Hks Evc 1 Questions

[Timtim123]

Hello, the gts-t I just recently bought has an HKS EVC installed. The actual controller is sitting in the center console not hooked up. I just got around to looking into the wiring for it beneath the steering wheel and had a couple of questions. The car has an aftermarket boost gauge installed and under full throttle, is only reading about 0.25 bar. This seems pretty low to me.

First question -- Does the set boost from the EVC remain even when the controller is not plugged in? If so, I'm wondering if perhaps the previous owner has the boost low. Either that, or I have a leak, or the gauge isn't reading correctly. The car feels like it's pulling decent and boost is definitely building, however this is my first experience with a skyline/rb20, so I'm not sure what is 'normal'.

Second question -- There are two harnesses on the back of the controller. Only one looks to plug into anything under the dash. Any idea what the other harness could be? I can post pictures if it would help anything.

Any help is much appreciated. I searched around online but couldn't find any clear answers. Hoping the boost is just set low on the car so I'm not chasing a leak/trying to fix the gauge.

[GTSBoy]

Stock wastegate pressure on RB25 is 5 psi. That is ~0.33 bar, which would/could read as 0.25bar on a shitty aftermarket gauge. That's how your boost is so low.

The stock boost control solenoid on an R525 will bleed some off to get you 7 psi. You will not get that if it has not been re-instated upon removal of the EVC.

If the EVC is not hooked up, then it cannot do anything to control boost. You will get wastegate pressure.

Why do you not google up the manual for the EVC so you can see the wiring diagrams and looms for yourself?

[tridentt150v]

Does it have the stepping motor part in the engine bay area? Black box should have HKS written on it.

One set of wires go to the stepping motor, the other set are for ignition, earth, and power etc.

I'm talking from a IV knowledge so yours could be a bit different but you still need both components - the electronic in cabin controller and the stepping motor that controls the wastegate.

Try this:

[Timtim123]

Thank you both. I just found installation/setup instructions so I'll read that over. I'm reading a few places that people are saying 7 to 10psi stock for the rb20's. Mine's only reading about 0.25 bar though (~3.6psi). Like GTSBoy mentioned though, the shitty aftermarket gauge is likely reading low though.

Trident, it does have the motor under the hood as well. I did see that video also before I posted here, but mine looks to have a second harness pretty close looking to the first one as shown in that video. Can't seem to find anything about what that second harness is but I'm assuming it goes to the stepping motor then. The first harness, which has a connection that I found, powers it on and it sounds like the stepping motor just buzzes constantly. I'll look around some more though and see what I can find.

[GTSBoy]

RB20 wastegate pressure is 10psi natively. You might have a car that someone has messed about with and stolen the (desirable) 10psi actuator for use on an RB25, leaving an (undesirable) 5 psi actuator on the RB20. With a boost controller it would still work up to 13-14 psi anyway, so not a huge problem.

[tridentt150v]

Also have a look at this:

http://1jzmerc.com/hks-faq/accessories/hks-evc

bottom of the page is manuals for most of them [knew I'd seen it somewhere for mine just had to find it again, been a couple of years lol]

[Timtim123]

Awesome, I'll read over the manuals and get more familiar with it. Might have to order a new boost gauge here soon as well to make sure I know what I'm working with. Thank you both!