# Hks evc how to repair it for those who dare



## zimnismoboy34 (Apr 18, 2012)

Hello fellow enthusiasts.
So after 3 years of the car being a rebuild i have it running and rebuilt and finished the run in process.
So was tempted to switch on the boost controller 1900 kms down the road.
So flipped the switch and monitored boost pressures with a keen eye and eerrrm no change boost was same as factory stock 0.65Kpa blaah so tried readjusting boost settings A and B and tried resetting all settings and no change so a boost controller departed the technological living .
So opened it up and gave it a good looking over found the magic STEPPING motor and inspected for free movement and all seemed fine so oiled it assembled and tried again with a test drive and still no boost ..

So came back and decided to open it and feed some air into the Map sensor for boost that comes from the intake manifold it connects to the B line on the three pipe outlet/inlet and tested with a small syringe connected to a pipe directly feeding compressed air into the port and check the stepper motor for movement and nothing .....  so its dead .
So went hunting for a motor nothing available.
Now dont get me wrong this isnt a bad controller its a 2001 hks evc 4 and it works like a dream up until the time it might have gotten dirt inside and stuffed the motor .
So i found a old hks EVC III stepping motor unit and opened it and low and behold the magical stepping motor was inside .
so i cut it as far away from the wires of the stepping motor as i could and there was 6 wires in total .
black and Red x2 and Brown and yellow and orange i think.
So i cut the stuffed motor out of my nice evc 4 control motor box and got some heat shrink tubing. 1mm .
Soldered in the new motor making sure i had heat shrink on all the wires before i soldered them in place.
And carefully and i mean CAREFULLY inserted the motor making sure the pin was located in the slot inside the casing as this alows the bleed pin to float upward and downward inside the motor housing and essentially bleeds off air.

Now inside the unit it looks very and i mean very similar to the hks EVC III unit and has two MAP sensors that measure actual manifold boost and actually waste gate boost its a really good system.

So now i have soldered in the motor and heatshrinked all the wires and installed it with the pin in place and connected it up to my boost control unit as before and low and behold we now have a working boost controller.
i tested by setting a low boost pressure and closed the unit up.
I then fed again into the B pipe some pressure using the syringe.
I think blew using my small lungs lol into the I port and checked for a bleed off point and listened for the stepping motor to purr away as it moved the pin upward and down into the top seat and bottom seat.

I then checked high boost by setting a high setting close to 80% that of stock boost.
I then pressurised the B port again .
And blew into the I port and waited for a bleed off and only at a really high pressure was i able to pass air through the I port, it will be closed at idle or minus boost and will not allow air through until the desired boost is reached.

If we can find a good source for the stepping motors we can definitely repair them and save an easy few penny 700 USd for a new one EVC 6.

However i dont see any harm in using a older unused version of the Hks Evc series to repair a newer version .

Dirt kills these motors always always use FILTERS on the I and B ports as they are fed ports meaning air passes into them .
And this contaminated air could be carrying fine dust that can lock and seize the stepping motor inside .
Just to give some insight the motor has some bearings  
These ball bearings give the motor its long lasting life span .
Infact from research the motor was never designed to ever fail based on how the cork screw mechanism is designed inside the stepper motor .

If necessary i can post pics as well.

Im still yet to go on a test run and confirm that it is repaired.
but im certain from my testing that the motor is ok and that it will control boost the way its supposed to.

For the last warning i give please make sure you dont tug on the stepping motor wires they are soldered internally and are very very weak and can snap off in a flash .

Dont remove any Gum or glue around the motor area or on the outside the gum is there to protect the circuit board from moisture.
And the Glue behind holds the sensors flush so that they dont leak boost pressure .

Remember this boost controller has a before and after MAP sensor .
So these boost controllers are so accurate and potentially failsafe.

If any one needs pics please let me know i tried to take as many as i could .
and i can post them just really tired after soldering and heatshrinking the wires.
The heat shrink is to ensure that we dont use insulation tape and also ensures that each soldered connection doesnt come out .

On the Evc board close to the red LED there is a resistor that has a split wire with each half neatly placed next to the LED on either side .
Leave it disconnected it was done at the factory heavens knows why .

If any one else has had any experiences with the Evc stepping motor please do share this will be great to get out there and help others who may have resorted to using a manual bleed valve or Dawes device lol.


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## R32 Combat (Jan 29, 2004)

Good info. Well done. Thanks for sharing.


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## zimnismoboy34 (Apr 18, 2012)

I am currently looking into motors and i need the aid of the electronic gurus on here .

From what i can tell the motor is a 2 phase 6 wire or 5 wire motor .

Dimensions are 25x15 width is 250 mm x 150 mm

im looking for a suitable replacement on alibaba and if i can find one then we all will have a field day knowing that the only part that can become faulty because of dust can be repaired .

Im struggling to find a stepper motor with the internal diameter that will allow the spindle to be pressed in that drives the needle ....
as far as i know its a permanent magnet type ..


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## zimnismoboy34 (Apr 18, 2012)

not much Diy enthusiasts here ?


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## R32 Combat (Jan 29, 2004)

What are you trying to repair?


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## Multics (Apr 27, 2008)

Good thread that, thanks for sharing. I also had an evc4, good bit of kit. Never had to repair it though  As far as I know only the HKS evc's use stepper motors, all other boost controllers use solenoids.


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## zimnismoboy34 (Apr 18, 2012)

exactly and hence the reason why they are pretty much the best on the market they are precise and effecient and catch boost spikes as they are happening.
Im still trying to find a stepper motor though but my controller is working now that i bust the old evc to repair this one


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