, with cylinders and cylinder heads. I made sure that the cylinder heads had the air deflectors underneath on the center of the cylinder heads, as these are missing on aftermarket heads, but they are important to properly cool the underside of the head. I have the cylinder deflectors, OEM cylinder tins that have the proper deflector on the upper side of the head, that directs air towards the sparks plugs and exhaust ports (the hottest parts of the heads). All the tin that wraps around the bottom is present, along with empty pushrod tubes, spark plugs and plug wires. The internal air directional flaps are present as well. I also put in the oil cooler with all the tin to have the air exit out the front, just like in a car. Even the throttle cable tube is present. All these elements add to the static pressure of the system, so must be present to get accurate measurements. With all that in place, I was ready to take measurements.

What I tested

Since I had customers asking about fans for early VW fan shrouds, Porsche 356's and Type III's and IV's, I decided to initially create products for early VW and Porsche 356's along with my original Doghouse fan shroud fan ('71 and later). While most people convert to Doghouse fan shrouds, and that covers the vast majority, there are quite a few early VW fan shroud folks that wanted a fan that worked in their shroud, and the Porsche 356 fan doesn't perform that well, but they try to make up for it by spinning it faster (more on that later). Type III's and IV's require a whole different animal for testing, and a completely different fan design, so I have not tackled that yet, but may do so in the future.

So, I have tested early VW (pre-'71 and earlier), Porsche 356 and Doghouse versions of the "Next Generation" lightweight cooling fan, and will be releasing Doghouse first, followed by early VW and Porsche 356.

Results for early VW

For early VW, I had an early VW fan and shroud configured on my test platform, and took baseline measurements to be able to compare too. The baseline measurements were with and without an early VW fan shroud velocity ring. In the following graph, the baseline measurement without the velocity ring is represented as 100%, and everything else is relative to that baseline. So, anything over 100% is an improvement over the baseline. The first graph is airflow, the second is air speed, and the third is air pressure in inches of water. The blue are the OEM results without and with the velocity ring, and the green are the "Next Generation" lightweight cooling fan results.

As you can see from above, the overall performance of the "Next Generation" lightweight cooling fan performs between 5.35% better up to 16.1% better than the OEM. Of course, if you compare the OEM fan with a velocity ring to the "Next Generation" lightweight cooling fan without, there is a -2.71% difference, with the OEM fan with a velocity ring outperforming the "Next Generation" lightweight cooling fan without one, but it's an apples and oranges comparison. It does show how well the velocity ring works to improve cooling though, but my fan cools much better, and improves more with the velocity ring as well. The pressure readings are even greater increases as you would expect based on the fan affinity laws. As airflow and speed go up, pressure goes up in a very particular ratio (a little over 2 to 1) which is why pressure is so much greater at 11.54% to 34.62% higher air pressure vs. flow and speed.

Results for Porsche 356

Porsche 356 results are interesting in that the 356 fan shroud is quite a bit different than the early VW, but the opening diameter is identical, and the internal structure on the air inlet is exactly the same as well. The air directional vanes inside are different as there are not heater outlets, but the fundamentals that effect the fan the most are the same. Also, the Porsche 356 used a backward curved blade design making it perform worse than an early VW OEM fan, which was a surprise to me, but after thinking about it, I realized that they used a smaller diameter pulley, making the fan spin faster. That makes up for some of the performance difference, but if you kept that ratio and just used an early VW fan you would get much better cooling on a Porsche 356. However, from what I have heard, Porsche 356 owners don't want to use VW parts on their cars, which if I was a Porsche owner, I think I would feel the same way. So, with that, let's look at the Porsche 356 results.

With the Porsche 356 results there is one additional baseline, which is Porsche's own volute, which is similar to the velocity ring, but as you can see from the results, doesn't help with the airflow nearly as much as a velocity ring.

The results are purely stunning. The "Next Generation" lightweight cooling fan for Porsche 356 outperforms the OEM fan from 13.22% up to a whopping 25.8% on airflow, with virtually identical numbers on airspeed (as one is calculated from the other), as expected, and from 33.33% to 61.11% on air pressure in inches of water. Just phenomenal results, which demonstrates just how much difference a forward curved blade makes compared to the backward curved blade Porsche chose to use.

For all you Porsche 356 owners that struggle to enjoy driving your car because of overheating issues, you can install one of the "Next Generation" lightweight cooling fans, and you'll have an entirely new driving experience. Besides the much improved cooling, you'll also get the great throttle response that these fans deliver, and it will feel like your driving an entirely new car!

Results for late VW Doghouse ('71 and Later)

Again, we used an OEM Doghouse fan shroud, just like with early VW and Porsche 356, without and with a velocity ring for our baselines and here are my results.

As you can see from above the "Next Generation" lightweight cooling fan for Doghouse fan shrouds performs from 4.71% to 13.75% better on airflow than the OEM. It's a little down percentage wise in comparison to the early VW results, but actually closer on the apples and oranges comparison of the new fan compared to OEM with a velocity ring, as there is only a -0.54 percentage difference compared to -2.71%. One of the interesting aspects of the Doghouse fan shroud, is it actually has a smaller diameter air inlet. I'm not sure why VW did that, as it's 2 mm smaller in diameter (148 mm vs. 150 mm) than the early VW fan shroud (and the Porsche 356 for that matter). This does stifle the performance of the "Next Generation" lightweight cooling fan a little bit, but overall the results are still very good, and again you see that much bigger jump in performance with the velocity ring than you get with the OEM fan. So, some of you may be thinking that this might be a small step backwards compared to the first generation lightweight cooling fan. After all, I did advertise 7% to 9% improvement with the first generation. Yes, that is true, and it was accurate, but I now have a fan that has a wider performance envelope with the velocity ring than ever, and no matter whether you have a solid decklid (higher static pressure) with an early car, or are driving a bay window bus at high speeds, or any other possible issue that could cause reduced airflow into the engine bay, you will always get this improvement, and that is what I set out to tackle with this new version.

What about the weight?

With the new design, obviously the weight is going to be different than the first generation fan, and you would be correct. All of the testing was done with prototypes that were not made with the production fan material, so I didn't weight them to see what the difference was because it wouldn't be accurate for the actual shipping product. Having said that, I have now made some of the late model, doghouse fan shroud fans, and was able to get a weight and a comparison.

For the doghouse fan shroud version, it weights a mere .43 lbs. (around 195 grams). That is 83.71% lighter than the welded OEM fan (2.64 lbs.), and it's another 10% lighter than the first generation fan. This actually caught me a little by surprise, as I thought it might weight a little more than the first generation due to the geometry. What this means is you'll get even better throttle response than the first generation!

For all the other versions, I don't have their weights yet, but they will be somewhat similar in weight reduction, although it will vary a bit from version to version.


So, after completing all this testing, with many different fan design iterations, I am pleased with the results, and am confident that everyone, regardless of their particular vehicle situation will get improved cooling along with the improved throttle response that these fans deliver. All of the hard work put into the design of these will also show up in future products, as I am in the process of developing two entirely new cooling systems, with their own fan shrouds that will evolve the Type 1 cooling system to another level. Right now, I'm thinking of calling them Evolution One and Evolution Two, as they are just an evolution of the OEM cooling system with a new fan shroud, backing plates and fan that will fit with the existing cylinder head/cylinder tins. In fact, it will fit better than most aftermarket fan shrouds, that's for sure. I'm looking forward to getting those on the market, and I have a more radical design that I have had on hold for quite awhile, and it might be called the Revolution, as it changes virtually everything about the cooling system in a bid to make really high horsepower combinations live on the street. That one is going to take awhile because of the entirely new concept, and will be for a smaller market as well, since not very many people are running, 300, 400 or 500 horsepower combinations on the street.

Anyway, thanks for taking the time to read this, and I'm in production now, so hopefully all of these fans will be available soon!

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