Specific Question on Accelleration

<div class='quotetop'>QUOTE(Fibb222 @ Aug 15 2007, 06:25 PM) [snapback]496483[/snapback]</div>

I think the "sweet spot" is the acceleration with only the ICE and avoid adding the electric motors to help.

 

Ijust give it all I want. I hate people who hold everyone up in traffic, just get going.
Once at the speed you want to cruise at, back off and cruise.
Watch well ahead and if you think a light will be red when you get there, back off and coast to the light. Try to judge the light so you arrive at the light or the back of traffic still rolling so you don't stop as the light changes or the cars in front roll away.
The brake pedal is your enemy, avoid pressing it hard but press it lightly to take off speed as that results in higher regen ready for acceleration or cruising along on electric power.

If I came upon you coasting down to 28mph when the speed limit is 40mph on a single lane road you better have ear plugs and sun glasses on ready for road rage. And after you accelerate back up to 40mph then slow back down to 28 be ready for a dangerous overtaking with fist shaking and swearing out the window.
The harm this slow driving does the reputation of Prius and hybrids is terrible. People already say hybrids are slow so why give them reason to think it?

 

If you zoom by me, I will swear and shake my fist at you...wasting gas, speeding too fast...aiding terrorists...just slow down, you can't be in that much of a hurry.

 

<div class='quotetop'>QUOTE(theorist @ Aug 21 2007, 05:52 PM) [snapback]499984[/snapback]</div>

I can't recall the thread, but I do recall someone having reviewed ScanGauge data to help answer this question. The writer found a correlation between speedometer MPH and MFD mpg. The writer suggested the optimum FE would result from keeping the MPH at about double the instantaneous MPG readout from the MFD. This sounds just like what you are suggesting.

I have no idea whether this proposition has any real support, but I've been trying it of late, and I find I have increased my FE in short trips (stop and go in town). Of course, I may just be getting more and more accustomed to my Prius!!

 

<div class='quotetop'>QUOTE(finman @ Aug 31 2007, 10:14 PM) [snapback]504828[/snapback]</div>

You don't own the road to be holding other road users up on the road.
I can be in that much of a hurry, while you're coasting down to 28mph I might miss the next green light.
If you paid for my petrol and if you got better consumption than me I'd listen to your concerns of wasting petrol. You are getting an average of 5 litres per hundred kilometres and I get 4.4L/100km.
Please explain how driving at the speed limit helps terrorists? Sorry I'm Australian.
What actions do you take to counter the harm you do to the reputation of Prius? How do you counter the slow little electric car reputation you are creating which damages Prius sales and ultimately increases oil consumption.

 

<div class='quotetop'>QUOTE(FireEngineer @ Aug 15 2007, 10:31 PM) [snapback]496631[/snapback]</div>

Wow, I wonder how/why I missed this thread earlier.

I proposed a rule of thumb awhile back, which has since been validated by a small handful of folks. Here's the full thread, but the rule itself: Keep the instantaneous MPG between MPH/2 and MPH x 1.2. The higher end of that iMPG range, as one might suspect, won't provide much acceleration except downhill. It is more to help decide between ICE-on cruising and gliding (or "warp stealth" at 41+ MPH).

As for keeping iMPG above MPH/2, Theorist of course suggested that earlier in this thread. He actually proposed it much earlier than I in another thread, unbeknownst to me at the time. (When I later discovered his earlier post, I cited it in my thread.) It's interesting that two of us independently arrived at nearly the same conclusion.

When I competed in the MPG Challenge at Hybridfest, my goal for pulsing was to keep accelerator position at 40 as indicated by Can-View. (See Ken1784's posts in my thread, and my follow-ups, for more.) This keeps RPM below 2300 up to about 30 MPH, pretty much my maximum pulse speed during the Challenge. I finished the Challenge at 87.9 MPG. The top two finished at 110 (PC member Locutus) and 106 (PC member Dan.). (As an aside, I think Dan could have won if he hadn't made a wrong turn early in the course. Not to knock him -- I made the same wrong turn, but I re-did my run, whereas he chose not to. My run with the wrong turn was only 78 MPG.)

Part of the difference can be attributed to new tires on my car, which by my estimate caused a 5-10% MPG hit. But I wonder now if more conservative acceleration would have made a difference. I didn't have a chance to talk to Jerad (Locutus) about his technique, but Dan told me he tried to hold a steady 1600.

Since then my pulse goal has been 1600, which for those without added instrumentation seems to keep iMPG equal to MPH. In fact, Dan told me he tried to maintain that for his entire HF trip from Texas to Wisconsin during ICE-on segments, when travel conditions allowed. He verified my (unreported) observations that iMPG = MPH at pretty much most speed ranges until somewhere in the 60s where aero drag starts to alter it. At higher speeds, that's not an acceleration target but could be one for steady-state cruising on level terrain or slight downhills. It probably won't get you up to speed on an interstate entrance ramp, nor will it climb any significant hill.

What's best? Who knows? Approaching it from a scientific standpoint, I would advocate, and I plan to eventually perform, a test under controlled conditions. Meanwhile, all we have are anecdotes, though admittedly some convincing ones. For example, the results of the Japanese hypermilers speak for themselves.

But for the average driver I'm not sure it matters too much, as long as extremes are avoided. And that's the purpose of my rule of thumb. EricGo's advice is great: modest acceleration, anticipatory driving, learn how to glide, plan and learn your routes, and stay off the highway. And add Patspark's advice to that list: "The brake pedal is your enemy." Kinetic energy is precious.

Good discussion by all!

 

Patsparks, you are *so* not helping here...
.
_H*

 

<div class='quotetop'>QUOTE(hobbit @ Aug 31 2007, 11:59 PM) [snapback]504863[/snapback]</div>

I have to sleep now, after 12am and up at 5am
What am I doing that isn't helping? I think my question is valid. While you are slowing to 28mph then speeding up to 40mph on a road with a 40mph speed limit, what are you doing to repair the damage you do to the reputation among conventional car drivers who think because of your 28mph antics a Prius is some slow electric car that holds people up?
Because they form this opinion they will wipe away any thought of buying such a slow car.

 

<div class='quotetop'>QUOTE(patsparks @ Aug 31 2007, 09:30 AM) [snapback]504836[/snapback]</div>

I have that smugness that you hear so much about. I don't care what others think...I'm way beyond that! I do care that others' actions endanger me and my fellow citizens. Those who are speeding and blindly, excessively consuming fuel are feeding the terrorist money train (oil, gas imported from several countries, some of which...um...disagree with the US). I am only doing a small part by setting the example. It's really all i can do since my vote and voice just don't make a difference anymore.

 

Having a 27 mile commute with over 70 possible stopping points from downtown chicago to the suburbs in heavy traffic conditions and monitoring results and trying just about every technique suggested here for the past six months, my opinion is that acceleration rate is the last thing you want to try and fine tune. The biggest mpg killer is wasted pulses. If you accelerate to 40 and immediately get hit by a red light with hard braking you should've just accelerated to 30 then glided or regen coasted to the stop. The gas to get you to 40 instead of 30 was just wasted.

The slower rpm acceleration that FireEngineer suggests will keep greater buffers to glide into so you don't have to use your brakes and you'll see traffic stopping and lights changing to cut off your pulses much sooner.

In some cases harder acceleration is good because you can get space behind you so you can glide back while traffic catches up, or make it through a light you know you can make if you go faster.

The objective is to glide as much as possible and minimize wasted pulses. Once you have mastered that, then fine tune your target rpm based on your route and knowledge of the lights, traffic conditions, and where you sit in traffic.

 

<div class='quotetop'>QUOTE(patsparks @ Aug 31 2007, 11:55 AM) [snapback]504880[/snapback]</div>

Hi Pats...

You know, we do not have those signs in the US, that tell what the optimum speed is to make all green lights like they do there in some Australian cities. So, people around here tend to cruise too fast, and end up getting in the way of somebody travelling at such an optimum speed.

Consequently, there is a cultural difference. You are thinking people are going slow, when here in the US, they are going at a sane speed (probably like you are there) to make the next green light. Whereas you are getting the jist off the comments from the Prius drivers that have had harrasment from "fast" drivers. The fast drivers just being red light racers ( hit the gas peddle when they see red lights, and then get in the way when the lights are green).

The typical Prius driver doing 28 mph on a 40 mph road knows he will be just be wasting energy, and slowing nobody down if he were to speed up. Because there is a red light off in the distance, and he drives the road every day. So, he knows when its going to go green, and knows he will get there within one car length of it going green.

 

<div class='quotetop'>QUOTE(JimboK @ Aug 31 2007, 08:42 AM) [snapback]504838[/snapback]</div>

Best I've found is to moderate acceleration up to 15 MPH, then have the MFD MPG match or slighty better MPH for the rest of the acceleration. And stay out of the battery everyone, you have to put it back to 6 bars eventually.

Wayne

 

<div class='quotetop'>QUOTE(finman @ Sep 1 2007, 12:27 AM) [snapback]504881[/snapback]</div>

(1) But you are happy to drive a mobile road block? Funny the rule about dangerous driving only applies to others.
(2) Aren't you just discouraging others from buying one of them slow little electric cars from Japan? Doesn't this have a nett negative impact on your stated goal of a reduction of the import of mid east oil? If you discourage one driver from buying a Prius and he buys a Corolla or some other 30mpg car you now have to achieve 100mpg to undo that damage you did, which, using your rolling roadblock technique will discourage another etc.
(3) You are not setting an example, you are discouraging others from helping out.

We don't have those signs either. But if you hold me up and I get to a light as it goes yellow, I'll be blaming you in your stupid slow *&^(ing electric car.
We aren't talking about gliding to a stop at traffic lights and timing lights which I whole heartedly endorse as a fuel saving technique which should be taught in schools. I'm talking about gliding down to 28 mph on a section of road with a 40mph speed limit, for no other reason but to save fuel. This must do immeasurable harm to Prius' reputation. I also wonder if anyone has tried cruising at a constant 32mph to compare mileage? There may be no saving in pulse and glide compared to cruising at 32 and at a constant 32 you would annoy just as may motorists. but they would never come upon you at a speed diferential of 12mph, only 8.

 

Hi Patsparks,

Funny you should mention getting caught by Yellow Lights. I was swearing at the damn slow ICE-only cars this evening for the same reason!

 

I'm hardly a pro, and have no extra equiptment, but I am able to get about 70-75mpg in normal suburban driving with my methods. THe best I've come up with on accelaration on a warm engine is as follows:

Start out gentle, I try to let the car naturally EV to about 15mph (I get very low MPG with the ICE at this speed, and the computer seems to prefer EV in this range, so I figure the toyota engineers knew it to be more efficient)

Once the ICE kicks on I give it a little juice, 40% throttle seems about right, then back off slowly between 25 and 30, trying to get red/green arrows only at around 30mph, then keep it red/green until 41.5, where I glide back down to 30 (with no cars following) or 35 (with trailing traffic, green lights ahead) before doing the next pulse.

This acceleration technique was an improvement over my old steady MPH=MPG technique, but only a modest one. My bigest FE improvement came with increased traffic awareness, and better timing of lights.

So, there's my 2¢, in case you wanted it!

 

<div class='quotetop'>QUOTE(donee @ Sep 1 2007, 11:22 AM) [snapback]505230[/snapback]</div>

So you understand where I'm coming from?
Unfortunately because a Prius is different people will blame the car unlike when it's an ICE vehicle, then they stereotype the driver. When a person is stuck behind you at 28mph that may be the only Prius they see all week.
It's important that we get good mileage with the Prius and spread the word about our achievements but if we tell a person about the brilliant mileage when they have already formed the opinion the Prius is slow they will just think, "yeah, there are lots of tiny slow cars getting good mileage, so what?" But if they see Prius as a car which is keeping up with traffic or even setting the pace they may be more receptive to the idea of owning a Prius.

Sorry I got off topic sort of, accelerate as quick as the traffic around you, that's my opinion.
Not everyone has unlimited time to get where they are going, if they did they would be on a bus or train or walking.

Thankyou GreenKeeper, I agree, Me too.

 

Patsparks, we *were* talking about timing lights and gliding down to
the red [or about-to-be-red] ones, and you jumped all over everybody
for it. Before anyone was talking about steady-state P&G over long
stretches, you took issue with non-blasting-RPM acceleration away
from a stop. Someone driving more gently like that, in ANY car,
trying to save fuel and be safer on the road, doesn't make all
hybrids look bad. It's the a55hole crammed up behind them trying to
be intimidating that looks bad, but of course that happens all the
time and unfortunately seems to be accepted practice in a lot of
the world's society. That doesn't make it right.
.
_H*

 

<div class='quotetop'>QUOTE(patsparks @ Sep 1 2007, 03:35 AM) [snapback]505341[/snapback]</div>

This is certainly a bit off-topic, but a very valid point. Think there is a certain wisdom to showing other drivers the Prius can be a peppy car. It might just be the best thing we could do to improve the nation's collective fuel economy.

While it hurts our FE (something I get great enjoyment out of maximizing) to accelerate quickly for 3-5 seconds out of a red light, it might just give somone a positive impresion of this vehicle. There is a chance that that might open somone's eyes enough to set a chain of events in motion that results in a new prius owner.

If that chain of events actually occured, your minor FE hit (i'm thinking ~10-15%) would result in a MAJOR FE improvement averaged over you and the new prius owner.

When you actually multiply out the hypothetical lifetime fuel usage for these two vehicles the picture becmes even clearer. Let's assume your MPG drops from 60 to 51, other guy buys a prius that he gets 45mpg out of, instead of a 20MPG ICE dinasour.

The tempting thing to do here is average the MPG, but that math would be somewhat innacurate. Instead, let's look at fuel usage of 1 120K mile lifespan of the two vehicles (nevermind that the prius will likely last longer).

Prius would have burned 2,000 gal of fuel in that time, but decreasing to 51mpg increases that consiumption to 2,353. The dinasour would have burned 6,000 gallons, but the uneducated driver in his new prius will only use 2,553.

The net effect of this hypothetical situation is that by accelerating more quickly for the lifetime of your ownership you take a 16% hit in fuel economy (costing you 353 gallons of fuel over 120K mi) but, by creating a favorable impresion that results in one changing one mind to buy a prius you save the other guy 3,447 gallons of fuel. This saves our nation, planet, etc. 2,094 gallons of fuel.

I know this is something of a far-fetched hypothetical, but we need to remember we are the pioneers of a movement that will need to extend way beyond our personal FE numbers to be truly effective. Creating a positive impresion of our vehicles, and bieng good amasadors of this technology should be a top priority.

With that bieng said, I applaus the work of Hobbit in his tireless efforts to understand and document the wonderful technology that makes this all work. I also recognize that hypermilers are doing a great service to the community by showing what is possible, but submit that we should make every effort to create the image of the prius as a modern, zippy, virule vehicle that even a macho redneck should be proud to own.

----

Let the flames begin!

 

<div class='quotetop'>QUOTE(patsparks @ Aug 31 2007, 09:30 AM) [snapback]504836[/snapback]</div>

Perhaps you will listen to my results that are at 3.13L/100KM when I say that driving style does make a considerable distance.