Shuddering feeling around 8 mph when accelerating

From what I understand, and I am sure one of the resident experts can chime in with the details, but when you first take off from a complete stop, you are using MG2 to accelerate up to about 10 mph (depending on how hard you are accelerating). Then the ICE kicks in and assists with the further acceleration.

What you may be feeling is the ICE starting around 8 mph. I would not consider mine to be shuddering, though I can feel the ICE when it starts and stops.

 

And if the engine is "cool" it tends to shudder more when starting up. By the time the OP gets to the dealer the ICE is warm and shudders less when starting.

 

It's the ICE or gas engine starting. it's normal. Also our cars have no gears so they never shift. MG2 is the main electric motor that drives the car.

 

MG2 is Motor-Generator 2. It is the big electric motor used to move the Prius and do regenerative braking.

MG1 is Motor-Generator 1. It is the small electric motor used to start the internal combustion engine (ICE) and act as a generator powered by the ICE.

As pointed out above, the shudder is the ICE starting. Also pointed out above, the Prius never shifts gears. The gearing is fixed, and always engaged.

Tom

 

What did the dealer tell you?

 

"It's not shuddering. Stop drinking so much coffee."

Tom

 

I spent dozens of hours learning about the prius. It does seem like the dealers don't know much at all.

You will notice the harder you press down on the pedal the harder the ICE kicks in. I still noitce my car doing this. In a perfect world we wouldn't be able to notice it.

 

That is the standard answer for any complaint. :madgrin:

 

Amen to that! The dealers should require their service personal to read the forum on a regular basis.

 

Not sure if I have this exactly right, but I believe I read that the Prius starts its engine by spinning it up (using the smaller electric motor MG1) and then adding gas/ignition to the chambers one at a time until all 4 are "lit". (unlike traditional engines which spin and add gas ignition all at once to all chambers)

With a warm engine, this is almost transparent - and as spiderman said, with a cold engine this is rougher. It is also more noticable at lower speeds, when there's less wind noise and the engine isn't spinning as fast.

(and if you're really into the technical detail, starting the ICE "pushes" against the outer ring gear, which is what sends power to the wheels, so you're likely to feel that as a slight variation in acceleration until the ICE is running and the computer smoothes things out)

If it still shudders when warm, then you might have a problem - but a little roughness when cold is pretty normal.

 

My Prius has a similar shudder when I accelerate moderately or rapidly. It does not shudder when I am gentle on the pedal.

 

I noticed it too but as others have said I figured out it was the normally unnoticable ICE starting up. This is usually only noticable when the car is cold. Check out the Insight posts...in the Honda every ICE start up is plainly noticable.