Rpm

Are you getting a Prius v wagon? Your profile says 2009 Prius.

Correct. Prius has no tach. Besides installing a tach, you can get a tach via a device like http://www.scangauge.com/products/scangaugeii/ or the Torque app on Android (and you'd need a Bluetooth to OBD II dongle).

 

The RPM at 50 mph will vary over a wide range depending conditions.

 

There are two Motors/Generators, (MG1 and MG2) usually one acts as one while the other act as the other, depending on the car's needs, and a Internal Combustion Engine (ICE)

MG2 is tied linearly to the wheels At any given speed, the wheels are at the same speed. (So obviously MG2 is at 0 RPM at rest and at it's redline at 190 kPH. No Clutch, no Transmission, no Variation. If you are in Reverse, MG2 is just spinning 'backwards'.

Up to about 72 kPH, the ICE may not be spinning at all. Above 72, the ICE rotates all the time, even if no fuel is being injected. Idle is about 960 RPM, redline is about 5200 RPM, You have to be going over 70 kPH to get to redline. The computers will choose an RPM that makes as much torque as the conditions need. (in 6 RPM increments) (With no tailwind, at a perfectly flat 98 km, my Gen 2 Prius is often at 1800 RPM. Very few roads are perfectly flat, very few days is there no wind)

MG1 can go from -10,000 RPMs to 10,000 RPMs, under the control of the computers. (The 'gas pedal' is just a hint to the computers of what you expect, it is not connected to fuel injection)

I use a ScanGaugeII to watch RPMs and I live in a VERY Flat part of the US (20 meters gain in 246 km) With any elevation change, wind, weather the answer to what RPMs at X speed is 'whatever the computers choose'.

This is a simulator of the Gen 1 Prius, while the numbers are different, the ideas are not.

http://eahart.com/prius/psd/

 

ICE = Internal Combustion Engine = petrol engine = gas engine

MG1 = Motor Generator 1 = electric motor = electric generator

MG2 = Motor Generator 2 = electric motor = electric generator

Note 1: MG2 is used to generate electricity from "regenerative braking"
Note 2: MG1 is used to start the ICE when needed if the vehicle is not moving.
Note 3: Depending on conditions, either MG1 or MG2 can be used to generate additional electricity as needed.
Note 4: MG2 is used to move the vehicle when the ICE is not running, and used to move the vehicle in reverse.

 

So, which do you have? A 3rd gen (2010+), 2nd gen (covers models years 04-09 in the US and most countries), or a v wagon (2012+ only)?

If you don't have a Prius v (might be known as the Prius+ or alpha in your area) wagon (hope you can view this page Toyota Prius Family), then you've posted in the wrong area.

 

lol. The proper group is gen III 2010+, which is below this group.

Engine Rpm in the prius are quite independant of speed. What the car does is it takes your input from the gas pedal, then determines how much power it needs. It then adjust the engine speed to produce this power in the most efficient way, and uses mg1 and mg2 to set the transmission to that engine speed. In the typical scenario, mg1 acts like a generator, putting a load on the engine and generating electricity which it sends to mg2 to provide for more torque at the wheels. The battery acts as a buffer, providing extra energy to mg2 if higher acceleration is needed, or recharging from mg1. At higher speeds and light loads motor duty might be reversed and mg2 might generate electricity reducing torque, and sending it to mg1 to push the wheels, think of this as an overdrive.

 

Welcome! The first thing you have to understand, besides all the different motors, is the Prius has a CVT (Constant Velocity Transmission) transmission, so the engine(s) out put is somewhat regulated by the CVT. But to answer your question, I do have a ScanGuage attached with an RPM out put. The RPM's range from 920 (downhill) to 3,500 (uphill) of course there are lots of variables, but it is amazing to watch. The RPM's will go to 0, when you are going downhill and at slow speeds (less than 40 mph) as you are traveling by the electric motor. Hope that helps, at least a little.

 

CVT stands for Continuously Variable Transmission, not Constant Velocity Transmission (which would be a whole different thing, and not very useful in an automobile).

The continuously variable part about it means it doesn't shift in steps, but can run at any engine speed for any vehicle speed (within limits). Engine RPM is not directly coupled to the speed of the wheels.

As a technical point, the CVT in the Prius is not really a CVT in the mechanical sense. Mechanically it is a fixed set of planetary gears, but because of the electrical path provided by the two motor-generators (MGs) the transmission is equivalent to a CVT. This electrical path is often called an eCVT for electrical or electronic CVT.

Tom

 

Many Thanks. That is by far the best description / demo I have ever seen on how the Prius drive train functions!!!

In terms of moving parts, the only simpler hybrid automotive design would be direct electric drive.

Keith

 

Others have explained why it is so highly variable.

I'd add that at 60 mph (97 km/h) in flat windless conditions, it will probably settle in to the range of 1400 - 1500 RPM. But the slightest breeze, slope, or speed change will move it out of that range. In changing highway traffic, even a small downhill can drop it to its 992, the slowest steady RPM available without stopping. A small uphill in gradually accelerating traffic can easily push it up to 2500.