The rpm's are right. If it was 55mph then it wasn't on 6th gear. Probably 5th. The gearing and rpm is fine. You get 24 mpg so it's not that better than mines. How many miles you have?
Noticed the gear doesn't up shift immediately when I take my foot of the gas pedal...
- Thread starter mikeee2
- Start date
The rpm's are right. If it was 55mph then it wasn't on 6th gear. Probably 5th. The gearing and rpm is fine. You get 24 mpg so it's not that better than mines. How many miles you have?
Correct. But it was holding for 2+ seconds (after I let go of the gas pedal) before it upshifted and that's why I started the thread.
I don't realy get what all the fuss in this tread is about... The initial post has to do with RPMs when no gas is given negatively affecting MPG. Well, RPM makes no difference whatsoever. No gas is injected in the motor in that case, no matter the RPM, and fuel consumption is zero (the wheels provide the energy needed to prevent the motor from stalling). On the other hand, coasting in neutral or with the clutch pedal fully pressed down will increase fuel consumption, since gas needs to be injected in order to prevent stalling. This important point has been mentionned previously in this thread, but I think it might have been missed.
Now as to the behaviour of your automatic tran in that case, I think it is completely normal. The transmission simply attempts to anticipate what you are going to do next, and might need a few seconds to determine that no, you are not going to gas it again (as stated in GAXIBM's post). But again, this will not affect your MPG.
Just my 2c...
Now as to the behaviour of your automatic tran in that case, I think it is completely normal. The transmission simply attempts to anticipate what you are going to do next, and might need a few seconds to determine that no, you are not going to gas it again (as stated in GAXIBM's post). But again, this will not affect your MPG.
Just my 2c...
Yes really. The engine uses energy to turn, not necessarily gas. When you are not giving the engine gas, it uses up the car's cinetic energy to turn, which in turn causes the car to slow down faster. This is what engine braking is. This is also why the higher the RPM, the more engine braking is felt (because maintaining higher RPMs require more energy). So Higher RPMs = More fuel consumed ONLY when actually giving the car gas.
Think about it this way: if you would suddenly run out of gas at highway speeds, would you suddenly stop with tires screaching. Obviously not. But your motor is still coupled to the road trough the transmission, and trough the wheels, so how can the wheels turn while the motor is not? Since your motor is still coupled to the road trough the wheels, it will keep on turning untill your car slows down, gas or no gas.
Here in Canada, we can even prove this. Our cars read out liters per 100 km (which is basically the inverse of MPG with different units). As soon as I lift my foot off the gas pedal (and my car is warm enough), the instant fuel consumption reads 0.0, no matter the RPM, as it should.
Think about it this way: if you would suddenly run out of gas at highway speeds, would you suddenly stop with tires screaching. Obviously not. But your motor is still coupled to the road trough the transmission, and trough the wheels, so how can the wheels turn while the motor is not? Since your motor is still coupled to the road trough the wheels, it will keep on turning untill your car slows down, gas or no gas.
Here in Canada, we can even prove this. Our cars read out liters per 100 km (which is basically the inverse of MPG with different units). As soon as I lift my foot off the gas pedal (and my car is warm enough), the instant fuel consumption reads 0.0, no matter the RPM, as it should.
TreyP
2018 Soul Red AWD Touring CX-5
I understand what you are saying, but I disagree. As long as the engine is turning, the pistons are compressing fuel and the spark plugs are igniting that fuel. If the cylinders then became void of fuel, then yes, the car would stall.
If you ran out of gas at highway speeds, the car would not come to a screeching halt, but the engine would stall.
If you ran out of gas at highway speeds, the car would not come to a screeching halt, but the engine would stall.
If you truly understand what I am saying, you will be able to answer this: how can the engine be stopped while the wheels still turn? You probably know that as long as the transmission is engaged, there is an physical connection between the motor and the road. So if the motor is stopped and the wheels are turning, where is the give?
Pistons are always compressing, true, but what is being compressed can also be air
...
Pistons are always compressing, true, but what is being compressed can also be air
...
TreyP
2018 Soul Red AWD Touring CX-5
I didn't say stopped, I said stalled, meaning out of gas, no more fuel being introduced into the cylinders and no more fuel being ignited. A turning engine does not necessarily have to mean a running engine.
And if the pistons are only compressing air, the engine will stall.
And if the pistons are only compressing air, the engine will stall.
costermonger
Member
- :
- CX-5
Stalling means it stops turning.
When you coast in gear the injectors go to 0% duty (closed) as long as the vehicles momentum is sufficient to overcome the pumping losses (force required to pump air into/compress/out of cylinders). If you slow down enough, the ECU decides it needs to either downshift to increase engine RPM or add fuel back into the engine to crawl along at idle.
Coasting downhill in gear really doesn't consume any fuel, and no, the engine is not stalled. It's just not adding any energy to the system on the combustion stroke (as there is no combustion).
Bingo. I drove a manual for years and generally dislike autos, but this transmission is just brilliant. It aggressively seeks to keep RPMs low, but yet it always seems to go straight to the right gear if you want power *now*.
When you coast in gear the injectors go to 0% duty (closed) as long as the vehicles momentum is sufficient to overcome the pumping losses (force required to pump air into/compress/out of cylinders). If you slow down enough, the ECU decides it needs to either downshift to increase engine RPM or add fuel back into the engine to crawl along at idle.
Coasting downhill in gear really doesn't consume any fuel, and no, the engine is not stalled. It's just not adding any energy to the system on the combustion stroke (as there is no combustion).
Bingo. I drove a manual for years and generally dislike autos, but this transmission is just brilliant. It aggressively seeks to keep RPMs low, but yet it always seems to go straight to the right gear if you want power *now*.
Last edited:
TreyP
2018 Soul Red AWD Touring CX-5
Actually, stalling means it is no longer running, which is not the same thing as no longer turning if the engine is still being turned via the wheels/transmission. An engine needs 4 things to run: Fuel, compression, air and ignition. If you have no fuel, but crank the engine, the engine is turning but not running.
costermonger
Member
- :
- CX-5
Stall is not synonymous with "ceasing operation" though. Most people only associate a stall with an engine that quits due to an excessive torque demand (popping the clutch too fast on a manual) or improper fuel/air mixture. By your definition (which is to say the opposite of "developing power") most modern automatics "stall" every time the accelerator pedal is released at speed.
TreyP
2018 Soul Red AWD Touring CX-5
No, that is not by my definition. Not sure where you got that from. It is stalled when stepping on the gas will no longer increase RPMs. Stalled means no longer producing internal combustion. I do agree that stalling can be caused by popping the clutch with insufficient RPMs to keep the engine running.
So everyone said my morning commute is what's killing me because it never warmed up. So tonight, I drove a little so the car is "kinda" warm up and then went and get gas and reset the avg mpg. From there I drove about 90% highway and 10% local in NO traffic at speed limit. GRANDMA style. I don't ever remember driving on the highway at about 55 mph. It was very painful. Very. After 8.9 miles, I came home with these result. By the way, when I filled up before it was 21.5 mpg. I am almost positive if I continue like that for another 20 minutes I might of hit 30 mpg. But...but...but...how do you guys drive like that? I think I perfer to have my 21.5 and drive like a maniac. (thumb)
Exactly! Its nice when people state verifiable facts, supported by logical arguments and using exact terms correctly, and not just stating you are wrong just because they "know"... costermonger is quite correct.
I agree. This is my first automatic and I was cringing at the fact that the MT was not offered on all but the base model, and assumed I would learn to hate driving an automatic. I am actually learning to like it quite a lot!
costermonger
Member
- :
- CX-5
But that's not consistent. One can satisfy the first part, and not the second, vice versa. First part first:
According to this, a (modern) car coasting in gear is not stalled.
What happens when you step on the pedal is entirely up to the ECU. As far as it's concerned, when you're not stepping on the gas pedal something has to turn the engine at an RPM equal to or greater than X (I haven't played around with it enough to figure out what the number really is, but I'd bet it's around 1000). Whether the engine is spun by the power it's creating or by backload transferred through the drivetrain from the momentum of the vehicle, the ECU doesn't really care. If it has to provide fuel to the engine to maintain the RPM at the threshold, it will, but if the RPM is 2000 because the engine is coupled to the wheels and the car is coasting, there's no reason to provide fuel at all, and so it does not. The engine isn't creating any power, but it is rotating and it is getting air and a spark*, just no fuel.
Now, if you step on the pedal, the ECU decides you want more power, so it alters the throttle position if necessary and commands the injectors to open as required. Instant power. Because the only thing missing was fuel, the 'non-running' (freewheeling, or windmilling, depending on terminology) engine is immediately developing power again because it was only missing 1 component of the internal combustion cycle.
So coasting uses no fuel, but the engine is maintained in a state where stepping on the gas will immediately yield power, since only fuel was removed in the first place.
By this definition, a car coasting in gear is stalled, because there's no combustion happening. There's no need for it. The engine will happily spin due to the rotational energy provided by the transmission, until the car slows too much, and then it's not coasting anymore and the ECU steps in with fuel to keep things running.
costermonger
Member
- :
- CX-5
Cheers mate. I really didn't expect to like this transmission as much as I do, but it's quite the technical marvel. It's not just something the marketing people came up with when Mazda says they're committed to creating a car that's fun to drive and economical at the same time.
Same way I've always driven Mazdas.. I go around corners really fast
Cheers mate. I really didn't expect to like this transmission as much as I do, but it's quite the technical marvel. It's not just something the marketing people came up with when Mazda says they're committed to creating a car that's fun to drive and economical at the same time.
Same way I've always driven Mazdas.. I go around corners really fast
What's your mpg?
