2012 Prius unusual acceleration when warming up

Yes I have it too, think it is normal for the car when switching between electric and gas when cold, especially in my case when going up hill. I imagine the tech will say it is normal for the car, if he can reproduce it (if he even trys).

 

There is a change in throttle feel right around the time the engine coolant hits 185F to 191F but I've never experienced an actual acceleration. What mode are you driving when this happens? Does it occur in other modes?

 

I also feel this most of the time during a cold start within the first minute, or so.
With a light load on the engine while leaving the neighborhood (uphill), I feel a little boost of power from the engine.
It feels like an old school car when the AC compressor kicks off.

I suspect what is being felt is the 'Exhaust Gas to Coolant Heat Exchanger' has switched to open flow.
During warm up the exhaust gases are redirected through this heat exchanger.
Most likely there is an increase of exhaust back pressure and when switched back to open flow there is a noticeable little surge in engine power.

This is my best guess.
You can find diagrams of this system, somewhere...

 

If this is happening within a minute or two of startup then I wonder if it has to do with the transition from mostly EV power to engine power which generally occurs within this time frame. For the first minute or two, undr easy acceleration, RPM is around 1,280 and you are running mostly on EV power while the engine warms up.

 

I've experienced a similar thing. What I think happens is that the Prius runs in EV mode at start-up even though the ICE is running, and it tries to stay in EV for as long as possible through the warm-up state, but switches to ICE only for propulsion if you're past a certain point on the throttle for too long. It's nothing to worry about.

 

I wonder if Torque could show the 'exhaust heat exchanger' actuator signal?
That would settle it for me and what I feel.
I know Torque can display MG2 current and such.
But why is this a sudden little surge, when no other EV to ICE transitions feel like this?

 

I've taken to starting the car (and the engine) as soon as I climb in, giving it close to the first minute while I buckle up, etc. before moving off.
I have no regrets. My mileage is as good as it's ever been and the driveability for the first 1/2 mile is improved.

 

That's one way of doing it.

I hit R as soon as I get READY and I'm up the driveway and on the street in D, without touching the brakes, and on up the road before the engine starts.
I am not leaving any of the worst stink these cars make in my drive and getting it in my vent.
I think it's 12 seconds before the stink comes, right?
I like to be turning gas into motion.

But still, back on topic, what is that little surge?
Maybe it is only apparent if the engine is making some power, like on an uphill, from a cold start.

 

I honestly haven't noticed any stink (my tailpipe is aimed out of the open garage).

I like to be turning gas into motion too, but during that first minute you're depleting the HV battery faster than you're charging it (unless you're more or less coasting downhill) while I'm accumulating some extra charge to assist when I depart with a (still very cold) engine, helping with the efficiency there. It's a zero sum game (unless your car is a plug-in) so you have to burn extra gas to replenish what you drew from the battery during that first minute.

Mostly I do it because I prefer to involve the engine in the initial acceleration.
I believe the surge is a stage transition to adding engine output to the electric motor output.

 

I get in my car and start the engine and drive off. I average 35mph and the ICE is running right from the get go. I feel no acceleration at any point. The ICE only shuts down at a stop.

 

I have only experienced it when accelerating moderately on a slight upgrade probably within the first minute of the engine starting.

 

My '07 and my '13 do the same thing...

 

css,
By 'stink' I mean pollution. It is the worst on a cold start. It is there, stink or not.
You are not doing yourself, or anybody around you, a favor by idling your car in a garage.
Engines warm up quicker if they are producing power instead of idling.
Prius engines warm up faster than any other because of this Exhaust Gas to Coolant Heat Exchanger.
There is definitely more back pressure on the exhaust when it has to go through that maze during warm up.
I assume the actuator for this system is an on - off butterfly valve. That's the way it is shown in diagrams.

This 'little surge' is all speculation until someone displays the data log of a warm up with this actuator signal shown.
I'm not proficient at Torque yet. I don't know how to gather data logs.

 

Your engine isn't warming up any faster in stage 1 because it's not being loaded to power the wheels. It's loaded by the MG1 while it's charging the battery but no more so than mine is when I'm sitting still.

 

We'll need data logs to settle these questions, the surge and is a cold engine adding power to an uphill drive immediately?
Why is the tach responding to the pedal?
I'm pretty sure I'm getting more than just MG2 power.
We need a geek, like me, only with a 7" tablet running Torque and take a screen shot with lot's of easy to read analog gauges: water temp, tach, throttle position, MG1 and 2 torque or power, timing, fuel flow, Exhaust H/E valve position,,, (I made this up, hopefully it can be displayed) ,, what else?????

As I've said, if it's a electric/gas transition, why is this noticeable and all the other routine transitions are seamless?

 

My Dashcommand screen seems to show a steady 0.64 gph fuel rate in stage 1 whether I'm sitting or driving. That's what I'm basing it on. That being said, I drive in a pretty flat territory. I have not viewed this information while doing the moderate uphill acceleration that I described above.

 

Here's a screen shot of my Engine Gauges. It doesn't display anything that I need for this discussion.
I use a block heater. It was 50° outside. It takes awhile for my Garmin ecoRoute HD to boot up. I can't see water temp before the engine starts and I don't know when the water pump starts. I didn't feel the little surge this time.
I think maybe it needs to be colder. Note: intake air temp is always higher than ambient. Do others see this?

 

I can see all of my sensors before I enter Ready mode. The bluetooth adapter starts in On mode.

I believe the water pump runs continuously as soon as you're in Ready. The temperature starts its steady climb as soon as the engine fires up.
Air intake is definitely higher as soon as the engine has run for any time since the engine compartment is warmed by it.

 

I noticed that a long time ago. While ICE is cold and warming up doing fast idle, car is using EV only for slow propulsion. But, if you punch in the gas pedal and ask for more power, after a sec or so ICE kicks in and delivers the "war power". Maybe the delay is built in to filter out false gas pedal moves? After all, ICE should be spared from revving too high when cold.