Jump to content
SAU Community

Recommended Posts

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.

Link to comment
https://www.sau.com.au/forums/topic/459707-hks-evc-1-questions/
Share on other sites

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?

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:

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.

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.

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]

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • The average previous owner for these cars were basically S-chassis owners in the US. Teenagers or teenager-adjacent. I often tell people that neglect is easier to fix than something that was actively "repaired" by previous owners.
    • Update 3: Hi all It's been a while. Quite a lot of things happened in the meantime, among other things the car is (almost) back together and ready to be started again. Things that I fixed or changed: Full turbo removal, fitting back the OEM turbo oil hardlines. Had to do quite a bit of research and parts shopping to get every last piece that I need and make it work with the GT2860 turbos, but it does work and is not hard to do. Proves that the previous owner(s) just did not want to. While I was there I set the preload for the wastegates to 0,9bar to hopefully make it easier for the tuner to hit the 370hp I need for the legal inspections that will follow later on. Boost can always go up if necessary. Fitted a AN10 line from the catch can to the intake hose to make the catchcan and hopefully the cam covers a slight vacuum to have less restrictive oil returns from the head and not have mud build up as harshly in the lines and catch can. Removed the entire front interior just shy of the dashboard itself to clean up some of the absolutely horrendous wiring, (hopefully) fix the bumpy tacho and put in LED bulbs while I was there. Also put in bulbs where there was none before, like the airbag one. I also used that chance to remove the LED rpm gauge on the steering column, which was also wired in absolute horror show fashion. Moved the 4in1 Prosport gauge from sitting in front of the OEM oil pressure gauge to the center console vents, I used a 3D printed vent piece to hold that gauge there. The HKB steering wheel boss was likely on incorrectly as I sometimes noticed the indicator reset being uneven for left vs. right. In the meantime also installed an airbag delete resistor, as one should. Installed Cube Speed premium short shifter. Feels pretty nice, hope it'll work great too when I actually get to drive. Also put on a fancy Dragon Ball shift knob, cause why not. My buddy was kind enough to weld the rust hole in the back, it was basically rusted through in the lowermost corner of the passenger side trunk area where the wheel arch, trunk panel and rear quarter all meet. Obviously there is still a lot of crustiness in various areas but as long as it's not rusted out I'll just treat and isolate the corrosion and pretend it's not there. Also had to put down a new ground wire for the rear subframe as the original one was BARELY there. Probably a bit controversial depending on who you ask about this... but I ended up just covering the crack in the side of the engine block, the one above the oil feed, with JB Weld. I used a generous amount and roughed up the whole area with a Dremel before, so I hope this will hold the coolant where it should be for the foreseeable future. Did a cam cover gasket job as the half moons were a bit leaky, and there too one could see the people who worked on this car before me were absolute tools. The same half moons were probably used like 3 times without even cleaning the old RTV off. Dremeled out the inside of the flange where the turbine housing mates onto the exhaust manifolds so the diameter matches, as the OEM exhaust manifolds are even narrower than the turbine housings as we all know. Even if this doesn't do much, I had them out anyways, so can't harm. Ideally one would port-match both the turbo and the manifold to the gasket size but I really didn't feel up to disassembling the turbine housings. Wrapped turbo outlet dumps in heat wrap band. Will do the frontpipe again as well as now the oil leak which promted me to tear apart half the engine in the first place is hopefully fixed. Fitted an ATI super damper to get rid of the worn old harmonic balancer. Surely one of the easiest and most worth to do mods. But torquing that ARP bolt to spec was a bitch without being able to lock the flywheel. Did some minor adjustments in the ECU tables to change some things I didn't like, like the launch control that was ALWAYS active. Treated rusty spots and surface corrosion on places I could get to and on many spots under the car, not pretty or ideal but good enough for now. Removed the N1 rear spats and the carbon surrounding for the tailpipe to put them back on with new adhesive as the old one was lifting in many spots, not pretty. Took out the passenger rear lamp housing... what do you know. Amateur work screwed me again here as they were glued in hard and removing it took a lot of force, so I broke one of the housing bolts off. And when removing the adhesive from the chassis the paint came right off too. Thankfully all the damaged area won't be visible later, but whoever did the very limited bodywork on this car needs to have their limbs chopped off piece by piece.   Quite a list if I do say so myself, but a lot of time was spent just discovering new shit that is wrong with the car and finding a solution or parts to fix it. My last problem that I now have the headache of dealing with is that the exhaust studs on the turbo outlets are M10x1.25 threaded, but the previous owner already put on regular M10 nuts so the threads are... weird. I only found this out the hard way. So now I will just try if I can in any way fit the front pipe regardless, if not I'll have to redo the studs with the turbos installed. Lesson learned for the future: Redo ALL studs you put your hands on, especially if they are old and the previous owners were inept maniacs. Thanks for reading if you did, will update when the engine runs again. Hope nothing breaks or leaks and I can do a test drive.
    • No those pads are DBA too  but they have colors too. I look at the and imo the green "street" are the best.
    • I’m not sure what happened I told them about sonic tunes free OTS tune and the next the I know .. I was booted..   To funny 
×
×
  • Create New...