Mistakes of a Newbie Hybrid Owner

This is very interesting. I will be suprise if this is true. I alway believe that the power mode is wasting gas, the efficiency in power mode is much lower than normal or eco mode, so the less power mode you use, the better mpg you get.

 

But the theory is that if you are in pwr mode for 5 seconds and then maintain speed you save more than if you are driving under pwr mode, but above the eco band for 20 seconds to get to the same speed before maintaining. I'm not sure which way is better, I just drive it like a car.

 

Just stumbled upon this post from the home page...
I drive mostly in city conditions in San Francisco. I've been trying different driving styles along some of the same routes and definitely notice that this method improves my MPG, but the trip has to be over a certain distance to actually work (e.g. > 2 miles).

I notice it sort of works for going uphill too - unless you can switch into pure EV mode. I guess the theory goes, I take longer to go up a hill at medium throttle vs. full throttle, and depending on conditions, I could actually save gas if there was a hill with multiple start stops.

I'm not going to speak to the lifespan of the vehicle by engaging in "driving it like I stole it" methods, but it's certainly a bit more engaging to drive!

 

No way. Imagine the following scenario..

Two drivers, Leadfoot and Featherfoot, test your theory. They have the road to themselves, and drive side-by-side. Leadfoot guns it every time after stopping or slowing down, to get back up to speed, Featherfoot keeps his HSI display in the eco range.
At the first red light, Leadfoot accelerates in the power zone, and pulls ahead of Featherfoot. As they have the same cruising speed, Featherfoot never catches up. At the next stop Leadfoot pulls even further away. After a while, Leadfoot is out of sight.

At their destination, they compare notes. Leadfoot got there quicker, so had a higher average speed. But Leadfoot used more gas, as the faster you go the worse your fuel economy ( see Bob Wilson's chart).

The HSI shows an eco range and a power range for good reason. Your choice, but smooth steady acceleration will give you the most economical performance. Extending that idea to the "driving with load" approach, this results in a drop in speed while climbing which you don't recoup going down hill. So your trip time increases, your average speed drops, and your mpg goes up.

 

In just the first few days of ownership, I've noticed this suggested style of driving increases my mileage. Unfortunately, it also means I have to hear more of the ICE buzz than I want.

 

Except that Bob's chart isn't for average speed, its instant mileage at a given speed. At cruising speed, both cars would be getting the same MPG, the difference is how much gas the acceleration used. I'm a firm believer in brisk acceleration (probably not quite leadfoot, but my car doesn't have the HSI so I can't tell exactly how my acceleration compares), but there are also times where light acceleration is best (traffic, another stop soon). I think the biggest difference comes from how you maintain cruising speed, especially at speeds low enough that the ICE can turn off. Most of your driving (hopefully) consists of cruising, so its probably better to focus on learning to P&G or how to hold the pedal in just the right spot to provide just enough power. A leadfoot that has a good cruising technique should generally get better mileage than a featherfoot that doesn't.

 

Maybe the on board computer cannot compute as well when WOT so its providing even greater inaccuracy in the MPG calculation. I wanted to hear this from someone that has a repeatable route and tracks their MPGs by fill ups not the cars display. Its amazes me the car can meter fuel but not directly correlate that with MPGs.

 

Does the C have the Hybrid System Indicator display? When I'm accelerating from a stop, I keep an eye on it, try to keep it in this zone:



Except on steep hills. Then you do what you gotta do.

 

Except that they were driving the same max speed, so nobody had a faster speed. Yeah he had a higher average, but not a faster top speed. As you indicated, faster speed is the main drag on the mpg's.

 

Now Imagine this, same 2 drivers L and F. L took .1 miles to accelerate to 50 mph and F took .3 miles to go the same speed. In a 1 mile stretch, L has .9 miles of 999999MPG while F has only .7 miles of 999999MPG

 

I wonder if Leadfoot understands that the engine in the Prius is a high expansion Atkinson cycle engine, and I doubt anyone but Toyota would dare take a wrench to it.

If it goes, you are toast. I can't imagine a normal mechanic shop wanting to take on the risk.

 

I think the most important thing in improving your mpg where there are lights it to keep your momentum. if you accelerate quickly this may keep you with the flowing trafic that will make the next light. if you accelerate slowly this may prevent you from having to stop and start up again. you really must do your best to either make the next light or get off the gas early to stop the ICE and start regen. I also wonder if the mpg estimate on the display is as accurate durring the times I quickly accelerate. It seems that I use less fuel over the short run to get up to speed fast. This may be the car using both the batt and ICE, I'm not sure.

 

But the point IS that if you are relying on the computer readout to give you accurate readings on which method produces the best actual fuel mileage you might be fooling yourself.

To a point it makes sense though as a "brisker" acceleration should use more battery and less gas engine......to a point.

I suspect that if you track actual usage over time the difference will be a LOT smaller than what you quoted above.

For instance.......WalMart is about a mile and a half from my home.
When I drive there, the engine has a chance to warm up and get the battery charged.
On the return trip, if I am real careful, I can make it show an average MPG of anywhere from 65 to 95 MPG.
Of course, the next time it runs the first few miles will be really crappy because it's going to recharge the battery.

Simply changing the way you accelerate really does not make THAT much difference in fuel usage.

 

(1) I don't want an imagined answer, I want a real world answer. Do the experiment and actually measure it.
(2) As noted earlier, you are misapplying Bob Wilson's chart. It is strictly a constant speed instantaneous fuel consumption chart, the acceleration portion is removed.
(3) Leadfoot and Jackrabbitfoot are not the right drivers to illustrate this hypothesis. BriskP&Gfoot is a better choice.

 

You seem to have convinced yourself, but if you don't cite or link the studies you refer to, your readers can't check them out.

You haven't indicated anything about your commute, including how much of it is stop/start city driving. If the cruise miles are most of your journey, then the fuel usage during the accelerations will be relatively insignificant overall, and any variations will be more likely due to what happens during cruise.

You might look at doing the following:
Display your Eco Savings screen, the one that shows your running cost (assuming you have entered the fuel cost last fillup).
At a red light note the current cost. At the end of an quick acceleration up to cruise, note the cost again to see what the acceleration cost you. Repeat this a few times to get a good approximation.
Now do the same thing for slower acceleration, and report back here with what differences you find. If you do a count of how often you accelerate quickly on a commute (how many red lights etc), it should allow you to roughly cost your acceleration phase compared to your total commute cost.

 

Can you provide a reference for that study ?
I think your memory has failed you just a bit.

Cars of that vintage virtually poured unburned gas out the tailpipe at or near WOT.......so I don't think that part is quite right.

 

WOT equals Wide Open Throttle, right? And the premise is that acceleration with Wide Open Throttle is the way to get up to speed, right? Saves gas?

 

Duh...
If it looks like a duck and walks like a duck and quacks like a duck, then it's a duck. Bob's chart shows increasing speed reduces fuel economy, end of story. The methodology is irrelevant.

Real world evaluation of mpg looks at the big picture, not the acceleration, not the cruising speed, but at total distance, total time, total fuel consumed, total cost at the pump. All your average punter wants to know is how much their commute is going to cost them relative to their weekly/whatever income, and the time they have to travel. It's all about averages, the minutiae is academic trivia.