HKS EVC issues

[Backlash2032]

I have a first generation EVC, and while I was super excited to wire it in and experience 17 psi of boost to red line, I got a little more than I bargained for. It gave me 15 psi of boost when I was supposed to give me 8. No control over the boost level on any setting. So I dug into it a little bit.

I was assuming best case scenario, and the line I hooked into the EVCs MAP port had a check valve in it, and it was never seeing positive manifold pressure, therefore keeping the valve sealed. Unfortunately, that was not the case. So I dug a little deeper.

Removing the 4 socket head cap screws holding the center portion of the valve together, I revealed the stepper motor at the heart of the EVC. Powering on the system revealed something incredibly strange. Every 5 seconds or so, the pin in the stepper motor would extend itself as far as it could, which would seal the valve. You could push it back in and it would come right back out in a couple seconds.

So I thought, okay, it's only seeing ambient pressure, not the pressure I had the valve set for.. So I grabbed my handheld vacuum / pressure pump and gave it some pressure on the MAP port. Same deal. No idea what's going on, as the stepper motor seems to be doing it's job, just at the wrong time. But I just don't know if it's a controller, stepper motor, or map sensor issue, or where to even start diagnosing this issue.

I called HKS USA and they were ZERO help. Basically they said that nobody knew about those units and HKS doesn't even care anymore since its over 3 months old or something along those lines. Definitely not how I would operate my business, but I'm also not HKS. It's really making me rethink my goals with this car.

Anyway, any help is appreciated! If anyone knows how these things work or could help me work through figuring it out (ie what signals do what) that would be so much help. Thanks in advance!

 

[Backlash2032]

Well, I think I've muddled through the issue in my head. I haven't been able to check anything out, as I'm not at my car right now, but! first gen EVCs do not have external switches for internal or external wastegates. They are sold as either or from HKS back in the day. However, they do have the switches inside the control unit to change it from internal to external or vice versa.

So, on a external gated setup, the diaphragm side of the wastegate is fed with constant pressure from the charge pipes. Then, your boost controller feeds the spring side of the wastegate with pressure. So the boost from the boost controller actually helps "increase" spring pressure. So spring pressure with a boost controller would be the boost controller sealed shut.

On an internally gated setup, boost from the charge pipes is feeding the diaphragm side of the wastegate. Very simple... Spring pressure with a boost controller would be the boost controller wide open.

So in my (hopefully) case, with the EVC set to an external gate setup, when I first noticed that the boost was over 10 psi, I switched it over to manual, and turned the volume knob all the way down, which would basically result in stock boost... Since the EVC is setup for external gates, then it would seal the valve shut. Which would be correct in an externally gated setup. This resulted in my completely uncontrolled boost. Then, I switched the control units power off, which also results in stock boost. Again, since it is set up for external gates, it sealed the valve shut, resulting in complete loss of boost control.

Also, the reason it didn't control boost on the low setting, is because the way it controls boost for internal or external gates is completely different. For one psi over spring pressure in a external gate, the boost controller has to feed the spring side with 1 psi of boost (it's probably a hair bit over that since the spring would take up some surface area on the diaphragm.). In order to raise the boost pressure one psi the boost controller needs to feed the diaphragm side with spring pressure once the manifold reaches spring pressure, plus one psi.

So yes, EVENTUALLY the pressures would equal out.. Maybe if I switched it over to the high side, then it would hold 15 psi or something like that... But I think I'll just move the dipswitches around...

 

[Backlash2032]

Well... I wish I'd have noticed this earlier...

How the switches are supposed to be setup for an external gate

And the proper setup for internal. Just flip everything.