2014 Subaru Forester CVT question

How high is it revving? I'll bet it's nowhere near redline.

Depends on the situation. Have you really never slowed down a car by downshifting yourself? Although a straight downhill road at freeway speeds isn't the first example that comes to mind, there are plenty of circumstances where downshifting is much safer than braking. Yeah, it's cheaper to replace brakes than transmissions, but that doesn't make brakes always the best means of slowing a car.

Patty

Hi,

My comments > In article ,

Cresting a hill at 60 mph the engine is turning at 1900 rpm or so, at its m aximum going down the hill, it gets up to 3500-4000 or so.

No, it isn't at red-line (I believe that is at 6000 rpm)

I've slowed every vehicle I have owned with the engine, that still doesn't make it the _best_ way to slow a car.

For strictly front or rear wheel drive cars, I really have to use my imagin ation to come up with a scenario where it is actually _better_ to engine br ake a vehicle, and in certain sub-optimal traction situations, it can be le ss safe to engine brake (than use the brakes), especially with today's ABS- equipped vehicles.

Do other CVT-equipped vehicles engine-brake?

Thanks, Duane

I guess we'll have to agree to disagree here, but prior to the advent of ABS brakes, people used to use engine braking (especially on manual cars) to prevent wheel lockup, to bring the car down to a slower speed from high speed. It was also known by the name of "lifting off the throttle". Of course, below let's say 10 or 20 mph, the engine braking had no effect, so at that point people used the regular brakes to slow it down to a halt, but the engine was really scrubbing off the majority of the speed from the high speed situation. The reason people used to use the engine braking was because the engine was always still turning, so you were never in danger of lockup.

Now, it is a bit disconcerting to see the engine revs go so high, but while the engine is braking, the throttle is closing or closed, so no actual extra fuel is being used up to slow the car down, so no added fuel consumption.

As for any danger to the life of the transmission. This is the CVT transmission itself that's deciding to downshift, if there was any danger of it getting destroyed, then they wouldn't have programmed it to do this.

Every older safe driving course I've heard about have always stated that you should always lift off the throttle first, before braking, to avoid locking up. The braking only provided the final slowdown. Of course that was in the days prior to ABS. What the relative safety of engine braking vs. ABS braking is, is probably debatable. But at higher speeds, lifting off the throttle and using engine braking was an easy way to prevent lockup.

And a full-time AWD system like Subaru's has an added benefit as the engine braking will work through all 4 wheels, and not just 2 driven wheels.

I don't know about other CVT vehicles, but I would assume so, since even old-fashioned hydraulic automatics used to downshift on steep downhills prior to engaging the brakes.

Yousuf Khan

Umm, I didn't say it was. I clearly said that it "depends on the situation." IOW, sometimes braking is better than downshifting and sometimes vice versa.

Patty

My 1998 downshifts. Most of the time I like it. As far as economy, your suppose to slow down up hills, and speed up downhills.

Greg

Consider a three-mile 7% downgrade; the kind where there are runaway truck ramps. Brakes can overheat and lose effectiveness in that situation.

I had my clutch replaced while doing the 110K or so cam belt replacement. The problem was actually the throw out bearing. The mechanic mentioned the clutch discs had gotten hot at one time or another. He specifically asked me if I downshifted to slow the car. I'm sure I have sometimes. Farm kids grow up double clutching. This is in Nebraska so the hills aren't all that much in my area.

Hi,

I appreciate your comments. M> >

Well, since I was taught to drive using my right foot for both accelerator and brake, I always let off the throttle before braking :)

For me it runs deeper than that. In slippery winter conditions, where I may be asking everything of my tires for traction, having the CVT decide to slow me down while going downhill may be something I don't want.

I have not tried kicking it into neutral in that case. I assume that would let me free-wheel.

Perhaps.

The transmission did this of its own accord? I have never heard of this. That would make winter driving interesting!

Thanks, Duane

If you waited a few seconds before hitting the brakes, you may have noticed that the car slows down very nicely on its own, without even touching the brakes, if you had a manual transmission. Used to rely on this effect especially when going around slippery corners. It would be dangerous to touch the brakes in some of these ice-strewn corners, so the only way to safely slow down was to let the engine revs bring the speed down. Even with the advent of ABS, I would never touch the brakes when given an icy corner. I've actually experienced a fishtail after applying the ABS brakes on black ice, on just a mild turn. The ABS were definitely working, I could hear the vibrations. That was on my last Subaru Outback that I had, with a manual transmission. Fortunately it was way late at night, and there was nobody else around for miles to hit, and the guardrails were still pretty far away too.

I think relying on your tires to accelerate, brake and turn you all at the same time is asking too much of them. If there is an ultimate traction limit in all directions, applying any two directions at the same time will quickly send you over the traction ultimate limit. So letting the engine slow you down while you let the tires do the turning will keep you within the traction limit of that tire.

I'd say these are concerns for manual transmissions, not for CVT's. In manuals, if you are downshifting to slow down, then the downshift may create a jerking action between gears, which may lead to a momentary lockup, unless you're absolutely smooth with your clutch work. But with a CVT, by definition, there is always going to be a smooth downshift, as the downshift is done along a continuously adjusting gear ratio, with no sudden jumps.

My feeling is let the CVT do what it wants to do, it probably knows better.

Yousuf Khan

Definitely, on highway and elsewhere is better to brake first with engine a nd then breaks. I hope cvt transmission is suitable to it. Everybody who dr ives manual, loves to use engine as a brake more than breaks, and it never damaged my transmission. Iv had 33000 on my Toyota carina without replaceme nt .

I made two trips to the Santa Cruz Mountains over the holiday weekend, and putting my Outback's CVT into manual mode saved me a lot of braking on those windy mountain roads.

Patty