G4X - Add Geartronics or not to flatshift setup

[Ronague]

hello all,

this post relates to the setting up of flatshift in a high torque turbo (700NM) rally cars with sequential shifter (not paddle) running anti lag.

i would like to open up a discussion on the benefits of having gear cut setup using closed loop direct to G4X vs adding a gear shift ECU like Geartronics to the setup and sending the signal to G4X telling it when to cut.

obvious cons are the extra cost, and small amount of additional wiring. 

historically with older ecus the inclusion of a shift system like geartronics makes the flatshift smoother and thus less wear on the gearbox.

thoughts on whether adding a shift ecu would improve the smoothness of flatshift and have less gearbox wear when using it with a G4X ?

 

[mapper]

In short, absolut no. In fact the upersit is the case. The latest gearshift strategy in the g4x is much more advaced than any external gearbox controller I have seen (incl. Geartronics). Checkout the the?gearshift strategy in G4x. Its fantastic?and works like charm. Give you set it up correctly.

I highly recommend to use a strainge gauge and a barel position sensor on the gearbox. Additional a whelspeed sensor and e-throttle helps for perfect autoblip downshifts.

[tbase]

You have a hard time for gearshift on Rally gravel due to wheel slip on lower gear? 

[Ronague]

14 minutes ago, mapper said:

In short, absolut no. In fact the upersit is the case. The latest gearshift strategy in the g4x is much more advaced than any external gearbox controller I have seen (incl. Geartronics). Checkout the the?gearshift strategy in G4x. Its fantastic?and works like charm. Give you set it up correctly.

I highly recommend to use a strainge gauge and a barel position sensor on the gearbox. Additional a whelspeed sensor and e-throttle helps for perfect autoblip downshifts.

that is music to my ears. g4x gearshift strategy being more advanced because of the software? 

this is for a Kotouc sequential gearbox which has a gear position sensor and gear lever strain guage.

my reference to earlier ecus relying on the likes of geartronics was with experience of motec M800 and drenth sequential shifter with strain guage. this definitely works better with geartronics and reduces gearbox wear.

9 minutes ago, tbase said:

You have a hard time for gearshift on Rally gravel due to wheel slip on lower gear? 

allot of wheel spin in every gear including 5th in the gravel with 2.2 bar. thus the flatshift strategy has to be perfect to protect the box.

[mapper]

It's always difficult to shift a sequential box with spinning wheels. I highly recommend to use wheelspeed and adaptive cut control. This adjust cut level depending on input/ouput shaft speed.

[Ronague]

34 minutes ago, mapper said:

It's always difficult to shift a sequential box with spinning wheels. I highly recommend to use wheelspeed and adaptive cut control. This adjust cut level depending on input/ouput shaft speed.

Makes sense. easy to get wheel speed input for Ecu on Mitsubishi Evo 7-9 ? I don’t know if it can pull the data from the diff controller which is connected to all 4 wheel speed sensors 

[tbase]

7 hours ago, mapper said:

It's always difficult to shift a sequential box with spinning wheels. I highly recommend to use wheelspeed and adaptive cut control. This adjust cut level depending on input/ouput shaft speed.

@mapper Can you give more detail how to do so? Now I have front and rear wheel speed set up already. 

[Adamw]

@tbase

I will first explain a couple of things as there are two different parts of the shift involved here.

First the unload for disengagement:

With a car on tarmac for example, to make an upshift you briefly cut ignition, this suddenly reverses the torque load on the dogs because you have gone from "engine driving the wheels" to "wheels driving the engine".  The dogs are easiest to disengage somewhere just as this torque reversal starts to happen. 

In contrast, on a low traction surface when there is significant wheel spin, when you cut ignition to make a shift all that happens is the wheels just slow down closer to the speed of the road surface - there is no complete reversal where the road surface is driving the wheels as it does in the first example.  So typically you need a longer cut to get enough unloading to allow the dogs to disengage.

Generally for this dog unload stage you want as much torque reduction as possible (usually 100% cut).

 

Now, engagement of the next gear:

What you are trying to achieve during engagement of the next gear is to have the dogs on the engine side turning at a similar speed to the mating dogs on the output side so that they have the best chance of the dog making it into the mating gap - and as gently as possible.  If the speeds are significantly different the dogs will just sit there grinding on top of each other or they will actually make it in with a very harsh impact, or they will make it in then bounce straight back out from  heavy impact.  With traditional gear shift strategies you had a fixed cut percentage that was present through the whole shift so it was a balance between getting enough cut to unload/disengage, but not so much cut that the input/output shaft speeds were vastly different.  This was especially an issue on rally cars where the disengagement might need a long cut, but then once disengaged the engine speed was much lower then it needed to be.

 

Related G4X improvements:

1. The disengage part of the shift (called dog unload) is now separated from the engagement part (called main shift stage), so you can have the 100% cut for best unload and less cut for the engagement stage where you just want enough cut to get the shaft speeds to be similar.  
2. There is a shaft speed matching option, this uses the gear ratios and (optionally) driving wheel speed to calculate what engine RPM is needed to match the shaft speeds for engagement, it will vary the amount of cut to achieve the target.  Using the "gear ratio and speed" target calculation means if the wheel speed changes during the shift then that will be taken into account by varying the target RPM to match.  

 

I dont have a lot of personal gravel experience but probably know enough to offer some suggestions if you give more detail of the car.

 

@Ronague  I tune a couple of sports cars with geartronics paddle shift controllers on them so can speak from experience with both - I dont think geartronics have any real advantages over G4X now in terms of shift quality.  They do have an autoshift option (but pay extra to unlock) for paddle shift setups that we dont have yet and they have a couple of extra failsafes that we dont have yet such as dual track gear position sensor monitoring.  And in some ways I do kind of like their visual "barrel rotation" GUI thing with all shift settings related to "degrees of barrel rotation", but that's about all.  They can do a nice shift.  Negatives: Analog inputs are quite low resolution, they can only detect about 0.05V change and dither about 0.1V, logging is horrible, documentation is non existent, software is very buggy. 

[Ronague]

31 minutes ago, Adamw said:

I will first explain a couple of things as there are two different parts of the shift involved here.

First the unload for disengagement:

With a car on tarmac for example, to make an upshift you briefly cut ignition, this suddenly reverses the torque load on the dogs because you have gone from "engine driving the wheels" to "wheels driving the engine".  The dogs are easiest to disengage somewhere just as this torque reversal starts to happen. 

In contrast, on a low traction surface when there is significant wheel spin, when you cut ignition to make a shift all that happens is the wheels just slow down closer to the speed of the road surface - there is no complete reversal where the road surface is driving the wheels as it does in the first example.  So typically you need a longer cut to get enough unloading to allow the dogs to disengage.

Generally for this dog unload stage you want as much torque reduction as possible (usually 100% cut).

 

Now, engagement of the next gear:

What you are trying to achieve during engagement of the next gear is to have the dogs on the engine side turning at a similar speed to the mating dogs on the output side so that they have the best chance of the dog making it into the mating gap - and as gently as possible.  If the speeds are significantly different the dogs will just sit there grinding on top of each other or they will actually make it in with a very harsh impact, or they will make it in then bounce straight back out from  heavy impact.  With traditional gear shift strategies you had a fixed cut percentage that was present through the whole shift so it was a balance between getting enough cut to unload/disengage, but not so much cut that the input/output shaft speeds were vastly different.  This was especially an issue on rally cars where the disengagement might need a long cut, but then once disengaged the engine speed was much lower then it needed to be.

 

Related G4X improvements:

1. The disengage part of the shift (called dog unload) is now separated from the engagement part (called main shift stage), so you can have the 100% cut for best unload and less cut for the engagement stage where you just want enough cut to get the shaft speeds to be similar.  
2. There is a shaft speed matching option, this uses the gear ratios and (optionally) driving wheel speed to calculate what engine RPM is needed to match the shaft speeds for engagement, it will vary the amount of cut to achieve the target.  Using the "gear ratio and speed" target calculation means if the wheel speed changes during the shift then that will be taken into account by varying the target RPM to match.  

 

I dont have a lot of personal gravel experience but probably know enough to offer some suggestions if you give more detail of the car.

This all makes perfect sense thank you. Very useful thanks. 
 

with a Mitsubishi Evo 7-9 (being used on gravel) having oem wheel speed sensors on all wheels and a separate diff controller, what input does the G4x need to read the wheel speed to do what what you have suggested above ?

[Adamw]

Is it an oem diff controller or motec or gems?

[Ronague]

4 hours ago, Adamw said:

Is it an oem diff controller or motec or gems?

Gems