Gear shift control

[João Silva]

Hello

I need advices about the gear shift control settings.

Shift control is totally new for me.

The combo in question is BMW S54 engine whit sadev 6 speeds sequential, I have the ecu read barrel position, all gears read correct. The cuts settings I not have idea were start.

Best regards

João Silva        

[Adamw]

I can give you some basic settings as a starting point, attach a copy of your map.  Do you have a strain gauge on the lever?  

[João Silva]

Hi Adamw

Thanks the replay, the basics settings help o lot  .

The lever don´t have strain gauge, I plan use the gear position sensor, is not good? 

 

polo Nuno Map 2.pclx

[David Ferguson]

As an alternative to a strain gauge:  I have used a position sensor (like a linear pot or a high resolution rotary pot).   Attach this to the gear lever, and calibrate like a strain gauge.  Above a certain voltage is one direction, and below a different voltage is the other direction.

I don't believe you can use the gear position sensor, as this would need to have two different voltage values for each gear that could go up or down.

[Adamw]

Barrel voltage or a position sensor as David suggests often doesnt give a great shift quality in my experience but you can give it a try.  I have drawn a rough ms paint picture below to explain.

If you have a strain gauge a typical shift sequence would look like this picture.  Just before point A the driver has started to pull the lever, so lever force ramps up.  At point A we see a little step in barrel voltage as the force from the lever rotates the barrel a little as it takes up the mechanical backlash in the barrel slots, shift forks etc.  Once the backlash is taken up then the barrel voltage flatlines as there is nothing further that can move except for possibly a little flex in the shift fork.  As the driver continues to pull on the lever, the force increases which is applying mechanical load or "preload" to the dog ring.  At point B, the lever force reaches the set shift force threshold so the ecu cuts ignition which unloads the dogs, we already have significant preload on the dog ring so it should quickly release and travel towards the next gear.  At point C the barrel voltage has reached the "next gear voltage margin" so the shift is considered complete and the cut is ramped out. 

In contrast, to use gear barrel voltage as the start shift request, the only place barrel voltage moves is at point A just as the backlash is taken up. So your cut is going to be much earlier than ideal, before there is any preload on the dog ring.  This means it is going to come out of gear slower and the cut is going to be much longer.  This method can also be more prone to false requests as it only takes a small bump to reach the barrel voltage threshold to trigger a shift.

Note this picture is probably a little exaggerated but I was just trying to make it clear.  In reality you are probably talking 20ms longer and it wont feel as seamless as a well-tuned shift will feel.  You can use the "start shift validation time" to make up for some of that delay between point A & B to allow some preload to build etc, but it will never be as nice as a strain gauge shift. 

I will take a look at your map later when I have a bit of free time.   

 

[João Silva]

Thanks David and Adam for the explanations.

Adam the explanation is great, answer me lot questions. Now I understand why use barrel position and strain gauge

[João Silva]

Hi Adam

Do you have time see the maps?

Best regards

João Silva 

[Adamw]

Sorry, I forgot about you.  I will do that later today.

[Adamw]

Attached is your map with some basic gear shift settings added.  You will need to fill out the gear ratio table with the actual gear ratios.  I have only set up driven upshift, you will need to be above 2000RPM and 20% throttle for the shift cut to activate.  I have added some gear related channels to the ecu logging, try some gentle shifts at about 30% throttle then download the ecu log and attach here for review.  

polo Nuno Map 2 Shift set up.pclx

[João Silva]

Thanks Adam

Best regards

João Silva