I recently drove a Subaru Forester with a CVT, and I noticed one thing that seems to be a safety problem.
Driving at low speed, say 30-40 MPH, when I floor the throttle, there is a long delay before anything happens, about 1 second. This seems to be a safety problem. An ordinary automatic downshifts in a fraction of a second, and I can shift a manual from 4th to 2nd also in a fraction of a second.
Is this indeed a safety issue?
bill
That’s a common problem with many of the cone-and-belt CVTs. I’m not a fan. But is it a safety problem? Some other autos have a similar delay (not all, of course).
Flooring the throttle at 30 to 40 mph is such a seldom used maneuver, I would suggest you try to determine how important it is to you. Compare the passing times in that range rather then just that impression. If the over all times are the same, it doesn’t matter where the delay occurs. If still uncomfortable, move on to another choice.
I can’t remember the last time I had to floor my accelerator. I guess it’s because I look around while I’m driving.
I once rented a Dodge Caliber with the CVT. Wretched vehicle, with only one redeeming quality. Despite my constant flogging it still returned 30 MPG, it was deplorable in every other aspect. CVT’s tend to have a bit of lag time when the engine is reving up and the transmission is getting to it’s chosen ratio for the conditions the driver has specified. I too am not a fan.
For a lot of people, that would not be an issue. Just don’t do anything like quick lane changes when in that speed range.
Driving at low speed, say 30-40 MPH, when I floor the throttle, there is a long delay before anything happens, about 1 second. This seems to be a safety problem.
That might actually be a fault of drive-by-wire, not the CVT. When I drive my mom’s Fusion, it takes almost a second, flooring the accelerator, to get useful propulsion (from a stop). I wholeheartedly agree: it IS a safety issue.
It would seem fairly easy to have a “rough draft” map of gas pedal position to throttle position, that could be refined as you move. I’ve heard the delay is built-in, for emissions purposes. I wish the Powers That Be would weigh the pros and cons of 1 second’s worth of pollution versus driving safety–after all, wreckers and ambulances burn a lot of diesel fuel, and not all that cleanly!
I can't remember the last time I had to floor my accelerator. I guess it's because I look around while I'm driving.
Wow–you must live somewhere desolate! Ever have to make a left turn, across a 4-lane, during rush hour? You can wait minutes, and have a 2 or 3 second window to get going, then wait anouther two minutes if you’re not “Johnny-on-the-spot.” Of course, I drive a vehicle with a 40:1 weight:power ratio fully loaded, and a 2.56 final drive ratio–I’m “all-in” pretty much every freeway upgrade to maintain speed, and every freeway on-ramp.
@meanjoe75fan "I wish the powers that be would weigh the pros and cons of 1second of pollution vs driver safety…“
I hear you and agree with your sentiment totally. But, I believe such issue at some point it will be taken care of when we have direct drive electric motors. (I would “love” to see them now where gas motors just power the power supply making everything instantaneous.) In my opinion, it’s a car performance issue and not necessarily a pollution issue. Remember how carb cars before pollution controls hesitated to high heaven. So the best thing to do is, only buy the best performing cars and say to car makers. " don’t care how you do, just do it” . The technology is there as some cars, both mine, don’t do this. Neither does my son complain about any issues living in and around Boston with his CVT driven Rogue.
I drove a Nissan Sentra on a 600 mile round trip that my institution rented for me to go to a convention. This Sentra had the CVT transmission. It reminded me of the old Buick Dynaflow revving up when I would accelerate from a standing start. However, the gas mileage was good and after driving it for half an hour, I didn’t even think about the transmission.
Good ones aren’t very noticeable. We had one for a week in New England last year and I be with myself that my partner wouldn’t notice anything unusual about the car. He didn’t and didn’t believe me when I told him it was a CVT. If there is good sound insulation so you can barely hear the engine (and aren’t watching the tach) they don’t seem unusual at all. Anyway, what is so ‘normal’ about a geared transmission. The rpm climbs in a very odd pattern, with drops whenever you upshift (or the car does). It’s just as easy to get used to a CVT.
I’m the OP. I do think it’s a safety issue. Yes, it’s not something you use very often. I’ll have to be careful passing, and in similar situations.
I also think I’ll get used to it.
@dagosa You think flooring at 30-40 is a seldom used maneuver?
Think two lane road with dashed yellow indicating legal passing. Speed limit is usually around 50, but its all too common to be behind someone going 40 on these roads.
I don’t think that CVT transmissions have evolved to the point where they are as reliable as the automatic transmissions we have now. I drove some brand new vehicles with CVT and it took a while to get used to the way they “shifted.” I’ll pass for the moment but I do like the theory behind them.
I remember the debate back in the 1950s between an automatic that depended completely on a torque converter (the Buick Dynaflow and the original Chevrolet PowerGlide) and the GM HydraMatic which had a fluid coupling (no torque multiplication) backed up by 4 speed gearing. Ultimately, cars had a torque converter, but the transmissions had three forward speeds.
Now we have the debate between six and more speed automatic transmissions or the CVT. History repeats itself in interesting ways.
@Starman
Maybe it’s my rural environment and winter icy roads but along with frequent trips to the Boston area, no, never that I can think of. That just isn’t my technique. Guess it’s from driving old carb cars where suddenly jumping on an accelerator often brought out the worse in a car. My acceleration technique has always been to push the accelerator gradually and continuously till my foot was on the other side of the firewall, as I monitored the environment. But suddenly jumping on it…no . Proper passing for me has been to hang back far enough so I can gradually build up speed before I go into the passing lane. Always avoid sudden acceleration if I can.
I haven’t had this issue with any of the hybrids I’ve driven with CVTs (a Toyota Camry and a Ford Escape). I hear it’s an issue on the Smart Fortwo, but I don’t think it has a CVT.
Having said that, I’ve never subscribed to the idea that being able to accelerate quickly is a safety issue. I think if you have rely on acceleration to avoid a collision, you’ve made an avoidable error, perhaps mistakenly, to put yourself in danger in the first place. A typical example would be someone who doesn’t take advantage of the acceleration lane when merging into traffic. Another example is when someone pulls out into an intersection without being able to see in all directions. Having extra power might help mitigate these situations, but these situations could also have been mitigated by using good judgment.
My 1998 Honda Civic DX has about the lowest power-to-weight ratio you can find on American roads, but in the 257,000 miles I’ve driven the car, I’ve managed to not collide with another vehicle, because instead of utilizing a high power-to-weight ratio to mitigate dangerous situations, I utilize my brain to help me avoid getting into dangerous situations in the first place. It’s not as fun as accelerating quickly, but it keeps me safe.
If I want a vehicle that accelerates quickly, I’m happy to admit it’s because it makes driving/riding fun. I don’t need to come up with other reasons.
I had a rental Altima once, it has the CVT. The first take off required more engine rev’ing than I am used to in my conventional cars. But I got used to it. As far as “downshifting”, it is probably still faster than a stick shift.
@dagosa
Must be a difference in the cars then, because my experience is largely based in New England as well. The cars I’ve driven have always had very good acceleration, so I don’t need a lot of room to build up speed. And the icy roads really only apply mid-november to mid-march, the other eight months normal driving conditions apply.
You should be careful passing, delay or no delay.
It sounds like an oddity of the transmission or throttle programming of that car. There is nothing unique to a cvt that makes it more likely to do that.