TiVo Community
TiVo Community
TiVo Community
Go Back   TiVo Community > TiVo TV Talk > Now Playing - TV Show Talk
TiVo Community
Reply
Forum Jump
 
Thread Tools
Old 06-14-2013, 09:18 PM   #31
midas
I heard that
 
midas's Avatar
 
Join Date: May 2000
Location: Montgomery, IL USA
Posts: 9,216
Quote:
Originally Posted by cwerdna View Post
Umm, non-hybrid automatics I've driven can be restarted while in neutral.
Most, but not all. Either way, it doesn't matter. I still find it very annoying and distracting. It's still a very different driving experience compared to an auto stop/start system.
midas is offline   Reply With Quote
Old 06-15-2013, 06:09 AM   #32
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by john4200 View Post
No, you missed the point. They were avoiding braking of any kind in order to keep their momentum up and save fuel. If you brake (with the brakes, or the engine) before going into a turn, then you need to use more fuel later to speed up again.
All that extra momentum won't do you any good if you can't stay planted on the road and end up crashing. A good hypermiler will know where he/she will have to slow down due to a tight corner, and let their speed naturally scrub off before they get to that point. It's really no different than anticipating stop lights and stop signs.
RonDawg is offline   Reply With Quote
Old 06-15-2013, 06:12 AM   #33
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by Waldorf View Post
I'm currently driving a Hyundai Sonata Hybrid rental and find the engine cut-off at stops to be a bit unnerving. Starts right up like a golf cart, though.
I got used to it very quickly. I don't know about the Hyundai, but on the BMW there is an area on the tach to indicate if the engine is in "standby" as opposed to totally off (0 RPMs).

Quote:
Originally Posted by vertigo235 View Post
I assume you can turn it off. What about those times when you're in heavy traffic and Need the air conditioner while you're stopped?
On the BMW, yes you can turn it off. It's just above the starter button. If the car senses a need to run the engine for some reason (for example, heater usage) then it will do so.
RonDawg is offline   Reply With Quote
Old 06-15-2013, 06:22 AM   #34
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by JYoung View Post
I'm not sure but I thought that I saw a CHP escort for Kari and Grant when they ran out of gas on the hypermile lap.
Perhaps that prevented them from being victims of road rage.
Even with the CHP escort, a car still honked at Tory and (according to him) the female driver flipped him off.

45 MPH on any California freeway is just plain crazy unless everybody else is doing that speed. Many freeways that are posted at 55 still have traffic going by at 65+. Bay Bridge is posted 50 up to the temporary s-curve, and even then people are racing to that curve at 70, and going through the curve at higher than the posted 45 limit.
RonDawg is offline   Reply With Quote
Old 06-15-2013, 06:29 AM   #35
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by Hank View Post
They prob could have shifted into neutral on the down slopes and idle the engine, but I know that's not generally legal.
It's not legal (certainly not in California where this was filmed) and quite dangerous if you let your speed get out of hand. It's even worse if you tried to control your speed by "riding" the brakes, because if they are overheated, they don't work at all.

From what I've been told on this very forum, on a modern fuel injected car if you downshift in order to control your speed on a downhill run, and don't put your foot on the gas, the engine is using zero fuel and is just one giant air pump powered by gravity, so you're not using any gas whatsoever.
RonDawg is offline   Reply With Quote
Old 06-15-2013, 06:37 AM   #36
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by cwerdna View Post
For example, if they were approaching a red light, they should've shut off their engine at some point before the red light and just coasted to the intersection.
Problem with that is on a non-hybrid, you lose power braking and steering assist once the engine is off. Definitely not recommended on San Francisco's hilly streets.
RonDawg is offline   Reply With Quote
Old 06-15-2013, 09:42 AM   #37
john4200
Registered User
 
Join Date: Oct 2009
Posts: 3,310
Quote:
Originally Posted by RonDawg View Post
All that extra momentum won't do you any good if you can't stay planted on the road and end up crashing.
Really? If only I thought of that before my last crash.
john4200 is offline   Reply With Quote
Old 06-15-2013, 07:10 PM   #38
Waldorf
Super Duper Member
 
Waldorf's Avatar
 
Join Date: Oct 2002
Location: Phoenix, AZ
Posts: 996
Quote:
Originally Posted by RonDawg View Post
I got used to it very quickly. I don't know about the Hyundai, but on the BMW there is an area on the tach to indicate if the engine is in "standby" as opposed to totally off (0 RPMs).
I have two BMW's as well as a "fun" car and you can really sense the engine running at stops. On this hybrid (and most others, I imagine), it's just kind of strange to be sitting there with no vibration coming through the car as if it died. And yes, like others have stated, the radio and a/c and everything will still run off battery, I'm just not sold on it yet as I feel disconnected from what's going on.

Has anyone tried the Honda CR-Z? I have read it has a 6-speed manual transmission option on the hybrid. Sounds interesting.
__________________
"Waldorf is a Super Duper Guy!" -wannaB

Last edited by Waldorf : 06-15-2013 at 08:48 PM.
Waldorf is offline   Reply With Quote
Old 06-15-2013, 10:37 PM   #39
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by john4200 View Post

Really? If only I thought of that before my last crash.
I'm not sure why you're being so snarky here.

Yes I can understand why a hypermiler doesn't want to slow down. But driving in real life conditions means eventually you have to slow, if not come to a stop. A hypermiler will anticipate these and try to let the car naturally scrub off speed before getting to such an area, rather than racing up to red lights and stop signs as I often see.

I was also only commenting on their assertion that their methods are legal and safe. 45 on a posted 65 is borderline rolling traffic hazard, and taking curves so fast that you cause the tires to squeal means you're on the verge of losing traction.

BTW I drive an all-electric car as my commuting car, so I'm acutely aware of these techniques myself. When your usable range per charge is only in the double digits, you learn to adapt real quick.
RonDawg is offline   Reply With Quote
Old 06-15-2013, 11:53 PM   #40
Waldorf
Super Duper Member
 
Waldorf's Avatar
 
Join Date: Oct 2002
Location: Phoenix, AZ
Posts: 996
This may be the source of the "double your mpg by hypermiling" myth as they mention getting 50mpg in a car rated for 25mpg

http://www.cnn.com/video/#/video/tec...ypermiling.cnn

I saw another one similar to this where guys driving insights and priuses were getting over 100mpg but I haven't been able to source it yet.
__________________
"Waldorf is a Super Duper Guy!" -wannaB
Waldorf is offline   Reply With Quote
Old 06-16-2013, 12:05 AM   #41
john4200
Registered User
 
Join Date: Oct 2009
Posts: 3,310
Quote:
Originally Posted by RonDawg View Post
I'm not sure why you're being so snarky here.
You astound me with your lack of surety!

Perhaps you will share some more words of wisdom. Do you suppose the gas mileage of a car will be lower if you drive it immediately after a crash? Do you think a crash you can walk away from is better than one where you end up in critical condition at the hospital? Is someone with a sense of humor more likely to survive a crash than someone lacking in that department?

Last edited by john4200 : 06-16-2013 at 12:23 AM.
john4200 is offline   Reply With Quote
Old 06-16-2013, 01:46 AM   #42
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by john4200 View Post

You astound me with your lack of surety!

Perhaps you will share some more words of wisdom. Do you suppose the gas mileage of a car will be lower if you drive it immediately after a crash? Do you think a crash you can walk away from is better than one where you end up in critical condition at the hospital? Is someone with a sense of humor more likely to survive a crash than someone lacking in that department?
Rather than continue to sidetrack this thread with any more futile attempts at rational discussion with you, I will just ignore you from now on.
RonDawg is offline   Reply With Quote
Old 06-16-2013, 01:50 AM   #43
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by Waldorf View Post
Has anyone tried the Honda CR-Z? I have read it has a 6-speed manual transmission option on the hybrid. Sounds interesting.
A friend of mine test drove one and found it totally...underwhelming.
RonDawg is offline   Reply With Quote
Old 06-16-2013, 03:01 AM   #44
john4200
Registered User
 
Join Date: Oct 2009
Posts: 3,310
Quote:
Originally Posted by RonDawg View Post
Rather than continue to sidetrack this thread...
So, no more words of wisdom about how crashing is bad, then?

(I would have gone with "no more running this thread out of control" myself)

Last edited by john4200 : 06-16-2013 at 03:07 AM.
john4200 is offline   Reply With Quote
Old 06-16-2013, 03:12 AM   #45
cwerdna
Proud Tivolutionary
 
Join Date: Feb 2001
Location: SF Bay Area, CA
Posts: 8,568
Quote:
Originally Posted by RonDawg View Post
Problem with that is on a non-hybrid, you lose power braking and steering assist once the engine is off. Definitely not recommended on San Francisco's hilly streets.
Well, you get at least 1 or 2 presses of the brake power assist w/the engine off, but yeah, there is the loss of power steering.

To me, it'd be not too terrible if to shut off the engine when approaching a traffic light that's only straight ahead and you know how well the car's speed scrubs off when the engine's off, so that you don't need the brakes at all/much.

Quote:
Originally Posted by Waldorf View Post
I have two BMW's as well as a "fun" car and you can really sense the engine running at stops. On this hybrid (and most others, I imagine), it's just kind of strange to be sitting there with no vibration coming through the car as if it died.
It's not too weird anymore, but then again, I've had my Prius for over 7 years now. For me, it drives me nuts to be in a regular car w/the stupid engine idling away when stopped. And, it irks me greatly to be in such a car and using the brakes, to know all that kinetic energy is being thrown away as heat and brake dust.

The BMW 3-series cars that I drove w/auto-start stop have a comical restart noise. I heard it from other BMWs on the test drive loop. It was just hilarious to me (from someone having driven hybrids from Toyota, Nissan (well it's Toyota HSD based), Ford, Honda and Kia).

Last edited by cwerdna : 06-16-2013 at 03:18 AM.
cwerdna is online now   Reply With Quote
Old 06-16-2013, 03:22 AM   #46
cwerdna
Proud Tivolutionary
 
Join Date: Feb 2001
Location: SF Bay Area, CA
Posts: 8,568
Quote:
Originally Posted by Waldorf View Post
Has anyone tried the Honda CR-Z? I have read it has a 6-speed manual transmission option on the hybrid. Sounds interesting.
No, but its fuel economy are disappointing along w/its straight line performance.

See how it did in CR's FE tests at http://www.consumerreports.org/cro/2...ginMethod=auto. It scored too low in their tests to recommend.

In their tests, it did 0-60 in 9.3 seconds so ok it's faster than a Prius but a Camry Hybrid blows it away (http://www.consumerreports.org/cro/2...ance/index.htm). My mom's Altima Hybrid got identical acceleration times to the '12+ Camry Hybrid (not surprising since they're only 2 hp apart).

I also wouldn't trust the battery longevity of any Honda hybrid. Their track record is not particularly good. It's unfortunate that Honda's not putting up a better fight against Toyota.
cwerdna is online now   Reply With Quote
Old 06-17-2013, 11:19 AM   #47
Waldorf
Super Duper Member
 
Waldorf's Avatar
 
Join Date: Oct 2002
Location: Phoenix, AZ
Posts: 996
Quote:
Originally Posted by Waldorf View Post
I saw another one similar to this where guys driving insights and priuses were getting over 100mpg but I haven't been able to source it yet.
This is in the same vein as what I was thinking of.. he averaged over 106 mpg on a tank:

http://www.startribune.com/lifestyle/22053954.html

I think he may have been part of a group of people I saw on another episode of 20/20 or Dateline or something else, but I haven't been able to find it.
__________________
"Waldorf is a Super Duper Guy!" -wannaB

Last edited by Waldorf : 06-17-2013 at 11:27 AM.
Waldorf is offline   Reply With Quote
Old 06-17-2013, 12:38 PM   #48
voripteth
User Advocate
 
Join Date: Apr 2003
Posts: 324
We regularly get 100+ MPG but then again we have a Volt.
voripteth is offline   Reply With Quote
Old 06-17-2013, 01:20 PM   #49
verdugan
Registered User
 
Join Date: Sep 2003
Location: Sacramento, CA
Posts: 2,076
Quote:
Originally Posted by RonDawg View Post
Rather than continue to sidetrack this thread with any more futile attempts at rational discussion with you, I will just ignore you from now on.
The ignore list is a powerful thing. Use it. Shout if you have quesitons on how it works.
verdugan is offline   Reply With Quote
Old 06-17-2013, 02:01 PM   #50
Waldorf
Super Duper Member
 
Waldorf's Avatar
 
Join Date: Oct 2002
Location: Phoenix, AZ
Posts: 996
Quote:
Originally Posted by voripteth View Post
We regularly get 100+ MPG but then again we have a Volt.
How long have you had it / how is it so far? The Volt is a certainly different beast... I remember reading that Jay Leno had 11,000 miles on his Volt and still had half the original tank of gas.
__________________
"Waldorf is a Super Duper Guy!" -wannaB
Waldorf is offline   Reply With Quote
Old 06-17-2013, 02:26 PM   #51
Flop
Registered User
 
Join Date: Dec 2005
Location: Oklahoma
Posts: 329
Quote:
Originally Posted by secondclaw View Post
I was actually hoping they would do another HM thing - accelerating 5mph above posted speed limit then coasting down ... I've always been curious if that method actually does anything but been too lazy to try it myself. I suppose they don't want to break the law on TV, even if its a 5mph over limit.
I can't imagine how that would save any gas. Since the drag on the car is more or less constant at those speeds, it seems you would burn more gas to produce the amount of energy required to accelerate the mass of the car and to overcome drag from air resistance and tire friction than you could possibly save by coasting back down. It's been many years since I took physics, but I believe the power required to overcome aerodynamic drag increases as the cube of the velocity (it might be the square not cube... it's been a while). At high speeds (say going from 65 to 70) that power difference won't be a lot, but it's still additional power required, and you still have to add the power required to accelerate the mass of the car as well.
Flop is offline   Reply With Quote
Old 06-17-2013, 02:42 PM   #52
Hank
AC•FTW
 
Hank's Avatar
 
Join Date: May 2000
Location: Boston, MA
Posts: 17,868
It's the square.
Hank is offline   Reply With Quote
Old 06-17-2013, 02:43 PM   #53
john4200
Registered User
 
Join Date: Oct 2009
Posts: 3,310
Quote:
Originally Posted by Flop View Post
It's been many years since I took physics, but I believe the power required to overcome aerodynamic drag increases as the cube of the velocity (it might be the square not cube... it's been a while). At high speeds (say going from 65 to 70) that power difference won't be a lot, but it's still additional power required, and you still have to add the power required to accelerate the mass of the car as well.
The third power is correct.

You are certainly correct about speeding up and coasting being an inefficient technique in general.

Although I can imagine a more sophisticated technique, that slows down a bit when there is a headwind and speeds up a bit when there is a tailwind, could be effective. It would probably need electronic automation to do it well -- a digital speedometer or GPS to monitor ground speed, an anemometer to monitor airspeed, and a computer to compare them and determine if there is sufficient headwind or tailwind to merit a throttle change.

Last edited by john4200 : 06-17-2013 at 03:24 PM.
john4200 is offline   Reply With Quote
Old 06-17-2013, 02:52 PM   #54
john4200
Registered User
 
Join Date: Oct 2009
Posts: 3,310
Quote:
Originally Posted by Hank View Post
It's the square.
No. The drag is proportional to the second power of velocity, but the power required to offset the drag is proportional to the third power of velocity:

P = F * v = ( k * v^2 ) * v = k * v^3
john4200 is offline   Reply With Quote
Old 06-17-2013, 04:39 PM   #55
RonDawg
Registered User
 
Join Date: Jan 2006
Posts: 15,582
Quote:
Originally Posted by verdugan View Post
The ignore list is a powerful thing. Use it. Shout if you have quesitons on how it works.
I'm well aware of how it works, thank you.

Last edited by RonDawg : 06-17-2013 at 05:10 PM.
RonDawg is offline   Reply With Quote
Old 06-17-2013, 05:52 PM   #56
kdmorse
Registered User
 
kdmorse's Avatar
 
Join Date: Jan 2001
Location: Germantown, MD
Posts: 4,198
Quote:
Originally Posted by john4200 View Post

You are certainly correct about speeding up and coasting being an inefficient technique in general.
I wonder about the hypothetical engine/transmission combination that is more wasteful maintaining speed than accelerating. Where accelerating briskly and efficiently for 10 seconds then idling for 50, is more efficient than maintaining speed at an inefficient RPM for 60 seconds.

Not that it would ever be the case in a modern automobile, but I wonder if it was at least partially the case for some model of 60's/70's vehicles, enough so to generate the idea....
__________________
"I disapprove of what you say, but I will defend to the death your right to say it"
"Stop slouching! It's two O'clock in the afternoon, PUT PANTS ON!"
"Statistically speaking, there are two Popes per square kilometer in Vatican City..."
kdmorse is offline   Reply With Quote
Old 06-17-2013, 08:02 PM   #57
alansh
Registered User
 
Join Date: Jan 2003
Location: Phoenix, AZ
Posts: 1,175
The speed up and slow down thing is "pulse and glide", and may be specific to the Prius or at least hybrids in general.

The idea of the hybrid is to keep the internal combustion engine at the most efficient point in its power curve, regardless of the amount of power you actually need. So if the ICE is generating too much power, the excess goes into the battery and is used when you need more power than the engine is creating.

There are losses in the process, so pulse and glide aims to use 100% of the engine's output for acceleration, rather than having an excess that goes into the battery. You accelerate to above your target speed, with the goal of none going into the battery. Once you're above your target speed you coast, with the engine turning off automatically. Once you've slowed enough, you repeat.

You could theoretically do this in a non-hybrid, but the shifting into neutral and turning off the engine for the glide part is going to be a problem.
alansh is offline   Reply With Quote
Old 06-17-2013, 08:19 PM   #58
john4200
Registered User
 
Join Date: Oct 2009
Posts: 3,310
Quote:
Originally Posted by alansh View Post
There are losses in the process, so pulse and glide aims to use 100% of the engine's output for acceleration, rather than having an excess that goes into the battery. You accelerate to above your target speed, with the goal of none going into the battery. Once you're above your target speed you coast, with the engine turning off automatically. Once you've slowed enough, you repeat.
While that technique may be able to increase mileage in city driving, I thought we were discussing freeway driving, where such a technique would surely hurt your mileage, for reasons already explained by Flop.
john4200 is offline   Reply With Quote
Old 06-17-2013, 10:16 PM   #59
alansh
Registered User
 
Join Date: Jan 2003
Location: Phoenix, AZ
Posts: 1,175
Yes, pulse and glide is typically used around 40mph or less on the Prius. At those speeds, the difference in the power curve is enough to make a bigger difference than the wind resistance. Above 40mph, the gen II Prius has to run the gas engine because of the way the gearing between the electric and gas motors is done, so the engine never really shuts off. I haven't really looked into the difference for the gen III.

Anyway, as I mentioned, this would be really difficult to do on a non-hybrid.
alansh is offline   Reply With Quote
Old 06-17-2013, 10:26 PM   #60
cwerdna
Proud Tivolutionary
 
Join Date: Feb 2001
Location: SF Bay Area, CA
Posts: 8,568
Quote:
Originally Posted by alansh View Post
Yes, pulse and glide is typically used around 40mph or less on the Prius. At those speeds, the difference in the power curve is enough to make a bigger difference than the wind resistance. Above 40mph, the gen II Prius has to run the gas engine because of the way the gearing between the electric and gas motors is done, so the engine never really shuts off. I haven't really looked into the difference for the gen III.
On Gen 3 Prius, I believe the max speed at which you can drive w/the ICE not turning is ~46 mph, rather than 40 or 41 mph.

There's also the efficiency map at http://priuschat.com/threads/2010-pr...ncy-map.62586/. 1NZ-FXE is the 1.5L engine used in the Gen 2 (04-09) Prius while the 2ZR-FXE is the 1.8L engine used in the 2010+ Prius liftbacks.
cwerdna is online now   Reply With Quote
Reply
Forum Jump




Thread Tools


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Advertisements

TiVo Community
Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
vBulletin Skins by: Relivo Media

(C) 2013 Magenium Solutions - All Rights Reserved. No information may be posted elsewhere without written permission.
TiVo® is a registered trademark of TiVo Inc. This site is not owned or operated by TiVo Inc.
All times are GMT -5. The time now is 01:04 AM.
OUR NETWORK: MyOpenRouter | TechLore | SansaCommunity | RoboCommunity | MediaSmart Home | Explore3DTV | Dijit Community | DVR Playground |