[coiedulci]

As far as i know, the ZF8HP can shift from 8th to 2nd on extreme situations, but let's say i'm just driving aggressive and i have the gearbox on Sport ( not manual mode ):

When i'm hitting the brakes quick and hard from 100 km/h to 60 km/h does the torque converter inside the gearbox remains locked and the gearbox downshifts, thus performing engine braking ?
Or the gearbox just downshifts in order to be ready for the acceleration, and the torque converter is not locked in order to avoid wearing ?

[njdangelo]

Typically engine braking is only done by the transmission when the gyro in the car registers a decline of over 6 degrees and deceleration.

I've actually never even heard of engine braking under hard braking as hypothetically your brakes would have stopped the car long before the transmission would provide any sort of benefit. Modern cars can stop from 70mph in under 2 seconds, not sure what your tranny would do in that situation.

In the example you give the transmission downshifts during braking strictly in conjunction with the speed algorithm it is programmed with from the factory.

[coiedulci]

Well, just tested out driving on flat surface and manually up shifted to 3-rd gear at about 40-50 km/h i think, and no engine brake whatsoever.

[Londoner]

In sport or sport + engine braking is very noticeable to me.

[njdangelo]

I think you might be trying to use engine braking incorrectly. Yes, when you down shift without gas input the higher RPMs will slow down the engine, that's physics and is completely dependent on gear rations. That being said, the reason you downshift before a corner isn't to slow down its to put yourself in position for the turn exit. Using your brakes before will always be faster and more efficient than trying to use your transmission. you would have to start slowing down way too early if you intended to use the transmission to slow you down. I guess hypothetically you could downshift and let the engine slow you down for a stop light or turn in normal driving but that seems a little silly. Not to repeat myself but engine braking via the transmissions ECU only occurs on declines.

[Wires]

The torque converted lockup is just there to eliminate any losses through the converter (not a wear thing). Normally 10 turns on the input only results in 9 turns on the output. The lockup makes it 10=10 so you get better mileage when you no longer need the torque multiplication from the converter.

The car will always downshift when braking hard or soft, unless you've did a transmission flash to eliminate lugging the engine.

[HighlandPete]

Engine braking on 5, 6 & 8-speed AT have all been limited in normal to hard braking, in my experience. I agree with a previous post, that brakes work faster than the transmission can respond. Transmission management simply keeps it in the appropriate rev band.

It's a different matter on hills, when depending on how you use the brakes, can trigger different degrees of down changing and quite aggressive engine braking, if you want it. I drive in the mountains and see the different way it works quite often.

[LA1Z24]

Yes it does. If I hit the brakes moderately hard, the trans will downshift gears fairly aggressively. If in Sport or Sport+ it happens even more.

[njdangelo]

Originally Posted by LA1Z24

Yes it does. If I hit the brakes moderately hard, the trans will downshift gears fairly aggressively. If in Sport or Sport+ it happens even more.

correct, so that your transmission stays in the powerband, specifically in sport and Sport+ like you mentioned. NOT to slow down your car.

[bgalakazam]

I've noticed engine braking going downhill. It doesn't have to be in Sport. If you want more control, do manual shifting. Hard braking you just have the brakes from my experience.

[HighlandPete]

We have to remember with adaptive transmission management we will find different users will be experiencing different results. There is no 'one answer', it is driver/situation based.

Driver type adaptations, involving brake evaluation, will be involved in determining if more (or less) engine braking is needed.

[Wires]

Originally Posted by bgalakazam

I've noticed engine braking going downhill. It doesn't have to be in Sport. If you want more control, do manual shifting. Hard braking you just have the brakes from my experience.

I've found if I apply the brakes to pull the car into a speed on a steep decline, the car will then start holding that speed. I think it intervenes with the brakes and not the transmission though. For me to do the same thing, I need to downshift to 6th gear which the car wasn't doing "automatically".

Also, in case others don't know, 7th and 8th gears are actually overdrive gears, so you won't get any (minimal?) engine braking in those.

[coiedulci]

Well, did some tests yesterday.
Indeed when on Sport + and gearbox on Sport if i lift the foot from gas pedal the engine braking is pretty-much-present.

[Wires]

They might be unlocking the torque converter in those modes, hence more engine braking. Now that being said, I wonder if they ever lock up the torque converter in sport+?

[njdangelo]

Originally Posted by coiedulci

Well, did some tests yesterday.
Indeed when on Sport + and gearbox on Sport if i lift the foot from gas pedal the engine braking is pretty-much-present.

I know I sound like a broken record but this is not engine breaking. This is due to throttle mapping.
In comfort and sport (and when traction control is disabled) the throttle mapping is more linear and bell curved to give the driver better control of the throttle. In sport+ its sharper, like mountains, so that even an orangutan could get the most out of the engine. If gives you close to 100% throttle at about 30% input (I'm sure someone smarter than me will chime in with the actual figures). what you are feeling and calling engine braking is a sharper throttle cut. Does that in turn make the car slow faster than a throttle that closes slowely? Yes. Is that "engine braking" in the traditional sense that most people use the term for? No. Does this fit into a Websters dictionary definition of "engine braking" sure, but I think we can all agree that no one uses engine braking for performance driving because it's slow. Brakes are ALWAYS faster.

The natural effects of transmission shifting is not engine braking. If you want to see engine braking, find a hill, start going down with transmission in auto and watch the transmission AUTOMATICALLY DOWNSHIFT TO ASSIST THE BRAKES. this is engine braking in the commonly referred to sense of the term. Everything else being discussed is literally just physics of internal combustion engines linked to a geared transmission.

[HighlandPete]

Originally Posted by Wires

They might be unlocking the torque converter in those modes, hence more engine braking. Now that being said, I wonder if they ever lock up the torque converter in sport+?

Does stay locked in my model, when using Sport+, the gears are fast, can be hard hitting and felt through the drivetrain. No 'elastic band' at all.

[Billfitz]

Originally Posted by coiedulci

Well, did some tests yesterday.
Indeed when on Sport + and gearbox on Sport if i lift the foot from gas pedal the engine braking is pretty-much-present.

Engine braking is always present when you take your foot off the gas, unless you're in Eco while not braking, then it's freewheeling. The situation where the bulk of speed reduction is caused by engine braking is when you're foot's off the gas pedal, and you're not braking. Engine braking will be greater in Sport than in Comfort because you're in a lower gear for the same speed in Sport. The only way to force greater engine braking is by manually downshifting. When braking does the transmission downshift? Yes, but it doesn't do so to assist in the braking. It does so to keep the revs up, lest you have hesitation or even lugging when you accelerate again.

[HighlandPete]

Originally Posted by coiedulci

Well, did some tests yesterday.
Indeed when on Sport + and gearbox on Sport if i lift the foot from gas pedal the engine braking is pretty-much-present.

Do you mean a fast lift off to zero throttle and the gear holds, rather than an up shift?

If so, that is simply a delayed (or suppressed) upshift, waiting for your next command. You could be intending to brake, or apply throttle again.

[HighlandPete]

Originally Posted by Billfitz

When braking does the transmission downshift? Yes, but it doesn't do so to assist in the braking. It does so to keep the revs up, lest you have hesitation or even lugging when you accelerate again.

Driving downhill, the transmissions will definitely downshift, for engine braking, if you trigger engine braking with the brakes.

Example; steep gradient, driving about 30mph, engine is perhaps running 1,000 - 1,100rpm, off throttle. Car slowly accelerates... I can control the speed with light braking and no gearbox intervention. Or... a quick dab on the brakes, the box drops a gear to give ~2,000rpm. Speed increases... I dab the brakes again, triggers a further down shift, ups the revs to about 3,000rpm. Engine braking controls the road speed, without further brake intervention.

Alternatively... as speed increases, a fast 'jab' on the brakes will trigger a 'block' down shift. Two or three gears in one action.

That's my experience with 5, 6 & 8-speed ZF gearboxes.

[njdangelo]

Originally Posted by HighlandPete

Driving downhill, the transmissions will definitely downshift, for engine braking, if you trigger engine braking with the brakes.

Example; steep gradient, driving about 30mph, engine is perhaps running 1,000 - 1,100rpm, off throttle. Car slowly accelerates... I can control the speed with light braking and no gearbox intervention. Or... a quick dab on the brakes, the box drops a gear to give ~2,000rpm. Speed increases... I dab the brakes again, triggers a further down shift, ups the revs to about 3,000rpm. Engine braking controls the road speed, without further brake intervention.

Alternatively... as speed increases, a fast 'jab' on the brakes will trigger a 'block' down shift. Two or three gears in one action.

That's my experience with 5, 6 & 8-speed ZF gearboxes.

This is exactly what I have been saying since the second and fourth post of this whole thread.[IMG][/IMG]

[HighlandPete]

Originally Posted by njdangelo

This is exactly what I have been saying since the second and fourth post of this whole thread.

I agree with your comments, simply illustrating a typical use I have in my normal driving.

To support your statement (in your first post) about brakes stopping faster than the transmission responding with any engine braking... another example.

At the end of many trips, I drop from 60 to 30mph as I come into my village. Could be in Comfort, Sport or Sport+. As my brakes don't get too much of a workout in local use, (quickly get corroded discs), I leave it late and hit the brakes reasonably hard to ensure the front discs take a decent part of the load. The gear box will down change (if braking hard enough), but the speed is scrubbed off before the engine could have any real influence on retarding the car. I then pull the right paddle, 'upshift' to trundle through the village until I reach my turn off.