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Engine Braking

22K views 52 replies 34 participants last post by  Gravy737 
#1 ·
Engine BRAKING, not engine breaking :)

Going on 4-5 weeks of ownership of my 2012 Sonata GLS Auto.

Is it just me or does the auto tranny downshift at about 35 MPH when coasting? I've never known another auto tranny to downshift while coasting (unless it's a truck with Tow/Haul mode enabled)...usually the torque converter with most autos just allows the engine to "freewheel" and return back to idle until I stop and then the tranny shifts back to first. With that Sonata, you can actually feel it downshift (into 3rd or maybe 4th?) when the speed drops down to 35 MPH or so. It is a noticable shift and the engine RPMs raise to 2K to 2.2K...and you can feel the engine braking helping to slow the vehicle down. Not saying this is necessarily bad or is a problem, I just find it odd and am trying to re-learn how to drive this car a bit. The only cause for concern is that this is often the speed (35-40) I run at when on some side streets and don't like the fact that the transmission immediately has to upshift when I press the accelerator pedal again. Seems to create unncessary shifting.

Additionally it is a little disconcerting me when someone is tailgating me and it suddenly downshifts. I find myself unnecessarily feathering the throttle just to keep the tranny from downshifting and putting the tailgator into my bumper.

SO, has anyone else noticed this?

For the record my Sonata is a 2012 built in June so I don't think the tranny TSB applies here. Also for the forum police, I did do a search and hadn't seen this brought up before. :)
 
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#3 ·
QUOTE (WarmFZI @ Aug 8 2011, 02:23 PM) index.php?act=findpost&pid=487658
I thought there was some description given that the battery is heavily charged during deceleration. So I always attributed this feeling to a sudden load on the alternator.
Interesting thought, but that shouldn't cause the engine RPMs to increase as the alternative is belt driven. So let's say the clutch on the alternator engages, then it could slow the car down from the extra drag created by the alternator BUT I don't think it would cause engine RPMs to increase, unless a downshift occurs as well...hmmm...or is my thinking incorrect here.

I guess one way to see what is going on is to switch the gear shift to manual and see what the gear indicator shows.

So does your Sonata do the same thing?
 
#4 ·
I have noticed it on both my 2011 limited and 2012 limited. Personally I dont like it much because I feel like it's stressing the engine and on other cars I was used to this not happening but it isnt too big of a deal for me personally. Now that you mention it I am going to put the car in manual and see what it is actually doing out of curiosity.
 
#5 ·
My 2011 SE seems to do the samething. It really feels like it is down shifting when you are trying to coast and help the gas milage a bit ..... and of course this has just the opposite effect. I mentioned this to one of the service techs when I was in having my first oil change .... and I was told that what I was feeling was to torque converter "locking up" and that I just wasn't used to driving a car with a lockup torque converter.

I decided not to argue but instead told the guy that I wasn't used to driving a car with an auto transmission that didn't allow you to freewheel when your foot was off the gas. This seems like a lot of excess wear and tear on the engine ..........and it does hurt your gas milage.
 
#6 ·
QUOTE (Mr. Peabody @ Aug 8 2011, 03:14 PM) index.php?act=findpost&pid=487678
My 2011 SE seems to do the samething. It really feels like it is down shifting when you are trying to coast and help the gas milage a bit ..... and of course this has just the opposite effect. I mentioned this to one of the service techs when I was in having my first oil change .... and I was told that what I was feeling was to torque converter "locking up" and that I just wasn't used to driving a car with a lockup torque converter.

I decided not to argue but instead told the guy that I wasn't used to driving a car with an auto transmission that didn't allow you to freewheel when your foot was off the gas. This seems like a lot of excess wear and tear on the engine ..........and it does hurt your gas milage.
I suppose it hurts mileage but maybe not in the same way you may be thinking. When it downshitfts (or whatever it does), and the RPMs go up, you actually aren't using any additional fuel. Your foot is off of the gas and so it isn't feeding the engine any more gas...essentially it is just dragging the engine and using the engine compression to slow the vehicle down. The mechanic is I think correct in saying that the torque converter is locking up...the wheels are spinning and when the converter locks up it is what causes the engine RPMs to then go up. Most autos, when you foot is off the gas, the converter just slips (freewheels) and doesn't engage with the engine, until you start giving it gas. However, I do think the mechanic is wrong in saying that your not used to driving a car with a lockup torque converter. As I understand it most torque converters do lockup once you get to a set speed in each gear.

Now how it does actually use more fuel, is if you get back on the gas. So instead of coasting a set distance, because of engine braking you slow down much quicker and therefore use more fuel if you then have to give it more gas. So some of the coasting efficiency is lost...difficult to explain at best :)

I'm actually wondering if Hyundai didn't do this on purpose to help reduce carbon buildup in the engine, which some believe can be a problem for direct injection engines. I do have to think that it does exhilarate wear on the engine a bit...as instead of the engine returning to idle while coasting, it actually uses compression (and therefore increases RPMs) to slow you down...more RPMs=more wear on engine, transmission, etc.
 
#7 ·
I have driven manual trannys for over half of my life including my motorcycles. When coming to a stop i always down shift to 1. let the engine help brake, and 2. to be in the proper gear if the traffic starts moving again. You say that your rpms jump to 2.2. If I remember correctly, red line is around 7. They tell you in the manual to drive between 2 and 4 to break the car in. That bump up to 2.2 is not damaging the engine or tranny in any measurable way. In fact, it helps lengthen the life of the brakes. I am sure that you will notice this happening at several different speeds. It is unfortunate that it happens at a very common speed in which we all travel. I will tell you this, on my bike, I am stuck between second and third, and constantly up and down shifting at 35. Same issue.

Jim
 
#8 ·
QUOTE (bostonjim @ Aug 8 2011, 05:40 PM) index.php?act=findpost&pid=487744
I have driven manual trannys for over half of my life including my motorcycles. When coming to a stop i always down shift to 1. let the engine help brake, and 2. to be in the proper gear if the traffic starts moving again. You say that your rpms jump to 2.2. If I remember correctly, red line is around 7. They tell you in the manual to drive between 2 and 4 to break the car in. That bump up to 2.2 is not damaging the engine or tranny in any measurable way. In fact, it helps lengthen the life of the brakes. I am sure that you will notice this happening at several different speeds. It is unfortunate that it happens at a very common speed in which we all travel. I will tell you this, on my bike, I am stuck between second and third, and constantly up and down shifting at 35. Same issue.

Jim
Hiya Jim.

2 things:
1) Two schools of thought with downshifting manual trannies. One some downshift to help with compression braking. Others recommend using just the brakes and slipping the car into neutral to slow down if coming to a stop. The one recommended by the Two Car Guys (or whoever they are) is the second method. Reason is less wear and tear on the clutch. While it does use the brakes more, their reasoning is, what is less expensive replacing brakes or replacing your clutch? Plus the second option is more like an automatic car, that typically doesn't use compression to help brake.

2) Sure the increase to 2200 RPMs isn't going to grenade your motor or hurt anything, but I still think you have to agree that an engine running at 2200 RPMs has more wear, as slight as it is, than a motor idling at 800 RPMs. Again very negligible but still wondering why Hyundai did what they did on the Sonata.
 
#9 ·
Ifd the car is moving, it is not idling at 800. It probably shoots up from 1500. When you are driving down the road and you need to pass some one, you give a little extra gas. Try this. Jump on it a bit, not even half throttle. You rpms will jump to atleast 3000 - 4000. That means it is down shiftjing atleast 2 gears. In my estimate,that is causing more wear and tear that jumping up 700 rpm to slow or stop. These cars have 6 gears. They are going to shift a lot more often then a 3 speed corolla.
 
#11 ·
Mine does the same thing. On one hand it's annoying having it downshift when you are trying to coast, but it should help extend the life of the brakes so I don't know. :whistling:

But with manuals, I have always downshifted to help save the brakes (only manuals I've driven are dump trucks). So I guess if I were really annoyed by it, I would put the tranny in "manual" mode and shift myself. :grin:
 
#12 ·
I have a 20110 Sonata and have experienced a similar thing. My 2002 Camry (which I traded in for the Sonata) did a similar thing and I am quite used to it. In my Camry I would go down a hill and take my foot off the gas. The car of course would increase it speed until I touched the bakes. At this point the car would shift or change something to maintain a constant speed rather than increase its speed as it went down hill. I did not need to use the brakes as much as before. I liked this feature as the Camry went through brakes pads like crazy.

It is nice to have the Sonata do something similar.

Anyone else have this downshift in other cars?
 
#16 ·
Getting back to the original post: The downshifting described did not happen prior to the infamous spring 2011 TSB reflash. IMHO this change was brought about as a reaction to one potentially serious problem with the 6sp auto. If the car was accelerated hard to somewhere in the area of about 40-50mph, then take your foot completely off the gas, wait about one full second, then floor it again. The result could be that nothing happened, no acceleration for what seemed like an eternity. The tranny was trying to work it's way to 5th, or 6th, and got confused at full throttle again. The reflash did away with this senario, and I'm pretty sure the downshifting described in post one is part of the fix. Yes, trannys cost more than brake jobs, but safety has an even higher value. Good move Hyundai.
 
#17 ·
The downshifting occurs in order to maintain "deceleration fuel shut off" during coasting. Depending on road speed, engine speed, and engine and exhaust temperature, the car will keep the injectors off (no fuel used) down to about 30mph. The reason you feel the downshift is that the transmission is reducing the overlap (between adjacent gears) because it needs to maintain enough torque flowing backwards from the wheels to keep the engine spinning without fuel.

You can sometimes avoid fuel shutoff by lifting off the gas pedal very gently. In you lift off the pedal normally, fuel cut is engaged within two seconds and will continue until you accelerate again, or until the speed drops below about 30mph.

To improve fuel economy, use this capability to coast toward slower traffic or on approach to a highway exit to cover that distance without burning a drop of gas.
 
#18 ·
QUOTE (DMLexpert @ Aug 9 2011, 12:00 AM) index.php?act=findpost&pid=487902
The downshifting occurs in order to maintain "deceleration fuel shut off" during coasting. Depending on road speed, engine speed, and engine and exhaust temperature, the car will keep the injectors off (no fuel used) down to about 30mph. The reason you feel the downshift is that the transmission is reducing the overlap (between adjacent gears) because it needs to maintain enough torque flowing backwards from the wheels to keep the engine spinning without fuel.

You can sometimes avoid fuel shutoff by lifting off the gas pedal very gently. In you lift off the pedal normally, fuel cut is engaged within two seconds and will continue until you accelerate again, or until the speed drops below about 30mph.

To improve fuel economy, use this capability to coast toward slower traffic or on approach to a highway exit to cover that distance without burning a drop of gas.
That could explain why when coasting around 30mph the rpm's jump back and forth between 1000-1500. I've noticed it almost every morning on my way home from work. Coasting down a slight hill with traffic, my speed stays the same, but the rpm is constantly bouncing back and forth. Not too big of a deal now, but if someone gets an exhaust this will sound retarted to everyone else on the road.
 
#20 ·
For what it's worth, my 2010 Tucson does the same thing. It downshifts while coasting at approximately 30 to 35 mph. It's done it since new (Feb 2010 build date) and was told by the dealer it was normal after I complained about it shortly after I bought it. It uses the (I believe) the the same 6-speed tranny as the Sonata, but the engine is not direct injection.

-Todd
 
#21 ·
QUOTE (DMLexpert @ Aug 8 2011, 11:00 PM) index.php?act=findpost&pid=487902
The downshifting occurs in order to maintain "deceleration fuel shut off" during coasting. Depending on road speed, engine speed, and engine and exhaust temperature, the car will keep the injectors off (no fuel used) down to about 30mph. The reason you feel the downshift is that the transmission is reducing the overlap (between adjacent gears) because it needs to maintain enough torque flowing backwards from the wheels to keep the engine spinning without fuel.

You can sometimes avoid fuel shutoff by lifting off the gas pedal very gently. In you lift off the pedal normally, fuel cut is engaged within two seconds and will continue until you accelerate again, or until the speed drops below about 30mph.

To improve fuel economy, use this capability to coast toward slower traffic or on approach to a highway exit to cover that distance without burning a drop of gas.
So you're saying that it completely shuts off fuel then and just downshifts and locks up the torque converter to keep the engine revving/turning over, until you apply gas again...and then the injectors come back online? Horrible grammar...sorry. I assumed it was still injecting enough fuel to maintain idle even though the engine is obviously revving much higher than idle speed.

Sort of makes sense, I have just never heard of this before. Not saying your wrong because I don't think that at all, just wondering where you got this information? I would like to read more.
 
#22 ·
QUOTE (DManInDFW @ Aug 9 2011, 01:37 PM) index.php?act=findpost&pid=488116
So you're saying that it completely shuts off fuel then and just downshifts and locks up the torque converter to keep the engine revving/turning over, until you apply gas again...and then the injectors come back online? Horrible grammar...sorry. I assumed it was still injecting enough fuel to maintain idle even though the engine is obviously revving much higher than idle speed.

Sort of makes sense, I have just never heard of this before. Not saying your wrong because I don't think that at all, just wondering where you got this information? I would like to read more.
Yes, the fuel injector pulse is 'off' during coasting, at those times when the computer decides it is appropriate. The engine needs to be fully warmed up, your foot needs to be off the gas pedal, the shift lever must be in a forward gear, and engine speed needs to be high enough (how high depends on several factors, assume 1800rpm+). The converter is locked at those speeds, so the engine has a direct mechanical coupling to the drive wheels. When you take your foot off the pedal, within a second or two, the injector pulses cease and the car's forward momentum spins the engine. If you step on the gas pedal, the injectors start again. It is instantaneous and transparent. The only way to know for sure if the car is "in fuel cut" is to look at a scan gage (or ultragauge) that is properly configured and you will see the switchover to "open loop" and "999.9mpg" instantaneous. Both my Elantra and Sonata behave in much the same way, although my Sonata is a stick and so the injectors pop back on when you press on the clutch and then then switch off again about a second after the clutch is released.

To learn more, go to google and search for "deceleration fuel cut off" (include the quotes for more specific results) and you will see articles that reference the technology. Implementation varies among make, model, and even different powertrain combinations, but it is almost universal nowadays. Some cars will stay in fuel cut and then drop out when the tach reaches 1100-1300rpm, but recent Hyundai products will downshift the transmission to keep the tach above that low-end rpm limit and will keep the fuel cut engaged down to about 30mph.

In my Elantra, I can use the ShifTronic to force fuel cut until about 15mph. Sonata automatics I have driven do the same exact thing. When using the ShifTronic, the low/reverse brake is engaged within the transaxle, and that clutch is connected "in series" with the overrun roller clutch. Translation - the wheel-to-engine connection remains down to much lower speeds, although with much more engine braking. This makes it possible to slow the car to below 20mph without using the brakes and without burning any gas. One caution - you don't want to do that when you have someone hanging on the rear bumper because these jerks rely on brake lights to judge when your car is slowing. Note to the "I've heard that damages the transmission" crowd - there is no harm done in manually shifting in this manner. There is far less torque borne by the low/reverse clutch when used in this manner (engine braking) than what is necessary to apply reverse (which uses the same low/reverse brake, but alongside the 3-5-R clutch instead of the underdrive clutch in order to provide "reverse" instead of "low 1"). If manual shifting could harm the transmission, the computer would ignore ShifTronic requests, and there would be one or more warnings in the owners manual stating that downshifting is only to be done in emergency situations. These transaxles are capable of millions of shift cycles, and think about it - the car still needs to downshift back to first gear every time you stop, whether you move the lever or not. The only variation in ShifTronic mode is that the low/reverse clutch applies during the downshift from 2-1.
 
#24 ·
QUOTE (Newport Ohio @ Aug 8 2011, 07:15 PM) index.php?act=findpost&pid=487773
Mine does the same thing. On one hand it's annoying having it downshift when you are trying to coast, but it should help extend the life of the brakes so I don't know. :whistling:

But with manuals, I have always downshifted to help save the brakes (only manuals I've driven are dump trucks). So I guess if I were really annoyed by it, I would put the tranny in "manual" mode and shift myself. :grin:
Tis true, I service commercial light to heavy trucks. The tranny is helping a little with break life. Also it helps give you the edge of response time if you have to hit the gas for any reason. I at times put mine into sport shift mode and manually downshift to let the engine back-pressure slow me down.
 
#25 ·
I was doing a search for an issue with my Sonata and found this thread. The car surges when going downhill. Although it happens in "D", You can really notice it when in 5th gear. Hated to do this, but I shot a video when traffic was light. The car speeds up quite a bit due to the surging, so I have to ride the brakes all the way down the hill.

Donno if this issue is related to this thread, as I am going about 65 mph in the video, not coasting to a stop. Can someone look and let me know?

 
#29 ·
I was doing a search for an issue with my Sonata and found this thread. The car surges when going downhill. Although it happens in "D", You can really notice it when in 5th gear. Hated to do this, but I shot a video when traffic was light. The car speeds up quite a bit due to the surging, so I have to ride the brakes all the way down the hill.

Donno if this issue is related to this thread, as I am going about 65 mph in the video, not coasting to a stop. Can someone look and let me know?
Hmmm...this appears to be different than what the rest of us are seeing with engine braking. Next time it starts doing this going downhill, slip the shifter into manual mode, so you can actually see what gear the transmission is in and whether or not it is shifting. It almost looks like the tranny is consistently going through downshifts (RPMs climb) and then upshifts (RPMs drop). Some vehicles (my Nissan Titan did it) are smart enough to downshift when going down a steep grade to help maintain a consistent speed, but don't know if that logic is built into our Sonatas.
 
#26 ·
I've noticed the same thing driving my wife's new 2012 Sonata GLS. Myself, like many people that have ever driven an automatic transmission vehicle, are used to feeling the car freewheel when you lift your foot off of the accelerator pedal while driving at speed. This car doesn't do that. Especially in a downhill situation, you can feel the transmission forcing the motor revs to climb and feel the drag. I'd like to think that it's a safety thing, but whatever it is there is a learning curve to get used to it.

While I really love the car, I came here looking for an answer to why there is a profound engine clatter upon a cold start. This bothers me a little more.

Sly
 
#30 ·
While I really love the car, I came here looking for an answer to why there is a profound engine clatter upon a cold start. This bothers me a little more.

Sly
Don't know if you found your answer regarding engine being more noisy at start up, but that's pretty common in most modern aluminum engines. On top of that, Sonatas are direct injected and the high pressure injectors are just noisier by nature.
 
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