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Discussion Starter · #1 ·
Hey all, back again with another question. Does anyone know of an electric hydraulic pump for an EV conversion? If there are no dedicated EV pumps, what are the alternatives? I would like to make my E46 bimmer direct drive to eliminate any risks with the transmission and/or differential blowing out under the high torque.

Any help would be great!
 

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What about brakes?
For brakes, you can add a vacuum pump (as Electric Land Cruiser did, and some production EVs had such as early Teslas), or you can replace the master cylinder with an electromechanically assisted unit such as a Bosch iBooster or similar units from other manufacturers (mostly used in hybrid and electric vehicles).
 

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Does anyone know of an electric hydraulic pump for an EV conversion? If there are no dedicated EV pumps, what are the alternatives?
What you're building was very common for years, and is probably still found in many production vehicles, called electro-hydraulic power steering (EHPS) or electro-hydraulic power assisted steering (EHPAS). The unit from the Ford C1 chassis (which includes the Volvo S40 and my Mazda 3) is very common; the one from the second-generation Toyota MR2 was an early example and may be desirable because it works with no computer network communication. These were never specific to EVs; they have been used in regular engine-driven cars and hybrids, but most of them - and probably all EVs - have gone to direct electric motor assist on the rack or column instead.
 

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Discussion Starter · #10 ·
What you're building was very common for years, and is probably still found in many production vehicles, called electro-hydraulic power steering (EHPS) or electro-hydraulic power assisted steering (EHPAS). The unit from the Ford C1 chassis (which includes the Volvo S40 and my Mazda 3) is very common; the one from the second-generation Toyota MR2 was an early example and may be desirable because it works with no computer network communication. These were never specific to EVs; they have been used in regular engine-driven cars and hybrids, but most of them - and probably all EVs - have gone to direct electric motor assist on the rack or column instead.
I guess you would find one of those units on eBay or something?
 

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There's no free lunch.

The PS and AC pumps are major energy hogs if you run them "on" all the time. You can, in order to keep it simple, but simple carries a price of range.
That's why EHPAS exists: manufacturers introduced it to replace engine-driven power steering pumps, because the electrically driven version only runs as required, saving fuel - it doesn't run at full speed all of the time. Directly driving the rack or column with an electric motor takes even less energy, but the difference is small (which is why EHPAS is still a reasonable choice in production).
 

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Discussion Starter · #15 ·
That's why EHPAS exists: manufacturers introduced it to replace engine-driven power steering pumps, because the electrically driven version only runs as required, saving fuel - it doesn't run at full speed all of the time. Directly driving the rack or column with an electric motor takes even less energy, but the difference is small (which is why EHPAS is still a reasonable choice in production).
So it only uses energy when you turn the steering wheel? Useful.
 

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Discussion Starter · #19 ·
Apparently the Z4 had a full electric system (EPAS) and not the hybrid system (EHPAS). I did see that the Z4 and the Mazda3 were being investigated by the NHTSA for steering assist failure at speed.
 

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There are two types of electric power steering; hydraulic and direct drive on the column. Maybe they are compatible somehow between BMWs. Also you can get shaft assistance kits which are pretty popular these days for muscle cars and the like: https://www.unisteer.com/collections/electric-power-steering
There are electro-hydraulic systems that use a normal hydraulic rack plus an electrically driven pump, and there are all-electric power assisted steering systems. The all-electric designs can act on the rack (not hydraulically), or on the column (both OEM and those aftermarket products).

I see that the 2002 BMW z4 had an electric power steering system. I wonder how compatible it would be with my E46 323i?
Apparently the Z4 had a full electric system (EPAS) and not the hybrid system (EHPAS).
Yes, the E85/E86 Z4 (but not the "M" version) had an all-electric system. The E85/E86 Z4 was mechanically related to the E46 3-Series, so the Z4's steering parts might bolt right into the 323i... it's worth checking out. This appears to be a system with the motor in the column, which makes sense because I know the 2014+ Mazda 3 is arranged that way (and you say that their steering systems were related); that means that you would need to change both the rack and the column, or use just the column (with motor) from the E85/E86 and keep the E46 rack but disable the hydraulic assist in it.
 
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