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Hypermiling

snakewispera snr said:
they know down hill is free so they compensated when they programmed the on board computer....
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Down hill is only free if the car is OFF.

If you are coasting with the engine OFF you are using no fuel. If you are coasting with the engine ON, you are using fuel.

D80
 
desertanimal said:
I saw on a documentary on hyperniling that modern fuel-injected cars don't really use that much fuel to start, so that if you're sitting for more than 10 seconds, you should go ahead and turn it off. I don't know the answer myself, this is just what I heard from a hypermiler on the documentary.
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Lol, no wonder, the person who told me that drives a '67 Nova...
 
I have to agree with Drizzt. If the engine is a gasoline engine, and it is RUNNING, it IS using atleast some gasoline. Be it idleing, or coasting.

That being said, has anybody tried the Brown's Gas conversions that are all over the internet? I am seriously thinking of trying this to see how well it works. The only thing stopping me is My car is computer controlled, and it is my only transportation, so I really can't afford to mess it up, with a half baked scheme.
 
O.K. guys I'll explain to you...Modern engine management uses the amount of fuel that is required to turn over an engine.....When it is at standstill but idling, some fuel is required to keep it going. But when it is in gear and coasting, the engine uses no fuel to maintain the turn over of the engine.......Gravity does it through the gears......
How about the Chrysler 300c.... A big v8 engine....You thrash it and all 8 cylinders are working, you poodle around in it and 4 cylinders shut down... They still move but use no fuel..... Then there is some Cadillacs... They have limp home technology... It will shut down cylinders to stop the engine over heating, in the event of no water in the radiator..... I guess you guys will still disagree, but modern engine management computers are a wonderful thing... try setting you fuel consumption computer to instant when you coast down a big hill it will read 999mpg. If I was any good at googling I could probably find where it was but I'm not.....
 
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snakewispera snr said:
Sorry guys but I have found another one to back up my lack of knowledge on the internal combustion engine...LOL.. ;)
http://www.popularmechanics.com/automotive/how_to/4230705.html
Have I failed to mention, one of my biggest passions is ....You guessed ....Cars... LOL
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Actually we're both only partially right, as Wikipedia says,

In cars with a manual transmission, fuel can be saved while the car is coasting in gear. This is because the car's movement is keeping the engine rotating, so there is no need to use fuel for this purpose. Control units on modern transmissions recognize this and stop all fuel flow to the engine when possible. (Automatic transmission cars rely on torque converters, not clutches, to transmit power from the engine to the gearbox, and whereas clutches can transmit power in both directions, torque converters, especially when tuned as they are in cars, are not good at transmitting power in the opposite direction.)
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Come on Cpt'n I'm right......I said modern cars..... in gear.... no throttle......computer......LOL...... And I can write wikipedia so thats not a recognised authority... The AA is... LOL...... na na nana na ROTFLMAO
 
So anyway, I checked my mileage today. 19.2, smallish SUV, half-heartedly trying some simple gas-saving techniques. For this tank, I am going to avoid braking if at all possible, especially in traffic, coast as much as possible, like around corners, up to stop signs, downhill from the parking ramp to the stop sign, try not to accelerate at an RPM higher than 2000, avoid idling as much as possible, try to park so I don't have to back up to get going, no AC (but I don't use it anyway) drive with windows up as much as tolerable, and biggest change of all- NOT SPEED! We'll see if it makes a difference. I run about 300 miles to a tank, since I don't have a gas gauge.
 
So my 19.2 mpg is apparently 112.94% of the combined EPA estimate! (15 city, 19 highway). I can't wait to see what I get now that I have my speeding under control. I also bought an air compressor (small) so I can have perfect tire inflation at all times. Ooh, and not only am I not accelerating over 2000 RPM, but at the speeds I'm driving, even on the freeway, I don't exceed 2000 RPM ever!
 
snakewispera snr said:
Come on Cpt'n I'm right......I said modern cars..... in gear.... no throttle......computer......LOL......
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When coasting in gear the fuel injection shuts off . . . BUT turns back on below 1500 rpms and also takes time to shut off. How much is really gained? What slope and distance do you need to really achieve no fuel consumption as you state? I will agree you gain decreased fuel consumption. Not quite as black and white as you made it out though. Whne coasting in neutral . . . the fuel still needs to be injected constantly otherwise your engine will stall.

Your statements are accurate and I thank you for them as I've learned some new info, but they're not as black and white or as "right" as you make them out to be.

D80

PS. Sorry for the late reply. Contrary to the information shared in your PM, I haven't been around reading this thread all week. I've been out of town and away from technology (YES!) since Monday morning at 6:00 am. :)

http://www.popularmechanics.com/automotive/how_to/4230705.html
Most fuel-injected cars turn the fuel delivery completely off when you lift your foot from the accelerator. They still burn fuel when idling in Neutral, so do the math. The amount of fuel burned at idle over, say, a couple of miles of coasting downhill is small, but it’s still more than zero. So if you’re driving a modern fuel-injected car, you’re wrong.

Older, carbureted cars would suck gas through the engine while coasting in gear, even if you turned off the ignition switch. In this case you’d be right.
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http://www.gassavers.org/archive/index.php/Fuel-Injector-shutoff-while-Coasting/t-865.html
Both my VW and BMW do it. My experience is that if the catalyst is hot and the engine speed is high enough, the ECU decides to shut down unnecesary idle fuel. Atleast in the BMW with an analog mpg gauge, I can see exactly when the shutoff happens. Assuming the cat is hot, if the RPMs are above about 1500 while coasting in gear, it usually takes about 2-3 seconds of normal idle flow but then shuts off. It keeps it off until the RPMs fall below about 1000 (idle is about 650). If I'm on a long hill and I have to keep the speed from increasing (either for traffic or to avoid speeding), I can sometimes do this for a long way. It really pushes up the average mpg.

It's an interesting game to play because it's often better to 'spend' the momentum I've already invested in, and coast farther with the clutch in letting the engine idle. In these cases I also consider how far I am likely to coast. If it's pretty far, sometimes it's better to speed up slightly (as in a pulse) and then glide at a higher speed. Since the idle fuel flow is constant, my higher speed in these cases turns into mpg numbers.

And then there are times when I need to slow down and surrender my precious momentum, such as for traffic, stop signs, lights, sharp corners, etc. Rather than just squander it on merely heating and wearing my brakes, I try to take advantage of the shutoff function. In these cases, vehicle speed is irrelevant and RPM is all important. I have to choose the right gear and then brake only when I finally have to stop. :)

Now if only there was a way I could derive the defining algorithim. Of course then I'd want to add automatic shutdown/bump starts, then automatic FAS and restarts when stopped, regenerative braking, not to mention aero, A/C and P/S mods, and... :p
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if the injectors shut down in an automatic, there's nothing to keep the engine turning (no direct connection to the wheels). the engine will stop when the fuel stops.

I was actually wondering about that. I do experience engine braking when deccelerating, but probably not to the point where if the fuel cut off the car would keep going. I keep thinking I should have bought a manual, but the 5th gear ratio at 0.525 is the only thing saving the automatic. I can cruise at 50mph turning over at 1600 rpms.
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From what I've read, I heard that the fuel injectors give slight pulses of fuel on decel instead of complete cutoff, but I didn't consider it to be a significant amount of fuel. As far as know, it pulses until around 800-900 rpm, then it kicks-into full injection mode to maintain idle, even in gear. Neutral coasting has yielded huge benefits, believe you me.
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http://www.mazda-speed.com/forum2/index.php?action=printpage;topic=13900.0
I'm interested in seeing a log too. But that's been my understanding: the ECU shuts off the injectors if you're coasting in gear, but can't do that if you're coasting in neutral, otherwise the engine would stall.

Those of you with AFR meters might be able to verify this. In neutral it should act like you're stationary and idling. In gear, it should go blank or show infinity (because there's only air, no fuel).
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My last tank of gas I got about 300 miles. This tank of gas I am on track to get 500(125 miles on a quarter tank). All I did was drive the speed limit and only gun it if it is actualy necessary. I was very surprised the difference it made. I wasn't a speed demon or anything in the first place, but the traffic on the main highways around here is always 10-15mph above the speed limit in the non-slow lanes.
 
It's surprising how much fuel can be saved by not being heavy footed....On our motorways cars used to travel at between 85-90 mph. Now that fuel has hit $12 a gallon I've noticed that they all seem to be doing between 60-70 (our speed limit)
I'm sure our government sees this as the best way to slow us down, and make a few bucks as well...LOL
 
So my nine days and 290 miles of driving without speeding has gained me 3 miles per gallon, or 63 extra miles per tank. That is nearly four trips to work for free! I got my air compressor yesterday and this next tank will see how much having the tires inflated to the max pressure helps.
 
Nanci said:
So my nine days and 290 miles of driving without speeding has gained me 3 miles per gallon, or 63 extra miles per tank. That is nearly four trips to work for free! I got my air compressor yesterday and this next tank will see how much having the tires inflated to the max pressure helps.
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Would that be the recommended tire pressure, according to the vehicles owner's manual, or the max pressure, according to the tires side wall?
 
Tire sidewall max pressure.

So I just filled up my truck, and my new mpg is 23.0578, or 144% of the combined EPA! I changed my air filter today, and topped off the tires. I really, really want to achieve 25 MPG! I can't believe how well this is working, and how much more relaxed my driving is. And I quit with the rolling stops- peer pressure! You guys made me feel too guilty. Not only was it my dad rolling in his grave, but cs.com silently shaking their heads. However, I have adopted face-out parking, to avoid backing up when leaving a parking space!
 
Nanci said:
However, I have adopted face-out parking, to avoid backing up when leaving a parking space!
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Remember that if it is a slanted parking spot, you can get a ticket for "parking against the flow" in many states. Plus, it is just rude to do drive up the down row if it is a "one way" row. LOL.

I've always parked that way on straight slots or gravel lots. It make it easier to get OUT if the plant starts to blow (oil field work in the past) or someone is after you, lets you get out first if everyone leaves at the same time (lol), it is easier to watch for people that DON'T look when they back out are driving up the down row, and makes it easier to find your car in the lot.
 
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