Many of you may have noticed a new motor brand popping up in the popular miniquad racing parts stores – EFAW, or “Earth Fire Air Water”. You may also have noticed that this motor is out of stock everywhere due to a reputation for power and efficiency that is spreading like wildfire across social media. What are these motors and are the worth the hype? I was lucky enough to get my paws on a set of 4 of the EFAW 2407R 2500kV motors and in this article I’m going to do my best to find out.
When I first saw pictures of the EFAW motors I found it quite amusing that they take on the appearance of the old-school CD-ROM brushless motors used in the ancient multirotors and model airplanes almost a decade ago. By this I mean the motor is constructed of a stator and bell housing with no lower support structure surrounding the mounting bolts. In this configuration, the windings and magnets protrude out of the bottom of the bell, giving the motor a fragile look.
It’s no surprise, then, that EFAW’s main claim-to-fame is the Titanium motor shaft. While the EFAW motors may have lost some strength with the lower mounting structure stripped away, they undoubtedly gain some of that strength back by using a strong TC11 titanium alloy in the construction of the backbone of the motor – its shaft. EFAW claims that this shaft makes the motors far stronger than the competition – and backs that statement up with an offer to replace any motor with a bent shaft.
Realistically – miniquad motors are already pretty durable. A manufacturer has to do much more than that to gain the following these EFAW motors have gathered in a short time. That “thing” is the EFAW motor’s efficiency. I have heard that these motors are producing similar thrust figures to other top of the line motors with a substantially smaller current draw. I have also heard from people outfitting these motors with outstandingly aggressive power systems – think 5S on a 6″ quadcopter with a 2500kV motor. Or 6S on a 5″ quad running aggressive 5051 props. Those are some motor-melting combinations which, if true, speaks to outstanding the outstanding efficiency required to handle that kind of power without melting motor windings.
It didn’t take long after unpacking the EFAW 2407 motors to realize why they could claim such impressive performance figures – the windings on the EFAW are big, fat single-strand copper wires that are beautifully wound around the stator. Many motor manufacturers are moving to multi-strand wires for the high-kV motors we are using in our miniquads. Due to the epoxy coating, multi-strand wires simply do not carry as much current for their weight as single-strand. For this reason, I certainly prefer the way the EFAW motors are built and suspect this has something to do with why they handle current so well. I took a picture of the windings of the EFAW next to those of an Emax RS2306, which is perhaps the next most powerful miniquad motor on the market:
The motor itself seems solid and well-built, although it’s tough to eyeball these things. The bearings on all four motors I purchased spun smoothly with no perceptible play or noise. I noticed some balancing putty in the bell (you can see it in the picture above) – meaning these motors were balanced from the factory.
The wires that come with the motor are 100mm long. I’ve been told that future batches of this motor will be shipped with 150mm wires. Either way, they should be just long enough to reach the center of the quadcopter on a 5″ build using a 4-in-1 ESC, but you will definitely wan to make sure to get the 150mm version if you are building a 6″ quadcopter with an AIO ESC. Being that these motors have no protection for wires chafing against the bell, I would have liked to have seen a soldering pad in lieu of wires.
The motor shaft is retained by a set screw like most modern miniquad motors. The shaft itself is hollow, saving a gram or two of weight. The footprint of the mounting pad that connects to the shaft is surprisingly small, but I was able to install it on my Chameleon with no problems.
Despite what seems like a lot of weight-saving design choices (lack of bell bottom, hollow shaft, titanium construction) – the EFAW is a pretty porky little motor. This shouldn’t be surprising with those monster windings or with the performance claims they are giving out – when it comes to electric motors, more power requires more metal in the windings which in turn requires more weight. Here is what the EFAW 2407 motor I received weighed with the Emax RS2306 (another porky motor for what it’s worth) next to it:
One rather glaring issue I found with the EFAW motors is that their motor leads can contact the mounting screws. The vibration from the motor will eventually wear through the wire sheathing such that the screw contacts the wires inside. This will cause strange electrical issues for your quadcopter, including video noise and reduced motor output. When installing the EFAW motors triple check the mouting screws to ensure they are not touching motor windings or the leads.
After flying my quadcopter with the EFAWs attached for about 5 hours, I noticed one of the magnets had come loose in the bell. I contacted EFAW’s customer support for a replacement bell, but was disappointed to get no response. This occurred in November 2017. If they handle their shaft warranty like they handled me, it is not likely you will ever be getting replacement parts.
I’m still hoping Ryan over at miniquadtestbench will give us his take on the performance figures of these motors. His consistent testing method and large database of previous motor tests will give us an idea of exactly how powerful and efficient the EFAW 2407 motors are.
While I don’t have his experience (or equipment) in testing motors, I was able to round up a couple of competitors for the EFAW and strap them to my prop test stand. I compared the three motors using a RaceKraft 5040×3 tri-blade prop – which uses the same airfoil as the popular HQProp 5040×3. I tested all the motors with a very large 10,000mAh 4S battery. As such, voltage drop should not have been an issue for any of these motors. For an ESC, I used the Littlebee Spring BLHeli_S 30A ESCs.
For competition, I am using some spare motors I have laying around. First up is an RS2306 2750kV edition. I would have liked to compare this motor with the 2500kV but I did not have it on hand. I also put an older ZMX v2 2204 2600kV on the stand for comparison as well. I did not have any lower kV motors laying around – we’ll have to wait for the miniquadtestbench results for that data.
|Motor||Thrust (g)||Amps||Watts||Eff (g/W)|
|EFAW 2407 2500kV||1120||28||441||2.54|
|Emax RS2306 2750kV||1280||36||565||2.27|
|ZMX v2 2633kV||1050||28||441||2.38|
As you can see, the EFAW’s strong point is its efficiency. It puts out respectable thrust but doesn’t quite top the beastly Emax RS2306 2750kV. That’s fine – I can’t even use the RS2306 2750kV motor with tri-blade props because they trash my LiPos when I do, so a less power by reducing thrust and gaining efficiency is certainly a welcome tradeoff.
The astute among you might note that these thrust figures are quite a bit lower than those put out by other testers. This is most likely due to the fact that testing was done at my home at an altitude of 4000ft, which means less thrust from a given prop than those tests done at sea level.
When I first armed my quad after installing the EFAW motors, I heard a soft rubbing sound. I’ve long since learned that any type of rubbing sound is a bad sign and disarmed the quadcopter immediately to investigate. I found that one of the motor wires was contacting the bell of the motor:
This could have become a disaster in a jiffy. The bell has plenty of sharp corners that would made short work of the wire jacket. In “standard” brushless motors, this would never happen since the lower support structure of the motor protects the bell from this sort of rubbing. In the EFAW’s case, you’ll definitely need to make sure your build doesn’t let this happen. Make sure you get as much slack out of your motor wires as you can and secure your ESCs so the motor wires are pulled away from the motor.
With that issue fixed, the rubbing sound was gone and I was off! For this review, I replaced the EMax 2306 2750kV motors on my Armattan Chameleon quadcopter with the EFAW 2407 2500kV motors. I equipped the EFAW motors with RaceKraft 5051 props. I immediately noticed that the EFAW motors were much quieter. This gave the perception of smoother flight but I’m not sure how much of that is a confirmation bias. When you really wind these motors up to full throttle, they have an interesting high-pitched whine that sounds almost like a jet turbine. I have heard from several other guys that their EFAW motors do the same thing.
In terms of thrust, these motors were a slight step down from the EMax 2306 motors. I didn’t have quite as much “pop” as I had before but I did notice that my current draw numbers were also down significantly. Whereas the EMax motors would regularly cruise between 40-50 Amps at high speeds, these motors sit in the 30-40 Amp range. This drop in current draw resulted in a noticeable drop in battery temperature after I landed as well.
Speaking of landing – the motors were cool as a cucumber every time I brought them down. True to their reputation, these things are clearly ready for some high power 5S/6S builds.
Should you join the large queue of people waiting for a set of EFAW motors for your next quadcopter build? For the average pilot, I would say “no”. There are plenty of motors on the market nowadays that are hitting pretty close to the performance figures of the EFAW motors on 4S. These motors can be had for $20 or less and will ship today.
That being said, if:
- You are planning a 5S or 6S monster build.
- You have a real soft spot for motor efficiency.
The EFAW 2407 motors might be a perfect fit for you. These motors fit a perfect niche in the market for well-designed, well-manufactured high-performance motors that can handle high voltages. Mark my words – the EFAW 2407 will be responsible for setting miniquad speed records in the near future. I think that’s awesome.
After my experience with EFAW customer support, I have a more difficult time recommending these motors. They are simply too expensive to justify purchasing when there are plenty of other good 2407 options on the market these days, considering you cannot buy replacement parts and you cannot get help if/when you break something.