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Chris Wilson

Power Steering Rack Solenoid

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How is the steering rack ("weight, effort, pressure", call it what you will...), solenoid triggered? Is it either open or closed, thus light or heavy, or does the ecu duty cycle it to give a linear steering effort change? Thanks.

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What type of car?

Most car the sensor on the rack is only a sensor for the ecu so it knows to bump the idle up so as the motor dosnt stall from the load of the power steering pump

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What type of car?

Most car the sensor on the rack is only a sensor for the ecu so it knows to bump the idle up so as the motor dosnt stall from the load of the power steering pump

Interested in both R33 GTS-t and R33 GTR

The idle up is via a pressure switch in the pump high pressure line. The rack itself has a bypass bleed solenoid to vary rack assistance effort.

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Varying duty cycle, ~square wave input, if it is the same as the '32.. I did have a couple of pictures from a scope capture when I was chasing problems, but they seem to be misplaced.

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Interested in both R33 GTS-t and R33 GTR

The idle up is via a pressure switch in the pump high pressure line. The rack itself has a bypass bleed solenoid to vary rack assistance effort.

Ah yeah I know what you are talking about now.

It should be liniar. the ecu (or might be another modul) ajusted the efford compared to the speed the car is doing. E.g. more asisted at low speeds in car parks and less assisted at hight speed on the highway

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I am pretty sure the hi-cas ecu in the boot controlls the unit, I am also interested in how it is operated.

My 33 gtst sometimes goes heavy and stays heavy. then next time i start it, it could be normal again.

Im looking at modding it.. possably removing it, would love to know how it is operated!

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i am having a problems with my steering aswell feels like its controlled electronically when driving and makes the car viere from left to right slightly, so i could be driving down a straight bit of road and the car will just turn itself to one side slightly and start heading that way then turn back all of a sudden, its freaking annoying.

do u think replacing the hicas ecu will fix this problem?

as the hicas was also playing up, and was wiggling the arse end intermittently, so i removed it. maybe they are all related, and the hicas ecu is responsible.

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Major thread revival.

So i'm trying to find out what signal the Hicas unit gives the power steering solenoid in an R33 rack.

As the rack isn't actually in an R33 i can't just hook up a scope to the plug and see what its doing.

I need to know the duty cycle and frequency of the output is at say 0km/h and 100km/h. I assume it will be a linear line between those two points, above someone said its a square wave, thats a start.

The above link from heller44 does not work.

I looked in the R33 workshop manual which was no real help. It just stated that you should see approx 6-8V at 0km/h and around 2V? at 100km/h.

No actual duty cycle or frequency data is given in the manual.

What i'm trying to hopefully do is control the solenoid from my Link ECU in my R31. I previously have driven the car with the solenoid completely off and it did feel heavy at a stand still and low speeds.

Any help would be appreciated.

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Sweet, cheers for that mate.

That should be pretty easy to work out the duty cycle from then.

Locked at 123Hz across the board.

At 0km/h if the Solenoid is meant to be getting Approx 4.4 - 6.6V that is a rough 32 - 47% Duty cycle

At 100km/h if the Solenoid is meant to be getting Approx 1.5 - 2.2V that is a rough 11 - 16% Duty cycle.

Calculated on the basis of 14V.

After 100km/h do you know if the duty drops off to 0 eventually or it stays at approx 16% after 100km/h?

Looks like its just a case of doing a linear graph every 10km/h from 0 to 100 using those duty cycle's as the start and finish points.

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On 3/19/2013 at 3:07 AM, kitto said:

Sweet, cheers for that mate.

That should be pretty easy to work out the duty cycle from then.

Locked at 123Hz across the board.

At 0km/h if the Solenoid is meant to be getting Approx 4.4 - 6.6V that is a rough 32 - 47% Duty cycle

At 100km/h if the Solenoid is meant to be getting Approx 1.5 - 2.2V that is a rough 11 - 16% Duty cycle.

Calculated on the basis of 14V.

After 100km/h do you know if the duty drops off to 0 eventually or it stays at approx 16% after 100km/h?

Looks like its just a case of doing a linear graph every 10km/h from 0 to 100 using those duty cycle's as the start and finish points.

Sorry to revive an old thread mate, wanted to know if there is a way to achieve this with some kind of dc converter? I got one of these racks with the solenoid in it but my r33 didn't have the solenoid type rack or wiring for it to begin with.

Edited by nicostar

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What do you mean "DC converter"?

If you just want a fixed voltage at the rack, you could just blow away the extra volts with a suitably sized (ohms and watts) resistor.

If you wanted to go to the effort of using more electronics to achieve the same goal and waste a little less electricity, you could certainly put a DC-DC converter on there.

Or, you could build an Arduino to run a PWM output to an SSR. Choose a suitable frequency for the PWM (maybe 100Hz) and just punch out the pulsewidths required to get the voltage you want. It's pretty clear that it wants somewhere around 6V to get max assist (at low speeds) and ~2V to get minimum assist at higher speeds. If you went to a little more effort you could connect an Arduino input to the VSS and give it full variable assist to the same extent that the HICAS CU would.

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