8- to 10-inch FPV motor
EMAX E3 3115
A 108–111 g motor for 8 to 10-inch quads: 31 × 15 mm stator, single-strand windings, an M5 shaft on a 19 × 19 mm M3 base, KVs from 400 (12S) to 1050 (6S), and up to 4,580 g of pull per motor on EMAX’s 25 V bench (900KV, GF1050).
- 8 to 10-inch long range and heavy builds
- 6S (900KV, 1050KV), 8S (640KV) or 12S (400KV)
- 10-inch props (8 to 9-inch for the 1050KV)
The spin is an illustration: the model turns at 1/600 of the no-load speed, and it is a generic 3115 motor drawn from EMAX’s published sizes, not its exact design. No-load speed is KV × 22.2 V, a nominal pack for this version. EMAX’s bench tables for it step by thrust rather than throttle, so they are in the bench data below, not on this readout.
- Max thrust
- 4,580 g
- GF1050 prop, 25 V
- Weight
- 108 g
- without leads; 400KV 109 g, 640KV 111 g, 1050KV 110 g
- Peak current
- 73.4 A
- full throttle
- Max power
- 1,835 W
- full throttle
from $76.83a motor at EMAX
A set of four: $307.32
Price seen Oct 19, 2026. Plain links: we earn nothing from them.
What you get for $76.83
4.58 kg on 6S
On EMAX’s 25 V bench the 900KV pulled 4,580 g at full throttle on a GF1050 three-blade, drawing 73.4 A (1,835 W).
Source: EMAX spec sheet and bench tables
4.76 kg on 8S
At 32 V the 640KV pulled 4,760 g on an HQ 1050 three-blade, drawing 58.2 A; at 48 V the 400KV pulled 4,630 g at 35.4 A.
Source: EMAX spec sheet and bench tables
7.31 g/W at 512 g
Making 512 g on the HQ 1050 at 48 V, the 400KV ran at 7.31 g/W, drawing 1.46 A.
Source: EMAX spec sheet and bench tables
Up to 12S
Four windings cover 4S–6S (900KV, 1050KV), 6S–8S (640KV) and 10S–12S (400KV) on one 3115 frame.
Source: EMAX spec sheet and bench tables, EMAX USA product page
What to pair it with
Our reading of EMAX’s numbers, so your build matches what the motor was tested with.
- ESC
- EMAX rates the peak current at 36 A (400KV on 12S), 59 A (640KV on 8S), 77 A (900KV on 6S) and 88 A (1050KV on 6S); its 900KV bench tests reached 76.4 A on an HQ 1050. The ESC has to match both the peak current and the cell count of the KV chosen. (EMAX spec sheet and bench tables)
- Props
- 10-inch for the 400KV, 640KV and 900KV, 8 to 9-inch for the 1050KV. EMAX tested on GF1050 and HQ 1050 props, and the 900KV also on an HQ 9050. (EMAX spec sheet and bench tables, EMAX USA product page)
- Battery
- 4S–6S for the 900KV and 1050KV, 6S–8S for the 640KV and 10S–12S for the 400KV. (EMAX spec sheet and bench tables)
- Frame
- Four M3 holes on a 19 mm circle (19 × 19 mm); five M3×10 screws come in the box. (EMAX spec sheet and bench tables)
Where to buy
- EMAX USAthe maker’s US store; 400KV, 640KV, 900KV and 1050KV at one price (all four were listed as sold out)$49.89seen Oct 19, 2026Visit
- EMAXthe maker’s global store; 400KV, 500KV, 640KV, 900KV and 1050KV$76.83seen Oct 19, 2026Visit
Plain links, not affiliate links. Prices change; the store’s page has the current one.
Full specs
| Spec | Value | Source |
|---|---|---|
| KV | 900 rpm/V (also 400KV, 500KV, 640KV and 1050KV) | EMAX USA product page, EMAX product page |
| Stator | 31 × 15 mm (3115) | EMAX USA product page, EMAX spec sheet and bench tables |
| Configuration | 12N14P (12 stator slots, 14 magnet poles) | EMAX spec sheet and bench tables |
| Battery | 4S–6S LiPo (900KV, 1050KV); 6S–8S (640KV); 10S–12S (400KV) | EMAX spec sheet and bench tables |
| Weight | 108 g (without leads; 400KV 109 g, 640KV 111 g, 1050KV 110 g) | EMAX spec sheet and bench tables |
| Dimensions | φ38.8 × 48.6 mm (with shaft) | EMAX spec sheet and bench tables |
| Shaft | Steel, M5 thread (CW), stands 17.5 mm above the bell; 5 mm through the bearings | EMAX spec sheet and bench tables |
| Mounting | 4 × M3 holes on a 19 mm circle (19 × 19 mm) | EMAX spec sheet and bench tables |
| Bell | 7075 aluminium, anodised | EMAX spec sheet and bench tables |
| Magnets | Arc magnets | EMAX USA product page |
| Bearings | G1-grade precision rolling bearings | EMAX spec sheet and bench tables, EMAX USA product page |
| Winding | Single-strand copper | EMAX spec sheet and bench tables, EMAX USA product page |
| Internal resistance | 42 mΩ (400KV 141 mΩ, 640KV 64 mΩ, 1050KV 35 mΩ) | EMAX spec sheet and bench tables |
| Idle current | 1.7 A (at 10 V; 400KV 0.6 A, 640KV 1.2 A, 1050KV 2.1 A) | EMAX spec sheet and bench tables |
| Peak current | 77 A (on 6S; 400KV 36 A on 12S, 640KV 59 A on 8S, 1050KV 88 A on 6S) | EMAX spec sheet and bench tables |
| Max power | 1,925 W (on 6S; 400KV 1728 W on 12S, 640KV 1888 W on 8S, 1050KV 2200 W on 6S) | EMAX spec sheet and bench tables |
| Leads | 18 AWG silicone wire, 270 mm | EMAX spec sheet and bench tables |
| In the box | 5 × M3×10 screws; an aluminium M5 nylock nut; a washer and screw for the shaft | EMAX spec sheet and bench tables, EMAX USA product page |
Bench data
Redrawn from EMAX’s test reports. Thrust is static pull on a bench, more than you get in flight. Power is volts × amps; efficiency is thrust divided by power.
400KV on 10S–12S, 48 V2 props
| Prop | Step | Current (A) | Thrust (g) | Power (W) | Efficiency (g/W) |
|---|---|---|---|---|---|
| HQ 1050 (3-blade) | 1.46 | 512 | 70.08 | 7.31 | |
| 3.2 | 915 | 153.6 | 5.96 | ||
| 5.85 | 1,410 | 280.8 | 5.02 | ||
| 9.49 | 1,952 | 455.52 | 4.29 | ||
| 13.9 | 2,564 | 667.2 | 3.84 | ||
| 19.5 | 3,182 | 936 | 3.4 | ||
| 26.2 | 3,785 | 1257.6 | 3.01 | ||
| Max | 35.4 | 4,630 | 1699.2 | 2.72 | |
| GF1050 (3-blade) | 1.39 | 436 | 66.72 | 6.53 | |
| 2.86 | 820 | 137.28 | 5.97 | ||
| 5.26 | 1,298 | 252.48 | 5.14 | ||
| 8.53 | 1,846 | 409.44 | 4.51 | ||
| 12.7 | 2,440 | 609.6 | 4 | ||
| 17.9 | 3,052 | 859.2 | 3.55 | ||
| 24.3 | 3,720 | 1166.4 | 3.19 | ||
| Max | 32.6 | 4,470 | 1564.8 | 2.86 |
Source: EMAX spec sheet and bench tables
640KV on 6S–8S, 32 V2 props
| Prop | Step | Current (A) | Thrust (g) | Power (W) | Efficiency (g/W) |
|---|---|---|---|---|---|
| HQ 1050 (3-blade) | 2.4 | 510 | 76.8 | 6.64 | |
| 5.38 | 964 | 172.16 | 5.6 | ||
| 10.1 | 1,510 | 323.2 | 4.67 | ||
| 16.5 | 2,132 | 528 | 4.04 | ||
| 25.1 | 2,810 | 803.2 | 3.5 | ||
| 35.6 | 3,508 | 1139.2 | 3.08 | ||
| 48.5 | 4,215 | 1552 | 2.72 | ||
| Max | 58.2 | 4,760 | 1862.4 | 2.56 | |
| GF1050 (3-blade) | 2.25 | 472 | 72 | 6.56 | |
| 4.85 | 910 | 155.2 | 5.86 | ||
| 9.06 | 1,445 | 289.92 | 4.98 | ||
| 15.1 | 2,060 | 483.2 | 4.26 | ||
| 23.2 | 2,729 | 742.4 | 3.68 | ||
| 33.1 | 3,435 | 1059.2 | 3.24 | ||
| 45.6 | 4,152 | 1459.2 | 2.85 | ||
| Max | 54.3 | 4,640 | 1737.6 | 2.67 |
Source: EMAX spec sheet and bench tables
900KV on 4S–6S, 25 V3 props
| Prop | Step | Current (A) | Thrust (g) | Power (W) | Efficiency (g/W) |
|---|---|---|---|---|---|
| GF1050 (3-blade) | 3.6 | 550 | 90 | 6.11 | |
| 7.72 | 1,035 | 193 | 5.36 | ||
| 13.5 | 1,576 | 337.5 | 4.67 | ||
| 21.5 | 2,153 | 537.5 | 4.01 | ||
| 31.1 | 2,718 | 777.5 | 3.5 | ||
| 42.4 | 3,274 | 1060 | 3.09 | ||
| 55.6 | 3,827 | 1390 | 2.75 | ||
| Max | 73.4 | 4,580 | 1835 | 2.5 | |
| HQ 1050 (3-blade) | 4.1 | 628 | 102.5 | 6.13 | |
| 8.53 | 1,087 | 213.25 | 5.1 | ||
| 14.8 | 1,596 | 370 | 4.31 | ||
| 23.4 | 2,170 | 585 | 3.71 | ||
| 33.3 | 2,774 | 832.5 | 3.33 | ||
| 45.6 | 3,347 | 1140 | 2.94 | ||
| 59.7 | 3,928 | 1492.5 | 2.63 | ||
| Max | 76.4 | 4,540 | 1910 | 2.38 | |
| HQ 9050 (3-blade) | 3.43 | 456 | 85.75 | 5.32 | |
| 6.88 | 820 | 172 | 4.77 | ||
| 12.5 | 1,296 | 312.5 | 4.15 | ||
| 20.4 | 1,837 | 510 | 3.6 | ||
| 30.5 | 2,370 | 762.5 | 3.11 | ||
| 43.2 | 3,028 | 1080 | 2.8 | ||
| 58.2 | 3,567 | 1455 | 2.45 | ||
| Max | 68.3 | 3,980 | 1707.5 | 2.33 |
Source: EMAX spec sheet and bench tables
Inside the motor
A brushless outrunner: the coils stand still in the middle and the magnets spin around them. From the top down:
- Shaft. Steel, M5 thread (CW), stands 17.5 mm above the bell; 5 mm through the bearings. (EMAX spec sheet and bench tables)
- Bell. 7075 aluminium, anodised. (EMAX spec sheet and bench tables)
- Magnets. Arc magnets. (EMAX USA product page)
- Stator. The coils are wound on a stack of thin steel laminations: 31 × 15 mm (3115). (EMAX USA product page, EMAX spec sheet and bench tables)
- Winding. Single-strand copper. (EMAX spec sheet and bench tables, EMAX USA product page)
- Bearings. G1-grade precision rolling bearings. (EMAX spec sheet and bench tables, EMAX USA product page)
- Base. 4 × M3 holes on a 19 mm circle (19 × 19 mm). (EMAX spec sheet and bench tables)
How fast it spins
KV is the motor’s no-load speed per volt. With nothing on the shaft, the 900KV version reaches about these speeds; a prop loads the motor and brings it down, typically to around 70–75% of these figures at full throttle.
| Battery | Volts | No-load rpm (KV × V) | Electrical frequency | ESC steps per second |
|---|---|---|---|---|
| 4S nominal | 14.8 | 13,320 | 1,554 Hz | 9,324 |
| 4S full | 16.8 | 15,120 | 1,764 Hz | 10,584 |
| 6S nominal | 22.2 | 19,980 | 2,331 Hz | 13,986 |
| 6S full | 25.2 | 22,680 | 2,646 Hz | 15,876 |
A 14-pole rotor has 7 pole pairs, so every turn of the shaft is 7 electrical cycles, and a six-step ESC switches the phases 42 times per turn.
About the 3D model
A generic outrunner drawn from EMAX’s published sizes: the 31 × 15 mm stator, 38.8 mm bell, 31.1 mm height, 5 mm shaft, 19 mm mounting circle and 12 teeth and 14 magnets. Anything EMAX doesn’t publish is typical for a motor this size, and the bell’s spoked top, the base and the inside are a generic design, not this motor’s. The colours are read off the maker’s product photos. There are no logos or markings: it is our drawing, not the maker’s.
Sources
- EMAX USA: EMAX E3 3115 Brushless Motor (product page, with its spec and per-KV electrical tables, each KV’s best full-throttle bench result and EMAX’s E3 infographics). Retrieved Oct 19, 2026.
- EMAX: E3 3115 400KV 640KV 900KV 1050KV 500KV brushless motor (product page on EMAX’s global store). Retrieved Oct 19, 2026.
- EMAX: E3-3115 motor specifications V1.0 (image on EMAX’s global product page): dimension drawing, spec table for the 400KV, 640KV, 900KV and 1050KV, feature list and bench tables (400KV at 48 V, 640KV at 32 V, 900KV at 25 V; none for the 1050KV), in steps of rising thrust ending at “Max”, full throttle. EMAX’s rpm column is left out because it has no figure at full throttle.. Retrieved Oct 19, 2026.
