As I wrote in my blogpost Rear wheel drive EV conversion motor options back in 2022, in my view the most beautiful motor of my shortlist was the Engiro 260W. Especially after ruling out the possibility of using a Tesla Small Drive Unit. That would have been the best power to euro ratio.
Due to its high torque it is one of the few motors that is actually available which is suitable to be coupled to a driveshaft of a car with solid rear axle and still have an impressive performance.
In this blogpost:
- Engiro 260W specs
- Power at the wheels
- Too much power to handle?
- Best rear axle ratio for electric motor?
- Leadrive inverter
Engiro 260W specs
The biggest downside of the Engiro motor was the costs. I received some unexpected support due to the fact that my car had caught fire and was offered an Engiro motor for an amount I could afford. Thanks!!!
The Engiro 260W series are permanent magnet motors with exceptional high torque and temperature robustness. I ended up using the 260W 13202 SFR 400V Traction set (datasheet @ Engiro). Here is why:
| Continuous / Min. | Peak (60 sec) / Max. | |
|---|---|---|
| Torque (Nm) | 335 | 670 |
| Power (kW) | 149 | 227 |
| Battery current (A) | 416 | 665 |
| Battery voltage (V) | 190 | 450 |
| Speed (rpm) | – | 5000 |
That peak torque of 670 Nm is / should be sufficient to drop the gearbox and drive the prop shaft directly and only rely on the reduction in the rear axle.
The graphs from the datasheet are really impressive.
Simulated Motor Characteristics. Solid lines = continuous and dashed lines = maximum (source Engiro).
Only downside of the motor is that at 106 kg it still is relatively heavy and not the smallest either (diameter 32 cm and length 40 cm).
Power at the wheels
To get a feeling about if this 670 Nm will indeed be sufficient I did some calculations. I used the various ratio’s and torque curves to calculate and visualize the force at the wheel / street. There are five lines in that graph:
- Combustion engine (ICE) shifting around 3000 rpm
- The Engiro 260W motor (orange line)
- The Siemens motor that used to be in there in 3rd gear
- The Siemens motor that used to be in there in 2rd gear
- The Siemens motor that used to be in there in 4th gear
Rear axle reduction used in this calculation is 1:3.99 and the gear ratios are based on the M400. So the setup I used to have.
From that graph you can see the Engiro 260W will be amazing even without gearbox. Due to it’s max rpm of 5000 the top speed will be 150 km/h.
It also explains why you need a gearbox or other reduction when using a ‘normal’ motor like the Siemens (300 Nm) or a Nissan Leaf motor (340 Nm) for a car with solid rear axle. The graph shows that the feel of the car with Siemens or Leaf motor without using reduction (so 4th gear / prise direct) is similar to driving away in second gear while keeping the B20 combustion engine idle high at 2000 rpm. Too sluggish if you ask me.
With the 3,99 rear axle the motor RPM’s at 100 km/h are around 3350 and at 120 km/h this is 4000 rpm. For comparison, a Volvo Amazon with overdrive has around 2800 rpm’s at 100 km/h. Since the sound level / dB of an electric motor is significantly lower this a bit comparing apples with pears.
Too much power to handle?
Very likely the 670 Nm of the Engiro would be too much Nm for the Volvo Amazon rear axle to handle. Plus the rpm’s at cruise speeds are a tad too high. So along with the upgrade to the Engiro motor I decided to upgrade to a Volvo 240 rear axle. Other benefits are: slightly bigger track width (Amazon is 1314 mm and 240 is 1360 mm), rear disc brakes and wider choice of rear axle reduction ratios.
Available Volvo 240 rear axle ratios: 3.31 / 3.54 / 3,73 / 3.91 / 4.10 / 4.30
These are all Dana axles. First model 1030, then two variants of the 1031 and finally the 1041. The 1041 is the same as the late 1031 but is equipped with an Eaton ALD limited slip differential. This ALD limited slip differential locks either 0% or 100% and only at speeds up to 40 km/h. Ideal when driving away on slippery surfaces.
The 1041 is therefore perfect, but is mainly found in the more luxurious Volvo 940 series such as the 960 or 940 Sports Edition from the early nineties. Very sporadically you will find this in the very last 240s made in 1993 and 1994. This was available as a special option, especially for Switzerland. Since the 940 rear axle is too wide for a Volvo Amazon that means it is either a matter of finding a needle in a haystack or transferring an ALD to a late 1031 axle from a 240. That would be a nice future upgrade so I needed a later type 1031 axle. Then the next question is: what is the best ratio for my car?
Best rear axle ratio for electric motor?
The 3.91 is very close to the 3.99 that currently is in the car. However then the motor rpm at 120 km/h still is 3900 N. A 3.31 axle would result the lowest rpm (3300 at 120 km/h) but also the lowest N’s at the wheels. Therefore I decided to go for the 3.73.
| Speed (km/h) | RPM |
|---|---|
| 50 | 1500 |
| 80 | 2500 |
| 100 | 3100 |
| 120 | 3750 |
And even with the 3.73 Volvo 240 rear axle there still is plenty of ‘force at the wheels’: 7880 N until 105 km/h. More than the 5350 N peak at 25 km/h in first gear with ICE and the 4800 N of the Siemens in 3rd gear (the ratio we used most).
Top speed will increase to 160 km/h as a result but probably will never test this. Continuous top speed is 135 km/h.
Leadrive inverter
Every Engiro motor is tuned to match the inverter to achieve the optimal configuration and output. The beauty about this set is that the 260W is a 6-phase motor and thus is paired with a dual output inverter. This is a Leadrive / Engiro 400 V 2×3-phase motor controller capable for 480 A (rms continuous) and 900 A (rms peak) with two 400V auxiliary contacts.
The weight of the inverter is 15,5 kg.
Whats next?
Next blogpost will be about installing the Engiro motor into the car. Those who follow me on Instagram @oudevolvo or Facebook (oldvolvo page) already have seem some updates.
