# Nissan Leaf (2014) power steering in EV conversion (BMW 2002 - 1975)



## matthew.stead (Jun 8, 2020)

The Leaf seems to have a neat power steering system. It would be great to adopt this in my conversion if I can (which is a BMW 2002 form 1975 without any power steering).

From my understanding it seems all I need is:

Power from the original wiring harness
Original wiring control wires - not sure which controller these actually come from
Possibly steering orientation sensor - or this might only be needed for the braking controller
Does anyone have experience with this? or should I just give up and use the original manual system from the BMW.


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## brian_ (Feb 7, 2017)

I don't know anything about the Leaf's steering specifically, but modern steering power assist systems usually have a controller which gets steering angle and road speed inputs (as well as possibly driving mode selections) over CAN and use them to determine the amount of boost, which is then sent to the boost motor controller by CAN as well. If you're really lucky it runs at some default level of assistance without any communication, but I wouldn't count on it.

There are now power-assist units designed to be added to a steering column and intended for aftermarket use, not requiring any integration with OEM electronic controls. I have no idea how convenient they are to install, or their cost.

One issue with using the original rack with any kind of power assist is that the manual rack will likely be slower (more turns of the steering wheel required) than would be desirable with power assist.


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## matthew.stead (Jun 8, 2020)

brian_ said:


> I don't know anything about the Leaf's steering specifically, but modern steering power assist systems usually have a controller which gets steering angle and road speed inputs (as well as possibly driving mode selections) over CAN and use them to determine the amount of boost, which is then sent to the boost motor controller by CAN as well. If you're really lucky it runs at some default level of assistance without any communication, but I wouldn't count on it.
> 
> There are now power-assist units designed to be added to a steering column and intended for aftermarket use, not requiring any integration with OEM electronic controls. I have no idea how convenient they are to install, or their cost.
> 
> One issue with using the original rack with any kind of power assist is that the manual rack will likely be slower (more turns of the steering wheel required) than would be desirable with power assist.


Thanks for pointing out the expected "number of turns" or slower manual rack. 

the system looks relatively simple - power & control wires. I am planning to keep the core wiring / controls so hopefully it is just a mechanical question (just like my other post on the brakes). I think I will keep the wiring etc to allow this steering to be reused and make a decision later. 

ps. the car drives in this state.


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## remy_martian (Feb 4, 2019)

That car has a rather unconventional assist on the steering column rather than down in the rack. Interestingly, Brian covered both 😂


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## brian_ (Feb 7, 2017)

remy_martian said:


> That car has a rather unconventional assist on the steering column rather than down in the rack. Interestingly, Brian covered both 😂


While the first electric assist systems mounted the motor on the rack (sometimes on a second pinion gear and sometimes parallel to the rack and running a ball screw), mounting the motor on the column (usually about at the point where it pivots to tilt the wheel) has become common. ZF offers all three types (dual-pinion rack, ball screw rack, powered column). Some companies use different systems on different models, to suit the vehicle's packaging; for instance, a Mazda 3 has a powered column, but a Mazda MX-5 has a powered rack because the engine position makes it too cramped around the column. This variety is handy, because it means:

there are options, 
electrically powered racks allow the use of original columns in older cars, 
electrically powered columns allow the use of original racks (with removal of any hydraulic assist), and
due to the use of powered columns there are modern racks with fast ratios that don't have a motor on the rack (for applications where assist is not wanted or not practical - they're effectively abnormally quick manual racks for someone building a vehicle with a light front end.


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## matthew.stead (Jun 8, 2020)

I have attached a few more photos for those that may be interested.


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