When im going downhill in my MO and take my foot completely off of the accelerator...my RPMs still goes up...personally I don’t know what is going on because as far as I know this isn’t normal...Is it?
sean103
Actually, with a CVT transmission, this is normal. As far as I know it is kind of like downshifting in a manual gearbox car which uses the engine to slow you down. I noticed that this usually occurs around 20 MPH when I go down this hill frequently.
I wish I had a more technical explanation, however, I do know that one of the more CVT-knowledgeable people will be along shortly to elaborate, so in the mean time I figured I would ease your worry by telling you that everything is working as it should! :29:
I wish I had a more technical explanation, however, I do know that one of the more CVT-knowledgeable people will be along shortly to elaborate, so in the mean time I figured I would ease your worry by telling you that everything is working as it should! :29:
CVT on Murano has a grade logic build in. What it means is that when you take the foot off the accelerator pedal while going downhill the car is trying to maintain constant speed. Engine is used to do so. This feature is not peculiar to CVT or the Murano. Actually I had it in my 1998 Mitsubishi Magna with “classic” automatic gearbox. I like it as it save my brakes……..
I think if the CVT had a grade logic of sorts, Nissan would have advertised it. From my understanding of Honda's grade logic, it is meant more for going up inclines on the highway than for descending grades. For example, on many 4 speed automatics, the transmission annoying hunts between 3rd and 4th gear on the freeway when you start to ascend a grade. Honda's transmission is supposed to be "smart" and downshift into 3rd gear and keep it there to prevent the uncomfortable shifting back and forth feeling.
The reason why you feel the RPMs continue to climb briefly after you let off the gas is because the inertia built up on the CVT belt and pulley takes a moment to dissipate all its built up inertia. This is something I also feel on my Murano, but only after really gunning it (I do not feel it if say, rev to 2000rpm, but I do feel it if I rev to 4500rpm such as in Ds).
I have driven up and down hills in San Francisco and I did not find that the Murano engine braked going down those 30 degree hills any more than the 4spd automagic on my Maxima.
Also, its normal for the RPM to go up while descending a hill, since it is likely you are gaining speed. If you are braking and slowing down, the engine speed might go up slightly as the CVT "downshifts" to a lower ratio to keep the engine form stalling.
The reason why you feel the RPMs continue to climb briefly after you let off the gas is because the inertia built up on the CVT belt and pulley takes a moment to dissipate all its built up inertia. This is something I also feel on my Murano, but only after really gunning it (I do not feel it if say, rev to 2000rpm, but I do feel it if I rev to 4500rpm such as in Ds).
I have driven up and down hills in San Francisco and I did not find that the Murano engine braked going down those 30 degree hills any more than the 4spd automagic on my Maxima.
Also, its normal for the RPM to go up while descending a hill, since it is likely you are gaining speed. If you are braking and slowing down, the engine speed might go up slightly as the CVT "downshifts" to a lower ratio to keep the engine form stalling.
Eric,
No disrespect by “grade logic control” works both way. My Magna had it and it worked perfectly going uphill – no gear hunting as you mention, always locked up in the right one (2nd, 3rd or 4th). And as you said Honda has it as well as a number of other manufactures. It worked also during descending. The gearbox would be smart enough to lock to the right gear. I remember driving downhill one day (pretty steep, long descent, winding road). I was following a Ford and could see his brake lights lit for well over a mile. I had to brake after a time as he cooked his brakes and the smell was unbearable! I just touched mine a couple of times as the gearbox was locked to 2nd gear!
I feel that CVT in Murano behave in a very similar way – is this grade logic control? I do not know. What I do know is than driving downhill and taking foot off the accelerator the car is trying to maintain speed. It does so by adjusting CVT ratio.
Any expert out there who knows all the details?
No disrespect by “grade logic control” works both way. My Magna had it and it worked perfectly going uphill – no gear hunting as you mention, always locked up in the right one (2nd, 3rd or 4th). And as you said Honda has it as well as a number of other manufactures. It worked also during descending. The gearbox would be smart enough to lock to the right gear. I remember driving downhill one day (pretty steep, long descent, winding road). I was following a Ford and could see his brake lights lit for well over a mile. I had to brake after a time as he cooked his brakes and the smell was unbearable! I just touched mine a couple of times as the gearbox was locked to 2nd gear!
I feel that CVT in Murano behave in a very similar way – is this grade logic control? I do not know. What I do know is than driving downhill and taking foot off the accelerator the car is trying to maintain speed. It does so by adjusting CVT ratio.
Any expert out there who knows all the details?
It is "grade-logic" working. The transmission is adjusting to a lower gear ration to offer engine braking during decent.
And yes, Honda's grade logic works both uphill and down hill. My other car is a 01 Acura CL and it's got a traditional 5-speed auto with grade logic build in. It will hold a gear when going up hill, and will dowshift automatically when decending.
And yes, Honda's grade logic works both uphill and down hill. My other car is a 01 Acura CL and it's got a traditional 5-speed auto with grade logic build in. It will hold a gear when going up hill, and will dowshift automatically when decending.
Ok I stand corrected.
Wish Nissan automatics had grade logic! I have a feeling the CVT does not have an explicit grade logic feature built in, it is more of how the CVT functions that gives the feel of engine braking.
Wish Nissan automatics had grade logic! I have a feeling the CVT does not have an explicit grade logic feature built in, it is more of how the CVT functions that gives the feel of engine braking.
Eric,
you could be right. The end result is that the Nissan CVT does feel and work like it had a grade logic build in........and I like it!
you could be right. The end result is that the Nissan CVT does feel and work like it had a grade logic build in........and I like it!
Kris said:
Hehe. Anything to save me from having to ride the brakes and share my brake squeal with the entire neighborhood!
I've given up trying to have the dealer correct the noisy brakes. When the brakes go, hopefully by that time Porterfield will have some brembo blanks (they are normal rotors which are cryo treated, none of that crossdrilled or slotted nonsense that does no good on a street car) and R4S brake pads.
Do a sharp, but short stab on the brakes and you'll feel the CVT shift even more to anticipate braking. (You may also kick in the Braking system faster as it anticipates an emergency stop.)
I'm sure most have you noticed how you can brake and when you let off, the CVT continues to do a stronger than normal engine braking, whereas other transmissions don't. It's more noticeable under some conditions than others, but definately there.
I'm sure most have you noticed how you can brake and when you let off, the CVT continues to do a stronger than normal engine braking, whereas other transmissions don't. It's more noticeable under some conditions than others, but definately there.
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