Brake booster experiences

[muehlpower]

Has anyone used a Leaf brake booster in a conversion? The brake booster is not mentioned in the wiki under Nissan OEM parts, and I haven't found anything else about it here either. I have a Bosch booster, but it's too big for my application. The Nissan parts are easy to get and look a bit more handy.

[danjulio]

I have one too (from a 2017) and would like to use it in my conversion but I'm a little afraid it won't fit. I have it on my lab bench test setup. I haven't yet been able to make that system successfully power up in drive mode but when I press the brake pedal (which is physically disconnected from the booster) I notice that the linkage on the booster moves in and out. I've done lots of reading in the Nicoclub 2015 manual and it appears the booster talks to the ABS module privately, and the VCM and instrument cluster over the CAR CAN bus. It sends a "requested braking torque" to the VCM and gets back a "amount of regeneration torque" which I think it uses to decide how much to engage the brakes.

My goal in the new year is to be able to reverse engineer the communication enough to spoof the VCM to enable this (and the ABS and EPS) to work. Maybe in the worst case one could just always send 0 for regeneration torque available and let this fully drive the brakes when the pedal is pushed.

[jrbe]

Check out the recalls first. Looks like there are some post recall failures as well.

[muehlpower]

which is physically disconnected from the booster)

What do you mean? The pedal is normally connected to the threaded rod (on the right in the picture). Opposite is the master brake cylinder. What exactly does your experiment look like and what have you connected electrically (pin assignment)?

[danjulio]

What do you mean? The pedal is normally connected to the threaded rod (on the right in the picture). Opposite is the master brake cylinder. What exactly does your experiment look like and what have you connected electrically (pin assignment)?

I didn't have room in my table-top setup to connect it back to the pedal. It sits a couple of feet away. When I power on the system I can depress the brake pedal (changing the input to a potentiometer mounted on it) and watch the threaded rod pull into the booster. I guess that it is "assisting" the human press? I should disconnect the VCM so that it is really operating stand-alone and see if that still happens.

[muehlpower]

Sorry, I don't understand yet. Is there anything else in your test setup that isn't shown in my picture? A potentiometer, control unit, or anything else besides a 12V power source? When you apply the brakes in a car, you mechanically press the threaded rod in. What do you mean by “applying a remote brake pedal”? Do you have a picture of your setup?

[danjulio]

Sorry. Here's the messy setup:

It comprises all the electronics except inverter/PDM/battery. You can see the brake booster isn't connected to the pedals. When I apply 12V the brake booster becomes functional as seen in the video I link below. There is a potentiometer attached to brake pedal and connected to the brake booster electronics. I found pressing the brake pedal will activate the brake booster - even when the rest of the car is turned off (no CAN bus traffic) or when it's turned on and the VCM removed.

[cnstrct]

I'm interested in this project for my project, great work. I'll give it a try too.