[sarathlal]

Originally Posted by sgiitk

There is no engine braking unless you are in 2 or 1. Definitely not in D. Even my Civic has no engine braking in D (I hear that Grade Control comes in on slopes, but have not tried that out as yet). Almost all AT boxes have no engine braking in D. The result is a higher brake wear. I remember in my student days the AT versions often came with uprated brakes.

Remember I have owned at least one AT since 1999. Even, before that I have driven hired AT cars.

Have to disagree here. With what I have experienced, 'D' in a normal AT like Civic is more than enough for whatever we might get to experience in a day to day drive, including engine braking.
By engine braking, in this context, I would say, the ability to drive down a slope in the same gear in which we were able to climb it, without using brakes.
Put the mode in D, drive down a slope, brake and make it crawl at the speed you want to descend, leave the brake, the Civic WILL keep that gear without us having to brake.

[Mpower]

Originally Posted by sgiitk

Not exactly. No reverse engine braking on downhill, and also 'hunting' between 3 & 4 in the 60-70kph range (at least in my Santro). I got so fed up I just disabled 4th.

Sir, as long as the engine is connected to the wheels you will have engine braking. ie, as long as you are 'not in neutral' you have engine braking. To a certain this can be manipulated by unlocking the converter (dictated by calibration) but thats rarely (if ever) done during braking.

Higher the gear, lower the engine braking and therefore putting it in D3 will give you more braking.

Originally Posted by Harbir

And the i10 4 speed AT is a true overdrive. Its 4th gear ratio is 0.71:1. This is a very tall ratio indeed, and explains why the i10 downshifts to third so much at high speeds. the engine just does not have the torque to drive such a tall ratio effectively in high power demand situations, causing the transmission to downshift to 3rd.

Great Point.

@All,
Lets say it was a 5 speed box with 4 & 5 being close ratios, 4th would be say 0.85 and 5th say 0.70 the trans would downshift to 4th and get the job done and you would't need the 'OD-off' button.

Transmission controller logic (algorithms) are a lot more sophisticated now and using signals like TPS and MAP they can 'read' the drivers's mind and therefore you hardly find that 'OD-off' button these days.

[manim]

Originally Posted by sarathlal

Put the mode in D, drive down a slope, brake and make it crawl at the speed you want to descend, leave the brake, the Civic WILL keep that gear without us having to brake.

Exactly!

Have driven the Civic-AT 76 times (in 5.5 years) on the Ooty-Mettupalayam hill-roads.
Always done it in plain 'D' mode and it does a wonderful job.

Only coming down very steep slopes (not on regular roads but in some private places), I had to use the paddle to hold the first-gear.

[Jeroen]

On this CVT; when talking about cars, when you see CVT, in most cases, certainly for Honda, its actually a Variomatic. Invented by a countryman of mine: Huub van Doorne

See:http://en.wikipedia.org/wiki/Variomatic

Or for all CVT variants: http://en.wikipedia.org/wiki/Continu...e_transmission

Anyway, the variomatic is not just for (little) cars. These days used on tractors and trucks as well. In most cases comes equipped with some sort of centrifugal clutch. Meaning that when you stop, you can take you foot of the brake. My mother loved that, she hated the crawl you get with an automatic.

Variomatics are ferociously fast of the line. But they tend to run very quickly out of puff. So when you want to race the guy next to you at the traffic light, you're probably good for 1-2 seconds. Then you're toast.

On a automatic you usually have the kick down and adjustment of up/down shift patterns. Since CVT's don't shift you don't have that, but they do respond to pushing the pedal down quickly, In essence they use engine vacuum, and they would adjust the CVT to produce more torque, ie accelerate faster.

Also, a variomatic goes in reverse as fast as forwards!! We had a special, hilarious show in the Netherlands where cars were raced in reverse. Special class were the DAFs, all equipped with CVT.

See:

http://www.youtube.com/watch?v=zoh8i0jfpTo

Enjoy,

Jeroen

[sgiitk]

To resolve the confusion. Almost all classic ATs freewheel if the road speed is lower than the corresponding engine speed in the interest of economy. The Civi had grade control which takes care of it on slopes, I doubt whether a cheaper end AT will have it. Definitely, my Santro and the earlier Zen do/did not. This is only in the lower gears.

As per the Brio AT manual (page 132) D3 is for engine braking when going up and down hills, 2 for more and 1 for even more. There was some confusion about braking in D3 but that is resolved. Basically D3 moves automatically between 3, 2 and 1 and gives braking corresponding to 3. 2 & 1 are fixed ratios giving the corresponding braking.

[sarathlal]

Originally Posted by sgiitk

Basically D3 moves automatically between 3, 2 and 1 and gives braking corresponding to 3. 2 & 1 are fixed ratios giving the corresponding braking.

Oh, what I thought was;
On selecting D3, the AT will select gears between 1, 2 and 3.
On D2, the AT will select gears between 1 and 2.
On D1, its always 1.

Also, is there indeed a relation between engine resistance/braking and the AT modes?
On a slope, descending, if the car is in D mode, and gear is in, say 3, wont if offer the same resistance, as the D3 mode?

[Guna]

Originally Posted by sarathlal

Oh, what I thought was;
On selecting D3, the AT will select gears between 1, 2 and 3.
On D2, the AT will select gears between 1 and 2.
On D1, its always 1.

Also, is there indeed a relation between engine resistance/braking and the AT modes?
On a slope, descending, if the car is in D mode, and gear is in, say 3, wont if offer the same resistance, as the D3 mode?

Most of the times there is no D2, D1
D3= limits gear changes within 1, 2 ,3
2= slots to 2nd gear
1= slots to 1st gear

[Vid6639]

Originally Posted by Guna

There is no D2, D1
D3= limits gear changes within 1, 2 ,3
2= slots to 2nd gear
1= slots to 1st gear

So what happens when the car stops when in 2. Will it start in 2 or will it go to 1?

Usually it goes to 1 to prevent stalling which is a normal feature in all automatics. Even in paddle shift mode it will downshift back to 1 if you forget to do it via the paddles.

[sarathlal]

Originally Posted by Guna

Most of the times there is no D2, D1
D3= limits gear changes within 1, 2 ,3
2= slots to 2nd gear
1= slots to 1st gear

The example i quoted was for the vehicle having D, D3, D2 and D1.
And for D2, it is the upper limit that is restricted, it will indeed cycle between 1 and 2.
Most AT's will slot into the 1st gear, irrespective of the mode and the gradient, if the speed is close to standstill.
(We can quote this as one of the disadvantages of AT against manual, wherein for a manual, there is an option to move the vehicle, even from standstill, in 2nd gear)

[sgiitk]

Originally Posted by Vid6639

So what happens when the car stops when in 2. Will it start in 2 or will it go to 1?

Usually it goes to 1 to prevent stalling which is a normal feature in all automatics. Even in paddle shift mode it will downshift back to 1 if you forget to do it via the paddles.

Agree. never tested this out. When I was doing a RT of a Civic in 2010 this is what it was doing. When the road speed became too low it shifted down, but came back up asap. Incidentally, the Brio AT does NOT have paddles.

[Vid6639]

Originally Posted by sgiitk

Agree. never tested this out. When I was doing a RT of a Civic in 2010 this is what it was doing. When the road speed became too low it shifted down, but came back up asap. Incidentally, the Brio AT does NOT have paddles.

Actually I dont think that the Civic box shifts up in the Paddle shift mode without any driver input.

Once it shifts down due to lower speed and no input from driver, it is the driver who needs to upshift back to the higher gear.

Example: You are in M4 in a Civic and you reduce your speed so low that the box on it's own goes down to M2. Now you accelerate again and pick up speed. The box will not upshift back to M4. It is the driver who needs to again manually upshift. If you do not perform any paddle shift operation for some time (I think 30s), the box just goes back to S mode instead of M mode. Being in S mode you will notice it up shift on it's own.

[sgiitk]

Originally Posted by Vid6639

Actually I dont think that the Civic box shifts up in the Paddle shift mode without any driver input.

Once it shifts down due to lower speed and no input from driver, it is the driver who needs to upshift back to the higher gear.

Maybe. I did a TD, never tried it on my Civic. In fact almost all the time I am in D with occasional inputs to shift up, in the interest of economy.

[Harbir]

Originally Posted by sgiitk

To resolve the confusion. Almost all classic ATs freewheel if the road speed is lower than the corresponding engine speed in the interest of economy. The Civi had grade control which takes care of it on slopes, I doubt whether a cheaper end AT will have it. Definitely, my Santro and the earlier Zen do/did not. This is only in the lower gears.

Firstly, they don't freewheel, though it may seem like they do. Due to tall ratios and their dividing effect on back torque, and the torque converter's limited ability to transmit back torque at low engine speeds means that you get very little engine braking in high ratios, so little to seem non-existent. But this is not freewheeling because the engine remains connected to the wheels via the fluid coupling and continues to present an inertial resistance to the car's acceleration due to external forces though much reduced due. A car with intelligent algorithms will either use torque converter lock up or down shifting, or both to curtail the sensation of free wheeling, which is what Honda grade logic does.

Secondly, I am not sure what confusion was resolved. You post doesn't explain the 3+1 vs true 4 speed idea, which you have been requested to either explain or to desist from.

By the way, everyone,

all this tamasha about what D1, D2, D3 indicates confusion about the purpose of the AT. If D is not taking care of 99% of the miles you cover, and you can't go your entire life without knowing what D1, D2,3 do, you've bought the wrong sort of transmission. You should almost never need to use anything but D in forward motion. And on the rare occasions where it would benefit you to use a lower ratio manually, you should be able to get by with jusing the brake instead. Most people in the world who use automatics have no understanding of O/D switches and Dx modes. They just put the thing in D and use the throttle and brake as necessary to get the results they need. Now, the more savvy driver can and should use the modes other than D to get better performance when the circumstances justify human interference, but it is not necessary!

If you are finding it necessary or desirable to intervene frequently, then you have made the wrong choice of car. You should either have bought a car that COULD get you around in D without your intervention 99% of the time, or you should have bought a manual transmission car.

Unless you are the sort of person who has to drive a lot in the hills and in urban areas and you are more willing to putz around with D modes in the hills than to give up the convenience of automatics in urban areas. But unless you are person in those circumstances and with that personality, the D modes should be a forgettable and unimportant part of your life.


If you just want to know what the modes do just for the knowledge and to use them correctly in the appropriate circumstances, just remember that the modes lock out higher ratios. So D3 will allow the box to go no higher than 3rd gear. It does not actually select third. You'll want to lock out higher ratios on some downhill sections if you want the engine braking that comes from lower ratios. You'll want to lock them out on some uphill sections to prevent the transmission from hunting (go up a gear, its too high, drop a gear, its too short, up a gear, over and over). Which mode is appropriate? that depends on the speed, steepness of slope, and how heavily the car is loaded. ON the spot, experiment. Start withe the highest, D. not enough engine braking? hunting? Go to D3. STill doing it? go to D2, and so on.

Automatic transmissions are made to be brainlessly simple to use. They are intended to and designed to reduce the operation of a car to throttle, braking and steering. If you are expending a lot of thought power to figure out their usage, you're on completely the wrong track and have completely missed the essential attribute of the automatic transmission! If you are doing a lot of manual intervention in your automatic transmission car, you've bought the wrong car!

[sarathlal]

Originally Posted by Vid6639

Actually I dont think that the Civic box shifts up in the Paddle shift mode without any driver input.

Once it shifts down due to lower speed and no input from driver, it is the driver who needs to upshift back to the higher gear.

If you do not perform any paddle shift operation for some time (I think 30s), the box just goes back to S mode instead of M mode. Being in S mode you will notice it up shift on it's own.

This is exactly how the Civic behaves.

Originally Posted by Harbir

If D is not taking care of 99% of the miles you cover, and you can't go your entire life without knowing what D1, D2,3 do, you've bought the wrong sort of transmission.

Same thing that i mentioned couple of pages back. We bought an automatic, so, just slot to D mode and enjoy the drive.
Use S or D2 or whatever, only if you fall into a sand ditch and cant come out without involving all of your 132 horses.

[Guna]

Originally Posted by Harbir

So D3 will allow the box to go no higher than 3rd gear. It does not actually select third. You'll want to lock out higher ratios on some downhill sections if you want the engine braking that comes from lower ratios. You'll want to lock them out on some uphill sections to prevent the transmission from hunting (go up a gear, its too high, drop a gear, its too short, up a gear, over and over). Which mode is appropriate? that depends on the speed, steepness of slope, and how heavily the car is loaded. ON the spot, experiment. Start withe the highest, D. not enough engine braking? hunting? Go to D3. STill doing it? go to D2, and so on.

If you see the markings on the shifter, they are D3, 2, 1 and not D3, D2, D1 (they could be D4, D3, 2, 1 in some cars).
The way I have understood them is, D3 limits the gear changes to first 3 gears but position '2' (which is not marked as D2) directly slots it to 2nd gear. Again, this is what I have assumed and I could be wrong. But then, the question which arises is - why are they marked as '2' and '1' and not 'D2' and 'D1' (just like D3)