the "jolt"

[fred]

as all us prii owners know every once in a while we get the "jolt" when the ice kicks out or in or whateveer. once you are used to it its no big deal. i was wondering, however what the heck that jolt is doing to the motor mounts and is it going to break them prematurely. i dont know about everyone else but sometimes that jolt is almost a kck and will get your passengers attention!

[Ray Moore]

I have 29,000 miles on my car and have never experienced a jolt. I have never had the sensation of even half of what an automatic transmission shift feels like. I think you should have this fixed. It is rare that a passenger can tell me when my engine is on even if I ask them to.

[8AA]

The only thing I've experienced close to what you're describing is when I'm in EV mode and get up to 42 MPH. At that speed the ICE has to spin (but not necessarily run) to keep MG1 under 10K RPM. I wouldn't describe the sensation as a jolt, but for a car with no shift points, it does kind of feel like an automatic transmission shifting gears.

If you're describing something else, I would agree that a dealer visit is in order.

[CHART]

Uhhhhhhh, I'm not ready to send Fred to his dealer, but I'm not ready to say he is imagining things either I've had my 04 for 16 months now and while I do not think I have any major shimmy problems, I would say that once a week or so, particularly when I am slowing to a stop or have just recently started the car, I get a noticable shimmy with my shake. Noticable to me anyway. But I don't think anything is wrong.

[efusco]

I, not infrequently, experience what I'd call a shudder as the ICE starts or stops. It's never bad enough that I'd have any concern about engine mounts or anything like that.

[rflagg]

Yeah, there's definately a shudder, or slight jolt, or whatever term you want to use. I suggest Fred try going back into a "regular" car, perhaps a mid 90s American vehicle with 100k+ on it, and turn it over, and compare that to the 'jolt' he mentions. I myself tend to quickly forget how rough all other cars are on their engines to the point of overly worrying about this car. You have to be reminded sometimes that it's all relative.

-m.

[narf]

I've noticed a few minor jolts and shudders, still less than your typical automatic transmission. Wher it is most noticable is as I crest a hill at cruising speed and the car transitions from power to coast/regen.
I think the sudden shocl loads here are WAY less than typical loads on a manual transmition car. Sudden throttle transitions with a manual tranny are much harsher on the mounts and drivetrain than anything the Prius system hands out. I'm not worried.

[DaveinOlyWA]

i always equated that shudder to "dieseling" type of feeling and it seems to only happen when the car is cold. i have frequently felt the car was undecided as to whether it wanted to shut down or keep idling. some times it will idle roughly for a revolution and shut down and other times it will idle for 3-4 turns or more before shutting down. but i dont feel that its a problem.

i wonder if it has anything to do with the gas around here? (we have E10 here)

[Frank Hudon]

the normal idle speed on the Prius ICE is about 1020 RPM and when the ICE goes to shut down it drops down to about 925 RPM, this is when the compression ratio is dropped to it lowest value and then as the ICE stops MG1 reverses rotation if it car is moving. If the car is stopped the ICE and MG1 both stop rotating and that is when the shut down becomes less noticeable as the kinetic energy is almost balanced, but at low speed I think the "shudder" is MG1 reversing rotation. That is a fair chunk of metal to stop rotating one direction and rotate the opposite direction. There is a dampener on the drive plate on the ICE to help alleviate the pulses caused by the ICE stopping getting transmitted to the planet carrier in the PSD.

[Ray Moore]

Frank-
I believe you are right and way to go figuring it out. Brilliant.