Quote:
Originally Posted by Arthuar
I have an interesting question.
Between us, there is anyone, the whom, could be able to share the differences, between a hp26 and the more robbuts hp28, about astepronic automatic generation?
If it was possible, would be good to know the XHP effect even.
Maybe some owner with both 330d and 335d.
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The 6HP28 is part of ZF's portfolio of 2nd-Generation 6-Speed Automatic Transmissions — replacing the 6HP26. Other 6HP transmission technical revisions to 2.0 include:
- 6HP21 replacing the 6HP19
- 6HP34 replacing the 6HP32
Highlights of the 2nd-Generation (vs. 1st-Generation) 6HP units include:
- Shift times significantly decreased (by at least 50%)
- Shift response times significantly decreased (by at least 50%)
- Higher torque handling capability (for each of the new 6HP models)
- Ability to skip gears entirely (3-1, 4-1, 5-1, 4-2, 5-2, 6-2, 5-3, 6-3, 6-4) — not to be confused with sequentially targeting a gear that is 2 or more ratios away
- Ability to skip gears without compromising shift speed
- Supports Neutral Idle Control (NIC), which allows decoupling the torque converter at a standstill
- Oil cooling volume control (able to increase flow by up to 50%)
- Earlier torque converter lock-up (can lock the torque converter as early as at or below 1000 RPM)
- Torsional dampers filter out vibration from low-RPM torque lockup
- Much finer tuning of shift processes using Adaptive Shift Strategy (what ZF calls ASIS), allowing for extremely fast yet smooth shifts, regardless of torque input and over a very wide range of wear
- Between 3-6% improved efficiency
The 1st-Generation 6HP was released in 2001. The 2nd-Generation 6HP was released in 2006. And, while they have many similarities, they are significantly different in terms of shift dynamics, shift speed and response, and efficiency. The 2nd-Generation 6HP is the world's first mass-produced automatic transmission that was comparable to dual-clutch transmissions in terms of shift speed and response (capable of 80 ms shift times). The 2nd-Generation 6HP was also used as a shift dynamics benchmark when developing the 8HP. And, even after the 8HP was launched, ZF claimed that the 6HP 2.0 was still the benchmark in terms of shift speed and dynamics — with shift speeds/response at the level of dual-clutch transmissions (and, in case you didn't know, ZF produces Porsche's PDK). Of course, BMW didn't tune the transmissions to fully take advantage of the 6HP 2.0's capabilities for non-M cars — however, they did for the X5M and X6M. For these 2 vehicles, some automotive journalists were unable detect any difference in performance from DCT-equipped vehicles (as they could execute extremely fast shift times, within the span of a single cylinder firing event). Now, XHP allows all owners of 6HP 2.0 transmissions to more closely reach their full potential. 6HP 1.0 transmissions can also greatly benefit from XHP — however, it is not possible for them to perform as dynamically as the 6HP 2.0 with an equivalent XHP tune.
[Slightly off-topic]
Most do not know/appreciate how incredibly capable, sophisticated, and complex the 6HP (namely 2.0) units are:
- Capable of shift times within threshold of human perception
- Adapts shifts dependent on
Individual clutch temperatures
Gradient
Load
Wear
Clutch friction coefficients (at varied temperatures and for each respective clutch)
Engine operating parameters
Shift mode
Steering angle
Wheel slip
Actual input torque vs acceleration
Traction/stability control inputs
And many others
And any/all combinations of the above
All of the above is conducted in closed loop, with each of the clutches independently operated by way of individual pressure regulators and commanded and coordinated by algorithms backed by thousands of tables and hundreds of maps — with each of these being adapted in real time, depending on the situation. And, with short-term and long-term adaptation capabilities. By far and bar none, the ZF6 2.0 and ZF8 transmissions are some of the most sophisticated, well-engineered, over-built automatic transmissions ever produced.
To XHP's credit, XHP simplifies XHP features and the work that has been done for each vehicle and application — so that most consumers can (more/less) understand what they're getting. However, the ACTUAL WORK that goes into tuning these units is beyond most people's wildest imagination. It literally requires thousands of development hours to tune each shift (imagine having to time and tune each off-going clutch and on-coming clutch while reducing engine torque at the precise moment, all in milliseconds, for different engine speeds, different gear shifts, different torque levels, different vehicle weights, different ratio spreads, different final drive ratios... and on and on and on) — and maintaining smooth/seamless driveability. And, we're not even talking about what is required to crack through the security layers of the TCU and reverse engineer all pertinent functionality to allow for a proper flash. And, yet, all we do is pay a modest sum, connect an Android device, and flash. Even only partially understanding the amount and work and complexity involved in this endeavor, I would be willing to pay $1,000 or more for this product (don't misunderstand; I'm glad to pay less; however, I'd be willing to pay more). If you think that's outrageous — there are TCU tunes in the wild, for other vehicles, that cost several times what XHP asks, without any of the added customization features afforded by the XHP app.
[Back on-topic]
You can read more about the 2nd-Generation 6HP here: