I've noticed there are times when accelerating from a full stop, the MFD will show about 6-9 mpg until I hit ~20mph. During this time, the engine really sounds like it's straining and the acceleration isn't as responsive. I know that decent acceleration usually shows about .5 mpg/mph, but this seems a little unusual. The ambient temperature will be anywhere from 30-70 when I've seen this happen. There will be other times when I can accelerate purely on battery up to about 40mph at a pretty respectable rate of acceleration. This will sometimes even happen about 5 minutes after turning the car on, obviously in warmer weather. I've tried figuring what variables could affect this. I'm not on an incline when the car won't go to battery, the weather is warm, it's several miles since initial startup, etc. All are what would be considered ideal conditions. I guess it would help if I had a Scangauge but I don't want to plunk down that kind of money. I'll even feather the pedal and the engine/MFD will still sound like it's straining. My MPG for right now is about 51.5 with the temperature hopping around from 40-70, so I'm not really too concerned about the hit on mileage. I'm more curious as to why this is happening because the obvious reasons don't seem to jive (temperature, road, time from start, rate of acceleration, etc). Any ideas on how to ensure that the car will go primarily to battery from a complete stop other than installing an EV?
Going to battery from a stop is not efficient unless you're simply creeping forward in a traffic jam or something. Don't sweat that low appearing number...in fact, don't even look at it. If you have or can get a Scan Gauge shoot for a target RPM around 1850 for any acceleration (from a stop or otherwise), as this seems to be a range of peak efficiency (b/w 1700-2300rpm). If you use the battery as your primary source of energy you incur losses in recharging the battery and again when using the battery for motive force whereas you can directly use the energy of the ICE for acceleration when it's the prime mover.
The engine and HSD system behaves differently depending on the temperature of the engine. Basically, the engine has to be warmed up for the car to get into 'full hybrid' mode. During the first few minutes of operation, the engine will run a lot to get up to temperature. Sometimes when you hear the engine 'straining', it's just running at a higher speed, which will not be directly driving the wheels. It's most likely running MG1 as a generator and sending that electric power to MG2 to move the car. If you can look at the Energy screen on the MFD, you'll see the arrows going from the engine to the wheels and from the engine to the motor to the wheels. So basically - the gas engine doesn't only turn the wheels. It can turn the generator (MG1) to send electric power to the motor (MG2) to move the vehicle.
Evan, for those of us without a scangauge are there any tips you have for hitting the 1700-2300 rpm range? Does the display look a certain way in that range? Is there a sound you can describe? The rpm in my prius seems to ramp up in a fairly linear manner, as I apply more throttle, then suddenly jump up. Might I be aiming for just below the "jump"? Or should I just bite the bullet and get a scangauge? Thanks, Cedar
Nooaah is in the ballpark. I will modify his suggestion to say: Keep the instantaneous MPG at least half the vehicle speed when the ICE (internal combustion engine) is on. See this for more.
Why is it the past two tanks I've been getting like 51.5 no matter what. 50 miles into the tank it's 51.5. 200 miles into it I'm at 51.9. The MFD consumption screen since I've been keeping track at 50 miles consistently shows more 5 minute increments of high 50's to 99 and the tank MPG barely moves. Like the first increment will be about 25-35mpg after startup but after that I'm able to hit high 40's/low 50's then the next 5 or 6 are all closer to 60-75 (if I'm not on the highway, that's consistently 50's-60's). Completely different routes, too. I must be really unlucky with my route selection and hitting red lights.
You probably didn't hit the RESET button on the consumption screen. So what you're seeing is your cumulative MPG since the last time you did do a RESET. The more miles you have gone the less impact any given drive will have on that overall MPG.
So, while the miles on the tank can zero out, my MPG will remain until I reset? Interesting! I used to reset after every fill-up and then stopped last month because it was reseting the miles immediately and I just figured the reset button was redundant. good to know. I must be getting like 54mpg considering I got about mid 51's for 370 miles and I've raised that by 1 MPG now on this tank.
That's correct, the tank miles zero out, but the MPG remains cumulative on any Prius '06+ (and maybe the '05s too, I can't remember) On my '04 both zero out automatically, but Toyota changed it after some griping that there was no way to track cumulative MPG.
Evan, The '05 behaves the same way as your '04 [they both do automatic resets of both the miles & the MPG (when you put in at least 3 gallons)]. So, basically there were no changes between the '04 & '05, but there were a lot of small changes from there to the '06. I don't think however that there have been any changes from '06 through the '09 model (but I may be wrong). Ken (in Bolton,Ct)
Well, I don't know if this was due to Jimbo's advice, but for my last tank I really took extra care to get about .60MPG/MPH while accelerating. I went over 400 miles before going down to 2 pips for the first time ever! Also, I believe this was more Jimbo advice, but when filling up today, I clicked off after 7 gallons. I pushed my car from side to side several times and sure enough I filled another gallon! After 50 miles on this tank I'm sitting at a cozy 60.7 MPG on the MFD and it was only 55 degrees.
Has anyone noticed that if you are light on the gas pedal when you first fill up and drive a little in the city before you get on the frwy the fuel effeciency is far better. Any explanation why?
Because the engine is sufficiently warmed up slash in s4 before being severely stressed at high speeds? That's my only guess.
