ECU Flash affects MPG?

There's a growing rumor that the last Engine Control Unit program update has caused the engine to operate more frequently, thus lowering the miles per gallon. I thought I had lost some miles per gallon to the hot weather until I heard this. Anyone have any support for this?

Note to Toyota, I bought this vehicle because it looked like a good technological compromise to achieve higher mileage. You've released the Hybrid Highlander, the GX400h, and the Hybrid Camry with minuscule improvements in the mpg versus their gasoline only counterparts. I think you're missing a significant market if this rumor is true and you continue releasing vehicles with only minor mileage improvements.

Reply to
NeoPhyte_Rep
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Not sure where you are getting your infomation, but both our cars are fully updated and they are doing equal or better than the last time they were serviced. The older of the 2 averaged 58+ mpg on a trip from MA to NC and back.

Second, it's not only about the MPG's but about greatly reduced emissions from the hybrid synergy drive as well that makes the hybrid version a 'better' car than the gas-only version.

Reply to
Russ G

I didn't see any change in my fuel economy.

I call them feel-good-hybrids. They are essentially meaningless as far as conservation is concerned. I heard GM as some truly phony hybrids.

Reply to
Bill

...

Where did you hear that rumor?!

Reply to
Carpe Diem

From another owner who had his service performed about the same time I did and also had his mpg drop noticeably. That's why I came here, to see if it was only a small sample or a more widespread occurrence.

Reply to
NeoPhyte_Rep

To me, "growing rumour" seems to be an overstatement.

Reply to
Carpe Diem

After the ECU update, performed in conjunction with my 10K service, I too thought my mileage had been impacted, possibly because I had read this rumor in the Yahoo group. I checked my tire pressure to find they had seriously lowered it (low to mid 30's) in conjunction with the tire rotation. I put it back to 42/40. Over the next few tanks my mileage was as expected given the nature of the trips, wind conditions, etc.

I can't honestly attribute my initial and subsequent findings to the ECU update, tire pressure or paranoia arising out of the rumor but I suspect the latter.

Reply to
Bill

Rumor?

It's a learned ISC. Some owners have reported slightly lower MPG, while the ECUs "relearn their driving habits" (store some data over time/mileage, to help the tune the vehicle's future performance) after the 50P ECU upgrade. But it will return to normal in a little while. Most owners haven't noticed anything after the upgrades, though.

The bigger culprit is that if you live in a hot climate, and are running the AC a lot, that energy comes from somewhere... Your engine will come on more often to help power the AC. Whether you have a Classic (unlikely, as you can't flash the Classic Prius' ECUs) where the engine has to run to belt-drive the AC compressor, or if you have a NHW20 (most likely for you) where the engine will come on whenever the hybrid battery gets low (most likely from powering the electric AC compressor).

Just remember that the the governmental fuel economy tests (such as done by the EPA) are done in ideal temperatures (usually in the 70sF) and do not use the heater or AC...

Reply to
mrv

Please expand the acronym ISC.

Are you saying the Prius' ECU uses more than atmospheric conditions, accelerator pedal position, and the state of charge of the traction battery to determine how to control the engine? Do you have a Toyota document that explains this?

This is not in regards to any governmental fuel rating. This is in relation to my personal recorded tank fillings and computer readouts. I record both and both are down about 5 mpg. I consider that statistically significant.

Reply to
NeoPhyte_Rep

What Michelle is telling us is that the standard does not use heater or A/C, and for that reason we can expect those to have an impact on our economy when we do use them. 5 mpg isn't unusual for A/C when the efficiency is so high initially. It's a matter of fuel used; using a liter of gasoline out of a tank of gas shows up less on a 20 mpg vehicle than t does on a 50 mpg vehicle.

Mike

Reply to
Michael Pardee

I am not comparing my mpg with the EPA mpg.

I am comparing my mpg with my mpg.

From the day I drove it off the lot I have had my air conditioning on and set to 75 degrees. So all my comparisons include the loss due to air conditioning. I was getting about 47 mpg. I am now getting about 42 mpg. The two possible explanations are a weather change (it's been what I consider hot) or an ECU flash. I am still monitoring my mpg and now that the weather is back to normal, I am still down about 5 mpg. That's why I requested the experience of others.

Reply to
NeoPhyte_Rep

what dealer, what other person at that dealer, check you air and emergency brake just cause:) could be a good heads up, I run my business on windows

3.1 , never crashed, have never lost data, hate to go backwards but sometimes it's the only direction that work's.

Reply to
MFH

check your tire pressure, the level of the oil, and the emergency brake is fully disengaged, otherwise i have no other suggestions as i did not have your experience with our updated cars...

best of luck bro!

Reply to
Russ G

good question. For some reason, I had ISC stuck in my head. Basically, I meant that the ECU does store information about your driving and external parameters and adjusts accordingly.

Hm, buried in ome of these technical threads is the answer...

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unfortunately, I'm having trouble searching back in my archives farenough for when the ECU upgrade was released, or when the Classics hadthe battery resealing done (where many more peoplenoticed/complained)...

Just a reminder about the governmental ratings - they don't take into account heater or AC use, which both will lower fuel efficiency.

other thoughts:

  1. It's summer in the northern hemisphere, and winter in the southern hemisphere. Temperatures are more extreme than a few months ago, which means that the gasoline engine will be running more to provide for the added climate control for these extremes.
  2. did any change in fuel occur since your upgrade? summer/winter blend? addition of ethanol?
  3. did you have anything else done at the same time as the upgrade? dealers are notorius for using the wrong grade of oil, oil overfill, and not setting tire pressures correctly.
  4. have you checked your parking/emergency brake? sometimes they do get a little sticky.
  5. have you hit a pothole or curb, that may have knocked your alignment out?
Reply to
mrv

  1. As I said I first suspected more use of the air conditioning, but that is back to normal and the mileage isn't.
  2. I don't remember if the service occurred at the same time as the seasonal mixture change, but that would affect more than my Prius, which is why I came here for the experience of others.
  3. I think I'm going to research these possibilities deeper. I haven't been in the habit of checking the dealer's employee's work, but maybe I should be more careful.
  4. I'll dig into this one, too.
  5. No potholes of significance. Lot's of small bumps since there's a growing lack of road maintenance to save budget.

Thanks for your suggestions.

Reply to
NeoPhyte_Rep

I'm not sure what this has to do with the Prius.

Reply to
Mike Rosenberg

Found it. ISC = idle speed control.

It was stuck in my head from reading the TSBs for the Highlander Hybrid:

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if the 12v battery is disconnected or drops below 7 volts, thereis a procedure to reinitialize the idle speed control. to quote those TSBs: "If this procedure is NOT performed, the following customer complaints may occur: Engine runs too long or more frequently than normal Reduced fuel economy Transmission gear "clatter" noise at idle is more pronounced"

Reply to
mrv

As usual, the twit twat twins, Victor/Victoria, uh, Michael/Michelle reply with babble that the OP finds useless. They are the same person?

Reply to
today

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where if the 12v battery is disconnected or drops below 7 volts, there> is a procedure to reinitialize the idle speed control.>

Thanks.

I'll see what the service manager has to say about this information. I saw no indication that the battery had been disconnected, but you never know.

Reply to
NeoPhyte_Rep

How did I get involved in this little flame war? I thought that you just stalked Mr. Pardee and Ms. Steiner across usenet. (The last time I was stalked, the police were involved.)

Pretty bad when one cannot even remember who it was that they were stalking.

Whomever said that a post had to be useful for the OP? Your post certainly isn't, so why should any others be? oh, do as I say, not as I do. At least my post was useful to someone, other than myself. Mr. Pardee understood the intent of my post, but it was maybe unclear to the OP, maybe because of cultural differences, or that Mr. Pardee is used to my writing style from other Prius discussion forums that he could infer my intent better.

Reply to
mrv

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