The Phi Fan Performance Standard – PFPS
Cybenetics named its fan performance Standard, Phi, after the Greek letter «Φ,» which, among other things, represents the golden ratio.
The Phi Fan Performance Standard, or PFPS in short, includes both 120mm and 135-140mm fans, but with different requirements for each level. The requirements are set for both airflow and static pressure since these two are the key performance factors for each fan.
All fans are tested under 25 dBA normalized noise output, and Cybenetics takes into account these results to rank them in the following categories. Why did Cybenetics chose this specific noise level for its standard? Because at 25 dBA, a fan can spin fast enough to achieve decent performance, while this noise level isn’t high enough to annoy the majority of users. Anything higher or lower than this noise level would be too noisy, or performance would be hugely affected.
What about the fans that don’t even reach 25 dBA noise output? Unfortunately, these are not rated, but these fans are not performance-oriented anyway, so there is no need to have a performance badge. The Cybenetics fan database only includes a handful of fans that cannot reach 25 dBA noise output.
PFPS – 120mm Fan Airflow Levels/Requirements – 25 dBA Normalized Noise Output
| Performance Levels | Requirements |
| Bronze | ≥34 CFM & <38 CFM |
| Silver | ≥38 CFM & <42 CFM |
| Gold | ≥42 CFM & <46 CFM |
| Platinum | ≥46 CFM & <50 CFM |
| Titanium | ≥50 CFM & <55 CFM |
| Titanium | ≥55 CFM |
PFPS – 120mm Fan Static Pressure Levels/Requirements – 25 dBA Normalized Noise Output
| Performance Levels | Requirements |
| Bronze | ≥0.8 mmAq & <1.0 mmAq |
| Silver | ≥1.0 mmAq & <1.25 mmAq |
| Gold | 1.25 mmAq & <1.5 mmAq |
| Platinum | ≥1.5 mmAq & <1.75 mmAq |
| Titanium | ≥1.75 mmAq & <2.0 mmAq |
| Titanium | ≥2 mmAq |
PFPS – 135/140mm Fan Airflow Levels/Requirements – 25 dBA Normalized Noise Output
| Performance Levels | Requirements |
| Bronze | ≥45 CFM & <50 CFM |
| Silver | ≥50 CFM & <55 CFM |
| Gold | ≥55 CFM & <60 CFM |
| Platinum | ≥60 CFM & <65 CFM |
| Titanium | ≥65 CFM & <70 CFM |
| Titanium | ≥70 CFM |
PFPS – 135/140mm Fan Static Pressure Levels/Requirements – 25 dBA Normalized Noise Output
| Performance Levels | Requirements |
| Bronze | ≥0.7 mmAq & <0.9 mmAq |
| Silver | ≥0.9 mmAq & <1.1 mmAq |
| Gold | ≥1.1 mmAq & <1.3 mmAq |
| Platinum | ≥1.3 mmAq & <1.5 mmAq |
| Titanium | ≥1.5 mmAq & <1.7 mmAq |
| Titanium | ≥1.7 mmAq |
This rating system is actively encourages optimizations of paper specs that do not matter on any real applications, and would only worsen the overall quality of fans if manufacturers try to score well for this rating system.
As mentioned in this piece, the airflow rating is only measured at zero resistance. Meanwhile, the static pressure rating is measured when zero airflow is produced. Neither scenario ever occurs when the fan is attempting to cool something.
At the very least, the impedence curves of multiple standard obstacles should be measured, and the working point should be identified based on the P-Q curve, which can then be used as the basis for the rating. Certainly not with the current environments that do not remotely reflect real world usage. This is already ignoring many factors that are not considered, like close blade-obstacle interactions leading to differences between the estimated working point and actual airflow, different obstacles significantly changing on-application acoustics (differently for each fan), and differences in noise profile.
For the sake of the PC fan market, please reconsider your approach to this rating system.
We implemented this scheme after almost 2 years of hard work and over 100 fan evaluations. Let me clear this first.
Also, please read how the Longwin machine operates because it is tiresome for me to have to repeat that all over. Not real word usage? So 1-2 radiator tests, or 10x would suffice for you? What for the next 100s of them available on the market? Again, read how the Longwin can apply all possible loads.
Acoustics: I have been running acoustics tests for 15 years now. You tell me that I need to test under possible scenarios? Seriously? So I need to mount the fans in 1000 radiators to take all relevant measurements?
You try to pass your thoughts using several technical words, which I am not sure if you fully understand, but I don’t see you suggesting something practical. So please feel free to suggest something real, using plain words for everyone to understand, and we can discuss it. I am known for being always open to suggestions.
Please don’t get me wrong for my reply, if it is kind of harsh. But I busted my a@@ to make this happen and I did it after a LONG period of studying and experimenting. This is NOT a review methodology, but a certification methodology for which we will apply for an ISO 17025. So again, if you have any practical ideas and not a generic scenario and thoughts, tell me please hey Aris I think you can do that and that. And I will seriously consider it.
I appreciate your hard work, and you spending the money to get a known, reliable fan testing machine instead of building one by yourself that you cannot confidently say is accurate. That said, it does not mean your methodology is perfect. However, no, I am not telling you to throw all the data away.
Yes, I have a pretty good understanding on how the Longwin machine works. Two main chambers. Perforated plate stops airflow and allow air to diffuse through. Orifices of variable sizes allow air to pass through to the second chamber. Pressure in both chambers are measured. Pressure difference between the two chambers, alongside the area of orifice, are then used to calculate airflow. A variable exhaust system (essentially, a fan) simulates different impedence, allowing P-Q curves to be drawn.
My biggest gripe with your methodology is, perhaps, the fact that you constantly stress that the machine can measure P-Q curves, but you never actually look at the curves when evaluating the fans. You are only looking at the X and Y axis intersections and ignoring everything else!
Since you’re very familiar with PSUs, I’ll use them as an analogy. Fans working against different backpressure is comparable to PSUs working at different loads. Evaluating fans based only on max airflow and static pressure, is comparable to evaluating PSUs only based on their max load and idle performances. You do not evaluate PSUs that way; instead, when giving them a rating, you look across the entire range. This is the same for fans. You must evaluate them based on the entire performance range to give them a fair judgement.
P-Q curves can be useful estimations, even if they cannot 100% predict performance directly on obstacles. Or course, based on reasons I have stated in my first comment, P-Q curves alone cannot completely reflect the actual performance of PC fans. Still, you can make them useful. But first, you need to have an idea of the impedence of different obstacles.
Yes, you need to test a bunch of obstacles. Radiators of different sizes, thicknesses and FPI, hexagon vents, circular vents, slit vents, plastic filters, nylon mesh, metal filters, wire grills… No, you do not need to test every single one in the world, just enough to have a general idea. Just because you can’t feasibility test everything, doesn’t mean you shouldn’t try your best to draw a more complete picture. Select a few representatives that represent a wide range of obstacles the fans can potentially face. Test their impedence using the Long Win machine and validate whether the on-application airflow matches the predicted operating point well.
While it’s ideal to test directly on obstacles to account for on-application acoustics (which you really should try to do; yes detailed fan testing is hard work where you need to mount and unmount fans lots of times, though definitely not thousands so you need to pick a few), you can still draw good estimates based on P-Q curves. Based on your tests on the impedence of different obstacles, you can select a few representative impedences, and evaluate fans based on the predicted operating points based on the P-Q curves. So, instead of “Airflow” and “Static Pressure” ratings, you can also give the fans additional ratings based on their P-Q curves – say, “High Impedence”, “Mid Impedence”, “Low Impedence”. These values and ratings will be much more meaningful for real applications.