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Discussion Starter · #1 ·
Hello,

For our Jeep conversion, I want to replace the stock steering system which is really made to support heavy off-roading with it's crossover steering mechanism with something lighter and less complex since our EV Jeep will never be taken into heavy off-roading.

I know that there are many OEM EPAS steering units out there from GM (Volt, Cobalt, HHR, etc.) Ford (Explorer, Edge, Mustang, etc.)...

I would love to replace the entire steering system with a complete rack and pinion with integrated EPAS, and I know that often you need to send the vehicle speed and "turn-on" signals over CAN. This would be my preference as I want a EPAS system that is proportional with speed.

If this is not possible, my second choice would be to replace the jeep hydraulic system with a standard rack and pinion system to get rid of the heavy stock system and then use a inline EPAS on the steering column link. Maybe something like the DCE Microsteer (DC Electronics - EPAS).

The last option would be to just get rid of the hydraulic part of the stock system and use the existing steering system with the inline EPAS unit.

Suggestions or tips? For the primary option, is there any thread or source of good information on the wiring and CAN communication protocol for any suggested EPAS devices and/or any walk-thrus to help? We will be using the AEM VCU200 for vehicle control and I would be sending the vehicle speed CAN signals from that.

Thanks.
Don
 

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The can part is quite easy once you have sniffed the OEM signals. Here is a guy who did a swap on a Subaru, coincidentally I am using the same rack on my car. PDF at the bottom detailing it if you are on a desktop.

If you don't know about bump steer then google it, it'll make your life considerably more stressful when changing steering racks for another type. Best/easiest option is to stick with what the vehicle manufacturer provided, it gets a lot more complicated when swapping steering parts. The dirtiest solution is an electric-hydraulic pump, early 2000s OEMs used them.

You'll need a can message converter, I don't think the VCU200 is sufficiently developed yet to allow custom can message output- I'd be very keen to know if it is as I'm using the 300 and have the same issue.
 

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Discussion Starter · #3 ·
Here is a guy who did a swap on a Subaru, coincidentally I am using the same rack on my car. PDF at the bottom detailing it if you are on a desktop.

If you don't know about bump steer then google it, it'll make your life considerably more stressful when changing steering racks for another type. Best/easiest option is to stick with what the vehicle manufacturer provided, it gets a lot more complicated when swapping steering parts. The dirtiest solution is an electric-hydraulic pump, early 2000s OEMs used them.

You'll need a can message converter, I don't think the VCU200 is sufficiently developed yet to allow custom can message output- I'd be very keen to know if it is as I'm using the 300 and have the same issue.
Thanks!!

wow...nasioc...haven't been in there in years...since my 480whp Subaru build... I will check it out. Thanks for the suggestions on keeping the stock steering bits and finding another solution... Also, thanks for your feedback on the vcu200... Since I am also thinking about making some small Arduino CAN converters for the stock gauges (and least this is part of the plan) I could also output the needed CAN signals to the steering rack... But, I have not started to dive into that yet.

Thanks again!
 

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I am also thinking about making some small Arduino CAN converters for the stock gauges
There are widgets out there for very specific applications and the prices are silly. They won't be much more than an arduino inside. There is no reason a VCU can't do this, other than the will of AEM to implement the firmware updates, so I'm hoping they can get onto adding these features in due course. I have the same requirements as you do, how two drive two cross-fields gauges, two idiot lights and a mechanical speedo from can signals. I'm trying to avoid having arduinos onboard- they are not automotive/industrial rated and can cause far more damage than good. I have seen an arduino cause over 100k damage, but that is a story for another day.
 

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Interesting about the arduinos in automotive. Makes sense that they'd be overly sensitive to the not-so-great electrical environment in a car. Curious if anyone knows of any more robust development board options. I was shooting for an ESP32 for my VCU, with the heavy caveat that it wouldn't be responsible for anything safety sensitive.
 

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Anything with i/o pins going off the board is only suitable for hobbyist use. I/o buffering chips are available for this, it isn't too difficult to put an arduino on a board that meets automotive requirements- a Teensy even as they are natively can and lin enabled. An automotive module should be tolerant of any in-service voltage on any header pin, plus have reasonable spike/static voltage tolerance, watchdog timers, brownout detection... and so on. It shouldn't in any way be affected by external faults, and if it is internally failing, it should report and fail to a safe state. Fault trees are fun, but not as much fun as cascading failure scenarios
 

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Arduino is a design environment, not just a board.

If you build your own hardware vs using a stack of Chinesium boards off Amazon and crappy reused shield connectors, then it can be extremely robust, even in an automotive environment (use auto qual'd parts).
 

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All that is fine. Was planning on designing a PCB with an automotive rated voltage regulator. The VCU would drive onboard signal level relays to drive automotive 12v relays externally, all in normally-whatever configuration such that if the board died everything would go to a safe state. Am a bit worried that the board could fail in a way that held it's control voltages in the last state though. All that said my main design goal is still that anything I code doesn't control anything related to actual safety.
 

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Loss of power steering is not considered a safety issue, afaik. Having a board fail that results in full assist or no assist is not a big deal.
I agree that since it is only assist, loss of assist doesn't inherently lead to a loss of control... but in many vehicles a typical driver will have difficulty turning the wheel without assist and may not be able to turn it quickly enough for manoeuvres, particularly if the assist drops unexpectedly. My guess (and it's just a guess - I didn't check) is that if a vehicle had a production defect which caused loss of assist, it would lead to a recall based on a safety basis. Of course most DIY conversions would not meet production vehicle standards of design or construction in various ways.
 

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Unfortunately you cannot remove the stock heavy steering so easily. You have a solid front axle on that jeep which is basically incompatible with rack and pinion steering. There is a ton of aftermarket for Jeeps so it's possible you can find some lighter components. Just look at your axle, imagine how it moves while driving down the road.

I have a similar suspension design on my truck and I'm using an electric power steering pump with the stock steering hardware.

Secondly I have a Megasquirt in my Miata which is Arduino based ECU.
 

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I agree that since it is only assist, loss of assist doesn't inherently lead to a loss of control... but in many vehicles a typical driver will have difficulty turning the wheel without assist and may not be able to turn it quickly enough for manoeuvres, particularly if the assist drops unexpectedly. My guess (and it's just a guess - I didn't check) is that if a vehicle had a production defect which caused loss of assist, it would lead to a recall based on a safety basis. Of course most DIY conversions would not meet production vehicle standards of design or construction in various ways.
Loss of assist is a calculated risk in a production vehicle where cost won the battle. Otherwise, they wouldn't use a v-belt driven pump.

I've driven enough miles to have had a busted belt, lol. Surprising, pain in the butt at low speed, but deadly?

You keep denigrating DIY as being cavalier about how they do things, but there are many engineers and competent techs doing conversions, not merely the duct tape and JB Weld crowd.
 

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Loss of assist is a calculated risk in a production vehicle where cost won the battle. Otherwise, they wouldn't use a v-belt driven pump.
Everything is a calculated risk in technology. If a production vehicle had a defect which cause the V-belt driving the power steering pump to fail, it would be recalled as a safety risk.

I've driven enough miles to have had a busted belt, lol. Surprising, pain in the butt at low speed, but deadly?
I haven't had a belt failure stop power steering, but I have had power steering intermittently fail due electrical problems (a failing battery). The consequences depend on the vehicle, and the driver.

You keep denigrating DIY as being cavalier about how they do things, but there are many engineers and competent techs doing conversions, not merely the duct tape and JB Weld crowd.
It's just reality, not an insult. Even when an engineer or competent tech does a DIY conversion, it doesn't have a multi-million dollar budget for development or custom tooling.
 

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Unfortunately you cannot remove the stock heavy steering so easily. You have a solid front axle on that jeep which is basically incompatible with rack and pinion steering...
True: a rack mounted to the frame with a beam axle suspension will have bump steer and toe changes with suspension travel. Imagine the rack at axle height so that the tie rods are level, then move one end of the axle straight up or down... the tie rod angles up or down and pulls the steering arm, making the wheel steer. If the whole axle moves up and down (a bump for both wheels instead of just one), the bump steer effect is toe-in or toe-out. A conventional system doesn't do this as badly because the left and right sides are tied together by a rod, and the rod from the steering box to the linkage on the axle is arranged to swing in an arc as close to the axle movement arc as practical.

The straightforward fix is to mount the rack on the axle beam, so there's no problem with the hubs moving in an arc which doesn't match the tie rod arc. This has its own issues with unsprung weight and steering shaft movement, but it has been done. Freightliner does this on the Cascadia, and there are presumably others, as described and shown in a Commercial Vehicle Safety Alliance inspection bulletin.
The issue with the steering shaft with the rack on the axle beam is that the steering shaft needs to both flex (change angles at the joints) and plunge (change length). With a rack mounted to the body or frame, a steering shaft only does those things very slightly, or in a crash, but not significantly in normal operation, so at least the plunging part of the shaft would need to be much better than the usual column parts.
The unsprung weight may not be a huge issue, since live beam axles have stupidly high unsprung weight anyway, and it is common to mount steering assist rams or just steering dampers on axles. GM put an entire electrically powered steering rack on the rear axle of some pickups and SUVs as their Quadrasteer option, although with no mechanical steering shaft.
I would also not want the steering rack - particularly with power assist components - subject to the shock of suspension movement, but this doesn't seem to be a problem in practice.

The other obvious fix is to keep the original steering system and just change the boost method. This can be
  • an electrically driven hydraulic pump for a stock hydraulically assisted steering box, or
  • an electrically driven hydraulic pump for an assist ram, or
  • a steering box assisted by an electric motor (I've never heard of anyone doing that), or
  • an electric ram assisting the way a hydraulic ram usually does (I've never heard of anyone doing that, either), or
  • an electrically assisted steering column just like that often used with a rack-and-pinion system (using an aftermarket kit, or a salvaged unit from a production car).
Yet another solution is to use one end of a steering rack to drive the rod which is normally driven by the steering box. Here's an example:
Installing Unisteer Products Rack And Pinion Kit - Steering In A Different Direction
Presumably in this case one could do this in order to use an electrically assisted rack; it's not the easiest or most rational solution.
 

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It's just reality, not an insult. Even when an engineer or competent tech does a DIY conversion, it doesn't have a multi-million dollar budget for development or custom tooling.
....or meetings 🤨

Which is why a lot of American innovation happens in garages.....out of sight of the guardians, gatekeepers and of the worshippers from the Church of Consensus 😂

Jobs and Musk were reportedly dicks as managers...which is why they got stuff done
 

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Hello,

For our Jeep conversion, I want to replace the stock steering system which is really made to support heavy off-roading with it's crossover steering mechanism with something lighter and less complex since our EV Jeep will never be taken into heavy off-roading.

I know that there are many OEM EPAS steering units out there from GM (Volt, Cobalt, HHR, etc.) Ford (Explorer, Edge, Mustang, etc.)...

I would love to replace the entire steering system with a complete rack and pinion with integrated EPAS, and I know that often you need to send the vehicle speed and "turn-on" signals over CAN. This would be my preference as I want a EPAS system that is proportional with speed.

If this is not possible, my second choice would be to replace the jeep hydraulic system with a standard rack and pinion system to get rid of the heavy stock system and then use a inline EPAS on the steering column link. Maybe something like the DCE Microsteer (DC Electronics - EPAS).

The last option would be to just get rid of the hydraulic part of the stock system and use the existing steering system with the inline EPAS unit.

Suggestions or tips? For the primary option, is there any thread or source of good information on the wiring and CAN communication protocol for any suggested EPAS devices and/or any walk-thrus to help? We will be using the AEM VCU200 for vehicle control and I would be sending the vehicle speed CAN signals from that.

Thanks.
Don
 
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