on my work commute there are a good amount of downhills where i can glide in neutral for miles. I'm just asking if this is bad for the transmission. I would drive up to 40mph and pop it in N. Eventually it'll glide up to about 60mph...then pop it back to D once the car get's down to a slower speed.

Thanks!

 

This topic has been covered in several threads:

https://www.greenhybrid.com/discuss/...searchid=71436

Good luck.

 

thanks...but i've already searched. Didn't really find any concrete answers.

so is it bad for the transmission? yes or no?

 

I have experimented with this a bit myself. I would recommend rev-matching before re-engaging. First before going into neutral, ease off the gas and let the RPMs settle into the highest gear-ratio they're willing to go. Let's say you're at 1600rpms, before you re-engage, rev the engien up to just under that number of RPMs then pull it back into drive. If you do that, the tranny/wheel speed mismatch shoudln't be any more strenuous than what happens when you come out of auto-stop.

One problem I have heard about for netural costing in automatics is that the wheels spin the gears etc, but that since the transmission fluid pumps are powered by the engine, the parts run the risk of overheating. Thi shoudl not be a problem on the Honda CVTs though as the transmission's belt and pulleys are on the engine-side of the clutch, rather than on the wheel side, so they will onyl spin at the engine's idle speed rather than being spun by the wheels.

Ultimeatly however I believe the whole desire to shift into Neutral is cauesd by a major design flaw from Honda's battery charging algorithms-- they attemtp to charge the battery pack every time you let go of the gas, when they really only should charge when the driver wants to (pressing the brake pedal, or using an "engine brake" switch on the shift lever like on the Prius) making costing essentially impossible without going into neutral. On the rare occasions I've had the battery pack completely filled though, there is almsot no perceptible difference between in-gear, and neutral at anything below about 45mph, since 3 of 4 cylinders are shut down there's very minimal engine braking -- almost all of the engine braking effect is from undesired charging.

 

I'm no expert but I've decided to not pop it into neutral when driving downhill.
I suspect if it can't actually hurt the CVT it can't be good for it.

Also you are not charging when the system is designed to charge.
Perhaps the battery will suffer long term from being less charged.

I've decided to trust that Honda's engineers are smarter than me.
There are a million other no-risk things I do to get 60 MPG; I don't do this one.

 

To add more confusion I will add my piece.

Don't rev match in a CVT. There is no point. Even at 60mpg the car is only going about 2000 rpm anyway. I have used it several times on the highway without a problem. Make sure you foot is off the gas when you put it back in gear (this is the opposite of what you do in a MT with rev matching).

Kenny has stated in the past he gets a thunk when he goes back into gear. I don't notice this in my car at any speed. I don't think it will drop the transmision if you test it yourself so you will have to see how your car reacts.

Like the above poster said, honda uses charging at the most in oportune times. I say if your pack is above 1/2 use a neutral coast. Below that and you will start getting into forced regen and its not worth it.

 

Pro's of coasting in neutral:
- no pumping losses from the cylinders pushing air through ("engine braking" on normal cars)
- less friction overall
- further overall coasting range for given slope/terrain

Pro's of coasting in gear:
- fuel injectors are shut off- ZERO fuel being used as long as rpms > idle speed
- full lubrication to tranny
- more regen for use later on

Con's of coasting in neutral:
- not full lubrication in some cases
- engine consuming fuel at idle rate
- forgetful drivers might forget to place back into D in a hurry
- no regen, if it matters

Con's of coasting in gear:
- engine braking (PLUS regen in hybrids) reduces coasting range significantly

In my case (HAH) I can normally get better overall FE by coasting in gear instead of neutral, since pumping losses only affect 3 of the 6 cylinders- the other 3 are sealed at low-load and normal speeds. Plus, in neutral, all 6 of my cylinders are banging away at idle consumption. On balance, my overall consumption is often lower while staying in gear, despite the shortened coast distance.

This may or may not hold similarly true for the HCH-I. It comes down to what uses less fuel for your particular model: zero used for some distance (but some used for the remaining distance), or a little used the whole way for that entire distance. The optimum configuration slides from one to the other depending on the ratios of fuel used and distance coasted- different for each model. In calculus it would be referred to as a max/min optimization problem.

I spent several months neutral coasting before switching to in-gear coasting. My FE took a noticeable jump up when I went to in-gear back in the winter.

My recommendation:
find representative stretches and see what your 'segment' FE for that stretch is both in neutral and gear. The preferred configuration may be different for different grades and even road surfaces on flat terrain! This way its not a guess. You know for sure.

 

I have experimented with this a lot. I used to do it all the time, but have now found that shifting into neutral is unnecessary. If you back off the gas and max out the instant FE display, but keep on enough gas to stop the regen from engaging, then you're coasting as freely as you would in N. There's no regen and no engine braking, it's just like coasting along in a normal automatic.

If you do use N, DO match the rpm before re-engaging, it does work and it is better than slamming it in. If you don't rev-match, it probably won't do a lot of damage but it puts more wear on the tranny. You can't always anticipate what rpm the cvt will shoot for when you return to gear, so I just rev it to about 3k and let it take up the diff. This is a lot smoother than dumping it into gear from idle.

My technique to make sure I didn't forget to switch back to D was to never remove my hand from the shifter until I had shifted back.

 

Thanks, Gonavy and Zimbop! I've been wondering about this point since I got my HCH2. I used to coast in neutral with my stick shift all the time and was wondering about using FAS and/or shifting into N with the CVT. Your posts are very clear and helped alot. I'll stick to maximizing the FE, (no regen or assist) and only allowing regen if it does not slow the momentum.

 

Just make sure you don't get into an accident while coasting in N -- it's illegal in most states.