Anyone shifts to Neutral when going downhill in their IS350?
#16
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you don't save any gas by shifting into neutral while going downhill--the engine is coasting in either case. As far as the 30 lb saved from removing the spare, that's miniscule too. One G35 forum members once gave a quick tip to remove 250 lb from his car--telling his GF to get out of the car.
#17
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Originally Posted by al503
When you're not on the gas and in gear, your engine is slowing the car down due to compression braking, which is basically the energy required to compress the air in the cylinders in the compression cycle. Racers use this compression braking when they 'heel toe' downshift to help prevent brake fade.
#18
Originally Posted by jlin101
you don't save any gas by shifting into neutral while going downhill--the engine is coasting in either case. As far as the 30 lb saved from removing the spare, that's miniscule too. One G35 forum members once gave a quick tip to remove 250 lb from his car--telling his GF to get out of the car.
#20
Originally Posted by jlin101
you don't save any gas by shifting into neutral while going downhill--the engine is coasting in either case. As far as the 30 lb saved from removing the spare, that's miniscule too. One G35 forum members once gave a quick tip to remove 250 lb from his car--telling his GF to get out of the car.
that was Funny
Regarding Conserving Gas have you guys used unocal 76 use premium ofcourse.
My take on this two Gas station
Chevron=Aggressive Driving 24mpg Normal driving 27.5mpg
Unocal 76 =Aggressive Driving 23mpg Normal Driving 28.8mpg
Im going by the Tank Average
I Use Chevron all the time.
The only thing i dont like when i put unocal is the Power to get up and go seems to be less.
Try unocal i bet it will give you more MPG
#21
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Originally Posted by DirtySouth
Correct me if I'm wrong, but if you're going 70mpg and you shift into N, it will disengage the wheels from the engine and in turn the engine will rev up even higher until it slows itself down. I don't think thats the best idea.
Now, maybe shifting into neutral while at a stop-light/sign might save you a bit.
Now, maybe shifting into neutral while at a stop-light/sign might save you a bit.
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Originally Posted by Shinobi-X
Shifting your vehicle into neutral does not save gas when coasting. If you want to save gas, leave your car in gear.
When you let off the throttle and start coasting, the cars drivetrain turns the engine, while the ECU signals for the fuel injectors to shut off, going to 0% duty cycle...meaning you save gas. When putting the car in neutral, the drivetrain cannot turn the engine anymore, therefore the engine must turn under its own power, meaning you burn gas at a similar rate that you would by letting the engine idle. Again, to save gas, just let the car coast while in gear...momentum will be your best friend.
When you let off the throttle and start coasting, the cars drivetrain turns the engine, while the ECU signals for the fuel injectors to shut off, going to 0% duty cycle...meaning you save gas. When putting the car in neutral, the drivetrain cannot turn the engine anymore, therefore the engine must turn under its own power, meaning you burn gas at a similar rate that you would by letting the engine idle. Again, to save gas, just let the car coast while in gear...momentum will be your best friend.
and like someone else said, there is engine break when the car is in gear, so even though i'm going down hill with my foot off the accelerator, my car's speed is decreasing due to the engine break. on the other hand, if i'm in neutral and going down this same hill, i might gain some speed if not maintain my current speed. when i get ot the bottom of the hill, i just put the car back in D and keep going.
#23
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Originally Posted by 2Fast0
assuming what u said is true. it doesnt change the fact that my engine drops down to 600rpms when in neutral. I think an engine in gear going at 2500rpms will use more gas than an engine in neutral going at 600rpms, assuming they are both going at the same speed, say 70mph.
An example would be my other car, where I have an ECU which also has a commander visual display which shows the injector duty cycle, just as the ECU sees it. At coast, at any speed, in any gear, at any RPM, it will read 0%, because the drivetrain is doing the work, in combination with gravity and momentum. If I want to accelerate or cruise, then pressing the throttle will subsequently inject fuel, and the duty cycle (fuel used) will raise according to how much I'm trying to accelerate.
when i get ot the bottom of the hill, i just put the car back in D and keep going.
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Originally Posted by Shinobi-X
RPM is not a measure of fuel injection, its a measure of how fast your engine is rotating. If you roll faster while in gear, the drivetrain will turn the engine faster, obviously raising the RPMS...however, your injectors are not injecting fuel, because you are not pressing the throttle...remember, you're not accelerating or cruising, but coasting.
how can the engine rotate without burning fuel? I thought it's the combustion of gasoline that creates the force to push the pistons downward. therefore, the faster the engine is revolving up and down, the more fuel it needs to perform the mechanical work. right?? You said the injectors are not injecting fuel cuz i'm not pressing the throttle, but I would think fuel is being fed to the engine via some other route. the throttle can't be the only mechanism that is controlling how much fuel is being fed to the engine.
#25
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Originally Posted by 2Fast0
how can the engine rotate without burning fuel?
I thought it's the combustion of gasoline that creates the force to push the pistons downward. therefore, the faster the engine is revolving up and down, the more fuel it needs to perform the mechanical work. right??
Try accelerating to 60mph, then just let off the gas, and you'll see how far you travel on a fairly flat road in an automatic car...you'll be hard pressed to find your engine braking dramatically, as your car will most likely be in its final gear (again, engineered for fuel savings). It will downshift into the next lower gear before the engine slows too much (stall), but with each drop in gear (due to the different ratios), your engine will have more leverage on slowing the car. In a manual car, its even eaiser to see this.
You said the injectors are not injecting fuel cuz i'm not pressing the throttle, but I would think fuel is being fed to the engine via some other route. the throttle can't be the only mechanism that is controlling how much fuel is being fed to the engine.
#27
even a 600cc bike will get only about 40-50mpg, but is much more fun and dangerous than a comparable car (prius). as for shifting to neutral, you dont save fuel. coasting downhill in 6th means your RPMs will drop to above idle, but below 2000rpm. you would have to go pretty fast downhill for the rpms to climb when youre not adding gas. at the stop light, again no savings because the car is idle whether you put it in drive or neutral? ....
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Originally Posted by Shinobi-X
Have you ever turned your key, and heard the engine cranking, but not turn over? Thats your engine being spun by the starter motor. Have you ever seen a person push start a car in order to get it running? Thats essentially using the drivetrain to rotate or turn the motor over. Torque is what rotates your engines crankshaft, and that can be created by an outside motor, a person pushing, or combustion. Keeping this idea in mind, remember that your drivetrain is always connected to your motor when in gear, and as such, has the ability to rotate the motor (by applying torque), so long as the car has enough momentum behind it...meaning the car does not need to inject fuel, since torque is being applied to the crankshaft from elsewhere. This is a mechanism engineered into cars, which among other reasons, saves gas. Its easier to demonstrate with a manual car, but its the same reason why you will stall an engine if you don't put a manual car into neutral when stopped- the engine is halteded by the drivetrains lack of twisting motion. Placing the car in neutral allows it to rotate freely under its own power, but to do so, it must now consume fuel. This is why when coasting, it doesn't make sense to put the car in neutral...since the car is rolling, you can use that 'free' energy to rotate the engine, instead of having it turn by itself. RPM will just let you know how fast its turning, whether it be by the drivetrain, or its own power, in case you need to select your gear again.
Yes, but thats when you've used your right foot to depress the gas pedal, and open the throttle. As air enters, your ECU senses the throttle position via a sensor, and along with a host of other sensors, it injects a specific amount of fuel, which is then ignited for our familiar end result. The more you depress the gas pedal, the more air is allowed in, and your engine rotates faster (rpm) to allow more air in over a shorter period of time, for what amounts to stronger acceleration. However, the key here is mechanical work, which can also be done by other portions of the car now that its already in motion. You cannot accelerate or even cruise (maintain your exact speed 'indefinately') without using fuel (unless you're going downhill), but you can coast (slowly losing speed at a gradual pace) for a pretty good distance from most speeds depending on your gear.
Try accelerating to 60mph, then just let off the gas, and you'll see how far you travel on a fairly flat road in an automatic car...you'll be hard pressed to find your engine braking dramatically, as your car will most likely be in its final gear (again, engineered for fuel savings). It will downshift into the next lower gear before the engine slows too much (stall), but with each drop in gear (due to the different ratios), your engine will have more leverage on slowing the car. In a manual car, its even eaiser to see this.
Without making it too complicated, in a nutshell, your right foot is the main contributor to how much fuel your ECU is deciding to inject into your motor. There are a HOST of other mechanisms which work in conjuction with your right foot, which read everything from air temperature, to how much oxygen you have in your exhaust, which dictate how much fuel is injected, but for all intents and purposes, your right foot dictates how much air comes in, and your car does its best to match that.
Yes, but thats when you've used your right foot to depress the gas pedal, and open the throttle. As air enters, your ECU senses the throttle position via a sensor, and along with a host of other sensors, it injects a specific amount of fuel, which is then ignited for our familiar end result. The more you depress the gas pedal, the more air is allowed in, and your engine rotates faster (rpm) to allow more air in over a shorter period of time, for what amounts to stronger acceleration. However, the key here is mechanical work, which can also be done by other portions of the car now that its already in motion. You cannot accelerate or even cruise (maintain your exact speed 'indefinately') without using fuel (unless you're going downhill), but you can coast (slowly losing speed at a gradual pace) for a pretty good distance from most speeds depending on your gear.
Try accelerating to 60mph, then just let off the gas, and you'll see how far you travel on a fairly flat road in an automatic car...you'll be hard pressed to find your engine braking dramatically, as your car will most likely be in its final gear (again, engineered for fuel savings). It will downshift into the next lower gear before the engine slows too much (stall), but with each drop in gear (due to the different ratios), your engine will have more leverage on slowing the car. In a manual car, its even eaiser to see this.
Without making it too complicated, in a nutshell, your right foot is the main contributor to how much fuel your ECU is deciding to inject into your motor. There are a HOST of other mechanisms which work in conjuction with your right foot, which read everything from air temperature, to how much oxygen you have in your exhaust, which dictate how much fuel is injected, but for all intents and purposes, your right foot dictates how much air comes in, and your car does its best to match that.
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