Frustrated with insconsistent mpg

Are your using the A/C when it is 90degrees? What do you have it set at?

What you are describing sounds like a hot battery issue. If the HV battery gets too warm you will lose power. There is usually not much of an issue at freeway speeds unless you have the A\C on the lowest setting and it's really hot out such that you cannot cool the cabin to the desired temp. This loss of mpg is related to A/C5 compressor speed. You can easily lose 10mpg if the compressor stays on full blast.

If you are not using the A/C then you wind up in the same boat. The battery will get hot and reduce power. There is a saying in the Prius world that relates to cabin temperature that states "if you are uncomfortable so is your battery.

 

Can you hear the HV battery fan running? The intake duct is in the back seat area on the passenger side next to the door. If the duct is clogged or covered, that could make the difference. The sluggishness in hot weather is just the car trying to protect itself.

 

http://priuschat.com/forums/other-cars/95536-car-driver-mileage-no-its-your-gallonage-really-counts.html

When you're talking about the mileage variance, are you basing this on the MFD or on manual calculations? You will see significant variance in the manual calculations due to the guess gauge and bladder tank. Sometimes the manual calculations will be way higher than MFD and at other times, it'll be the opposite.

As for the pedal feeling different, I seriously doubt there's any sort of feedback mechanism on the accelerator pedal side. However, I suppose you could be feeling a difference in response.

By "nightmare to maintain 60-70 mph", you aren't saying the car has insufficient power to maintain that speed, right?

If it's worth it to you to upgrade, go ahead, but I'm not sure it'd be worth the expense, purely from a mileage improvement point of view.

 

A red flag in the OP is where the OP states that the pedal gets really soft. The accelerator pedal on the Prius connects to a couple of electrical sensors and is no way influenced by external factors. The accelerator pedal feels the same even with the car turned off.

This indicates that at least a portion of the OP's issue is one of perception. The variation in mileage is well within normal bounds. I suspect the variation in performance is also normal. Generally this sort of problem is one of false expectations, or a lack of understanding of how the HSD works.

Tom

 

Hmm...

I'm going to offer a different opinion..and a different angle.

Reading the OP's post? He say's "suffering through the ownership of my 09" and also "I am thinking of upgrading mine to the Gen 3 as it drives much more like a normal car and the pedal has a nice linear feel and does not put stress on my feet and mind."

Well? In my opinion lifes too short. You could experiment, and maybe should. You've had some good suggestions for area's to check and investigate. But actually? If "normal" car drive and feel and MPG's are a priority, upgrading right now might not be a bad idea. Demand for Prius is high, so your trade in value should be pretty solid. It would cost you, you'd be paying a price, but you'd end up with the latest Prius, with advantages like a Non-Bladder gas tank, and a heat reclamation system as opposed to coolant thermos. Also a beltless engine. I like 2nd Generation Prius, but I think 3rd Generation does represent an evolution on many fronts.

So if you are talking about perhaps trading in an "used" 09 that you suspect might of had a tough genesis of ownership with the previous owner, inwhich it is demonstrating a symptom that is hard to track down and driving you crazy? Then trading it in on a new, under warranty, 3rd Gen..might not be as bad an idea as some are thinking.

If I was in your shoes? I'd probably investigate some of the more easy and obvious things suggested...clogged vents...ect...give it a chance to be a simple problem.

But if I continued to be frustrated, I might simultaneously start putting feelers out locally on how much it would cost me to upgrade.

If you do "upgrade" the only thing is make sure you know what you are getting and what to expect. Hanging around "Prius Chat" for as long as I have, I know that MPG's can vary seasonally and for a lot of varied reasons, and actually a 50-55 mpg to 40-45 mpg swing, due to a lot of factors isn't necessarily a problem.

So I wouldn't make the upgrade based on a MPG's alone. But if you look at the whole picture of going from "used" to "new"...to 2nd Gen to 3rd...from worrying about your current vehicles unknown 1st owner history..to being the first owner...then perhaps the move you are considering isn't as horrible as it sounds.

I believe a vehicle is a luxury item. If for any reason you aren't enjoying ownership...to the point of "stress"? Then lifes too short...get what you want...if you can.

 

As others have mentioned it does seem like an issue with the cooling of the hybrid battery pack - as far as I know this is the one thing that can easily explain the loss of power. I have never had to deal with this so I do not know what steps to recommend, but if this was happening to me this is the first thing that I would start to investigate.

My guess is the pedal feeling relates more to the fact that you need to stop on the pedal much more than normal and get less power from the car in return. However, you could have some sort of issue with the pedal and that is not a part of the car that I would want to risk - if I felt sure that there was a change in the pedal's feel I'd bring the car in to be looked at by a pro. There has been at least one pedal recall so there is a chance that something got messed up.

Lastly, I might hold off on getting a Gen 3 to replace it. Toyota has done a great job of making a very different vehicle respond and drive like every other car on the road, but it is a car with a few quirks. It does seem like Toyota made the Gen 3 a bit more mainstream than the Gen 2 but that does not mean that you will not have the same issue with a Gen 3 if indeed this is a quirk and it is rubbing you the wrong way.

 

how does your friend's pedal feel? mine, on both my 04 and 08 have always felt exactly the same. my mileage can vary seasonally by weather, heater and a/c use from a low of 45 tank average to a high of 68.

 

i just can't get past the pedal feel. if it's more than perception, something is going on. and you shouldn't have to stress your feet out to get decent mileage. you should rent a gen III to make sure it's everything you want.

 

I think pedal feel is a red herring. I believe the OP is really saying pedal response, as in the car responds differently at different times for the same amount of pedal input. They are two different things, but commonly confused.

Most likely the OP's Prius is having hybrid battery issues or some other problem limiting the performance of the electrical system. Heat is a possibility, but it could also be a failing battery pack.

Tom

 

If the previous owner was a dog owner then take a look at this thread:
http://priuschat.com/forums/gen-ii-...-fur-dirt-causing-major-battery-problems.html
Good luck!

 

My 2 cents, I am familiar with the pedal feel change.
This happens when the Hybrid battery goes to purple lines (low) and so the ICE engine starts screaming and pouring energy to wheels and HEV battery. Sometimes this happens on "level" highway, not sure why, subtle up-hills? I wonder if 12-volt battery is weak? Is car being left in sun/heat so HEV battery is real hot? Maybe driving habits are tending Hybrid batt to go to purple lines on highway (like me).

 

Yes, the colors change according to you state of charge (SOC). The highest level is green, then blue, then purple. Most people spend the majority off the time in the blue range. When you see purple you are very low on battery power and the engine will work to replenish the battery and you will feel a reduction in horsepower/acceleration. That is why I asked what your SOC was when you experience your loss of power.

 

Hi Prius_2009. Same here - see avitar.

Take a look at the phtos I've posted of the HV battery cooling system at the top of this page (reply #31) here: http://priuschat.com/forums/gen-ii-...ur-dirt-causing-major-battery-problems-4.html

The photos show that you can access the blower fan very easily by just removing the right-hand side panel in the rear hatch. My photos show what a blower fan clogged with dog hair looks like.

Those photos were taken at the start of summer last year and I'll soon be pulling the panel to take another look at the start of next (southern hemisphere) summer. This will give me a good idea of how much accumulation there is per year and based on that I'll probably make a blower fan cleanup part of my annual maintenance.

BTW. I got a small but noticeable improvement in hot weather performance after that blower fan maintenance.

 

John has many useful instructions, this page shows the different battery display colors (see various screen shots on right side of page). He calls it Iconic Prius, and see the "SOC" state of charge pics that F8L was saying.

John's Stuff - Toyota Prius, How It Works