Toyota Prius Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
I thought the car could go in stealth mode for some time before the ICE kicks in. I was stuck on a freeway the other day, what's new?, anyway, my ICE started once I got to 11 mph. What the? The ground was level and I was inching along in the freeway snarl. I wonder if this is the reason why I am only getting 44 mpg on average.

My location is So. Cali so cold weather is not an issue. Is it true that winterized fuel also lowers the mpg?
 

·
Registered
Joined
·
141 Posts
Assuming the ICE doesn't need to run to warm itself, the turn-on algorithm is a function of main battery state-of-charge (SOC) and the amount of current being drawn from it (i.e. how far you are pressing the pedal). Note that speed is not a factor unless you're going quite fast (42 mph in the NHW11), so that the ICE is required to spin to protect MG1.

Specifically (for the NHW11), when your SOC is 60% and above, you can pull 30A from the battery before the ICE will turn on to help. However, when your SOC is down to 45%, you only get 5A before ICE turn-on. The function is linear between these points but flat beyond them. The numbers are probably similar for the NHW20 ('04 Prius), if that's what you're driving.

So, if you were creeping along in the traffic jam for some time, your SOC was probably dropping pretty steadily. If you goosed it a little to fill in a gap in front of you, you probably drew a few more amps than the HV ECU wanted to give you (remember, saving battery life is one of its primary goals).

Note: even though the ICE comes on when so many amps are being drawn from the battery, it's not necessarily pushing the wheels. Sometimes it's only creating electricity (via MG1) to drive MG2. This takes less gas than pushing the wheels.

Douglas (2002 Silver, Wisconsin)
 

·
Registered
Joined
·
34 Posts
Petrolmeiser said:
I wonder if this is the reason why I am only getting 44 mpg on average.
I'm also in SoCal.

How many miles do you have on the car so far? I've noticed just as I got over 2K and the weather got slightly warmer I'm getting 48 overall instead of 44 ... so be patient.

I was also stuck in traffic last night going from LA to OC and noticed that there was a brief period where my battery was at its lowest level and the car just ran the engine to charge it up when I started moving at all. The trip down in heavy traffic was about 45-50 MPG and the way back (clear) was 52 MPG.
 

·
Registered
Joined
·
623 Posts
I have often seen the ICE kick in when the weather and ICE are warm and the battery shows seven bars. There are times when letting off on the pedal and then pressing gently will slip it into electric mode, and other times when it will not, even though I have satisfied all the conditions (engine has warmed up and I have exceded 40 mph or stopped for more than 10 seconds).

There are times when I can deplete the battery to 4 bars before it insists on running the ICE to recharge, and times when it insists on keeping the battery between 6 and 7 bars. I have never seen it below 4.

Someone posted somewhere that Toyota is aware of a problem with the algorithm and is working on a fix. I am inclined to believe that the present program is not optimal.

On the other hand, I only have about 1,100 miles on mine, and maybe the program changes after a break-in period.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #5
I got my '04 used. So it already had 8000+ miles already in it. So it is well broken into already. I have put about 700 miles on it already. My commute from and to work is about 10 miles, so maybe this is a factor in the equation as well. Bars on the battery is about 60-75% I don't recall how many "bars" it actually shows though.

I guess I will have to break myself into the car and learn how to eak out the most mpg out of her. Will check the tire pressure later on.
 
1 - 5 of 5 Posts
Top