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#3211826 - 12/09/13 11:13 PM Are my habits harmful to this CVT?
gr8gatzby Offline


Registered: 11/22/05
Posts: 597
Loc: Charlotte, NC
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.


Edited by gr8gatzby (12/09/13 11:14 PM)
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'95 Ford F150 | 4x4 | 5.8 | 13MPG
'96 Volvo 850 Wagon | I5 | 5SP | 24MPG

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#3211828 - 12/09/13 11:14 PM Re: Are my habits harmful to this CVT? [Re: gr8gatzby]
Rand Offline


Registered: 08/20/03
Posts: 10562
Loc: NE,Ohio
you will actually use more gas by putting it in neutral.
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#3211832 - 12/09/13 11:18 PM Re: Are my habits harmful to this CVT? [Re: gr8gatzby]
gr8gatzby Offline


Registered: 11/22/05
Posts: 597
Loc: Charlotte, NC
How so? 500rpm vs 2000rpm over 1 mile = less gas.


Edited by gr8gatzby (12/09/13 11:18 PM)
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#3211834 - 12/09/13 11:20 PM Re: Are my habits harmful to this CVT? [Re: gr8gatzby]
Shannow Online   content


Registered: 12/12/02
Posts: 33717
Loc: Oz
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).

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#3211836 - 12/09/13 11:21 PM Re: Are my habits harmful to this CVT? [Re: Rand]
JHZR2 Offline



Registered: 12/14/02
Posts: 38400
Loc: New Jersey
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.

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#3211841 - 12/09/13 11:27 PM Re: Are my habits harmful to this CVT? [Re: gr8gatzby]
gregk24 Offline


Registered: 04/13/13
Posts: 4464
Loc: FL, USA
Doing more harm than good.
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#3211856 - 12/09/13 11:49 PM Re: Are my habits harmful to this CVT? [Re: gr8gatzby]
daves87rs Offline


Registered: 02/23/09
Posts: 15782
Loc: Michigan
Honestly can't see it helping much....
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#3211861 - 12/09/13 11:55 PM Re: Are my habits harmful to this CVT? [Re: gr8gatzby]
CHARLIEBRONSON21 Offline


Registered: 08/28/13
Posts: 659
Loc: MEMPHIS, TN
No "L" slot? My fusion has that...
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#3211864 - 12/09/13 11:58 PM Re: Are my habits harmful to this CVT? [Re: gr8gatzby]
actionstan Offline


Registered: 05/22/13
Posts: 488
Loc: Ohio
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.
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#3211868 - 12/10/13 12:02 AM Re: Are my habits harmful to this CVT? [Re: JHZR2]
bvance554 Offline


Registered: 09/24/12
Posts: 1860
Loc: VA
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.

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#3211876 - 12/10/13 12:09 AM Re: Are my habits harmful to this CVT? [Re: JHZR2]
Shannow Online   content


Registered: 12/12/02
Posts: 33717
Loc: Oz
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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#3211877 - 12/10/13 12:09 AM Re: Are my habits harmful to this CVT? [Re: bvance554]
gr8gatzby Offline


Registered: 11/22/05
Posts: 597
Loc: Charlotte, NC
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?
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#3211878 - 12/10/13 12:10 AM Re: Are my habits harmful to this CVT? [Re: gr8gatzby]
Shannow Online   content


Registered: 12/12/02
Posts: 33717
Loc: Oz
Because you get a $180 ticket if the cop thinks you are coasting in neutral (in either an auto or manual) in my state.

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#3211880 - 12/10/13 12:11 AM Re: Are my habits harmful to this CVT? [Re: Shannow]
gr8gatzby Offline


Registered: 11/22/05
Posts: 597
Loc: Charlotte, NC
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?
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'95 Ford F150 | 4x4 | 5.8 | 13MPG
'96 Volvo 850 Wagon | I5 | 5SP | 24MPG

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#3211882 - 12/10/13 12:15 AM Re: Are my habits harmful to this CVT? [Re: Shannow]
Kuato Offline


Registered: 10/23/05
Posts: 5350
Loc: In transit...
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
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