Are my habits harmful to this CVT?

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My mother drives a 2012 Murano with a super sweet CVT. I've never met a CVT I liked, so for me to say this surprises me. Prior to this she drove a 2004 Murano with a [censored] arse piece-o-garbage how-i-loathed-thee CVT. The mannerisms and personality between these two are night and day, and I am amazed how much can change in a generation.

There is a single negative characteristic that has carried over to the current Nissan CVT: it will not "downshift" when going down hills. For example, I'm travelling 70mph at 2k rpm and approach a 1mi decline, revs stay at 2k rpm for the downward run. Being the engineer nerd that I am, I throw the gearbox to neutral to save this wasted energy and add the extra .0000001 miles to the tank of gas.

A regular geared automatic will drop to near-idle revs when the energy is not needed on a downhill slope. On my stick shift Volvo I drop it in neutral as well.

I am curious, is this shifting to and from neutral at speed doing any long term harm to the transmission? Can my OCD regarding wasted energy be justified? Thanks.
 
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You are, in all likelihood running fuel cut-off on downhill...dropping it into neutral, the engine will be idling, and using fuel.

You will also have some additional load on the brakes which will be costing you money over time (cents likely).
 
Originally Posted By: Rand
you will actually use more gas by putting it in neutral.



Thats arguable. In theory, yes, you will because the PWM on the injectors will be re-enabled to maintain idle, as opposed to turned off when closed throttle coasting in gear.

However, if at the end of the slope maximum momentum is required, going in neutral will save the pumping losses which effectively act as a brake.

My concern in any AT type vehicle is that the transmission may not be circulating lubricant properly if the pump is on the input shaft, thus causing increased wear. IIRC, only AT vehicles with a pump on the output side can be suitably pulled/coasted without potential for damage.
 
Originally Posted By: gr8gatzby
How so? 500rpm vs 2000rpm over 1 mile = less gas.


RPM isn't always equal to fuel usage. The computer will call for less fuel usage when rolling down a hill, as there is less strain on the engine. I feel like this is doing more harm than good, and you are better off staying in gear 100% of the time, until you are parking the car.
 
Originally Posted By: JHZR2
Originally Posted By: Rand
you will actually use more gas by putting it in neutral.



Thats arguable. In theory, yes, you will because the PWM on the injectors will be re-enabled to maintain idle, as opposed to turned off when closed throttle coasting in gear.

However, if at the end of the slope maximum momentum is required, going in neutral will save the pumping losses which effectively act as a brake.

My concern in any AT type vehicle is that the transmission may not be circulating lubricant properly if the pump is on the input shaft, thus causing increased wear. IIRC, only AT vehicles with a pump on the output side can be suitably pulled/coasted without potential for damage.


Its not arguable. Leaving it in gear and coasting you will use zero gas, versus coasting neutral and using a minimal amount of gas. Given that, there is absolutely no reason to coast down hill in neutral. Maybe even a little dumb and unsafe.
 
Originally Posted By: JHZR2
My concern in any AT type vehicle is that the transmission may not be circulating lubricant properly if the pump is on the input shaft, thus causing increased wear. IIRC, only AT vehicles with a pump on the output side can be suitably pulled/coasted without potential for damage.


Been through that in my head with the 4L60E in my caprice.

In neutral and idling, the pump is still pumping. On over-run, the power flow might be reversed, but the pump is still spinning and pumping normally...even with the ignition off (or a dead fuel pump), as long as you were coming from an operational state in drive, the pump is still turning and pumping.

All scenarios are different from rolling it down a hill with the engine off from the start.

Only ever seen a couple of powerglides and an old humber that could be push started.
 
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Maybe even a little dumb and unsafe.


I agree that it is dumb and unsafe. That is not my quandary.

If I am doing no harm to the CVT by shifting to and from neutral while in motion in an effort to prevent unnecessary revs to the engine, and willing to accept the risks to the safety of myself and my passengers, why not do it?
 
Because you get a $180 ticket if the cop thinks you are coasting in neutral (in either an auto or manual) in my state.
 
Originally Posted By: Shannow
Because you get a $180 ticket if the cop thinks you are coasting in neutral (in either an auto or manual) in my state.


You live in the state of North Korea?
 
Originally Posted By: Shannow
Because you get a $180 ticket if the cop thinks you are coasting in neutral (in either an auto or manual) in my state.


It's illegal lots of places in the US also.

/hijack
 
Originally Posted By: gr8gatzby
Quote:
Maybe even a little dumb and unsafe.


I agree that it is dumb and unsafe. That is not my quandary.

If I am doing no harm to the CVT by shifting to and from neutral while in motion in an effort to prevent unnecessary revs to the engine, and willing to accept the risks to the safety of myself and my passengers, why not do it?


It may not damage anything, but you win nothing by doing it. I think you should go back and read the last part, that just sounds ludicrous..safety among all else should be the #1 priority of whoever is in the driver seat. When rolling while in gear, fuel cutoff happens, to either completely cut, or minimize fuel usage. What are you trying to gain here?
 
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Originally Posted By: gr8gatzby
Quote:
Maybe even a little dumb and unsafe.


I agree that it is dumb and unsafe. That is not my quandary.

If I am doing no harm to the CVT by shifting to and from neutral while in motion in an effort to prevent unnecessary revs to the engine, and willing to accept the risks to the safety of myself and my passengers, why not do it?


1. Have you read the posts stating that:

a. The injectors shut off in many autos while engine-braking downhill;

b. The engine is braking, so you don't need to use your actual brakes to maintain downhill speed;

c. If an emergency arises, you have the vehicle in gear to provide acceleration.

2. Read what you typed and ask yourself if it makes any sense at all...
 
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a. The injectors shut off in many autos while engine-braking downhill;


Engine braking is not a factor when revving at idle speeds

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b. The engine is braking, so you don't need to use your actual brakes to maintain downhill speed;


Engine braking should only be used as a method of deceleration in emergencies. Engines are more expensive to replace than brake pads.

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c. If an emergency arises, you have the vehicle in gear to provide acceleration.


I agree, that's why I only shift into neutral on a downslope when not surrounded by traffic, and risk is at an absolute minimum.
 
Bad idea, leave it in gear - it will use less fuel with the injectors "off" and the car momentum spinning the engine than if the engine is forced to idle on its own.
 
Originally Posted By: Kuato
Originally Posted By: Shannow
Because you get a $180 ticket if the cop thinks you are coasting in neutral (in either an auto or manual) in my state.


It's illegal lots of places in the US also.

/hijack


+1
 
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