disconnet injectors for fuel savings?
- Thread starter mr.b
- Start date
txstang84
15 Year Member
that's why I take the wife's civic whenever we go somewhere 
...she's the sensible one-here I am getting ready to build a supercharged stroker with gas prices predicted to hit $4/gal in the near future-yeah that makes sense...
...she's the sensible one-here I am getting ready to build a supercharged stroker with gas prices predicted to hit $4/gal in the near future-yeah that makes sense...
but here gas is hitting close to 8 dollars a gallon (6.80 US) so uhhhh yeah the stang is staying in the garage for a while. My integra gets about 20 mpg more than my stang so i'll drive that to work for now.
I guess I need to explain this a little better, because you will see better fuel economy with the throttle plate more open.
First, engine efficiency is power made per unit of fuel used. This is different than fuel economy which is distance traveled per unit of fuel used. I am talking about engine efficiency. This does not take into account aero losses. But remember that at any given speed the vehicle will get its best fuel economy when operating at max engine efficiency.
Any restriction on the air intake passage will decrease engine efficiency. When the restriction is at the TB the restriction is known as Throttling Losses. The diesel is more efficient than gasoline engines, and part of the reason is that there are no throttling losses in the diesel. This is a very basic idea to wrap your mind around...Which would you call more efficient, breathing through a straw, or breathing through a garden hose? Which would mean less work/effort for you?
The amount of fuel used for increasing the throttle opening is not the issue. The issue is how much parasitic drag (as a result of having to pull air through a small opening) the engine has to overcome to fill the cylinder with air. Opening the throttle reduces this parasitic drag on the engine, which increases engine efficiency. As a result of less parasitic drag on the motor, engine efficiency will increase when the throttle is opened further (remember that engine efficiency is power made per unit of fuel used).
Driving habits need to change to take full advantage of this. For max economy the rpm range should be kept as low as the engine will tolerate. For my engine this is about 1600rpm. This means I shift well before the 2500 mark. If you keep the throttle open at about 75% then, yes, you will accelerate. This allows for another driving technique called Coast and Burn. When driving at 65mph you will accelerate at 75% throttle to about 70mph, then you disengage the trans and coast until you reach 60mph, and repeat. The "Burn" portion keeps the engine operating at peak efficiency, and the "Coast" portion reduces engine revolutions per mile traveled (which has large impact on fuel used per mile traveled). This driving style was made mandatory in some Asian countries in the 80s/90s (Japan if I remember correct).
Gear selection is crucial for this to work properly. Obviously accelerating to 65mph in third gear will not be as efficient as in fifth gear. Again use the lowest rpm range that the motor will accept. Also, consider the speed you are selecting to maintain. Aero losses will be greater at 75 than at 60mph.
If you have more questions on this please repost, or pm me. I have a degree in Auto Design, and I am very willing to share the knowledge that I have gained over the years.
I am still looking for the article I read a while back on the Chrysler system, but I seem to be missing some of my SAE magazines, so I may not be much help here.
jason
First, engine efficiency is power made per unit of fuel used. This is different than fuel economy which is distance traveled per unit of fuel used. I am talking about engine efficiency. This does not take into account aero losses. But remember that at any given speed the vehicle will get its best fuel economy when operating at max engine efficiency.
Any restriction on the air intake passage will decrease engine efficiency. When the restriction is at the TB the restriction is known as Throttling Losses. The diesel is more efficient than gasoline engines, and part of the reason is that there are no throttling losses in the diesel. This is a very basic idea to wrap your mind around...Which would you call more efficient, breathing through a straw, or breathing through a garden hose? Which would mean less work/effort for you?
The amount of fuel used for increasing the throttle opening is not the issue. The issue is how much parasitic drag (as a result of having to pull air through a small opening) the engine has to overcome to fill the cylinder with air. Opening the throttle reduces this parasitic drag on the engine, which increases engine efficiency. As a result of less parasitic drag on the motor, engine efficiency will increase when the throttle is opened further (remember that engine efficiency is power made per unit of fuel used).
Driving habits need to change to take full advantage of this. For max economy the rpm range should be kept as low as the engine will tolerate. For my engine this is about 1600rpm. This means I shift well before the 2500 mark. If you keep the throttle open at about 75% then, yes, you will accelerate. This allows for another driving technique called Coast and Burn. When driving at 65mph you will accelerate at 75% throttle to about 70mph, then you disengage the trans and coast until you reach 60mph, and repeat. The "Burn" portion keeps the engine operating at peak efficiency, and the "Coast" portion reduces engine revolutions per mile traveled (which has large impact on fuel used per mile traveled). This driving style was made mandatory in some Asian countries in the 80s/90s (Japan if I remember correct).
Gear selection is crucial for this to work properly. Obviously accelerating to 65mph in third gear will not be as efficient as in fifth gear. Again use the lowest rpm range that the motor will accept. Also, consider the speed you are selecting to maintain. Aero losses will be greater at 75 than at 60mph.
If you have more questions on this please repost, or pm me. I have a degree in Auto Design, and I am very willing to share the knowledge that I have gained over the years.
I am still looking for the article I read a while back on the Chrysler system, but I seem to be missing some of my SAE magazines, so I may not be much help here.
jason
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