The real question is if its better for the engine to run a no load idle, or in gear "idle". I would think there is less wear at an idle.
Shifting to neutral at stop light . . . Does this help reduce wear on a AT
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I think the reality is you would do more harm than good. The constant shifting in and out of gear along with the occasional crashing into gear when you step on the gas in neutral, realize you forgot to go to drive, and engage before you go back to idle will probably cause more overall wear than anything. Not to mention the potential risk of not being able to instantly move in case of an emergency.
The strain put on the torque converter when the car actually accelerating from a stop is going to far higher than the strain at neutral anyway. What about accelerating up a hill?
I think there is no real wear and tear advantage to shifting to neutral at a stop.
The strain put on the torque converter when the car actually accelerating from a stop is going to far higher than the strain at neutral anyway. What about accelerating up a hill?
I think there is no real wear and tear advantage to shifting to neutral at a stop.
i don't think it makes one bit of difference.
No, there is nothing wrong if idle speed changes in neutral. It should, there is less of a load on the engine in neutral. I think it would use about the same gas in neutral or gear, because even though it's idling slower in gear, it's got a bigger load...
Kestas
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All my fuel injected cars run at the same idle speed, whether it's in gear or in neutral. At idle, when you put it in neutral, the idle speed jumps up momentarily until the computer tells the idle air control motor to reduce the amount of air in order to reduce the idle. This action results is burning less gas.
Conversely, when you put it in gear, the idle speed jumps down momentarily until the IAC motor lets in more air, resulting in more fuel burned. You can't tell me that for the same idle speed no extra fuel is burned to accomodate the drag induced by the torque converter.
Conversely, when you put it in gear, the idle speed jumps down momentarily until the IAC motor lets in more air, resulting in more fuel burned. You can't tell me that for the same idle speed no extra fuel is burned to accomodate the drag induced by the torque converter.
It will NOT reduce wear on an automatic. If a tranny is an automatic, leave it as such! There are no general rules. The more you shift, the quicker it will break.
Transmission temperature will cool whether in park or drive at a stop. ATF needs to maintain an operating temperature. Get an ATF temp gauge and prove whether the temp changes during that redlight. If you are not happy with the temp, get an extra cooler.
Solenoids don't last forever. Exercise them excessively and they will fail along with mechanical devices which will wear quicker(like shifter cables/linkages). I pity your valve body.
Engaging/disengaging the bands/clutches will prematurely wear them out. Think of all that extra wear material, in your fluid, tearing into the seals/bearings/gears.... Thats OK. There are plenty of transmission rebuilders that have mortgages and boat payments to make.
Also, you should study the ATF flow through your transmission. Don't be surprised if ATF flow is reduced to certain hot or stressed components. ATF is a lube and coolant. Why would you purposely prevent internal transmission components form cooling? or reduce ATF PSI at various lube points?
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=16;t=000639
Transmission temperature will cool whether in park or drive at a stop. ATF needs to maintain an operating temperature. Get an ATF temp gauge and prove whether the temp changes during that redlight. If you are not happy with the temp, get an extra cooler.
Solenoids don't last forever. Exercise them excessively and they will fail along with mechanical devices which will wear quicker(like shifter cables/linkages). I pity your valve body.
Engaging/disengaging the bands/clutches will prematurely wear them out. Think of all that extra wear material, in your fluid, tearing into the seals/bearings/gears.... Thats OK. There are plenty of transmission rebuilders that have mortgages and boat payments to make.
Also, you should study the ATF flow through your transmission. Don't be surprised if ATF flow is reduced to certain hot or stressed components. ATF is a lube and coolant. Why would you purposely prevent internal transmission components form cooling? or reduce ATF PSI at various lube points?
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=16;t=000639
The idle speed will change between neutral and drive. It should go up to the factory idle speed in neutral or park and should drop down in drive.
Yes the best thing to do when idling for a period of time is place the transmission in neutral or park with the emergency brake on or simply shut the vehicle off rather than idle for an extended period.
Yes the best thing to do when idling for a period of time is place the transmission in neutral or park with the emergency brake on or simply shut the vehicle off rather than idle for an extended period.
Kestas
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The only car I have that changes idle speed between neutral and drive is my 71 Oldmobile. It does this because it has a carburator, where throttle position is constant. Fuel injected cars, which account for >95% of the cars on the road, have an idle control motor to keep the idle speed same between neutral and drive, and to compensate for any other load conditions such as air conditioning.
Remember before fuel injection in the early 80's cars were designed with a throttle solenoid that kicked in when the a/c came on. It openend the throttle just a tad to keep the idle speed from dropping too much and stalling the engine. Conversely, this also allowed cars with a/c to be adjusted for lower base idle speeds without having the engine stall when the a/c is engaged. Nowadays all this is done with the ECU via the idle air control motor.
Remember before fuel injection in the early 80's cars were designed with a throttle solenoid that kicked in when the a/c came on. It openend the throttle just a tad to keep the idle speed from dropping too much and stalling the engine. Conversely, this also allowed cars with a/c to be adjusted for lower base idle speeds without having the engine stall when the a/c is engaged. Nowadays all this is done with the ECU via the idle air control motor.
Some Ford vehicles do indeed drop the idle speed down when the transmission is in drive.
In fact, the EEC-Tuner (which is a way to alter the Ford factory settings) allows you to have separate idle speeds for neutral and drive:
NEUTRAL_IDLE 672 # Neutral Idle RPM
DRIVE_IDLE 672 # Drive Idle RPM
This particular example is from a car with a manual transmission, so that is why both values are the same.
In fact, the EEC-Tuner (which is a way to alter the Ford factory settings) allows you to have separate idle speeds for neutral and drive:
NEUTRAL_IDLE 672 # Neutral Idle RPM
DRIVE_IDLE 672 # Drive Idle RPM
This particular example is from a car with a manual transmission, so that is why both values are the same.
Two problems with that:
1)The ECU will remain in "acceleration enrichment mode" for far longer than it needs to. It is much more fuel efficient to accelerate to the speed limit at a reasonably quick pace and then hold the speed limit. That reduces the amount of time that the ECU is richening the fuel mixture, and also reduces pumping losses because the acceleration is done with the throttle open wider.
2)Traffic lights, in general, are timed with the expectation that traffic will not take 2.5 miles to get to the speed limit. Therefore, one who drives in this manner may well find themselves hitting more red lights than they otherwise would.
Usually these types of drivers keep going well past the speed limit, so they're not trying to save fuel, they're just not paying any attention to the task of driving.
[ June 12, 2004, 11:29 PM: Message edited by: brianl703 ]
Take your ************ and shove it. I dumped my last automatic in 1981. I do try to have it in gear when the light turns. It is just that I have seen people in things I know only came as automatics apparently shifting into gear after the light turns green.
As for the excessively slow acceleration, it takes more gas to drive slowly in a lower gear than to accelerate moderately and get into high.
People that dawdle when the light turns green, waste their own gas and even more gas for the people behind them. They are stupid, inconsiderate jerks.
Kestas
Staff member
If idle speed changes when you shift between drive and neutral, then something is wrong with your engine. You probably need to clean the throttle body bore and idle speed control motor. The computer controlling the engine aims for a certain idle speed regardless of whether it's in gear or in neutral. In neutral there's less load on the engine, and therefore should use less gas, not more, to maintain idle speed.
Especially when they do it during rush-hour traffic at an intersection that's backed up for a mile!!
Maybe that intersection wouldn't be so backed up if more cars got through on each green phase. Maybe more cars would get through on each green phase if the dawdlers realized that yes, there ARE other people using the roads besides them.
I do shift from drive to neutral in cars. One of the reasons is that I don't like to keep my foot on a brake pedal for 5 minutes. Secondly, if you used your brakes a lot just before stop it will generate significant amount of heat. Thus keeping brake pads pressed against rotors might possibly warp them. At least this is the idea proposed by a number of people. It does make a lot of sense for me. Thirdly, on a hot day (80F and above) I can clearly see my engine coolant temperatures rising with a drive gear engaged, whereas if I shift to neutral it tends to stay on normal mark or takes significantly longer to move temp needle a few degrees. It seems like most of you here suggest not to switch gears in AT to prevent wear. It also does seem to make sense for me. Well... I guess I have to change my driving tactics again
Regards,
Regards,
Titanium Alloy, I went through this whole string and was going to post the observation that pushing the brake pedal can cause uneven cooling of the brake discs, thereby warping them, but you got it first.
I shift into neutral at long stop lights to keep the transmission fluid cooler, and to avoid the uneven brake cooling that can lead to said warpage.
So far, I have 150K on my Infiniti Q45 transmission and have followed this practice since new. Knock on wood, no transmission problems over the life of this vehicle. The stock rotors on this vehicle are sensitive to warpage. If they get warped again, I intend to install aftermarket Brembo rotors.
I shift into neutral at long stop lights to keep the transmission fluid cooler, and to avoid the uneven brake cooling that can lead to said warpage.
So far, I have 150K on my Infiniti Q45 transmission and have followed this practice since new. Knock on wood, no transmission problems over the life of this vehicle. The stock rotors on this vehicle are sensitive to warpage. If they get warped again, I intend to install aftermarket Brembo rotors.
Sitting still causes uneven cooling of the brake discs, not pushing the brake pads against them.
Therefore it's probably best with hot brakes to leave the transmission in gear and creep forward every 5-10 seconds, thereby not isolating one part of the rotor from the same cooling rate as the rest of the rotor.
The earlier thread from a few months ago has valuable information about the logic of NOT putting an AT in neutral, especially
newer cars where the torque converter is very relaxed at idle anyway, and the act of shifting would cause more wear and shock to the mechanicals and controls. Whereas heat buildup is not as great as older cars which have heavy loading at idle causing quick fluid heat buildup.
[ June 14, 2004, 08:09 PM: Message edited by: S2000driver ]
Therefore it's probably best with hot brakes to leave the transmission in gear and creep forward every 5-10 seconds, thereby not isolating one part of the rotor from the same cooling rate as the rest of the rotor.
The earlier thread from a few months ago has valuable information about the logic of NOT putting an AT in neutral, especially
newer cars where the torque converter is very relaxed at idle anyway, and the act of shifting would cause more wear and shock to the mechanicals and controls. Whereas heat buildup is not as great as older cars which have heavy loading at idle causing quick fluid heat buildup.
[ June 14, 2004, 08:09 PM: Message edited by: S2000driver ]
That makes a lot more sense than many of the other posts on this thread. Especially combined with leaving a little distance between you and the next car when you stop. Another thing that contributes to the glacial start at stop light is the popular practice of pulling up within a couple of feet of the next car. The closer you are, the longer you have to set before having what ever minimal distance you are willing to live with to the next car when you start moving. I am so sick of stopping for every light whether it is red or green when I get there.
Since I've started this thread I do have a few confession to make. My 93 Honda Civic engine/tranny is approaching 200k miles and all seems to be well. I've been in this nasty habit of shifting to neutral for the entire life of the car. Also somewhere before 50k miles I inadvertently shifted into reverse while going over 25 mph
, I accidentally depressed the shift lock. Anyhow . . . after much ratcheting sounds, much profanity and a stopped motor. I restarted the car and it didn't seem to be any worse for the wear.
The only thing I've done to it over all these years has been a changes of AT fluid. Last 3 years has been on Mobil 1. Tranny shifts at the same points all these years, OD locks up just fine. I just can't chirp the tires, from a dead stop, like it used to when it was new.
Thanks for all the replies!
The only thing I've done to it over all these years has been a changes of AT fluid. Last 3 years has been on Mobil 1. Tranny shifts at the same points all these years, OD locks up just fine. I just can't chirp the tires, from a dead stop, like it used to when it was new.
Thanks for all the replies!
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