Slow Downshifts

[Richard.C]

My gearbox is upshifting quickly under load but downshifts are extremely slow.

In manual mode I will downshift the gear indicator shows the new lower gear but it will be at least 2 seconds before the gearbox actually shift and engine revs climb.

I'm not sure if this is a tuning issue or maybe a gearbox issue, any help and advice is much appreciated.

Richard

[Jar]

provide basic information.

What car
Whate engine
What engine ECU
What gearbox model
What TCU software version
What TCU base map version

[Richard.C]

Hi Jar,

It's an engine swap into a Mazda RX8.
Engine is Chevy L83 5.3V8
8HP70 gearbox from a Jaguar XF
TCU ver 10.73
The current BIN maps in the TCU have many different values than the latest 8HP70 base map available on the website. I purchased the car after the conversion was completed so I don't have details of it's initial set up.

Thanks

Richard

[Richard.C]

Sorry missed the engine ECU:

Emerald K6 ECU

[Richard.C]

Also, to confirm TCU firmware and XDF, ADX are all ver 10.73

[M4comp]

TBH you haven't really provided enough info to assume it's one table or another. There are several tables that can be changed to cause this - and not knowing what changes you've made or what base file you're using. I'll guess the table 'Min. RPM Limit 8-2' needs adjusted. Note that there are sooooo many factors that need to be accounted for. The first being the Program Selector table and Selector/Gear swap map table. Not knowing what settings have been changed could be your issue. If it was me and I knew the trans hadn't been set up by someone that knows the software, I would update the firmware and put the latest file in it for that trans ( saving the old one just in case for review, you could copy over the Tq values and basic settings as well).

When does it shift slowly? During short decels then when getting back on to the throttle under load - lugs then shifts?
When you take it up to 65mph and let it decel down to 20mph does it not downshift at all?
Or do you mean when you press on the throttle when in 8th it takes a long time to downshift?
Are you saying you're comming off wot it's slow or when at higher rpms?
Any datalogs? ( you should always be logging during issues / tuning )

[Richard.C]

Thanks for the reply and questions.

As soon as I get a day with a few spare hours I'll get some logs and test drive a few different downshifting scenarios to record how it's functioning. In the meantime I'll review some of the tables and compare against the latest base map.

Richard

[Richard.C]

When does it shift slowly?

The car is primarily a track car so my initial focus is manual mode. As per the note in my first post, if I am say driving along in 6th gear brake and downshift to 5th the gear indicator will drop to 5th but the gearbox maintains 6th gear for a few seconds before downshifting.

[M4comp]

For the situation you're describing I will assume you're running into the 'Max. RPM Downshift, torque lower at 0 (TQ<0)' table. So in an LS i'm guessing your turning higher RPM's and this table is your issue for downshifts at let off and braking. But won't know without a log file.

Also you need to make sure your TPS in the TCU software is at 0.0% when your foot is not on the throttle. If your TPS is not at 0% when at idle enable DBW Input Sensor Cal -> Sensor Input -> DBW Input. This must match your 'TPS Input' value normally 13. This is a mistake I see over and over at the track when we have meet ups. The software is looking for the PPS (pedal position sensor) but allows you to zero out your idle tps value.

Before making a change to your 'Max. RPM Downshift, torque lower at 0 (TQ<0)' I would set the TPS as above and make sure your 'Program Selector' table is set up for sport mode. Also note there is a shift 'UP' time AND and shift 'DOWN' time (meaning sport down shifts) you can set in your 'Program Selector' table.

Read this and set up your program modes accordingly or skip and go full manual if you want max control - just an option, Automatic mode: 0-OFF in the Program Selector table. The TCU will fall back to the 'Max. RPM Limit' table and force a shift if you exceed the table value.
https://manual.turbolamik.eu/docs/tunin ... up-tuning/


'Program Selector' table values
Automatic mode: 0-OFF, 1-Auto1, 2-Auto2, 3-Auto3
TIME shift UP: 0-Normal, 1-Sport1, 2-Sport2, 3-Neutral
TIME shift Down: 0-Normal, 1-Sport1, 2-Sport2
ST. GEAR- Start gear
END GEAR- Last Gear
TQ.R.T- Torque Reduction Table 0-2
Lockup config, 0-2
AWD: 0-Normal, 1-S1, 2-S2, 3-OFF

[Richard.C]

This is great, thanks for the direction you are giving it is much appreciated.

I'll report back when I've checked some of this and have a log to share.

Thanks