i have been running an HKS EVC IV on an EVO IX with few problems since i bought the car two years ago.

every 6 months or so the boost would change so i would re-calibrate it and all was well.

about a month ago my boost started pulsing, more specifically the wastegate would start to flutter open and closed. i will have the controller set at 21psi and it would quickly pulse between 22-17 psi or so. i re-calibrated and the problem was fixed. a few weeks later it did it again. i switched it to low boost setting (was on my way to autoX and didn't have time to re-calibrate) and it worked for a few weeks and started to pulse again.

now it is doing it all the time. checked all the vacuum lines, those are all good, and i have re-calibrated the boost controller several times to no avail.

when i calibrate the unit the first pull at wastegate pressure is smooth but the 2nd pull has the pulse. if i turn the unit off it runs wastegate pressure with no problems.

has anyone ever experienced this before? bad control box? bad stepper motor?

i tried calling HKS this afternoon at 1pm local time and they were closed... has anyone ever tried calling them before?

i am trying to get this taken care of so i can autoX this weekend.
thanks in advance, and sorry if i was supposed to post this is the interior/electronics section.

 

ever get it fixed?

 

well i found my factory vacuum lines in a pile in the garage... so yes?

VS Motorsports called HKS for me because i tired calling 5 times and they never answered. HKS said they no longer make that stepper motor. AMS told me to call a place in TX but they only had stuff back to the EVC6. so i guess no one supports a 10 year old boost controller, go figure.

so i will run the AMS boost maps for now and pick up another electronic controller in a few months. i am kinda pissed because i really like the EVC4, i don't like the gain knobs. the EVC4 is nice because you tell the car to run 1.45 bar and it does it.

there are other things on the list to pick up before i worry about running 2 more psi so right now the box is still wired up in the car but the stepper motor is sitting on my back seat.

 

Sounds like a freaky control system feedback kinda deal, is the EVC IV a fuzzy logic controller? It sounds like its doing fuzzy boost control