Supra 2jz Closed loop flat shift cut tuning using Haltech Elite 2500

Hi Andre,

i have a HGT sequential 6 speed with closed loop flat shift cut (via load cell) and Haltech Elite 2500.

I have a few general questions on closed loop flat shift cut tuning:

1.) Partial throttle, low rpm closed loop flat shifting

I have had conflicting opinions on flat shift cut at partial throttle/low rpm conditions, i was under the impression that instead of using clutch to unload drivetrain, the same could be achieved at lower rpm and speeds by closed loop flat shift cut? Or does it make no difference to the dog teeth if you unload drivetrain using shift cut or clutch? I ask because i drive my supra often on the street and in stop go traffic so its not a full on race car. WOT conditions and high rpm is good but i would like to know if i can apply it for the opposite - kinda of like Dual clutch gearboxes where you shift seamlessly at lower speeds.

2.) Flat shift cut percentage table

Initially the flat shift cut percentage table is set at 100% and i saw in your webinar that it doesnt necessarily need to be 100% - so what is the ideal level is it 85%. What are you actually looking out for to ensure the closed loop shift is done safely?

3.) Flat shift recovery time table

If the recovery time is mapped against increasing throttle position is it normal for recovery time to be the same across the board or should it decrease as throttle position is increased.

4.) Flat shift retard

For increasing flat shift active time should the flat shift retard stay constant at 20 deg for example?

5.) Flat shift torque reduction time

I'm assuming this is for the re-introduction of torque as the shift is complete so that it doesnt unsettle the drivetrain?

Is the flat shift torque reduction time a fixed value that the closed loop system is trying to meet. i.e. the 100ms torque reduction time is what the system is aiming to achieve everytime there is a shift?

Apologies if i have asked some silly questions but i'm trying to understand and learn. The haltech help files are not exactly helpful and don't provide more insight into the why and how for each shift cut setting.

I've attached screenshots for reference to each of my questions above.

Cheers

Clint

Hi Clint,

Firstly apologies for the delay in replying - You caught us mid prep for a race meeting so things were a little hectic. See answers below:

1. There is a throttle position above which the drive dog will be engaged and below which the over run side of the dog will be engaged. When the drive side is engaged you need a torque reduction from the likes of a cut, however on over run you may need a throttle blip for torque reversal. In reality a cut is usually fine as unless the engine braking is very aggressive a cut will still let the dogs disengage. I personally find I get a smoother result by using the clutch when I'm driving a sequential on the street.

2. Cut percentage is a tough one as there's no magic number. You need enough to unload the dogs. Insufficient and you won't be able to shift gears. I'd start at 100 and pull it back in 5% increments until you can't pull it out of gear then increase by 10%

3. I'm not sure what this is in Haltech language sorry. Recovery time could refer to the time post shift when torque is reintroduced or a lock out to prevent another immediate shift request. In the case of the former it's personal preference/feel and very dependent on engine torque. You will need to make some adjustments and see how it makes the shift feel.

4. The retard is normally a fixed value. 20-30 deg is a good place to start.

5.Again I'm not sure how Haltech manages this. This could be a maximum time which will be cut short when the shift is deemed to be complete. Otherwise it's not really closed loop. If that is the case then 100 ms is probably a bit light and you might want to extend that out to 150 ms to help with an occasional slow shift.

Sorry I can't offer more help but I haven't used this system personally.