i just bought my 03 evo about 2 weeks ago. it has a hks evc 5 boost controler set at 20psi. sometimes only sometimes the bust surges. like it will hit 20 psi and violently go down and up from 20-15-20-15-20 psi. The needle on the boost gauge will just flick very rapadly from 15-20 miltiple times. i can really feel it when the car is accelerating. what can be the problem. why is the boost surging.

this does not happen all the time. but whats up??

please i need some answers?
maybe i have a boost leak??? but i can hit 20psi at like 3200 rpm all the time like nothing.

maybe the cheep stock plastic bov is not holding the boost?

 

thats exactly what it sounds like. (the plastic bov). Upgrade to a jdm mr bov. Same one that comes stock in the IX,s. It will hold your boost and give you excellent driveability.

 

thats what i thought
i have a spare greddy type s i guess i'll throw that on later

 

try flipping plastic bov backwards and then if it does not help change it. (i have it that way for 1.5 years and running about 400whp, great results)

 

It works great until the valve stopper breaks from fatigue and shells out the compressor. I ran it like that, and your right, holds solid, but you can hear the tension on it - the thing wasn't designed to have aire flowing on it sideways.

Good for track though


About the topic here, how can boost fluctuate 15 - 20 20 times in one pull? Where is boost guage tapped?.

 

well normally i hit 20 psi at about 3k and it will slowly taper down to 17psi by redline

but on rare ocations the boost will surge. meening as i accelerate the boost will go from 20psi to 15psi and back to 20 then 15 then 20. it will do this very very fast all in one pull of one gear.

 

Boost guage only or do you feel the car loosing power in pulses too?

If so then MBC

 

yes i can fell the car loosing power and gaining the power back as the boost surges.

 

The vac line that comes of the plenum and attaches to the BOV (DV) should not operate other things except for guages and silmilar psi reading gadgets. Im guessing that the BOV line (mentioned) is being interferred with causing the 15-20-15-20 crap.

If you dont use the EBC for other than boost, you cant beat the following setup (disable wga solenoid but keep it electrically pluged in: