Yes, this is a perfect summary. Excuse me for another "mileage" thread as I found this rather peculiar. I believe many of the sarcastic comments were a bit off-topic as I had no necessary means of being "cheap" on gas; my apologies for not being clear. On the highway, I would typically accelerate to 65 MPH and coast to 60 MPH, then accelerate. Oddly enough, others who sit in my car find my habit of coasting unusual.

As per the previous comments, I bought a sports car because I can afford it. My habit of "feathering it" as JERZ350 mentioned was merely a method I tried when I was on the road. I don't condemn it, I just found it interesting if it was enough to actually save gas. As to what others mentioned about being a hassle/annoyance to others; yes, I would feel it to be awkward, but I typically drive like this on the highway, "feathering it" whereas others would be as viable to maintain constant gas pedaling.

 

thinking out of the box for gas saving tips....(my cousin tried this) while filling up at the gas station, do not hold onto the nozzle "full flow". He swears that if you go slower you get more gas (as opposed to air). Now, i don't know how or where the gas is metered, but if it where at the nozzle then I can see this working. It always sounds like the gas is slushing and creating bubbles at the nozzle....idk, i have yet to try this but my cousin swears by this.

 

No matter how you say it its just another MPG thread.

 

Worst. Thread. Ever.

 

FWIW, as a Prius owner your above comment is complete BS. That's not the way it works. The motor/generators actually provide little acceleration and the ICE will kick in from a stop even w/fairly light throttle. I can elaborate, if you care...

Anyhow, to the OP, I don't think your method will help. For mileage improvement techniques, please read http://www.cleanmpg.com/forums/showthread.php?t=1510. Cleanmpg is run by famed hypermiler Wayne Gerdes (I have met him briefly). You can read more about him at http://motherjones.com/politics/2007...cord-beat-punk. Stop and go, city driving and short trips kills mileage. Cold weather also doesn't help.

I do actually practice a few of the techniques (mainly relating to parking) and anticipate lights.

I think what's being discussed in post 4 is referred to as pulse and glide (see above cleanmpg link). I DO pulse and glide in my Prius when there's no traffic around and at speeds where it makes sense in the Prius (must be below 42 mph), due to its limitations.

I don't bother w/pulse and glide in non-hybrids. I'm not convinced it helps there (much, if at all) and certainly will NOT FAS while driving in a non-hybrid. Unfortunately, there's no instantaneous mpg gauge in my Z.

 

I bet this thread is going the way you imagined huh?

 

I was going to respond, but said F'it. go back to HS, take physics, learn about drag, energy, momentum. all over the same distance. your doing nothing. use your tractor beam and aim it at a big rig. they will pull you along.

 

I went on a road trip where the guy driving would NOT use constant pressure on the gas pedal. For some reason he would press down, let up, press down, let up. I felt seriously nauseous by the time we got there.

 

^^^^Cruise Control was invented for morons like that.

 

The pulse and glide method is very similar to what I do, but much more sophisticated. I was not calculating the Pulse and Glide mechanism of the car as I had not the slightest clue that even existed. But, to each his own, I do drive speeding up, letting it go, and speeding up as someone mentioned previously; it's not because I do it on purpose, but because it was how I was taught to drive on the assumption that it saves gas. Old habit dies hard. And for that, I guess I'm a moron.

 

seriously?? they taught that to people? drive at a constant speed, use your motor to slow you down, dont waste momentum, swerve to avoid a stopped car (if legal and possible) hence saving wear and tear on brakes and having to use potential energy in the form of petrol converting it to kinetic energy in the combustion chamber to accelerate back to speed.

your not a moron, just the driving habit you use is.

Drive smarter.

 

I doubt it's at the nozzle... that would be more complicated than just having it near the display.

 

Someone is sure excited to show off their physics knowledge!

 

They taught me that darn stuff back in HS and said i'd need it later in life. Raising my hopes that I may be able to help save the world; or something. Little did I know it would be for something this silly.

 

Conserving momentum by not throwing it away along w/a ton of other practices is helpful (e.g. not driving too fast, getting the car out of warmup mode and keeping it at operating temperature, proper tire inflation, avoiding useless idling, etc.).

However, pulse and glide is on full hybrids (e.g. Toyota Hybrid Synergy Drive vehicles and others similar to it) isn't a waste of effort. It allowed Gerdes + 3 others to achieve ~110 mpg on a 2nd gen Prius (1397 miles on a tank of gas).

On the 2nd gen Prius, you want to pulse up to 41 mph (at that speed and above, the ICE must run) and then glide, trying to minimize the losses due to regen by avoiding regen and also trying to avoid conversion losses by minimizing how much is pulled out of the battery. The key is the ICE can automatically shutdown (aka FAS) when <41 mph.

I can't speak to the effectiveness of P & G on non-hybrids without shutting off your engine (aka FAS) or shifting to neutral. Cleanmpg.com is the place to discuss that. Google queries for site:cleanmpg.com pulse glide conventional or site:cleanmpg.com pulse glide non-hybrid are places to start.

People who really care use engine efficiency maps (if available), such as http://priuschat.com/forums/gen-iii-...iency-map.html to try to keep their engine out of inefficient RPM ranges. (1NZ-FXE is the 1.5L engine in the 2nd gen (04-09) Priuses, 2ZR-FXE is in the 3rd gen (2010-2011)). Priuses have no tach, so one must install one or get something like http://www.scangauge.com/ (I have one) to monitor engine RPM.

If one is curious, more info on the proper pulse (on a 3rd gen) at http://priuschat.com/forums/gen-iii-...tml#post893892 and an example result at http://priuschat.com/forums/gen-iii-...tml#post874637.

There are other car specific techniques that also don't involve maintaining a constant speed (e.g. "super highway mode"). IGN is a standard gauge on a ScanGauge. Also, maintaining constant speed when there are hills isn't necessarily a good thing. Read the section on "DWL: Driving w/ Load..." in http://www.cleanmpg.com/forums/showthread.php?t=1510.

Back to going to speed, some folks have done tests of speed vs. fuel economy. See http://news.consumerreports.org/cars...l-economy.html.

 

I get better economy at 75 than 65 /shrug. As some have suggested, the driving technique you describe would drive me nuts to be behind you. It bugs me when people take forever to hit the speed limit and it bugs me even more when they're going 45 at the end of an on ramp and I have to hit my brakes to drop behind the semi that that is now slowing down so it doesn't flatten them.

/rant

 

There is a simple reason why pulse and glide isn't helping you.

Let E1 be the amount of energy needed to accelerate your car of mass M to velocity V. E1=MV^2. However, to impart E to your car and achieve E1, you burn fuel. The optimal E1 comes from 100% perfect transfer of energy from gas to mechanical, and then mechanical to kinetic energy (ie. moving car). Accelerating the mass of the drive train sucks down a bunch of energy in the form of wasted work. Thus, if you could obtain velocity V using a 100% efficient engine, the optimal method of maintaining speed is to keep the rotating mass of the drive train at exactly the same rotations. Any time you accelerate or decelerate the mass of the drive train you waste energy. Further, the engine is less than 100% efficient (more like 25%), and it gets less efficient the harder it is working. Thus, if you accelerate slowly, you waste less energy than if you accelerate quickly.

The sum total of this is the ideal conservation of energy to reach E1 is to accelerate using the optimal efficiency curve of the engine (ie. slow acceleration at a lower RPM, depending on engine, with the least amount of air and fuel consumed) and then to maintain your exact velocity. Pulse and glide needlessly uses the least optimized part of the engine output, and wastes energy and thus work accelerating and decelerating the drive train, wheels, etc. Wasteless CVT transmissions combined with the ideal constant engine RPM is the way to go for ideal effiency. (this is how the Juke works)

Electric engine efficiency is different than gas engine, and so talking about electric cars is not the same as gas cars; however, at extreme torque, electric motors become very wasteful of power by generating needlessly strong magnetic field strength.

 

My bicycle attains infinite miles per gallon. As long as you dont look at the alternative fuel of food which I intake to pedal it.

Nice find and post on the prius. Definitely understood with the dual setup. However typical cars are not designed to ever conserve and store energy, just use energy. So the drive-coast technique makes not sense. Instead of staying at a constant rpm and velocity using whatever amount of fuel that would be, the person attempts to conserve fuel by letting off and then re-uses that supposed saved fuel to accelerate again (which uses more than just coasting) Id say there is no positive effect, more likely a neutral if done within controlled situation, real world would be a slightly less of a savings IMO.

Actually this whole thread is speculation and comprised of Personal opinions. minus the prius info.

ugh. onto next thread

 

I appreciate the time you spent reassessing that to an oblivious person like me. I think that last summary was a clear-cut summary of the cons to my driving. I really thought for the longest time that accelerating, gliding, and accelerating would just provide me a bit of "extra" boost in mileage, however I can clearly see that it doesn't. Thanks to the previous commenters.

 

This thread is funny. I was pretty sure it was a joke, but I guess not.