Since having my transmission replaced I've noticed that when I go over the hills in my rural area that the engine will rev up when I'm going down. Basically I accellerate up the hill then let up when I go down (dangerous roads, you can't go over 35 - 40 mph.) I can hear the motor rev up and see the tack spike up over 3000 rpm. My service department says this is normal. The old transmission didn't do this, was it supposed to? I'm not convinced this is normal. Any comments?

It's normal. Nissan incorporated "engine braking" into the CVT on the Rogue. It's the same effect as going to a lower gear in a manual transmission car, causing the car to use the engine to slow down. This makes the car safer to drive, and puts less wear on your brakes.I usually upshift into 6th gear when going downhill myself, because often times it goes too slow for my taste, and it's less strain on the engine/transmission which I'm a bit more concerned with myself. But since Nissan designed the Rogue's transmission to do it, it should be fine.However, if you're coasting down a long hill doing 45+, one that normally wouldn't cause you to build up more than 15 mph more or so, and the engine braking is kicking in, then that's not normal. The engine braking should only be engaging at lower speed, around 30 mph or so.

That's just the transmission shifting into the next lowest gear and using engine compression to keep the vehicle at a certain speed. Or something like that.

If you have a manual transmission you can basically slow down and stop just by shifting and not using your brakes much. Similar thing...

indesign99,

I can only assume the new transmission included new software, perhaps the engine braking effect has been changed.

My Rogue's done this since day one going down steep hills, and its just the tranny doing some engine braking. I'm quite sure its normal. I'm not sure why your previous transmission didn't do this.

However for me this happens at relatively high speeds, 90 km/h or so, but the stretch I'm thinking about is probably 2 to 3 km long, all downhill, with a 300 to 400 ft vertical drop. There's even a pull-over lane at the beginning for 18-wheelers to pull-over and check their brakes before starting the downhill. I'll check the grade tonight.

I'm not so sure its a function of speed, more of the car recognizing that its accelerating even though there's no throttle input.

Those southern Illinois hills will get you, especially when you are just trying to spend a nice day on the wine trail. Luckily the husband is not a wine drinker and is willing to DD

Can I ask, did you buy your Rogue over in Marion? I have been saving up and researching for a while now and am about ready to buy. I just do not know anyone who has bought a car from the Nissan dealership over there and wondered how the buying experience was. Are they pretty good to work with?

I understand the purpose of engine braking, but to me, it seems like it's quite a bit of wear/tear to put on the engine when I can use the brakes that are much, much cheaper to replace. Now, I'll be happy to do some engine braking if I think I'm using the brakes too much so as to not burn them out.

Is there anyone out there that can give some technical/expert advice on the matter? I marvel at people that engine brake when coming to a normal stop sign/light.

youngdustin wrote:I understand the purpose of engine braking, but to me, it seems like it's quite a bit of wear/tear to put on the engine when I can use the brakes that are much, much cheaper to replace. Now, I'll be happy to do some engine braking if I think I'm using the brakes too much so as to not burn them out.

Is there anyone out there that can give some technical/expert advice on the matter? I marvel at people that engine brake when coming to a normal stop sign/light.

Engine wear from engine braking at the mid to low RPM range (under 4,000) doesn't introduce any significant amount of wear and tear, it is a common misconception for people who think that it does--the amount of friction involved is absolutely minimal. Any usage of brakes wears them down faster, because its function is based on friction. The reason why engine braking works is because on modern fuel injection cars, any time you lift fully off the throttle and the engine speed range is above idle fuel delivery limit, the engine becomes essentially an air pump and the result is an engine brake effect (zero delivery of fuel and air--full throttle cut-off). The amount of lubrication on the engine renders wear and tear from engine braking virtually nil, as the oil pump continues running any time the engine is spinning, regardless of fuel delivery. Leaving the gearing high (i.e. running the engine low RPM) and braking consequentially uses up your brakes, is a risk of excessively heating the brakes (on long, steep and/or high speed downhill grades) and uses more fuel if the engine gets down below the idle fuel cut-off range (once it goes below that mark, typically ~1400RPM) because now it has to feed in idle holding fuel and air.

As far as engine braking to a light, the only reasonable time to do that is if you're going a short distance between lights, and the next light stays red a while after the previous one turned green. I know this happens often here in Westchester, where at best I get into 2nd gear out of a green light before coming up to the next light and it is still red (crappy timing). Downshifting to engine brake to a light is stupid; in that situation, any intelligent driver has a foot over the brake pedal anyway, and should just use them. A red light implies you should be going fairly low speed already, and at those speeds, there isn't a significant amount of brake wear for applying them, so it is the best way to control your speed. In fact, on the vast majority of automatic cars, engine braking to a light is completely lacking control because the torque converter is not going to be locked and only a mere fraction of engine braking torque passes to the actual wheels. Only on cars with clutches and not torque converters (real manuals with a clutch pedal or multiclutch automated manuals) make any sense to engine brake into red lights, and even then, it's really ridiculous to downshift from a high gear into a low gear only to engine brake; more than likely, they anticipate that the light will change to green very soon and would rather be in the correct gear beforehand; as a driver with years of metropolitan stick shift driving experience, I know when that light is going to turn green soon, and I know I'd rather be in 2nd gear before it does, because I'm going to have to downshift anyway, and it would be wasted time shifting after the fact. But then again, I always did a proper throttle blip on ALL downshifts, braking or not (heel & toe, very very often).

Let me know in case my explanations don't make sense to you...

-Ed
Modified by EddNog at 11:04 PM 11/11/2008

eric_c wrote:I'm not so sure its a function of speed, more of the car recognizing that its accelerating even though there's no throttle input.

You're right, in my experience the CVT isn't programmed to do this at a set speed, but rather it gears down when your speed increases while not applying the throttle - i.e. the force of gravity. It is normal in the sense that Nissan programmed it this way, however it is debatable whether it is a good set up or not. I don't really care for it, but also don't find it to be a big deal.

EddNog wrote:But then again, I always did a proper throttle blip on ALL downshifts, braking or not (heel & toe, very very often).

-Ed

I miss manual transmissions... especially the older ones. Properly executed, it gave me great satisfaction as a driver. Too bad modern emissions controls have made manual transmissions less enjoyable to drive. Many (My '03 Altima included) would 'hang' for a second after you let off the gas. It made smooth shifting near impossible.

My 240SX race car was a better example. I would get a nice snarl and pop on the downshift... music to my ears.

FWIW, I kept an eye out for the various signs on this hill near the cottage. The first section of the hill is 11% grade, and the second half is 7% grade. As soon as I crest the top of the and start accelerating down the 11% portion, the RPM will increase to 3700 RPM and hold.

Its maybe 1 to 2 mins from top to bottom. In this case, I would think engine braking is preferable to riding the brakes all the way down. Judging from the pull-over lane at the top of the hill for the big rigs, they've had a few scares with overheating/failing brakes.

Thanks for your explanation, EddNog! I was mostly talking about engine braking for stop lights/signs; although it sounds like it doesn't really matter much. I realize and utilize the safety benefit of engine braking down long hills; even using my previous flawed logic, an engine with a little more wear on it is better than a dead self.

So, are you saying that with a manual transmission, I would get better gas mileage leaving it in a gear where the RPMs are above the idle fuel delivery limit opposed to throwing it in neutral and coasting? I believe my Passat trip computer might support this because anytime I would go downhill and would have it in gear but above the idle fuel delivery limit, it would not give me a MPG reading, but if I put it in neutral, it would still give me a reading...I have no idea if this is because of what you explained or the computer simply didn't know what to do, but it makes sense to me. Again, thanks you for the explanation.

Think of it like that: The car has to keep the engine running.

If you are in gear the road will take care of it as long as gravity has more potential than you ask from the car.If you are in neutral, the movement of the car cannot help you anymore as you broke the link between the two, so the car needs to put some fuel in it to keep it running.

youngdustin wrote:...So, are you saying that with a manual transmission, I would get better gas mileage leaving it in a gear where the RPMs are above the idle fuel delivery limit opposed to throwing it in neutral and coasting? I believe my Passat trip computer might support this because anytime I would go downhill and would have it in gear but above the idle fuel delivery limit, it would not give me a MPG reading, but if I put it in neutral, it would still give me a reading...I have no idea if this is because of what you explained or the computer simply didn't know what to do, but it makes sense to me. Again, thanks you for the explanation.

This is the case for any transmission type, not just manuals. I am not 100% sure with regards to the programming and logic of the VQ Passat's trip computer.

-Ed

My Nissan was recently revving up to 5,000 rpm’s when going downhill, then a grinding started. Learned it was low on transmission fluid and I think it is back to normal now only hitting up to 3,000 rpm’s downhill. I do hate how it downshifts and wish I can have that reprogrammed. My wife’s car, while I hate most things about it because it is a Chevy Malibu, the transmission seems to work flawlessly staying at 2,000 rpm’s even downhill. Maybe Nissan didn’t get the memo brakes are free and transmission are costly to fix.

I don't know what model you have, but on most of the CVT's the hill assist is programmable. On some it can be done in Vehicle Settings on the cluster menus. On models where that isn't available, CVTz50 can change the settings, or of course the dealer can do it.

Is it this feature ?

https://www.nissan-global.com/EN/INNOVA ... INE_BRAKE/

Yes, but on most models it's a simplified version which only reads the pitch of the vehicle and responds to hills. The full blown IEB system is only on very high end models and incorporates roll, yaw, and steering angle to assist in handling.