Issues driving at slow speed in traffic

MikeM. said:
The engine is not breaking (that would be bad!) but the CX-5 does make good use of engine braking.

Similar to the iActiv AWD, the transmission control unit uses real-time data output from a lot of different sensors and runs those data streams through various algorithms to determine what gear to be in. If you are descending a hill it will be more likely to downshift earlier than if you are going uphill (as but one example). Another example would be if you have let off on the throttle and touched your brake as if approaching a red light then the transmission will downshift at a higher speed than it would have had you not touched your brake. This extends the brake service interval and extends your cruising range (mpg) because when the vehicles momentum is used to keep the engine turning, no fuel needs to be injected (assuming the engine is warmed up). When approaching a traffic slowdown I'll often touch my brake briefly to kick in earlier downshift which saves my brakes and increases mpg. Often, the traffic ahead will start moving forward so I can gently roll on the throttle and mesh perfectly behind the pack without having to actually come to a stop.

A driver with the bad habit of over-accelerating and needing to use the brakes to check speed when catching up to traffic in front will find this behavior irritating because it will be downshifting when you don't want it to. That's because they're sending ambiguous signals about their intentions to the control unit. Always ease off on the throttle at the appropriate time so you don't need to touch your brakes to check your speed (assuming you want to coast without early downshift). A good driver with a smooth, non-erratic driving style will experience the best results. For all others there is the manual shift mode.

IMO, this is the best automatic transmission I've ever driven, bar none. And I've driven a lot of them. It's an expensive transmission to be sure but all indicators are that it has good longevity, even when driven hard. Mazda put a lot of the cost of the CX-5 into the engine, transmission and chassis which is why I find it so ridiculous when people ignorant of these facts criticize the lack of creature comforts vs. the competition who uses engines, transmissions and chassis that are not nearly as expensive or sophisticated. And one drive is all it takes for an experienced driver to notice the difference.
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As far as downshifting increasing MPG, I think you are slightly mistaking. As long as the car's momentum is driving the motor and sufficiently compensating for the internal loss of energy due to friction and compression, no gas will be injected. So as long as the engine is not close to a stall, a downshift is not necessary for increased MPG, simply staying in gear is sufficient. On the contrary, a downshift increases the energy dissipation trough compression, therefore "wasting" energy faster. So in theory, if your objective by tapping the brake is not to stop (say you simply wanted a slight reduction in speed to adjust to traffic), the faster downshifts would force you to get back on the gas sooner than you would have otherwise, thus reducing MPG. Now I'm approaching this with a purely physical perspective, I'm no automotive engineer, so correct me if I'm wrong, there might be other mechanical factors I'm not considering.

But I do agree that the faster downshifts save brakes and in most occasions mirror what I would do with a manual transmission, which is quite amazing. Someone without MT experience might need to get used to it though, but knowing why it works that way might let them learn to enjoy it more...
 
vroom said:
As far as downshifting increasing MPG, I think you are slightly mistaking. As long as the car's momentum is driving the motor and sufficiently compensating for the internal loss of energy due to friction and compression, no gas will be injected. So as long as the engine is not close to a stall, a downshift is not necessary for increased MPG, simply staying in gear is sufficient. On the contrary, a downshift increases the energy dissipation trough compression, therefore "wasting" energy faster.
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Obviously each situation is different but what you are missing is that by decelerating in too high of a gear, some fuel needs to be added to keep the engine turning. You can test this out by using manual shift mode to coast in a gear that is too high to keep the engine turning and noting that your instantaneous fuel economy is not necessarily greater than 99.9 mpg. This works best at slower speeds because at higher speeds it's possible to get 99.9 mpg while the injectors are operating. Better yet, use an OBD port reader to directly view fuel injection.

The other factor you are not considering is the sophistication of the CX-5's charging system which manages battery charging to maximize mpg's through reducing loss to the alternator. It does this by charging the battery when under engine braking and letting the battery discharge slightly when under throttle. In practice it needs to charge the battery sometimes when on throttle because there might not be enough deceleration events to produce adequate charging. But higher rpm engine braking assists in not needing to charge the battery under power.

So in theory, if your objective by tapping the brake is not to stop (say you simply wanted a slight reduction in speed to adjust to traffic), the faster downshifts would force you to get back on the gas sooner than you would have otherwise, thus reducing MPG.
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True, but I don't tap the brake to encourage downshifting every time I want to slow down slightly, I only do it to replace brake usage. Sometimes I simply let off the throttle and coast in the highest gear the AT shift logic allows.

But I do agree that the faster downshifts save brakes and in most occasions mirror what I would do with a manual transmission, which is quite amazing. Someone without MT experience might need to get used to it though, but knowing why it works that way might let them learn to enjoy it more...
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I agree, I love the feeling of the crisp (but smooth) rev-matched downshifts. (thumb) But some people complain it's jerky. (dunno)
 
MikeM. said:
Obviously each situation is different but what you are missing is that by decelerating in too high of a gear, some fuel needs to be added to keep the engine turning. You can test this out by using manual shift mode to coast in a gear that is too high to keep the engine turning and noting that your instantaneous fuel economy is not necessarily greater than 99.9 mpg. This works best at slower speeds because at higher speeds it's possible to get 99.9 mpg while the injectors are operating. Better yet, use an OBD port reader to directly view fuel injection.
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Well, no, I don't think I'm missing something here. That is exactly what I meant by "as long as the engine is not close to a stall". Meaning that as long as the car's momentum is enough to keep the engine turning at a speed the ECU is comfortable with... My point being that more aggressive than normal downshifts don't necessarily save MPG. I agree that a downshift is eventually required or gas starts to be injected again, but you need to be near the stall RPM threshold for this to happen. I've verified this several times by coasting to a stop on a flat or upward road without touching the brakes. My car reads 0 L/km (Canada!) at all times until the very last few meters at the point where my speed is not enough to keep the RPMs above about 750 or 1000 in first gear.

MikeM. said:
The other factor you are not considering is the sophistication of the CX-5's charging system which manages battery charging to maximize mpg's through reducing loss to the alternator. It does this by charging the battery when under engine braking and letting the battery discharge slightly when under throttle. In practice it needs to charge the battery sometimes when on throttle because there might not be enough deceleration events to produce adequate charging. But higher rpm engine braking assists in not needing to charge the battery under power.
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Now that, I did not know. Thanks for clearing it up. But the effect has to be quite subtle, and sufficient charging probably occurs under the normal downshifting (vs more aggressive) sequence anyway no?
 
vroom said:
I agree that a downshift is eventually required or gas starts to be injected again, but you need to be near the stall RPM threshold for this to happen. I've verified this several times by coasting to a stop on a flat or upward road without touching the brakes. My car reads 0 L/km (Canada!) at all times until the very last few meters at the point where my speed is not enough to keep the RPMs above about 750 or 1000 in first gear.
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The instantaneous reading is a two second average so, even if fuel is injected, the L/km reading can still read "0" for at least 4 seconds afterwards (in part due to the two second average and in part to rounding error). I'm not claiming that higher rpm engine braking saves more fuel than lower rpm engine braking, just that there is a point where fuel begins to be injected again.

Now that, I did not know. Thanks for clearing it up. But the effect has to be quite subtle, and sufficient charging probably occurs under the normal downshifting (vs more aggressive) sequence anyway no?
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I'm sure the fuel savings are quite small. But the Skyactiv philosophy is attention to detail, even small ones. This is true whether considering the weight of a part that weighs less than a kilo or programming the charge profile (when electrical loads are less than 2% of a vehicles energy consumption). Skyactiv philosophy acknowledges that all gains/losses, no matter how small, are additive. One dollar may seem insignificant but, get 20 of them together and you can have someone serve you a nice hot meal!
 
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Let's start with the basics.
Check the trans fluid level (unlikely, but possible).
Then check the air filter, replace if it's dirty (also unlikely).
While the filter is out, inspect the Mass Air Flow meter elements for any build-up (maybe). VERY CAREFULLY clean with a spray cleaner for MAF sensors, IF DIRTY and let dry before starting the engine.
How many miles? 50k or more, pull 2 spark plugs. If the electrodes are clean, some shade of tan and have crisp edges, return to the engine, if not, replace them all (possible).
Finally, buy 3 bottles of Redline Fuel System Cleaner (likely). https://www.amazon.com/dp/ (commissions earned) I get mine at Pep Boys. It does not clean direct injectors as quickly as port injectors, so it will take at least 2 bottles, mine did, but it stopped an intermittent miss.

Avoid gasoline with ethanol in it. E10 has 7% or so fewer BTUs and nets 10% worse fuel economy in my previous cars. Not sure about the CX-5, yet. It seemed to make my Colorado respond oddly to throttle changes.
 
MikeM. said:
True. As previously noted, the transmission doesn't start shifting into "N" on it's own until the transmission fluid is warmed up. Also, when shifting from "N" to drive it probably actually shifts into 1st as soon as you move it to drive so it's ready to go, I've never tested that. It's when you come to a stop and remain motionless for a specified amount of time that it shifts to neutral.

The Skyactiv engine/transmission is surprisingly sophisticated. For example, the engine control is tightly synchronized with the AT so when it shifts from "N" to 1st gear the engine's electronic throttle immediately adjusts to the anticipated drag of the torque converter. The same thing occurs as the A/C compressor clicks on which is why it's nearly impossible to detect the on/off cycling of the compressor.
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When I tried this the engine was fully warmed up. I had driven 35 miles of my 50 mile commute. Stopped at a red light. Waited 30 seconds or so and then put the selector in N. I could feel the drivetrain unload. It was definitely not in neutral until I put it in. How long is this supposed to take? Are you surmising this because of the fact that the idle RPM is stable or do you have some documented knowledge of the transmission programming?
 
rwortman The transmission logic - shifting into neutral at stops - is documented in the shop manual as is other logic...
 
I don't know have you tired this fix. Find somewhere you can drive safe and nobody or car around, put your gear into 2nd and keep driving for 3-6 mins(RPM will go up but it will be fine just keep between2000-4000), and then shift to 3nd gear(1500-4000), repeat it and more to 4th gear(RPM 2000-3000). Try if this will fix it, sometime the problem is due to lack of transmission break-in. I notice CX-5 gears shift fast, usually you don't see it use 3rd gear and maybe that is why you jerk forward when you give gas and it shift too fast. Also, this car does have jerk forward problem when you shift R to D and give some gas. That is why I call it Jerk-5, but I like this car. I will keep this car till 2020 and I will sell it.
 
It's odd, I've driven three brand new CX-5's, they all drove/shifted very much the same with no jerking. I actually appreciate the direct feel of the Skyactiv AT-6. Maybe some people prefer the slushy feeling of less efficient transmissions, different strokes for different folks.

You can tell which kind of person you are, go take one for a test drive and see if you like the crisp and direct feeling of the Skyactiv AT-6. If it feels "jerky" to you, this is not the car for you. If it feels refreshingly crisp and direct, you have found your match.
 
This thread is awesome! I've learned so much about my car (assuming the transmission in my 2014 6 is the same as the one in the CX-5).


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I going to throw a wrench in this thread's findings. I have a 2015 cx-5 sport(6spd manual) and I have the same lurching problem. It lurches in low speed driving situations(crawling at about 1k-2k rpm range in first gear. I assume it has to do with the electronic throttle of the CX-5. I had a similar problem in my 2008 scion xD, which was an automatic transmission. The electronic throttle in the CX-5 seems to adjust too quickly at low speeds in first gear and this causes the jerking motion. Its very annoying with a manual transmission because it causes the CX-5 to rapidly lose speed and get down below 1000 rpms and the engine starts to hesitate. My Scion had the same issue, and it was pointed out to me by the dealership as a common issue. My scion also had the annoying low speed whistling noise the CX-5 has, also caused by the electronic throttle.
 
guido2358 said:
I going to throw a wrench in this thread's findings. I have a 2015 cx-5 sport(6spd manual) and I have the same lurching problem. It lurches in low speed driving situations(crawling at about 1k-2k rpm range in first gear. I assume it has to do with the electronic throttle of the CX-5. I had a similar problem in my 2008 scion xD, which was an automatic transmission. The electronic throttle in the CX-5 seems to adjust too quickly at low speeds in first gear and this causes the jerking motion. Its very annoying with a manual transmission because it causes the CX-5 to rapidly lose speed and get down below 1000 rpms and the engine starts to hesitate. My Scion had the same issue, and it was pointed out to me by the dealership as a common issue. My scion also had the annoying low speed whistling noise the CX-5 has, also caused by the electronic throttle.
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Idle speed on these engines is around 600rpm, not the usual 800rpm like many older and other cars. Furthermore, there isn't a lot of torque or mass in a 2.5L 4 cyl, so you will feel lurching as it tries to not stall out.
 
guido2358 said:
I going to throw a wrench in this thread's findings. I have a 2015 cx-5 sport(6spd manual) and I have the same lurching problem. It lurches in low speed driving situations(crawling at about 1k-2k rpm range in first gear. I assume it has to do with the electronic throttle of the CX-5. I had a similar problem in my 2008 scion xD, which was an automatic transmission. The electronic throttle in the CX-5 seems to adjust too quickly at low speeds in first gear and this causes the jerking motion. Its very annoying with a manual transmission because it causes the CX-5 to rapidly lose speed and get down below 1000 rpms and the engine starts to hesitate. My Scion had the same issue, and it was pointed out to me by the dealership as a common issue. My scion also had the annoying low speed whistling noise the CX-5 has, also caused by the electronic throttle.
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I don't think you can blame the 1st gear jerkiness on the electronic throttle.
The 1st gear in these cars is shorter than most, so any throttle input you give in 1st gear has to be very smooth. If you're not smooth with the throttle it'll jerk very badly and you'll just have to push in the clutch.
The same applies to 2nd gear, to a lesser extent.
 
It's due to low rpm cam timing. My dad's v8 f150 does it as well. It can be seriously reduced/eliminated with a stiffer trans mount (rear motor mount/RMM). Corksport and jbr offer poly mounts, hardrace offers hardened rubber.
 
I highly advise against polyurethane engine mounts for a daily driven vehicle. The increase in vibration transmitted into the cabin can be substantial.
 
The hardened rubber would be less noticable. I have the poly myself 70 durometer, and really it's only noticeable at idle. Also nice with awd because the pull from high rpm (and wot) shifting is lessened. In some situations the peak torque during a shift change (particularly 1-2 wot), or even crusing high rpm low gear then adding full throttle with the oem mount is enough to trigger the dsc and cut throttle. Annoying surely.
 
I put poly engine mount inserts into only the front 2 (small) torque mounts on my Integra, and had to take them out the vibration was so bad. Didn't even do anything to the main 3 mounts, but the vibration was that bad. I replaced all the original suspension bushings in my Integra with HardRace hardened rubber, and I like them very much. :)
 
So, maybe it comes down to this:
1. If you have driven (and loved) manual transmission cars, then there is no jerking.
--or--
1. If you have only basically driven automatic transmission cars, then there is jerking.

I just purchased a 2018 CX-5 and have less than 3000 miles. The opening post for this thread is exactly what I experience, especially in stop-and-go traffic. I have only driven automatics and thinks the car jerks. However, after reading this thread, I agree the vehicle is operating as intended (through I don't care for it). Maybe Mazda is like Apple and antenna-gate (iPhone users were holding the phone wrong); i need to learn how to drive the car?
 
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