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Discussion Starter · #1 ·
The motor is hot, the battery is at a good charge, green or just below. I have been driving for perhaps 30 minutes, perhaps 4 hours, makes no difference.

I come to a junction and stop and have to wait for the lights to change. foot is hard on the break. The motor keeps running and running and running..... If I select EV, then the motor stops and remains off even after deselecting EV.

Whats going on?
 

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I have no idea, happens to me too. Likewise I have places where I can't get into stealth/glide mode for no good reason.

I just accept that it's one of those things that there must be some programming algorhythm that's telling the ECU to keep the ICE on due to some variable.

It's those times I'm glad I have my EV button so I can force the ICE off when I know it isn't needed.
 

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Blackhatch said:
How much is the EV switch and where does it install....?

Consider your thread hijacked....just kidding.
there are a couple of options out there, in addition to figuring it out yourself. Coastal Tech's uses the cruise control thingy on the steering wheel. Yes, you can still use the cruise control. The OEM part that you can order from out of the US goes in the rectangular blank on the dash to the left of the steering wheel. Check ebay for prices of the OEM. Usually one or more there. Check Coastal Tech's site (sorry, don't have the link) for the price of the CT mod.
 

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How are you determining this is happening? The MFD "indication" may be the culprit for all these observations.
Borrow someones "scan guage" and check engine RPM. You would be absolutely amazed at the times the engine is running and when it is not. That was why one of Coastal Daves first modifications for his classic Prius was an "engine run" light. Too bad he has gotten bored with the Prius and didn't follow through with the one he designed for the 04.
 

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I had the same thing happen and discovered that I had my defroster on and that was requiring my AC compressor to run to dehumidify the air blowing on the windshield.
 

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hyperion said:
How are you determining this is happening? The MFD "indication" may be the culprit for all these observations.
Borrow someones "scan guage" and check engine RPM. You would be absolutely amazed at the times the engine is running and when it is not. That was why one of Coastal Daves first modifications for his classic Prius was an "engine run" light. Too bad he has gotten bored with the Prius and didn't follow through with the one he designed for the 04.
It's not hard to determine, and I have used a scan-guage like indicator that shows RPM and it confirmed my 'seat of the pants' diagnosis.

I'm suprised you're questioning it actually. It's not hard to know when it goes on. You pull up to a light and all is quiet...the ICE is obviously off. You pull up to a light and feel the gentle vibration of the ICE then feel it shut off a while later. It's not difficult to determine.

Regarding the CAT heating...while this is certainly one of the parameters that determines whether the ICE shuts off or not I can tell you that it gets up to temperture VERY quickly and stays there...cool down takes quite a while (again, using my Dynascan to watch CAT temps). Likewise ICE temp (based upon coolant temp observations). The ICE does cool down a little more quickly than the CAT when it's off, but still stays above the 145 degree threshold for ICE shut off for a very long time.

Thus, I suspect there's something else going on, as Victor does, that no one's figured out just yet.
 

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No Evan, I have to disagre with you about any assumed knowledge that you always know when the ICE is running. After 18 months of driving I too believed I knew when the engine was running but I've been completely surprised during the past two months of driving continuously with a tach. The only time I could win a bet on predicting whether engine was running or not is at a complete stop. Other than that with just little speed and road noise I've discovered just how often the MFD is wrongly depicting "engine run" An engine run light like the one Coastal Dave came up with for the classic with an indication on the MFD would be a complete revelation. It would also destroy a lot of theory and assumption.
 

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If you have the leeway to do so, try waiting a full TEN SECONDS
while standing still in "Drive", and see if the ICE
finally turns off. Usually that lag is 5 seconds, really.
If that happens, you've entered stage 4 operation.
.
Using the heater or the A/C will tend to keep the ICE on
more than one might expect. Having hacked together something to watch engine
coolant temp, it's really astounding how fast even low fan cabin
heat can suck heat out of the block. Sitting at a
long light can whack you back into stage 3 again
just because the ECT has sufficiently dropped.
.
_H*
 

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hyperion said:
No Evan, I have to disagre with you about any assumed knowledge that you always know when the ICE is running. After 18 months of driving I too believed I knew when the engine was running but I've been completely surprised during the past two months of driving continuously with a tach. The only time I could win a bet on predicting whether engine was running or not is at a complete stop. Other than that with just little speed and road noise I've discovered just how often the MFD is wrongly depicting "engine run" An engine run light like the one Coastal Dave came up with for the classic with an indication on the MFD would be a complete revelation. It would also destroy a lot of theory and assumption.
I didn't say I assumed knowledge that I "always" knew when the ICE was running. Indeed there are times where it is very difficult to tell.

But I can tell you that I can tell 100% of the time when I'm at a full stop (which is what the original question was about btw). I can also tell about 95% of the time (confirmed with my dynoscan) when I go into a sub-41mph 'glide'...I can feel the slight shudder of the ice turning off after I let my foot off the accelerator and that is my cue to slightly depress the pedal to get rid of the green regen arrows.

I never even suggested that what the MFD showed was a factor in my decision of whether ICE is on or off. But at sub-41mph speeds I can tell with great consistance whether the ice is on or not...maybe 75% of the time.

Until a month ago it was pure guess work...but I've used my dynoscan to support and confirm my seat-of-the-pants knowledge and found it to be pretty dang good.

Back to the original question. I suspect it probably is some factor sending the system back into S3 most of the time, but it isn't always the cool ICE or cool CAT...I've experienced this lack of shut of while looking at a 176 degree coolant temp with no AC or heat or defrost. There's some "X-Factor" involved as well...maybe something to do with the HV battery temp or charge or something...I just don't know exactly what.
 

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Discussion Starter · #13 ·
hyperion said:
The only time I could win a bet on predicting whether engine was running or not is at a complete stop.
And that is exactly when Im talking about. I know the engine is running as I can hear it. At traffic lights here a 2 - 4 minute wait is not uncommon and on my way to work, I have 5 sets to cross, and I usually have to stop at 2 or 3 of them. I let the motor run yesterday at the lights. It ran for the full light duration, about 2 1/ minutes at the first and 90 seconds at the second.

As for the EV button, mine came as standard :)
 

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Under those circumstances Victor I would say that the ECU felt that your battery needed charging. The MFD info on the battery indication is probably no better than the indication of "engine run." and is more of a general advisory than an exact instrument. The car is probably just being itself.
I'm sure a Prius rep would not be able to give you an exact answer to "Why?"
 

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Victor, how cold is it outside? Are you using cabin heat? As was mentioned, that will often keep ICE running longer than expected.

There is a big difference between engine SPIN (detected by RPM) versus engine RUN (where fuel is used). Even with engine run, fuel usage can be slight, perhaps just enough to be sure ICE turns in the correct direction.

When I devise an ICE condition monitor, I will be monitoring RPM, fuel, and spark.
 

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Discussion Starter · #17 ·
DanMan32 said:
Victor, how cold is it outside? Are you using cabin heat? As was mentioned, that will often keep ICE running longer than expected.

There is a big difference between engine SPIN (detected by RPM) versus engine RUN (where fuel is used). Even with engine run, fuel usage can be slight, perhaps just enough to be sure ICE turns in the correct direction.

When I devise an ICE condition monitor, I will be monitoring RPM, fuel, and spark.
Currently about 20C and the heater is off. Someone suggested the motor is discharging the battery. I have never had this effect around where I live Battery is normally in the blue.
 
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