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Eliminate 2000 rpm over-rev in cold weather

15K views 30 replies 12 participants last post by  pcray1231 
#1 ·
It has taken me six months of cold weather driving to discover this. OK, I'm slow.
My 2014 OB was designed to provide comfort over fuel economy and performance in cold weather by revving the engine to 2000 rpm to warm it up faster. I guess, with the CVT, you're not supposed to notice, but it is VERY noticeable.

Two ways to eliminate the over-revving:
1. Turn OFF the air circulation fan in the cabin (I did discover this a while ago)
PROs: performs is as if engine is warm CON: cabin fogs up and remains cold

2. Reduce the temperature to LO setting (at any fan speed).
PROs: performs is as if engine is warm, windows remain clear, engine actually warms faster because of low cabin heat demand
CON: cabin remains cold longer

This Tip worth reading, is posted in "High Engine Revs in Cold Weather" by Lloyd123:
http://i13.photobucket.com/albums/a292/saabgeorge/rpm_zps48291c97.jpg~original
 
#2 ·
The high revs after a cold start is for emissions reasons and not your comfort.
 
#3 ·
I'm confused. How is this different from any car? You leave the blower on low/off until there is actually warm coolant circulating, then you turn it on. Sure, your 2014 will actually respond quickly to climate demands by adjusting the RPM of the motor which is not something that all cars do, but it doesn't really make any difference. Whatever car you drive, keep fan lo/off and wait until it warms up, then turn the fan on. It irks me when people turn the heat on high right when they get in the car, especially if it's cold out. It only prolongs the warm-up period.
 
#4 ·
It has taken me six months of cold weather driving to discover this. OK, I'm slow.
My 2014 OB was designed to provide comfort over fuel economy and performance in cold weather by revving the engine to 2000 rpm to warm it up faster. I guess, with the CVT, you're not supposed to notice, but it is VERY noticeable.

Two ways to eliminate the over-revving:
1. Turn OFF the air circulation fan in the cabin (I did discover this a while ago)
PROs: performs is as if engine is warm CON: cabin fogs up and remains cold

2. Reduce the temperature to LO setting (at any fan speed).
PROs: performs is as if engine is warm, windows remain clear, engine actually warms faster because of low cabin heat demand
CON: cabin remains cold longer

This Tip worth reading, is posted in "High Engine Revs in Cold Weather" by Lloyd123:
http://i13.photobucket.com/albums/a292/saabgeorge/rpm_zps48291c97.jpg~original
Can you tell us again why you think a peasly 2000 RPM is considered "over revving"?

I have driven manual xmission vehicles for a very long time including a Subaru. It is totally NORMAL to keep the RPMs up while the engine is cold. This reduces torque-load on the engine. In other words, it is BETTER FOR A COLD ENGINE to spin it a little faster so there is less load on the moving parts.

For a Subaru 2.5L, 2000 RPM is in NO WAY "over revving". Here is a typical power-curve for Subaru engine==>
http://www.autocity-curacao.com/subaru/forester/11MY_Forester/HTML/images/e000523-lg_img.gif

Notice that 2000 RPM is comfortably in the torque-plateau....nowhere near "over revving". Infact, falling below 2000 RPM can enter the leading edge of the curve.
 
#7 · (Edited)
There is no blue light in my 2014. I would be ecstatic if it was a stop sign or two. I live where the temp is below freezing from November - March. This 2000 rpm goes on for 15 minutes until the engine is completely up to temperature. Have you watched the video on youtube of this guy holding the camera while driving to show that it never warms up?
https://www.youtube.com/watch?v=tVJ5H5AXTR4

Usually, that is my entire trip since much of my driving is in the city!
 
#10 ·
Yeah, in winter, mine takes about 5-10 minutes of DRIVING, and closer to 15 if just sitting there. Less in the summer, obviously.

But the purpose isn't comfort. This is about PZEV. The catalytic converter allows more emissions when it runs cold. Therefore, the car is programmed to warm up the cat as quickly as possible, which means, running high rpm's, and even then, it's sending extra gas through beyond that to be burnt inside the cat, which means you don't even get power out of some of the extra. If you have a temp gauge, the revs will calm down as soon as the needle starts to lift. If you are driving with foot on gas, you will also feel a "surge" of power the moment it decides all is well, as you are no longer sending gas past the engine into the cat to burn there.


I just did the test in your video. My rpm's don't lower when I turn off the heater. They stay around the 2000 rpm mark. The only way to get em down is to warm up the engine.

Don't get me wrong, turning the heater off will indeed get you there a little quicker. That's heat that stays in the engine instead of warming the cabin. But the intended purpose of the "over-revving" is not your comfort, it's to lower emissions of NOX, ozone, and things like that.

It does really kill the gas mileage, especially for city driving.
 
#13 ·
Yeah, in winter, mine takes about 5-10 minutes of DRIVING, and closer to 15 if just sitting there. Less in the summer, obviously.

But the purpose isn't comfort. This is about PZEV. The catalytic converter allows more emissions when it runs cold. Therefore, the car is programmed to warm up the cat as quickly as possible, which means, running high rpm's, and even then, it's sending extra gas through beyond that to be burnt inside the cat, which means you don't even get power out of some of the extra. If you have a temp gauge, the revs will calm down as soon as the needle starts to lift. If you are driving with foot on gas, you will also feel a "surge" of power the moment it decides all is well, as you are no longer sending gas past the engine into the cat to burn there.

I just did the test in your video. My rpm's don't lower when I turn off the heater. They stay around the 2000 rpm mark. The only way to get em down is to warm up the engine.

Don't get me wrong, turning the heater off will indeed get you there a little quicker. That's heat that stays in the engine instead of warming the cabin. But the intended purpose of the "over-revving" is not your comfort, it's to lower emissions of NOX, ozone, and things like that.

It does really kill the gas mileage, especially for city driving.
What speed are you driving when you press the fan OFF button? The 2000 -> 1200 rpm drop happens at steady city speeds of 30-35 mph (50-60 km/h). It's not noticeable at highway speeds.

Are you saying that it takes 10 - 15 minutes to warm up the catalytic converter or in Randy's case 45 minutes to an hour? (see his youtube "Cold CVT 2013-12-30 A" and the comments he and others have made)
 
#11 ·
Cover half of the radiator with cardboard. Old low tech solution that still works. You're in cold enough temps that you won't have to worry about overheating. The car will come up to temp faster and the problem will be solved.
 
#14 ·
Takes 10-15 when starting cold, temps near zero F, idling in driveway, no heater, for rpm's to drop. When cold it idles a touch over 2k rpms, when warm its around 1200. At temps of 30 F instead of 0, takes bout half that time. At 50ish its only a minute or two.

My understanding is that this is PZEV warming the cat.

Driving it shortens the time a little, but not as much as you'd think. Power increases quite suddenly when the temp needle starts lifting. If currently on the gas you get a "surge" and the car just starts feeling more powerful. I.e keep your foot the same, and rpms stay same but more power. Keep speed the same, for instance level road on cruise, and rpms drop.

Separate this behavior from heat/ac behavior as 2 separate "things" (neither of which indicate a problem, per se, but you may not like it).

Yes, warm or cold, turning on heat or a/c raises rpms's, but only a little, and thats on top of the above, whether driving or not. All cars do that due to load on the alternator. My brothers dodge, fathers toyota, and mothers chevy all do the same.

But the first 15 minute pzev overactive warmup thing is pure Subaru (i.e cold engine high revs last MUCH longer).

I'm taking your complaint to be the pzev thing because of the time you said it lasts, though the heat/cool thing, since it does change rpm, may be masking you from seeing it as separate.
 
#16 ·
My 2014 Forester 2.5i Limited with X-Mode CVT exhibits the exact same "problem" of high heat demands made by the Automatic HVAC control to the CVT resulting in 2000 rpm at 45 mph, when it should be 1400 rpm. I drive my Forester 12 miles each way for my work commute and it is parked in a warm (not heated) attached garage. Dash thermometer may start at 40F when backing car out of garage on a 10F morning, so cabin is already pre-heated, but he engine goes to 2000 rpm immediately on the first drive away, even though the motor is still cold. This cant be any good for a cold engine, so the only recourse is turn the HVAC to OFF till the engine warms up a bit. Then turn the HVAC to ON to clear the frosted windows. Engine revs stay at 2000 rpm for the ENTIRE 45 minute commute.

Yes, I discovered the trick of turning the HVAC off and/or turning the temperature set point down. Both of which will pause this high-rpm problem. I have also discovered that there are two thresholds that this problem reacts to. A temperature of 50 F to 30 F triggers the "low heat demand" and will result in 1600 rpm. 30F and below triggers the "high heat demand" and will result in 2000 rpm.

I have taken my car back to multiple dealers repeatedly complaining about this. On my 9th visit, they gave me a copy of the TechTips April 2014 issue describing the problem. Prior to this, no one was able to acknowledge the problem, or even be knowledgeable about it.

Some simple programming updates by Subaru could allow the driver to enable or disable this high rpm problem. Software only, no hardware changes so this would be a low cost change to make knowledgeable Subaru owners happy. Control of software would be a "back-door" approach by using a combination actuation of existing switch inputs to HVAC. Example: Press OFF and DEFROST, or OFF and A/C, or any other combination simultaneously while starting engine could toggle this function on or off.

ALSO, I too have noticed a definite decrease in mpg with this 2000 rpm problem in activation. I wonder how the US EPA would respond to knowing what Subaru has done that results on lower than advertised fuel economy.

Frustrated...........
 
#20 ·
You have spent a long time documenting and attempting to troubleshoot your vehicle's behaviour. It is quite apparent that your vehicle is NOT behaving normally. There is something that needs to be fixed. I live in Ontario (about the same latitude as you). Even at 0ºF temps, my 2014 Outback will warm completely so the engine no longer revs above "normal" after 15 to 20 minutes max. I have a problem with software settings that take control away from me and give the decision-making to a computer that operates based on assumptions.
It assumes that I am OK with burning extra fuel just to warm up the cabin marginally faster by revving the engine. There is plently of heat after two or three minutes. Why does this "programming" persist for 15 minutes of driving at freezing temps? That's way too long.
It assumes that I don't mind the jerky ride as I take my foot on and off the gas on a flat road and the rpms jump back up to 2000 from 1400 suddenly. It's rather disconcerting for me as the driver when the car surges like that. I don't like that experience. I don't feel in complete control.

With the circulating fan OFF, the engine (cold or warm) behaves as efficiently as possible and there is no surging. I feel confident and secure driving it - no surprises. So I leave the circulating fan OFF except at intersections until the car is completely warmed up.
 
#17 ·
I am that Guy

I am the guy who made and posted the video https://www.youtube.com/watch?v=tVJ5H5AXTR4 about the 2000 rpm problem. I made it back when I was just starting to experience the problem.

Yes the video is only 7 minutes long, and I should have made it longer. The 2000 rpm problem goes for as long as 60 minutes in the Winter here in Michigan. Real frustrating, and really hurts gas millage.

Had car to dealer 9 times complaining about this problem since September 2013. They finally gave me a copy of the April 2014 TechTip describing this problem. They still have yet to get back to me to see if other cars do the same as mine with 60 minute at 2000 rpm.

A simple software upgrade could solve every-ones frustrations. No hardware change required, simply use a combination of activation's with existing HVAC controls to toggle this 2000 rpm problem on or off. Example would be to press OFF and DEF, OFF and ON, or OFF and A/C.
 
#19 ·
I did watch the video.

#1 I'm not sure it's a "problem".
#2 I'm not convinced it's the exact same "problem" as the OP is discussing. His ends after 15ish minutes starting with a very cold car, which is exactly what mine does with or without heat. 15ish minutes is on par with how long the PZEV related high revs can last in very cold weather.

Yours goes for 60 minutes starting from a warmer engine. i.e. it's not about PZEV for you. You're noticing the power requirements the car asks for when the cabin is calling for high heat. Running HVAC requires a lot of electricity, which demands a fair draw from the alternator, which then demands some power from the engine.

FWIW, 2000 rpm is not "high" for a smallish displacement 4 cylinder Subaru engine. Subaru makes low displacement high rpm engines to get favorable HP per liter.

As Brucep posted, that's roughly the BEGINNING of the torque curve, so it really can't do any real work below that number. When there's nothing calling for power, for instance when coasting and the cabin is at temp, yeah, the rpm's drop lower. But anytime you need any power at all, whether to run HVAC or to keep a fairly heavy car at steady moderate speed, it's gonna have to get at least into that range to do anything.

If you compare an Outback to a Forester when going a steady 40 mph, yes, the Forester will run a little lower rpm's, because the Forester is lighter. That's why it gets a little better mpg as well.

Also, it is BETTER for a cold engine to run faster.

Also, regarding the PZEV thing, this is semantics but it's not about heating the engine, it's about heating the catalytic converter.

In the end, the Outback, as a vehicle, gets decent mileage for a legitimately AWD SUV with that much weight. That said, there is a fairly large temperature penalty, as well as a fairly large dependence on what kind of driving you do. It does best in long-haul highway trips, and worst in shortish drives with lots of stops.

My numbers are as follows:

Winter around home: 20-24 mpg
Winter trips: 24-28 mpg
Summer around home: 24-28 mpg

Summer trips: 28-32 mpg. I do get 30ish pretty consistently on long trips in summer as long as I keep it around 72 mph and utilize cruise. Usually the difference between 28 and 32 is headwind or tailwind.

My commute is about an hour each way, mix of highway and some country roads. I get 24 mpg in winter and 28 mpg in summer on that commute. This winter I did worse than 24 mpg, but that's because of driveway warmups (taking a newborn to day care on my way, so putting him in a cold car is a no-no).

It's rated 24/30, 26 combined, which for me is dead nuts accurate.
 
#21 ·
Video: 2000 rpm unnecessary revving for heat

Here's a video my son took from the back seat about a week ago. I gave a copy to the head of service at my dealer at his request.
On a straight road at constant city speed with engine partially warmed up and A/C off, I turn the fan off and back on showing this 1200 -> 2000 rpm is ONLY about heating the passenger space.

The rise to 2000 rpm does not depend on the speed of the fan. It only rises back to 1600 rpm when the fan is turned back on.
BUT if you slow down and start again, the rpms return to 2000 at city speed.

This is not about controlling emissions, it is only about creature comfort and burning extra fuel to go the same distance. This has been consistently happening since the cold weather set in last October. The internal combustion engine produces plenty of waste heat without running it any faster.

https://www.youtube.com/watch?v=LV2YvOszwiU
 
#26 ·
I suspect it's more than that, but you're right- measurements would help.

What I'm getting from this thread is that some people with very short commutes are suffering from the one-size-fits-all approach to engine management.

Sacrificing extra fuel at startup in order to burn significantly less during the cruise makes lots of sense to me- but if the journey is too short to ever enter that cruise phase, there's no payoff.

The only real solutions I can see would be switching to a car with a far smaller engine or using an external heat source to preheat the engine.

Life is full of compromises.
 
#28 ·
This is interesting. First time Subaru owners here and certainly find it a different type of vehicle to drive. On startup today, it was -1C, not overly cold but I found the engine to be reving much higher than what I am used to (didn't think to look at RPM) but it was noticeable. Then engaged into reverse, I thought it felt as if I was on an incline, like when using regular automatic transmission, if on an incline you would feel some of the weight of the car on while shifting. And lastly, I was a bit startled when pressing on the gas how quick the car responded...
 
#29 ·
What I'm getting from this thread is that some people with very short commutes are suffering from the one-size-fits-all approach to engine management.
Agreed. All cars do worse in gas mileage in cold weather, short trips, stop and go driving. But the OB seems to have a larger penalty than most for that kind of driving. Would be interesting if it's due to engine management regarding HVAC, PZEV, or some combination of both. It's also a heavy car powered by a smallish engine, so stop and go will tax it more than cars with bigger engines, and you get greater benefits from steady speed as well.

Shage, in my state and all states around me, Subaru doesn't just offer PZEV, they ALL are PZEV. That could be different elsewhere. But in PA, you can't buy the 4 cylinder as non-PZEV (I think the 6 cylinder is not, though). It is cleaner in terms of smog, but not in terms of gas mileage. They've got a beefier cat, thicker walled gas tank, extra stuff to absorb evaporates from the gas, and yes, changes to the ECM. That's the part we're talking about. Since the bulk of smog forming emissions happen when the catalytic converter is too cold to be working efficiently, one of those changes to the ECM is to apply logic which heats the catalytic converter to operating temps as quickly as possible. And yes, it actually burns MORE gas to do that, in the name of environmental stewardship!

The blue engine light or meter, whatever you are equipped with, shows you ENGINE temperature, not catalytic converter temp. But it's catalytic converter temp that has to get to temp before the rpm's drop. When temps are very cold, my rpm's stay high for 10-15 minutes whether or not I have the heat on.

That said, yes, you are correct, that a high demand for HVAC also raises rpm's. And that demand will lessen as the cabin heats up.

So, I may have mis-"diagnosed" your car, I dunno. Maybe it is the heat you are noticing. The 10-15 minute comment is what had me thinking otherwise as that's exactly what my car does with temps in the single digits or below, even if I turn heat off. It is about 2100 rpm in park. When in gear, it'll go below that coasting, but even a slight touch of the pedal puts it over 2000.

rschmidt, on the other hand, has his last for 45+ minutes. That has to be something different. He's either got something wrong with his car, or else he's really blasting that heat!

On startup today, it was -1C, not overly cold but I found the engine to be reving much higher than what I am used to (didn't think to look at RPM) but it was noticeable.
Normal. Subaru's are rather high rpm's on cold starts, and sound a bit "rough" for a while as well. The rpm's will drop when it warms, but even so, a Subaru is gonna run higher revs than most cars you may be used to, and the engine doesn't run as whisper quiet as a GM, for instance. This is in part due to the exhaust note of a boxer engine (though exhaust design comes in as well). In a way, they seem less "refined", but it comes with plenty of advantages too.

Then engaged into reverse, I thought it felt as if I was on an incline, like when using regular automatic transmission, if on an incline you would feel some of the weight of the car on while shifting.
Not sure on this one, probably more to do with the CVT than anything.

And lastly, I was a bit startled when pressing on the gas how quick the car responded...
Ditto. Generally with a traditional automatic, when you press the gas (ask for power), it waits for the transmission to downshift and then adds revs. With a CVT, the revs come immediately, but it still takes a second for the transmission to "catch up" and translate it into power. This is the "rubber band effect" that some complain about with a CVT. Subaru's isn't bad but it's there. Nomatter the starting speed, when you press the pedal to accelerate, the revs spike immediately, followed by the power increasing and the revs falling. You'll get used to it quickly.

I came to like the CVT, as the torque converter rarely disengages and you have the fully connected "feel" of a manual. Also, it doesn't hunt gears at certain speeds or on hills. I drove my wife's 4 speed Forester recently. It shifted going up a hill. My first thought was "how rude", lol.
 
#30 ·
d you have the fully connected "feel" of a manual. Also, it doesn't hunt gears at certain speeds or on hills. I drove my wife's 4 speed Forester recently. It shifted going up a hill. My first thought was "how rude", lol.
Going up a hill I was waiting/expecting for the transmission to shift down but then realized that just doesn't happen with the CVT. Interesting.
It doesn't bother me at all. Just will take some time to get familiar with the differences.

And, thank you for the answers, that helps a lot
 
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