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Hello. Considering that gas prices are so high, I've a quick question:
Supposing FUEL ECONOMY is on your mind, then, for waiting at stoplights,
which is better the handbrake or the brake pedal? I'd like to ask if
anybody who knows about fuel efficiency improvement can tell me if using my
hand/parking brake to wait at stoplights conserves more fuel than if I,
instead, hold down my brake pedal?
I'm just, once again, wondering if, between the two brakes, there's at all
any major difference that might enable me to save a few pennies.
I can't find a simple "yes" or "no" or "doesn't make a difference" answer
anywhere online regarding footbrake v. handbrake on a standard
automatic-tranny vehicle with a standard hydralic brake system. Can
someone please help me(save me from ignorance!) or post a link to a webpage
providing info on this topic?
ofarqu1
Seems to me there wouldn't be any difference whatsoever...
.
.
BavarianWheels
There's no difference--neither one affects your engine. If you want to save
gas though, try some of the tips here
(http://en.wikipedia.org/wiki/Hypermiler#Techniques_used_to_maximize_fuel_e
conomy) and here (http://www.hypermiling.com/). When reading those tips,
just use common sense. Like it might say to time traffic lights so you can
brake as little as possible, but make sure you can stop in the distance.
chris_knows
Over the life of the car, you might save a penny if you use the hand brake,
because then the brake lights won't come on, reducing your energy
consumption. however, I don't think the danger associated with using the
hand brake is at all worth it, because, as I said, your brake lights won't
come on, and people behind you won't know you are stopping. I think you
would be better off shifting into neutral, or shutting the engine off
completely if it is a long light.
wow, my wording stinks, but you know what I mean:oops:
dvdrose18
Hmmm...you got me thinking. Power brakes run off of the motor. I seem to
recall seeing the RPMs jump while in park when I pump the brakes. So I
guess the handbrake would yield an extremely slighty better MPG.
However, DVDRose is right, to actually brake with the handbrake is
incredibly dumb. It's too easy to lock up the brakes with a handbrake.
Also, brake lights exist for a reason too. However, I wonder if a
footbrake could be made that doesn't run off of the motor?
giant016
as far as I know of, most power brakes just borrow a little vacuum from the
engine, not real significant power. when you pump your brakes, you might be
messing with the vacuum pressure, but I don't think the engine has to work
any harder for you to brake. think about it, when you turn the engine off,
you still have power brakes for a pump or two while you use up the vacuum.
and it doesn't use any vacuum to hold the brakes at a constant pressure,
just to apply them.
dvdrose18
Figure this way. You wont save significant if any money on gas, and youll
have to adjust your e-brake cable probbably monthly :laughing:
newyorker
and why would you have to adjust the cable any different than if you used
your regular brakes? your brakes are going to wear the same, and the cable
isn't going to get much more use than if you set the brake regularly.
dvdrose18
I mean if he uses the e-brake to stop the car instead of the pedal
newyorker
The best way to save fuel is slow down, don't make sudden stops/jackrabbit
starts and keep the car maintained/tuned up
tbaxleyjr
Well, thank you all who replied. So to clarify, I'd never suggest using the
handbrake to slow as you reach a stop, but I meant, instead, after stopping
could you pull up the break rather than lay on the break pedal.
Many of the tips are helpful 'cept now I've gotta suspect there's not a
definitive yes-no answer to this question. From a motorist standpoint, I'm
just confused as can be. After all, fuel economy is dependent, not just on
breaks, but so many other things. Well...an alternative solution might just
be busing my way around (or carpooling) since, as a motorist, I already
took the shortest possible route there is. There's no use, is there?
This has been a mesage from:
Maybe Losing Hope in Automotive Industry Explanation Deprt.
(just kidding, ofarqu1)
ofarqu1
Basically, the brakes run off the engine, so by using the hand brake, you
might save a couple cents every year--but it is dangerous, since the cars
behind you might not know you are stopped, so it's not really worth it.
chris_knows
not really, the brakes themselves don't use any power from the engine,
unless you have a separate vacuum pump. The only thing that uses power is
the brake lights, and in some cases, the ABS. Both of which use minimal
power from the engine, unless the ABS is activated. Of course you don't
want to be using the e-brake for hard stopping, because on many, if not
all, cars, the E-brake only applies the rear brakes.
To answer the original question, once a car is stopped, using the e-brake
instead of the regular brakes will have no significant effect on your fuel
economy, but will increase the danger of getting rear ended. To save money
while at a stop light, shift into neutral so the engine doesn't have to
work as hard, and see those links that Chris posted, they give good advice.
dvdrose18
best way to save fuel is to avoid sudden stops, jackrabbit starts and slow
down. Keeping the car tuned up and maintained helps too
tbaxleyjr
I dislike when people state to slow down. sure, your efficiency is going to
suffer if you are going 90 MPH, but most cars today (I am guessing, I don't
know for a fact) have their peek efficiency around 55-60 MPH. Older cars
maybe 45-50 MPH. I am thinking specifically of my parents newer (2006) Kia
minivan which will kick out of top gear when you go up a hill at 55 MPH. I
think instead of stating to slow down, you would be better off telling
people to hold a constant speed, and maintaining a safe distance, as in not
tailgating or weaving in and out of traffic, which would require excessive
acceleration and braking. :2cents:
dvdrose18
good ideas but lets look at this from an engineering perspective
The car's engine/drive train must overcome resistance from several sources
- internal resistance (moving parts), drive train (tranny, etc - you
mentioned some issues concerning gearing), tires (inflation pressure, wheel
alignment, etc) , and drag. All of these items are somewhat independent
variables.
Drag is a function of the drag coefficient (Cd - determined experimentally
for a given car body in a wind tunnel) multiplied by speed squared thus
vehicle speed is as much of a variable as anything.
The combustion process must take place efficiently (maintenance/tune-ups)
tbaxleyjr
I understand the drag and resistance, which is why your efficiency will
drop off sharply when you go at higher speeds, but with gear ratios, you
will travel (I believe, though I may very well be wrong) more efficiently
at 50 MPH in overdrive than you will at 25 MPH in second gear. I am sure
each vehicle has its own specific speed at which it is most efficint, but I
am just trying to say that slower isn't always better.
As an example, i refer to this
(http://www.car-forums.com/talk/showthread.php?t=29593) thread, bu
increasing my speed 2 or 3 MPH my car will shift into overdrive and the RPM
will drop by 30-40% which I would imagine is more efficient. Of course if
the car in front of me is thinking slower is better and is doing 5 MPH
below the limit, my efficiency will suffer (again, just guessing, no hard
facts for support)
:2cents:
dvdrose18
You are right - to a point. Each engine/tranny has a specific operating
curves. The faster an engine turns (rpm), the more fuel it consumes due to
increased mechanical losses, etc.
I do not have a scanner at home or I would provide a set of curves from
Internal Combustion Engines (E.F. Obert) which compare cars with various
engines ranging from a 1934 Packard V-12 (445 cid) through a 91 CId sub
compact with various rear ends/gear ratios, etc.) Also compared in the
curves are various compression ratios from the 6;1 in the Packard to a 10:1
in one of the 6 cyl engines. There are a few cases where the mpg vs speed
curves but a common characteristic is the steady state (no stop and go
driving, flat ground, etc) milage peaks @ between 30 Mph and 40 Mph and
steadily decrease as the car moves faster.
tbaxleyjr
sounds like an interesting spare time read, though I am sure many would
find it a bore...
dvdrose18
I got a question...In an automatic car, you can push the shifter from Drive
to Neutral with little effort without pushing in the button to shift. I
can't do that between other settings, so I figure it was done on purpose if
you're coasting or something. Question is, does that do any damage to the
transmission or is it perfectly fine?
chris_knows
A mandatory read for a college kid 25 yrs ago (myself) who was taking a
mechanical thermodynamics technical elective in internal combustion engines
tbaxleyjr
