cruising in neutral
03-31-2006, 09:28 AM
#13
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Originally Posted by xviper,Mar 31 2006, 10:10 AM
NO! "Coasting" as you describe it, where you have it in neutral with the clutch out, requires the engine to idle. This uses fuel. Having it in gear and rolling down an incline with the throttle closed, shuts down the injectors completely. This uses NO fuel. You decide.
I kinda thought you did this thinking it would save fuel. In this case, it's false economy and false reasoning. Not only do you not save fuel, you are relinquishing control over your car.
Not necessarily on this car, but on some cars, putting it into neutral when rolling confuses the hell out of the ECU. The engine revs sporadically and without much control. The ECU hates this.
I kinda thought you did this thinking it would save fuel. In this case, it's false economy and false reasoning. Not only do you not save fuel, you are relinquishing control over your car.
Not necessarily on this car, but on some cars, putting it into neutral when rolling confuses the hell out of the ECU. The engine revs sporadically and without much control. The ECU hates this.
03-31-2006, 09:39 AM
#15
Originally Posted by xman03,Mar 31 2006, 11:28 AM
what do you mean uses no fuel?!.. the throttle body is always partially open and the ecu determines the amount of fuel using two factors, your rpm and the map reading. When you are rolling downhill in gear, the ecu is sensing your rpm and the vacuum reading and gives sufficient fuel where as in idle, it't the same idea but your rpm would be lower so typically the car would consume less fuel.
When decelerating, the engine does not need fuel to keep running. It has the car's momentum to keep it turning. The ECU knows when you are "engine braking" and shuts the injectors off. If you had an A/F gauge as many of us do, you would see this very vividly.
03-31-2006, 10:27 AM
#16
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[QUOTE=xman03,Mar 31 2006, 12:28 PM] what do you mean uses no fuel?!.. the throttle body is always partially open and the ecu determines the amount of fuel using two factors, your rpm and the map reading.
03-31-2006, 10:29 AM
#17
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Originally Posted by xviper,Mar 31 2006, 12:39 PM
This is a well known S2000 concept. The ECU also knows the throttle position. Anytime you have it closed and the speedo registers road speed above a certain threshold (a couple of mph), the injectors shut off. In this case, the throttle plate is not always partially open. Next time you have the intake tube off, take a look just in front of the throttle plate. Notice that little hole? That hole takes air to the Idle Air Control. This is where the air comes from to idle. The plate can be completely slammed shut. I'm not saying that it's air tight, but it could be.
When decelerating, the engine does not need fuel to keep running. It has the car's momentum to keep it turning. The ECU knows when you are "engine braking" and shuts the injectors off. If you had an A/F gauge as many of us do, you would see this very vividly.
When decelerating, the engine does not need fuel to keep running. It has the car's momentum to keep it turning. The ECU knows when you are "engine braking" and shuts the injectors off. If you had an A/F gauge as many of us do, you would see this very vividly.
03-31-2006, 11:49 AM
#18
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This is actually very educational for me, for I coast all the time down the hills. Guess I have to break this bad habit. I used to also skip gears, but that was with CRX and bike. I'm still trying to break this habit, but catch myself doing it from time to time.
That's when I slap my hand and say, "No cookie for you!"
That's when I slap my hand and say, "No cookie for you!"
