Today we’re reviewing two high KV motors from the DYS’s Race Series line, namely the Storm 2800KV and Mars 2750KV. In this article we’re going to look closely at their specs and internals, paying attention to the small details. This review is written by Andrey Mironov.
To learn more about the basics of mini quad motors, make sure to check out our guide.
You can order the reviewed DYS motors from
DYS Storm 2800KV
Having a 2207 stator, The Storm 2207 motor is an evolutionary step forward from the original DYS Fire 2206. The bigger stator and unusually high KV make it an interesting choice for hardcore racing and freestyle flying, however the trend in mini quad motors is more towards wider rather than taller stators these days.
(We actuallywrote about the lower KV Storm motors before.)
Packaging includes a fancy plastic box, an aluminium wrench for prop nuts, a pair of nylock prop nuts, 5x M3*5mm and 5x M3*7mm motor screws for your convenience.
No spare c-clips nor brass washers included. I would prefer a pair of c-clips instead of this prop nut wrench which I never use (pretty sure that everyone has one in a better form-factor anyway).
The motor comes with 20cm long, 20AWG wires which allow for easy direct connection to just about any modern 4-in-1 ESC or AIO FC.
To my disappointment though, the design has lost the bell retaining screw and returned to using a C-clip. DYS explains this change in design is because they’re using titanium alloy hollow shaft instead of stainless steel – but is drilling a hole in titanium so much harder than steel? :-) On the other hand, some people are happy with this change including Ryan Harrel, who knows his motor business.
The Storm 2207 weighs at slightly more than 35g including the wires. That’s slightly lighter than most 2207 motors on the market, for example the TMOTOR F60, probably due to the titanium motor shaft.
The magnets used are claimed to be N54SH, and they should be marginally more powerful than N52 used in other motors. To my surprise, DYS did not adopt arc magnets to minimize the air gap, and the air gaps appear to be quite wide on this motor.
Bearings are 684ZZ 4x9x4 mm, this bearing size is typically used in today’s mini quad motors, hence it should be easy to find spares. Bearing brand label says ISC which I’m not familiar with. I’ve had bad experience with this kind of shielding though, and I prefer EZO, NMB or at least FuShi.
The tall and powerful 2207 stator has 0.1 mm laminations, which redeem the other shortcomings. As a comparison, take a look at the following photos, on the left is the 0.1mm lamination and on the right is the TMOTOR F40-II 2205 stator with 0.25 mm laminations. The difference is clear and distinguishable even to naked eyes. What would be the next step? Probably a cast or moulded stator, but we’re already close to the limit with these 0.1 mm laminations.
To check the motor constant I resorted to the drill press method and the result arrived at an estimate of 2850KV, slightly above the rated value.
2850kV seems a bit on the high side for a stator of this size. As you can see in the photos, the armatures are not completely filled with copper, which typically leads to increased speed at the cost of efficiency. Such a high kV and a pretty heavy bell narrows the tuning envelope, but I’m definitely curious to find out more about such an unusual motor design in my testing.
- Solid quality from DYS
- 20cm wires
- 0.1 mm laminations
- Price, at $22 it’s one of the cheapest 2207 from the top-tier vendors
- High kV bites into the efficiency, making Storm a questionable choice for racing
- Questionable choice of bearing
- Limited at 4S, but with 2800kV you’re unlikely to go higher on 5” props
- Flat magnets
DYS Mars 2750KV
The DYS Mars 2750KV motor has a 2306 stator and comes as a direct competitor to the Emax RS2306 and TMOTOR F40PRO and F40-III, because of the same stator size.
In the package there are the same stuff except for the plastic box which is replaced with a cardboard box, and you get two nylock prop nuts and two sets of motor screws of 5mm and 7mm long.
Motor weighs at 35.8g including the wires.
The Mars motors have an open bottom design which was common in some of the older motors. This design is becoming popular once again as stators are getting heavier, manufacturers are looking for ways to minimize motor weight else where.
The Mars has a titanium alloy hollow shaft secured with a retaining c-clip just like the Storm, and it also comes with 19-20cm long wires, which is a welcomed feature for many pilots.
The Mars motor seems to be slightly lighter than the Storm, which is not surprising giving the open bottom design. I have also compared the motor bells separately and Mars bell is noticeably lighter than that of the Storm, which could result in easier tuning.
Again we see 0.1mm laminations in the stator, allowing for increased efficiency and giving the stator a glossy look. However the windings look a bit sloppy, while many other manufacturers has moved onto using single-strand windings, DYS is still using 3-strand wire on each phase and some armatures overlap with the others. In practice I believe this rarely has a noticeable effect on flight performance or motor efficiency, but a nicely wound motor certainly looks more attractive.
You can see in the photos that the stator appears to be filled with copper, though I’m not sure if it’s due to sparser windings, stator being saturated with epoxy or the relative amount of copper has actually increased. The Mars features 684ZZ Japanese EZO bearings which we know well and love, it’s definitely a good choice of bearing by DYS.
The magnets used are flat and hence the air gap could be made narrower. When testing the Mars using the drill-press method, the actual KV value turned out to be about 2850kV, which is also higher than what’s stated in the package. Overall in terms of build quality, Mars is a solid choice if you’re in the market after a high KV 2306 motor. But this motor is going to be hard on your batteries, but hey, the additional speed and fun is worth it :)
- 0.1 mm laminations
- High-quality EZO bearings
- Sustainable weight
- 20 cm wires
- Up to 6S
- Higher price compared to other 2306 motors
- Flat magnets
More update to come!
Stay tuned for the actual flight test data, I’m going to test these motors on the exact same setup and provide my final thoughts about their performance in the next update.
Drilling Titanium is not “hard” per se BUT it does require special bits to do so and they wear quickly and are costly.. that would add unneeded costs to the manu ending up touching our wallets more so. The screw is a wonderful thing and I would happily pay a dollar more a motor for it over circlips.. I hate them..
Thread taps to tap titanium are also very costly and wear extremely FAST… to the point in mass production if thes3 motors the good quality thread taps for tapping Ti would start cutting progressively worse quality threads well within 50 motors… so to keep quality up they would need to replace taps at 35 to 40 motors… depending on the Ti alloy used in the shaft… if it’s a softer alloy they may be able to get 60 to 80 motors if it’s a harder alloy then 25 to 40 motors per tap and that is for high quality taps… them buying in bulk the taps they would be somewhere in the 4 to 7 dollar range per tap for mid quality taps that will last about half of the numbers I just quoted and high high quality taps that will give roughly the numbers I stated the cost per tap at whole sell/bulk buying would be 8 to 11 dollar range depending on whom they buy from and the amount of taps… along with the bits to drill the shafts and cut the outter threading you are talking about a heavy cost just to produce the shafts..
I work with Ti everyday and have for close to 15 years (20 years in cnc.. 14 years of owning 3 still running businesses in machine work mainly CNC part production, and a Custom long range firearm and extreme air rifle company.. this is not just internet talk.. this is how I make a living) when a company goes to Ti they increase production cost hugely… now I don’t know if they do the shafts in-house (in assuming they do) if they don’t and have machine company make the shafts for them their overall coat per shaft would likely be less so long as they order large amounts of shafts at a time.. there is no way a company that doesn’t have the special commercial grade tooling but have basic tooling (my assumptions are based apon that, they are making these in-house with basic minimum tooling to work with Ti) can make a product like that cheaper then if they outsource large numbers of them… and if they are making then in-house and have a lathe to cut the shaft and the outter threading the cost if minimum and they likely could make them cheaper at that point but when you add the cost of drilling the shaft and inner threading the cost of that shaft will nearly tripple… there is MUCH more to it then a non machinist would think or understand in manu costs.. when you think about it that way it’s much easier to see why they went that route.. if they are running one lathe (very costly piece of equip so they very likely only have one, so at that point drilling the shaft hollow will take 2 to 3 times longer just to drill out the shaft all the way thru than it did to just turn it down to a starightness and outter dia within their spec and lathe cut the outter threads.. notice the shaft is only hollowed out the length of the threads and not all the way thru.. all the way thru would take far longer to do and burn up buts much much quicker… then inner threading Ti takes time… much longer than just lathe turning outter threading so that further extends time per shaft on the lathe… the cost to just drill all the way thru the shaft and thread it will be 2.5 to 3 times as long as to make it just the way it is and raise cost per shaft 2 to 3 times… at that point they would be stupid to do so… it just doesn’t make sense…