View Full Version : Automatic transmission and fuel injection
goedel
Jun 16, 2009, 10:39 AM
Recently, I began driving a small, Japanese sedan with automatic transmission (AT). I had been driving a manual transmission vehicle (MT) for many years. I am enjoying the ease of an AT, but I liked the MT for its economy, control and deceleration. The deceleration is what I miss most now. My AT decelerates when I remove my foot from the gas-pedal, but very, very slowly. It is useless for slowing down, practically speaking. My MT would slow down usefully, so that I did not have always to brake when approaching a slower vehicle or a red light 200 yards ahead - until close to stopping. Driving with awareness of what lay ahead, I could avoid using my brakes very often, and they would last well over 50,000 miles before requiring replacement. Moreover, my gasoline consumption was low, because I did not unnecessarily have to brake.
Now, I am compelled to brake frequently, even driving with awareness of the road ahead. Why are AT cars not designed with a computer-feature that reduces fuel injection when the driver's foot is off the gas-pedal for one or two seconds - so that the deceleration will occur without braking?
suptclark
Jun 17, 2009, 02:26 PM
In the olden days AT cars would decelerate quite well by lifting your foot off the gas. Later model cars are the victim the federal bureaucracy. They ordered all automatic transmissions to be loosened up to improve gas mileage. The genius that decreed who change must have never lived in hilly country.
goedel
Jun 18, 2009, 05:20 PM
In the olden days AT cars would decelerate quite well by lifting your foot off the gas. Later model cars are the victim the federal bureaucracy. They ordered all automatic transmissions to be loosened up to improve gas mileage. The genius that decreed who change must have never lived in hilly country.
It seems to me that gas mileage would be better if AT cars decelerated like MTs. With an amber or red light 300 yards away, I can decelerate towards it in an MT by lifting my foot. In the approach to the light, I am not using as much gasoline while I am slowing down. Also, I am not wearing my brakes and putting asbestos into the air.
Sorry, I don't understand the logic of what you call "loosening up" the transmission.
suptclark
Jun 19, 2009, 05:26 AM
Loosening up equals less engine drag and permits more coasting and better mileage. It also means more brake wear. You said the same thing in your original post.
PS: I believe asbestos was eliminated from brakes years ago.
cowdough
Jun 20, 2009, 04:28 AM
What? Lol... you don't have more important things to worry about? Lol
goedel
Jun 22, 2009, 02:10 PM
loosening up equals less engine drag and permits more coasting and better mileage. It also means more brake wear. You said the same thing in your original post.
PS: I believe asbestos was eliminated from brakes years ago.
I would agree on "loosening up" and better mileage through coasting, if most of my driving were on the highway where coasting is possible. As things are, I drive in heavily trafficked, urban areas where slowing down to stop is more the situation. Cutting the fuel injection and decelerating would be a better savings under my circumstances. It would also save my brakes and my driving effort.
I find that when I take my foot off the gas, the car behaves pretty much as you say; it coasts. That is not so good for city driving. Thanks much for your replies.
(I am lucky. I don't have an awful lot to worry about! :) )