Engine hesitation when accelarating quickly

[Omegaphoenix]

I've been in a couple of sticky situations where I've had to step on the pedal all the way down. When I do that, the car starts to speed up fast like normal until it notices you want to go really fast. At that point it seems like it stalls out for about a little less than a second, which feels like a considerable amount of time when I'm trying to go fast, and then it jolts off like what I expect.

It's a completely different feeling from a regular car changing gears, and scares me almost. Anyone else ever felt this if anyone has sped up this fast?

While I'm on this topic, it seems that a lot of what I'm asking is how the continuously varying transmission works. I pretty much just know the concept, but I'd be glad to know more about how it works.

[qbee42]

I you sure you haven't caused the traction control to kick in? If traction control senses that the wheels are starting to spin, it steps in and controls the power, which can feel just like what you described.

Tom

[Marlin]

<div class='quotetop'>QUOTE(Omegaphoenix @ Apr 20 2006, 02:08 AM) [snapback]242528[/snapback]</div>

While I'm on this topic, it seems that a lot of what I'm asking is how the continuously varying transmission works. I pretty much just know the concept, but I'd be glad to know more about how it works.
[/b]

Check out this site:
http://prius.ecrostech.com/original/PriusFrames.htm

Click on the "Understanding the Prius" link in the left frame. Read the first two sections of the "The Power Split Device", and then read "What's going on as I drive?"

[richard schumacher]

You may also be feeling the half-second or so it takes for the engine to start when it happens not to be running at the moment you floor the pedal.

The better strategy is to avoid situations from which the only escape is to floor it. If not, some day you won't floor it fast enough.

[Omegaphoenix]

<div class='quotetop'>QUOTE(richard schumacher @ Apr 20 2006, 12:45 PM) [snapback]242687[/snapback]</div>

You may also be feeling the half-second or so it takes for the engine to start when it happens not to be running at the moment you floor the pedal.

The better strategy is to avoid situations from which the only escape is to floor it. If not, some day you won't floor it fast enough.
[/b]

nah it's not that, I know what that feels like and the engine starting up doesn't take as long. The pause I'm describing happens after I've already started to speed up a bit as if I was accelerating normally.

[galaxee]

from a stop you normally start out in electric mode. so it takes a second for the engine power to kick in, just as it would take a second for a normal car to realize you wanted quick acceleration and drop into a lower gear (assuming you are talking about an automatic)

i had it happen once and never put myself in a situation i'd need to do that again.

[usbseawolf2000]

<div class='quotetop'>QUOTE(Omegaphoenix @ Apr 20 2006, 07:12 PM) [snapback]242863[/snapback]</div>

nah it's not that, I know what that feels like and the engine starting up doesn't take as long. The pause I'm describing happens after I've already started to speed up a bit as if I was accelerating normally.
[/b]

Here is my hypothesis. If you were "Cruising at Moderate Speed", MG1 is spinning backward. When you floored it, for HSD to start the ICE, MG1 has to spin forward then start generating electricity. I think it is possible that in a rare situation where MG1 is spinning backward too fast and suddenly, it needs to reverse it's direction and bring ICE to 1k RPM to combust gasoline. It is also possible that the HV pack is also not in an ideal temperature for high rate discharge (too hot or cold) that could further delay the power delivery.

Can anyone confirm that with a simulator?

Dennis

[San_Carlos_Jeff]

<div class='quotetop'>QUOTE(usbseawolf2000 @ Apr 20 2006, 06:44 PM) [snapback]242875[/snapback]</div>

Here is my hypothesis. If you were "Cruising at Moderate Speed", MG1 is spinning backward. When you floored it, for HSD to start the ICE, MG1 has to spin forward then start generating electricity. I think it is possible that in a rare situation where MG1 is spinning backward too fast and suddenly, it needs to reverse it's direction and bring ICE to 1k RPM to combust gasoline. It is also possible that the HV pack is also not in an ideal temperature for high rate discharge (too hot or cold) that could further delay the power delivery.

Can anyone confirm that with a simulator?

Dennis [/b]

I've been wrong before, but I believe the only time the MG1 is going backwards is when you're driving in reverse. When it's in generating mode it's applying a load to the MG not changing it's direction.

[usbseawolf2000]

I edited my link. If you follow that, you'll see many other modes where MG1 spins backward (negative RPM).

Dennis

[ceric]

<div class='quotetop'>QUOTE(Omegaphoenix @ Apr 20 2006, 01:08 AM) [snapback]242528[/snapback]</div>

I've been in a couple of sticky situations where I've had to step on the pedal all the way down. When I do that, the car starts to speed up fast like normal until it notices you want to go really fast. At that point it seems like it stalls out for about a little less than a second, which feels like a considerable amount of time when I'm trying to go fast, and then it jolts off like what I expect.

It's a completely different feeling from a regular car changing gears, and scares me almost. Anyone else ever felt this if anyone has sped up this fast?

While I'm on this topic, it seems that a lot of what I'm asking is how the continuously varying transmission works. I pretty much just know the concept, but I'd be glad to know more about how it works.
[/b]

Ha, this just happened to me 5 minutes ago.
I was doing a right turn on red light. The on-coming vehicles are sufficiently far away, so I took it by pressing the gas pedal hard (not to the floor yet). The Prius launched forward initially (ICE is on. No doubt). After a couple seconds, the Prius hesitated for 1/2 second and then more power from ICE kicked in (high RPM sound). It is scary if you are not used to it (the hesitation, that is).

I need to tell myself that I am not driving my BMW 540 anymore. Slow down and be less agressive when driving a Prius.