carlsr's Forum Comments
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Pulse and Glide?
After reading these very informative posts, I thought I'd contribute a little bit.
Firstly, if your engine is on, the fuel is NEVER completely cut off...remember there is something called the power (or combustion) stroke in the 4-cycle engine that we all use. This is the process of fuel exploding in the cylinder thus forcing it down and creating the necessary revolutions of the driveshaft that moves us. I'm sure we all know that, but the general speak was that fuel is completely cut off when your foot is removed from the gas pedal. Not true, gas will always be used as long the engine is on.
The Pulse and Glide method attempts to capitalize on the kinetic energy created by the small bursts of acceleration and works best on flat roads. Addressing the concern of cylinder temperatures...well, we don't typically keep our foot on the gas pedal while we are driving (or coasting) downhill...thus the pulse and glide method is almost inherent in some of our typical driving. Some drivers just take it a step further. This process of coasting downhill would have a far greater effect on the temperature of the cylinder heads than a pulse and glide on flat land as the cylinder heads would cool much quicker. And again, the temperature of the cylinder heads would not cool much using the pulse and glide method due to the fact that there is still combustion occurring keeping the cylinders heated.
Some serious hyper-milers will take the pulse and glide method too far by turning off the engine and coasting for as long as they can...but you can see why. The fuel is truly off and they are then achieving infinite MPG at that point. Still, definitely not recommended. However, the pulse and glide method can be good as a speed check as well. I know I can get a heavy foot the longer I leave my foot on the gas pedal to "maintain" a constant speed. The pulse and glide method can allow you to check your speed and re-evaluate your driving methods. We tend to forget how inefficient we are driving...how many times have thought your were driving 65 mph and then look down...whoa! 80mph!
posted by carlsr January 15, 2009 at 8:32 AM
Mileage trends with amount remaining in tank
Nice info Pontiac, but what engineerdude is asking (and I have wondered why myself) is how come it seems like one gets better mileage from the top half of the tank (filling up when it is only half empty) rather then the bottom half (filling up when empty). I have noticed this on many occasions. One would think the extra weight from a full tank would adversely affect the mileage...but it doesn't seem to work that way...what other factors may be affecting this?
posted by carlsr November 13, 2008 at 7:51 AM
All about acetone in fuel
I tried it for about a month or so. It was recommended to use about 3 oz per 10 gallons of gas. So each fill up I would put about 3 - 4 oz in my tank. Never experienced any problems with using it, though I never experienced any mileage gains either.
posted by carlsr August 25, 2008 at 12:35 PM