dom

Last week in a thread (Sorry can't remember which) is was argued that downshifting a MT car to assist in braking does more harm than good as brakes are cheaper to replace than an engine so that makes perfect sense to me. I've stopped downshifting with my SS because of that post as well.

The TSX is my first Automatic car in about 6 years and this is my first SS car so this question may seem stupid and I think I already know the answer to the question but I thought I'd seek some confirmation.

Lets say the car is in fully automatic mode and in 5th gear. I see a red light so I begin to apply the brakes. My question is, does the Auto begin downshifting automatically to assist in braking? I'm pretty sure then answer to this is no as I never hear the engine nor do I see the tach move. But what actually happens? Does the car remain in 5th and then suddenly go into neutral when stopped? which is what I think happens.

The same questions applies to SS. If I simply start breaking until I come to a stop while in 5th gear, will the car downshift or just jump into neutral? I noticed it jumps into 1st automatically when the car has almost come to a complete stop.

01AWW1.8T

the car will definitely downshift itself when the revs are low enough. Automatics downshift themselves too.

dom

I know it won't remain in 5th gear when stopped, but will it physically start going through the gears like you can with a MT or when in SS mode?

And what gear is it in when slowing down? I don't think I ever see the RPM's move up when breaking so its actually not downshifting. I think it just remains in 5th and goes into first when almost stopped.

TinkySD

the tsx at in D mode will downshift to provide engine breaking...especially when you are going downhill.

XPLORx4

It does? I'll have to test this out on my way home tonight!

The answer to your first question is, Yes... and no. While slowing down (either by simply releasing the accelerator or by applying the brake), if the engine RPM for a given gear ratio is below idle speed, the transmission will downshift to the highest gear that won't stall the engine. At the same time, the torque converter is unlocked so that there is slippage between the engine and the transmission. When simply slowing down, the drivetrain does not perform engine braking in the same fashion as you might expect from a manual transmission vehicle or in SS mode.

Let's use this example:
*Let's say you're travelling in D at a constant 50mph on a level paved road. At this speed the transmission is in 5th gear.
*1/2-mile ahead the traffic signal turns red, so you release the gas pedal. There is a small amount of engine braking performed here, even in 5th gear, so the car slows down. Note: it will slow down faster this way than shifting into "N" when you release the gas.
*When RPM (in 5th) drops below a certain threshold (I believe it's somewhere slightly above the engine idle speed, say... 1200RPM) the transmission will shift to 4th. You won't see the RPM increase, however, because the torque converter is unlocked.
* As you apply the brake, your speed drops more quickly (from the brakes!), but you'll also note that the RPM stays very low. As you cross each "minimum" threshold for stalling at the current gear ratio, the transmission will downshift until the car comes to a complete stop. At that point, the transmission is in 1st gear with the torque converter unlocked.

Note: an unlocked torque converter is somewhat similar to a not-fully-engaged clutch. It allows for some slippage between the engine output shaft and the transmission input shaft. In certain gears at certain engine loads, the torque converter will lock, providing better efficiency.

One way you can tell that the transmission does indeed shift to lower gears as speed decreases is to do a rolling stop, then hit the throttle about 3/4 down. The transmission will be in 2nd, and then shift to 1st after a brief delay because 2nd isn't low enough to launch the car quickly enough at 3/4 throttle opening.

TinkySD

actually it will downshift to engine brake when going downhill. Read your manual AT owners...all part of the 'grade logic system'. If you use the brakes when going downhill the engine will downshift...and not just to keep the engine from stalling.

jcg878

I noticed this just a couple weeks ago - the AT engine braking. How common is this on today's ATs??? Pretty cool, methinks.

Skull One_RENAMED

My 2000 Volvo S80 T6 has this feature. So at least since '99 sport shift automatics should be able to do this.

XPLORx4

That is a cool feature that I'd like to check out. On a 0% grade, however, the AT does not perform engine braking in "D".

XPLORx4

I tested the "grade logic" in the AT yesterday. It's pretty cool. Near my home there are some hills that have 8-10% grades. I was able to verify that the AT does indeed hold a lower gear than 5th, depending on the steepness. I got the AT to hold only as low as 2nd gear, even though the grade needed 1st.

When ascending these hills, I was not able to get the transmission to shift above 3rd gear.

If you're familiar with other automatic transmissions, particularly when combined with low power-to-weight ratio vehicles, this is a pretty cool feature, because a) the transmission won't hunt between gears when your speed-to-engine-load ratio would normally cause the tranny to shift up, only to discover that the next higher gear can't maintain the desired speed, then shift down again, and b) optimum engine power is always immediately available at any throttle position; with a standard AT, you must press the gas further down to coax the AT to shift, then back off again.

This is a very cool feature for the average AT user (i.e. someone who doesn't even want to hassle with using the sportshift mode, like my wife ).

jcg878

Definitely a cool feature. I personally can't get over the idea of letting the car handle hills. Hillly driving is the main time that I'm using the SS.

One day I'll get used to the AT and let it drive... maybe.

gogozy

yes, each gneration of grade logic is getting better and better. the first generation of grade logic(94??) jerk a little bit when comming out of corners, but it provided downshifting in downhill and hold lower gear in uphill.
thank i now know why i don't feel it is downshifting when stopping for light on 0 grade!!

ralawren

I just came out of an '04 Audi A4 with TipTronic and now am in an 07 TSX. The TSX will definitely use the transmission to cause engine braking when going downhill, but I have not noticed it doing it on its own into corners or for stop lights. This is something I miss dearly, the Audit TipTronic was amazing. When I had it in Sport mode it would shift upon braking as if I was doing it manually. I couldn't get over how well the software worked to anticipate when to downshift. Oh well, I just put it in manual mode now and do it myself.

Regarding reliability, I am sure it is harder on the transmission to shift, but I am on a 3 year lease, so the car will be long gone before any real damage is done. So, unless you are going to keep the car for many years, go ahead and have fun.

By the way, the manual says you can't shift from 5th to 4th if you are going over 133 mph. Sounds like a challenge!

ck123

its always engine breaking no matter what gear your on(auto). if u put in neutral you will notice it will coast a lot futher. i think the auto downshift according to speed

godfather2

when i let off the gas before a red light in ss mode i notice something peculiar: my tsx downshifts automatically by the time i come to a stop. FURTHERMORE, THE TRANNY SHIFTS FROM 5 - 3 - 1. it never does hit 4th or 2nd gear