Thread: D2 auto modification to select manual mode when in high range.

Originally Posted by discorevy

Not meaning to cause offence here but that's not doing the car any favours, might pay to do a course and learn a bit more about the vehicle.

That's great advice though my car will be doing 3400 at 115kms/hr in 3rd which is what I believe to be too high. I know of course I could drop speed or change my ratios but with the big tires it's nice to have low gearing so if it's possible it would be the best way about it

if you have much bigger than standard tyres you cant expect too much from it cos the engine and gearbox managements are mixed up by the VSS which is not as expected at certain rpms cos both ECUs were "calibrated" from factory for std dimension tyres

Originally Posted by ENGINE MANAGEMENT SYSTEM - TD5

Vehicle Speed Signal (VSS)The VSS is an integral part of the ECM's overall adaptive strategy. The ECM receives the signal direct from the
SLABS ECU. The SLABS ECU is not connected to the controller area network (CAN) so therefore is hard wired.

Vehicles fitted with automatic transmission have two vehicle speed input signals to the ECM. One signal is from the
SLABS ECU and the other is from the automatic transmission ECU. The ECU compares these speed signals.

The ECM also receives transfer gearbox information. This allows the ECM to take in to account the vehicle being
driven using low range gearing and compensate as necessary. The signals generated by the SLABS ECU for manual
transmission, and by the EAT ECU for automatic transmission are received by the ECM in the form of a PWM signal.
The frequency of this signal changes in accordance with road speed.

Originally Posted by micky_b_25

That's great advice though my car will be doing 3400 at 115kms/hr in 3rd which is what I believe to be too high. I know of course I could drop speed or change my ratios but with the big tires it's nice to have low gearing so if it's possible it would be the best way about it

I'm not sure what the issue is as you get lock up in both 3rd and 4th so that you don't have to over rev the engine. You can change almost seamlessly between 3rd and 4th and 4th and 3rd but it does come out of lock up between changes and for a purpose. There are risks with a lock up override to the auto trans which in my opinion are not worth taking, anyway it is a great auto when you really get to know it.
Nick

Originally Posted by sierrafery

if you have much bigger than standard tyres you cant expect too much from it cos the engine and gearbox managements are mixed up by the VSS which is not as expected at certain rpms cos both ECUs were "calibrated" from factory for std dimension tyres

That is useful information thanks, I have been contemplating for some time to change the signal to the slabs to give me an accurate speed. Have not worked it out yet

The bigger tyres will not affect only the VSS, the torque is part of the management too and even if you use a VSS corrector the expected torque will be different too due to tyre's bigger diameter.

Originally Posted by sierrafery

The bigger tyres will not affect only the VSS, the torque is part of the management too and even if you use a VSS corrector the expected torque will be different too due to tyre's bigger diameter.

So to combat that change the vss and remap the ecu?

Originally Posted by micky_b_25

So to combat that change the vss and remap the ecu?

What size tyres are you running? Mine are 245/70 16 A/T and my speed is out about 4%.

Originally Posted by micky_b_25

So to combat that change the vss and remap the ecu?

that would be the correct way IMO