DangerousDan

iTrader: (8)

it's not the timing of the shift, but the throttle position, that affects your mileage more. as amby pointed out load varies depending upon RPM (among other factors) and accelerating with minimal throttle to 3.5k would probably create very little load compared to pulling the car along at 2k. in other words, you should monitor your injector duty cycle to determine which is better. same thing goes for cruising in 5th as opposed to 4th gear.

accelerating to 70 then letting the car coast to 60 will use more fuel than maintaining 65mph. it takes more fuel to regain your initial speed than it does to keep the same speed. this was proven by mythbusters, since someone mentioned them, but can be proven mathematically as well. regular gasoline engines don't recycle energy like hybrid or electric vehicles do, so there is nothing gained by coasting down from 70 in a gas engine.

also, shifting into neutral going downhill is a nice idea in theory, but if you accelerate over the limit and get pulled it's not a valid excuse. your ECU only uses the fuel necessary to keep the engine running unless you are on the throttle, and when you are off the throttle coasting in gear fuel is cut under certain conditions already. also, it is more difficult to control a car at speed that is in neutral than one that is in a drive gear. should something require quick steering inputs the car will dramatically change from it's normal attitude since there is no drag or pull on the drive wheels.

for the record, I don't like "hypermilers." I don't think that they should operate a vehicle too far outside the norm because traffic patterns are affected and changes in our traffic patterns cause accidents. It should be illegal to operate a motor vehicle in such a manner to impede the traffic flow, and if I was a police officer I would be pulling "hypermilers" over for erratic/reckless/inattentive/orwhtthefuxever driving left and right.

there have been multiple studies that show it only takes one car a few miles an hour off from the rest of traffic to cause a serious traffic jam during heavier traffic, imagine what one jackass "hypermiler" after another is creating for us. yeah, he's getting 150 miles to the gallon while the 37,000 cars that take an extra 5 minutes to get home are pouring tons more pollutants in the air because he wanted to coast down that hill instead of maintaining the speed of traffic around him. people will be changing lanes, cutting others off, accelerating harder to get around him; all this in heavy traffic will cause others to hit the brakes so they don't collide; it perpetuates itself and now you have a traffic jam. that's not his fault, but he is causing the problem. everyone else should drive like that guy, absolutely, but you can't expect them too. public safety is paramount; even if we end up destroying the earth our will to survive won't allow us to kill ourselves to save the planet. normal people won't change without a new technology to force it on them(or a gas price crisis I suppose, wait until it gets to 10$ a gallon...), and that means hypermilers should just stfu and drive.

however, and some of you know this, I am somewhat of an environmentalist and would like to say I really appreciate what you're trying to do. even if you are only doing it to put money back in your pocket it's still a step forward. do anything you can to save fuel and water, and to lower your "carbon footprint," because everything makes a difference. just make sure you don't drive like an asshat along the way.

/rant

chengstar

+1
startup uses a lot of gas son.

DangerousDan

iTrader: (8)

that's under debate in a modern engine, and I did hear the 10 second rule on TV the other night as shiroboi probably has. I would say it would have to be longer than 10 seconds though, especially if the car is still cold. I wouldn't suggest turning the car off unless you just hit the red, otherwise you may end up using more fuel you'd have to have a way to test how much fuel is expent at idle as opposed to used to start your particular car. you'd also have to take into consideration any "start up" mode your ECU has builty in for that particular car. if you start our cars in first gear and immediately accelerate, even with a warm car, it will sometimes cut fuel ~5000 or so. I've had this happen to me a few times in the past during testing so I know there is some sort of start up time before the ECU is in normal operation.

batmoEVO

I'm not 100% bought into this "Pulse and Slide" concept. I don't see how it could possibly be more efficient to throttle to 70mph, glide to 60mph, and then throttle back to 70mph rather than just maintaining a constant speed. As we all know, engines are not 100% efficient, in fact losing more than 60% of the energy contained in fuel to heat. They are even less efficient when accelerating as compared to maintaining a given speed. It seems like this would only work if you are going down a hill. Then, all you really need to do is let off the throttle, since you are barely buring any fuel anyway.

Any thoughts?

shiroboi

iTrader: (20)

Couple things. The "whole starting up your engine wastes more gas than leaving it idling" is a wives tale dating back to carbureators. Thats what my dad told me but with modern day fuel injectors you dont use much gas to start up. Does it use extra gas to start up? yes, but after a certain amount of time obviously an idling engine is going to be wasting alot more gas than one that isn't running at all. I think they're saying that that payoff time is 10 seconds. It very well could be longer than that in our cars. I only do it if I know I'll be sitting at the light for more than a minute and of course, not at every light. If you're at the bank, or waiting for a friend, its a sure bet that shutting off the engine will save you gas.

The true Pulse and Glide in a Prius is done essentially by shutting off the engine during the glide phase resulting in a slightly lower gas milage burst followed by a phase using zero gas. I read about people easily getting 70 MPG + in priuses using this techniqe, the best being 163 MPG. I'm trying to apply the general concept to the ralliart in the best way possible with obviously nowhere near the gains of the prius. I mainly have been trying to use the Pulse and Glide technique on hills but I'm not totally sure exactly how effective its being. I love input on this. I'm really in the testing phase. I'll see how dramatically my gas usage changes. So far, i'm seeing improvements but I don't know how much.

shiroboi

iTrader: (20)

Also, to comment on what Dangerous Dan said, he does bring up some good points. I do think that alot of the more extreme hypermilers are asshats and I refuse to drive like them. I haven't deviated a whole lot from my normal speeds and have yet to have anybody beep or cut me off. I think being more concious about wasting gas and how much you use will pay off in the long run. Also, I'm not so much on the environmental side but I'm curious to see how integrating some of the more reasonable hypermiling techniques can affect how many times a month I have to fill my car up WITHOUT pissing off other drivers. Everything in moderation.

DangerousDan

iTrader: (8)

shiroboi

iTrader: (20)

I'm updating the front page with my week long experiment.

After filling up today, looks like I went 3 days or approximately 190 miles on a half a tank. (5.7 gal) That would put my MPG at around 33+. That exceeds our EPA for the car. I'll get a more accurate reading this week and I'll make sure I focus on my techniques.

shiroboi

iTrader: (20)

Just discovered something. I was really wondering if when going down a hill, do you really save any gas by putting the car in neutral/pushing in the clutch? The answer is yes, you do save gas but I don't think its a whole lot more. My BMW has a MPG gauge and while it was high normally when going down a hill, it noticably jumped when I put it in neutral. May have to use the Bimmer as a test car. Just don't tell the wife. (Its her car)

uprockmankey

And if you're going on a steep downhill, braking hard comes. Don't brake to hard or you'd wear it out way too much and waste gas. Turning off the car at every stoplight is like a UPS truck going and stopping. Bad for our engines; those truck engines are designed differently.

shiroboi

iTrader: (20)

All of my hills are slow general sweeping highway grades. Nothing that would cause me to break hard. Car natually slows down as soon as it goes uphil again which is when I re-engage 5th.

As for stoplights, out of the 12 stoplights I drive through daily, only 3-4 of them are big enough intersections where its even worth turning the engine off and thats only in certain circumstances like when the light just turns red and I know I'll be sitting there for a few minutes. During an average commute day, I might only do the engine cutoff thing once or twice at most. No more than if you stopped at the convenience store to get something to drink.

Myszkewicz

iTrader: (2)

I got 60 mpg.









By buying a cheap motorcycle and parking my car on days it's not raining.

shiroboi

iTrader: (20)

Ahah, thats a good one. I'd consider a motorcycle but with a baby on the way, theres no way my wife would let me. For you I guess its also nice to not put so many miles on the Ralliart. Actually, I just hit 85K. It would be nice for me too.

Myszkewicz

iTrader: (2)

Having put about 10,000 miles on the bike instead of my car, I'm actually already ahead in cost savings. Well, I'm even, anyway, when I add in everything (cost of bike, helmet, licensing, etc). The more I ride, the more I'll save from now on.

rdc

iTrader: (3)

Has anyone thought of reducing the aero drag of our cars? I know it quite hard to do/test, but I really think that by having an undertray, a VG (possibly without a rear wing) and rear diffuser we can somewhat reduce our drag cf by at maybe .01 or .02 which at high speeds would yield a few more MPGs.

Also, I almost forgot to mention, since most of my driving is in the highway, everytime i go downhill I combine the put-it-in-neutral with the shut-off-the-air-conditioning (or at least leave it on blowing but with the a/c button in the "off" position so as it lets more air in than by just turning everything off).

Best MPG so far: 32.12mpg