8hp90 hellcat transs , down shift issues

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DrEFI-Hammam-6-7-26.bin

DrEFI-Hammam-6-7-26.bin

ubject: Request for Assistance – 8HP90 Automatic Downshift Strategy (LT4 / Holley ECU / Nissan Patrol)


I’m looking for some guidance regarding the calibration of my TurboLamik TCU. I’ve spent a significant amount of time tuning the transmission, but I’m experiencing an issue with the automatic downshift strategy that I have not been able to resolve.

Vehicle Setup

* Vehicle: Nissan Patrol
* Engine: GM LT4 Gen V (Supercharged)
* ECU: Holley EFI
* Transmission: ZF 8HP90 (Hellcat)
* Valve Body: Stock
* Differential Ratio: 4.10
* Tire Size: 30.6”
* Use: Street + Performance

Current Issue #1 – Automatic Downshift Under Full Throttle

The main issue is not kickdown activation, but the automatic downshift decision.

For example:

* Driving in D (Automatic Mode).
* Cruising in 7th or 8th gear.
* Applying 80–100% throttle.

The transmission will often remain in the current gear instead of automatically downshifting for maximum acceleration.

The engine RPM increases slightly, but the TCU continues to hold the gear.

Important Observation

If I switch to Manual Mode, everything works correctly.

* Manual downshifts happen immediately.
* The transmission pulls very hard after the downshift.
* It will accelerate all the way to the rev limiter without any issue.

Because of this, I do not believe the problem is mechanical.

It appears to be related to the automatic gear selection logic.

Current Calibration Investigation

I have already reviewed or adjusted:

* Automatic Target UP RPM
* Automatic Target DOWN RPM
* Automatic Maps Selection
* Kickdown TPS Threshold
* Minimum Gear Down (Kickdown ON/OFF)
* Maximum Down Target RPM
* Torque Calculation

None of these changes have completely resolved the issue.

Current Torque Model

The transmission is using TurboLamik Internal Torque Calculation.

I understand that torque calculation is fundamental because it influences:

* Line pressure
* Shift quality
* Clutch control
* Automatic shift decisions

If there are recommended torque model settings specifically for an LT4 + Holley combination, I would appreciate your advice.

Current Downshift Behavior

Another issue is the harsh automatic downshift during deceleration:

* 3 → 2 is noticeably harsh.
* 2 → 1 is also harsh.

I’m trying to achieve an OEM-quality calibration where:

* Full-throttle automatic downshifts are quick and responsive.
* Highway passing is immediate.
* Part-throttle driving remains smooth.
* Deceleration downshifts are smooth with no harsh engagement.

Request for Advice

Could you please advise:

1. Which base BIN is recommended for my combination?
* LT4
* Holley ECU
* 8HP90 Hellcat
* Nissan Patrol
* 4.10 differential
* 30.6” tires
2. Is there a preferred Automatic Downshift Strategy for high-torque engine swaps?
3. Are there additional tables (not obvious in the XDF) that influence:
* Automatic gear selection
* Full-throttle automatic downshift
* Highway passing response
* Downshift decision logic
4. Are there recommended settings for the Torque Calculation when using a Holley ECU with TurboLamik?

My goal is to achieve an OEM-like driving experience with:

* Fast and intelligent automatic downshifts.
* Smooth part-throttle operation.
* Strong full-throttle acceleration.
* Smooth 3→2 and 2→1 coastdown downshifts.
* Reliable clutch control based on accurate torque estimation.

Any recommendations regarding the correct base calibration or the key tables that control the automatic downshift logic would be greatly appreciated.

Thank you very much for your support