Gearbox software

[PsymonR]

Yeah I agree. This sounds like a software lockout, given that the Merc with the same gearbox doesn’t do this. Are we certain all engine/transmission controller components are the same? Perhaps something was changed and that accounts for the apparent issue/delay.

The ZF8HP is an amazing gearbox btw.

I'm not disputing your experience with your Merc, but in the video I linked in this post - a POV drive of an A45S, shortly after 1:46 there's a definite shift lag present when the paddle is pulled, you can hear the click of the paddle then a short gap before the engine note changes. So there's definitely examples out there of non-instantaneous shifting in the A45S.

 

[kb21]

I'm not disputing your experience with your Merc, but in the video I linked in this post - a POV drive of an A45S, shortly after 1:46 there's a definite shift lag present when the paddle is pulled, you can hear the click of the paddle then a short gap before the engine note changes. So there's definitely examples out there of non-instantaneous shifting in the A45S.

Hmm that’s interesting. I wonder if it was just a Merc thing all along. Perhaps my software version corrected it? I should say, I have a 2023 A45S though and the software was updated not that long ago. I do still notice lags in some instances but I think this is more to do with the DCT logic. For example, the way the gearbox knows which gear to pre-select (ie. next one up or down) is obviously based on a few variables such as throttle position, speed acceleration/deceleration etc etc. when I’m under load and upshift, it’s instaneous, if I just let off slightly and the speed isn’t increasing as much, it pre-selects the lower gear and then there’s hesitation/lag if I UPSHIFT as it then has to pre-select the upper gear first then make the shift. So yeah that lag I still notice but I guess that’s just DCT logic. Any case, let’s hope Lotus fixes this issue soon.

 

[Nova]

The DCT transmission itself is tuned/locked by Merc and there is nothing Lotus can do on that front. What may be possible is for Lotus to shorten the delay from the shifting paddle to the command to the DCT to change gears.

 

[kb21]

If this issue persists though I may have to rethink this whole i4 idea. Now that I’ve seen the delay, I can’t unsee it

 

[DJManc]

If this issue persists though I may have to rethink this whole i4 idea. Now that I’ve seen the delay, I can’t unsee it

I'm with you on this! Though, I do believe that in the real world the i4 transmission will probably be mostly ok on the road (rather than track), I just don't know if I could live with these little annoyances that have been persistently reported in the media. I am also closely watching the used market and if the right spec came up in a V6 I think I could be easily swayed to cancel my i4 order unless Lotus come up with some rapid improvements to the transmission. Surely Lotus cannot be so naive to think that these transmission issues would not make buyers think twice about their purchase!

 

[kb21]

I'm with you on this! Though, I do believe that in the real world the i4 transmission will probably be mostly ok on the road (rather than track), I just don't know if I could live with these little annoyances that have been persistently reported in the media. I am also closely watching the used market and if the right spec came up in a V6 I think I could be easily swayed to cancel my i4 order unless Lotus come up with some rapid improvements to the transmission. Surely Lotus cannot be so naive to think that these transmission issues would not make buyers think twice about their purchase!

Im in the same boat- I’d just as easily have the v6 manual if this became a long-standing issue. The main reason I wanted the i4 was the engine and transmission though, as it is in the A45S is just crazy and has this rabid dog-like character about it. Revs and bangs through gears with such a manic personality and of course it’s linear power delivery. its a really unique engine and I really wanted to experience it in a mid-engined rear drive setup like the Emira. Heres hoping lotus watches reviews and reads these forums.

 

[kitkat]

Im in the same boat- I’d just as easily have the v6 manual if this became a long-standing issue. The main reason I wanted the i4 was the engine and transmission though, as it is in the A45S is just crazy and has this rabid dog-like character about it. Revs and bangs through gears with such a manic personality and of course it’s linear power delivery. its a really unique engine and I really wanted to experience it in a mid-engined rear drive setup like the Emira. Heres hoping lotus watches reviews and reads these forums.

you can have all of that in the Emira — probably just without a warranty

 

[kb21]

you can have all of that in the Emira — probably just without a warranty

Where there’s a will, there’s a way right?

 

[digilotus]

The DCT transmission itself is tuned/locked by Merc and there is nothing Lotus can do on that front. What may be possible is for Lotus to shorten the delay from the shifting paddle to the command to the DCT to change gears.

My understanding is that Lotus may be using their own Bosch transmission controller, but this isn't confirmed.

 

[Nova]

My understanding is that Lotus may be using their own Bosch transmission controller, but this isn't confirmed.

That's impossible. They may have a Bosch box interfacing with the 8G-DCT controller, but it is impossible that anything other than a Mercedes box is controlling that transmission.

 

[M3DOC]

you can have all of that in the Emira — probably just without a warranty

If that's what it takes to make the DCT shift the way a DCT should than my warranty is history.

 

[kitkat]

If that's what it takes to make the DCT shift the way a DCT should than my warranty is history.

Friend, good luck with that lol — it’s a Lotus with an engine they’ve never before used.

 

[digilotus]

That's impossible. They may have a Bosch box interfacing with the 8G-DCT controller, but it is impossible that anything other than a Mercedes box is controlling that transmission.

Once we get access to an I4 service manual then all will be revealed.

 

[PsymonR]

Found a video from July this year with some discussion around modifying the gearbox software. The guy's running a stage 2 setup on his A45S (500 bhp / 630Nm) and from 6:30 says the gearbox is quite sluggish (even in stock form before tuning) and perhaps most relevantly goes on to say that the gearbox controller is locked and has not yet been cracked to allow for tuning.


So if the gearbox does have a Mercedes controller it doesn't seem that there would be any options currently available that would at least give tuners a starting point with any modifications to the software.

 

[Nova]

Once we get access to an I4 service manual then all will be revealed.

There is nothing to be revealed. The 8G-DCT, like the 7G-DCT that it was derived from, has an integrated control unit. The control unit sits inside the transmission and is mounted directly to the valve control plate. It communicates with the ECM via a CAN bus, through which it receives gear shifter position (D, N, P, R), transmission mode button (Eco, Comfort, Sport, Sport+, M), and paddle shifter inputs as messages. It performs the shifts accordingly by controlling the valves, solenoids, and relays that actuate the shifting forks and clutches while monitoring pressures, temperatures, and positions of various internal components. The TCM only communicates with the ECM, nothing else. All inputs and outputs are communicated through the ECM, which in turn communicates with other sub-systems and control modules. On top of this complexity is the fact that the 8G-DCT does not have a single fixed first gear, but rather a "winding first gear" that is a composite of gears 3, 4, and 2, through the use of a synchro that binds gears 3 and 4, thus locking the odd/even shafts together which normally operate separately. Consequently, there is no "pre-selecting" a gear for the 1-2 or 2-1 shift.

It is impossible that Lotus has somehow replaced this Mercedes TCM with a Bosch control unit.

I have also heard the mention of a Bosch control unit. What that may be is an interfacing box between the Mercedes TCM/ECM modules and the rest of the Lotus car. For example, the Mercedes TCM/ECM takes inputs from the steering column, coolant temperature, wheel speed, and parking brake status, and in return provides warning codes, current engine/transmission status, and cooling requests. Instead of teaching the Lotus boxes to speak Mercedes and vice versa, an "abstraction layer" box sits in the middle and translates between the two systems.

 

[digilotus]

There is nothing to be revealed. The 8G-DCT, like the 7G-DCT that it was derived from, has an integrated control unit. The control unit sits inside the transmission and is mounted directly to the valve control plate. It communicates with the ECM via a CAN bus, through which it receives gear shifter position (D, N, P, R), transmission mode button (Eco, Comfort, Sport, Sport+, M), and paddle shifter inputs as messages. It performs the shifts accordingly by controlling the valves, solenoids, and relays that actuate the shifting forks and clutches while monitoring pressures, temperatures, and positions of various internal components. The TCM only communicates with the ECM, nothing else. All inputs and outputs are communicated through the ECM, which in turn communicates with other sub-systems and control modules. On top of this complexity is the fact that the 8G-DCT does not have a single fixed first gear, but rather a "winding first gear" that is a composite of gears 3, 4, and 2, through the use of a synchro that binds gears 3 and 4, thus locking the odd/even shafts together which normally operate separately. Consequently, there is no "pre-selecting" a gear for the 1-2 or 2-1 shift.

It is impossible that Lotus has somehow replaced this Mercedes TCM with a Bosch control unit.

I have also heard the mention of a Bosch control unit. What that may be is an interfacing box between the Mercedes TCM/ECM modules and the rest of the Lotus car. For example, the Mercedes TCM/ECM takes inputs from the steering column, coolant temperature, wheel speed, and parking brake status, and in return provides warning codes, current engine/transmission status, and cooling requests. Instead of teaching the Lotus boxes to speak Mercedes and vice versa, an "abstraction layer" box sits in the middle and translates between the two systems.

You obviously know a lot about these transmissions, so thank you for sharing the detail.

Engineering wise, who would have thought putting electronics inside a transmission is a good idea? Heat is the enemy of electronics and replacing the TCU (if its available as a spare) would likely require a transmission pull. I guess these days most DCT transmissions are treated as one integrated non-repairable unit which is sad. Fortunately on the V6 auto the TCU is replaceable and external to the gearbox.

These DCT boxes are made by Star Transmission & Star Assembly who are fully owned by Daimler. They’re manufactured in Sebes Romania.

 

[kitkat]

You obviously know a lot about these transmissions, so thank you for sharing the detail.

Engineering wise, who would have thought putting electronics inside a transmission is a good idea? Heat is the enemy of electronics and replacing the TCU (if its available as a spare) would likely require a transmission pull. I guess these days most DCT transmissions are treated as one integrated non-repairable unit which is sad. Fortunately on the V6 auto the TCU is replaceable and external to the gearbox.

These DCT boxes are made by Star Transmission & Star Assembly who are fully owned by Daimler. They’re manufactured in Sebes Romania.

That's pretty much how all transmissions are these days I think. Wait till you hear where the oil pump belt is on the M139 probably a $16K job to get that done if it ever fails.

 

[digilotus]

That's pretty much how all transmissions are these days I think. Wait till you hear where the oil pump belt is on the M139

I was going to mention that, but thought better of it and didn’t want to go off-topic. Ans: Wedged between the transmission and engine. 😬

I’m very happy with my Camry V6 plus truck manual!👌

 

[Porter]

That's pretty much how all transmissions are these days I think. Wait till you hear where the oil pump belt is on the M139 probably a $16K job to get that done if it ever fails.

I was going to mention that, but thought better of it and didn’t want to go off-topic. Ans: Wedged between the transmission and engine. 😬

It's my assumption that the M139 with 8GDCT was designed to come out of the A Class as a "package" with a relatively low amount of work, and be repaired on a stand. That's how Porsche has been for years. There are clear work quality and worker ergo/safety advantages to the approach, as long as the removal is straightforward using appropriate specialty tools or cradle.

I hope Lotus have taken this approach. But I won't hold my breath.

 

[Nova]

You obviously know a lot about these transmissions, so thank you for sharing the detail.

Engineering wise, who would have thought putting electronics inside a transmission is a good idea? Heat is the enemy of electronics and replacing the TCU (if its available as a spare) would likely require a transmission pull. I guess these days most DCT transmissions are treated as one integrated non-repairable unit which is sad. Fortunately on the V6 auto the TCU is replaceable and external to the gearbox.

These DCT boxes are made by Star Transmission & Star Assembly who are fully owned by Daimler. They’re manufactured in Sebes Romania.

The TCM PCB and packaging is probably made by Siemens, which is an established expert in electronics manufacturing. My take is that they embedded the TCM inside the transmission because they are confident of its stability in that environment, and their goal with these compact DCT transmission is increased integration as a way to offset it's inherent complexity. Electronic components come with a variety of temperature ranges. Inside an DCT, the temperature usually hovers around 100 degrees C before the coolant starts flowing. While that seems high, automotive control module are usually relatively low tech - low clock speeds, low density, high signal level, high current flow (relatively). 100C is certainly well within the range of available electronic components for reliable operation within the specified mean time to failure. In short, I trust that the German engineers know what they are doing.