failure of hypermileage techniques?

Although you've answered some of our questions, it might be worth answering the questions at http://priuschat.com/forums/gen-iii...-answer-these-questions-esp-if-youre-new.html.

Since you mention "short trip segments", how short are these in time and distance? Short trips are a killer on gas mileage.

Another thing that might be worth doing is driving at a steady speed on the highway using cruise control for a length of time and recording the mileage. Make a pass in the other direction to help compensate for wind and elevation change. Report back to us on the mileage reported and speed. If it's too low, then there's we can explore the possibility there's a prob w/the car.

Bwilson4web has put up a graph at http://priuschat.com/forums/gen-iii...-ideal-highway-cruising-speed.html#post932052 but I'm pretty sure he has a more recent one...

 

Although you say it's getting warmer, you should still turn off your cabin heater/AC when you do mileage tests. I have noticed that the ICE will run much more when trying to maintain sufficient engine heat to keep the cabin up to the selected temperature. I played around with it to see if that was the case, and often could get the ICE to go on and off just by turning the cabin air on and off.

Ruling that out as the cause, I would say your description of barely pressing the gas pedal and having the displayed mpg go down that much is not the behavior I see, except during the first few minutes after starting the car, during its warm-up. What you describe seems abnormal.

 

Yep. On the 2nd gen, the cutoff (if the HVAC temp was at hi) was FWT (Fahrenheit Water Temperature) of 145. I can repro ICE on/off at will by turning the fan on/off w/heat at high if <=145 F.

I asked about threshold on the 3rd gen at http://priuschat.com/forums/gen-iii...6472-3rd-gen-vs-2nd-gen-questions-thread.html but got an answer I didn't totally grok.

FWIW, my mom's NAH also exhibits the same behavior but I've never connected a ScanGauge to it so I don't know the threshold.

I recommend not using auto and not having fan on w/heat above LO if the ICE is cold and you're not >42 mph (46 mph on 3rd gen?) or requiring hard accelerations. In the latter two cases, the ICE must run anyway.

 

I've started using Auto Enginuity to monitor the stock emissions parameters that includes vehicle speed, MAF and EGR setting. As I figure out the calibration, I hope to improve the mph vs MPG charts.

Right now, I'm trying to figure out how to map the HSI to ICE rpm, which I suspect has a linear relationship. This is a tricky problem although I have some ideas.

Bob Wilson

 

It's definitely not the temperatures right now!

Just to give some comparison: I'm mostly a highway commuter (75%-80%). I'm in Central Maine and at 61F this morning without trying hard (e.g. cruising at 55mph uphill on I95 and releasing cruise downhill) the MFD is creeping up to around 57mpg. Pushing it (~50mph, max 1400s rpm (I use a ScanGauge), idling downhill (it sits at 992rpm) I got 60mpg on my last tank.

Driven by my wife, I'm sure it would be getting over 50mpg calculated comfortably and she just drives.

I accelerate gently: I've been following Wayne Gerdes' suggestion to accelerate to 15mph in the EV zone and then use the ICE.

Last time I set the tire pressure was several months ago and it was 41/39 so it might be higher, but it also had its 5000 mile service during that time and the dealer might have reset the pressure.

I also currently have a 75% lower front grill block (the other 1/2" insulation tube is in the back of the car ).

I'm not using the climate control at all.

As suggested by others I'd suggest letting the Prius' cruise control do the work for a tank to give you a baseline. I'm cruising more this tank to see whether all my effort is pointless and the Prius can do better than me on the highway.

 

I'm sure it won't address everything you're facing, but you might also consider driving a bit harder when the engine is in warmup mode. I notice that the instantaneous fuel efficiency at very low speeds is extremely low, and it gets progressively better as speed gets up into the 30s. So I try to get to a more efficient speed as quickly as I can (obviously without flooring it). This won't get you to 55mpg during this phase but it will reduce the low mpg that could be pulling you average down.

 

Also, to see how big a factor warmup is, you might also stay in park until the warmup cycle is complete and then reset your trip meter and see how mpg fares on a typical drive to work.

 

OP, you are pressing the gas pedal a little and looking at the HSI when you glide, right?
There should be no assist and no regen during your glides.

You can accelerate moderately or more slowly with largely similar results. The harder accels are also shorter.

Minimize regen in order to conserve kinetic energy.

 

HI
I am enjoying this thread.
My observations over the last few months :

In summer : I do NOT use the climate control ( auto) as it turns on the AC for longer than what I need and if I set the temp to a little higher then when the AC compressor is in the off stage then more warm air blows in. I set the AC temp to very low and manually turn the AC switch on and off every few min when I need it. It gives me a better mileage.

In Winter : For early AM starts> if the battery is full or nearly full then I will start the car in EV and then accelerate as normal ( not very slow). At a certain speed the ICE will start automatically and the engine RPM is set at a certain level which it will not exceed. ALSO I will turn off the cabin heater in this phase for a few min ( even after the engine switches off ) as it takes about 3-5 minutes of my driving ( depending on my route to work and the external temp) for the engine to be sufficiently warm to turn on the cabin temp. You can experiment this yourself by slowly increasing the temp at every traffic light till the ICE turns on then go back by one degree back so that the ICE switches off.

My experiment with P&G has been a failure. I think its safer not to do it as I am concentrating more on the display to make sure I am gliding and this involves taking your eyes off the road which can be dangerous. I get excellent mileage without the p&g anyway. Maybe I will try it again in future.

ALSO IN US ITS MORE DANGEROUS AS YOU FOLKS DO NOT HAVE THE HEADS UP DISPLAY WHICH IS TO ME IS THE MOST USED FEATURE IN MY PRIUS. Its always on and I do not have to take my eye's off the road for speed or to see the HSE. If only Toyota had put the battery level in the HUD then it would have been better.

Mand
Australia.

 

You will probably not like my response because I have no scientific evidence to back it up (I am not using a scangauge); but I'm pretty sure that I've witnessed numerous times where a given point in the HSI led to different ICE rpm, you at least need to include the battery SOC into this relationship. Again that's my gut feeling so take it as such (i.e. discard it right away ), but I'm almost certain that you can't write a (Y = aX +b) function where Y would be ICE rpm and X the position of the HSI.

PS: I know I'm right at least at startup when the engine is not yet warm and also when the battery is at its max SOC.

 

well u r wrong. when hitting gas pedal and RPM's hit better than 2500, then mileage is going to be around 10 to 15 mpg on a regular car. u r just now getting into the summer formula gas season and i can guess that in your area, winter formula gas takes a major hit on mileage. continue to drive conservatively. concentrate more on maintaining a constant speed, keep your disply on the HSI and work on keeping the engine running (over half on ECO mode) as much as possible which means more than half the time if going less than 45 mph. but do so in a way that prevents any sudden acceleration or deceleration.

u only want to be in electric mode when you have greater than 6 battery bars. if 6 bars or less and doing more than 40 mph, you should be in gas mode more than 50% of the time.

brakes regen less than 5% of the power required to attain the speed you want. so DONT USE THEM. u can still get great mileage.

now, if your trips are short enough, 50 mph might the best you can hope for. my last tank which is last winter formula tank for the year, i had good mileage (see sig) but that is because i use my Zenn for most of the short trips. so 2010 is generally used for longer trips. a few exceptions since all family trips are done in 2010 and some are short in town jaunts which is the main limitation of my 2 seater

 

I have witnessed this with a ScanGauge, and posted some numbers last summer to hobbit's HSI thread. When holding the HSI bar at a fixed position on an accelerating run, near the limit of the ECO indicator, RPM was a strong function of speed, and possibly more factors.