Engine hesitation when accelarating quickly

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

 

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

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?"

 

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.

 

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.

 

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

 

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

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.

 

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

Dennis

 

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

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.

 

<div class='quotetop'>QUOTE(Omegaphoenix @ Apr 20 2006, 06:12 PM) [snapback]242863[/snapback]</div>

Maybe the anti-slip system? The drive has so much torque that the tires can start to slip on almost any surface. It doesn't take much oil, dust, water, etc.

Hey, is there karma, or what? Ten hours after I wrote that, I was nearly broadsided by some idiot who didn't appear to see me even after I passed in front. Flooring it saved my rear bumper.

 

<div class='quotetop'>QUOTE(ceric @ Apr 20 2006, 05:50 PM) [snapback]242908[/snapback]</div>

Yes, I've felt this too. I don't think it was traction. No lights came on the dash. The car was going on dry pavement at about 10 mph on the ICE. I was merging and floored it. The hesitation occured as rpm were building, about 1 sec after I had floored it. It only lasted about .5 sec. but felt like the ICE just stopped briefly. It is a very uncomfortable feeling. At first I thought something broke and now will talk with the service rep to understand what's going on. I don't want to wait to be in an emergency stiuation to find out it happens again.

 

If I floor it fast I notice the hiccup. Flooring a bit slowly you can accelerate faster without the hiccup.

 

I floor it all the time ! The Prius is so slow anyway...flooring it is necessary...in fact I kinda like driving a slower car at its limits more than a fast car at 10% of its capability anyway...and Im still getting great milage !

 

<div class='quotetop'>QUOTE(qbee42 @ Apr 20 2006, 07:54 AM) [snapback]242564[/snapback]</div>

This happened to me on the way home today. It was raining and the roads were wet. I was at a stop sign turning, with steady oncoming traffic, where you have no choice but to pick the best gap and go for it. I floored it and it started to go, then felt like it had stalled, so I quick tried again with the same results (I did see an orange light come on but I really couldn't take the time to see which one), and I had to merge in slowly. I think I really annoyed the oncoming driver. I've never had this happen in any other car, and it seems like it could be dangerous...

 

Cars can often only be as dangerous as the decisions we make in them. Practice that "zen-like" patience. Making an unsafe choice isn't the same as having an unsafe car. You don't have to go NOW; the traffic will die down eventually, even if it takes a few minutes.

 

<div class='quotetop'>QUOTE(Erik Tkal @ Jul 28 2006, 04:02 PM) [snapback]294031[/snapback]</div>

Rain slicked roads + torquely engine +crappy factory tires = predictable results.

I advocate taking your car to a lonely street/area and pushing the car for these types of emergency situations instead of finding out on the spot. Flooring it from stop when wet and nobody else around is a good test, do some high-speed cornering tests, etc etc..

A driver's license should include understanding and experiencing the limits of a car, and not before. An experienced driver is a safer driver.

 

Sounds exactly like traction control to me.

I kinda wish the light stayed on longer; generally by the time I'm finished dealing with the immediate situation, the warning lights have gone off. And I don't recommend pausing to look for the traction control light when in an emergency situation...

 

I only experience the pause when accelerating from a stop. The instinct is to mash the pedal to the floor when you need maximum acceleration, but you've got to force yourself to get the car moving with moderate acceleration first, then nail it after you've moved about ten or so feet.

Given that this is a fly-by-wire throttle with traction control, it's really stupid that the computer can't do this for you.

 

<div class='quotetop'>QUOTE(priusenvy @ Aug 21 2006, 02:13 AM) [snapback]306587[/snapback]</div>

Ah, you people need to drive on ice and snow. Anything other than gentle at the outset will guarantee you go nowhere until you let up a bit, Prius or non-Prius.
I would suggest people replace the OEM tires if they are in the mode of 'gotta get to speed fast' and have rain or sand/gravel on the road issues. About a year ago, my wife's cousin complained about the TC is his '04 kicking in when he tried to get out into traffic and there was sand under his front tires (I guess they could sweep the roads . It was the only thing he didn't like about the car. OK, he didn't like the fact that the passenger couldn't do Nav when the car was moving. I had just read the 'fix' here and he was a happy pup). I suggested he change the tires. He went with ComfortTreds since they don't get all that much snow where they live. All better now.