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Evo 4 boost issue

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Hi guys got a customers car at work that we have just built the engine for. It’s a evo 4. Running a link g4 plugin ecu. Turbo is a gtx35. With tial external waste gate and 3 port boost controller. Engine is fully built etc. The car starts and runs fine. Some fine tuning needed but no real problems. The problems come when boosting! So I had it on the dyno setting the fuelling sites and then as it got onto boost it’s like it his it’s map limit and just stuttered. Until I let off. So I tested the boost solenoid and it is clicking fine. So checked the boost control table again and had it set ok. But upped it a bit just incase. Same again. So put it back. Map limit set to 320kpa. Run it again and seemed ok 40% throttle fine. 42% throttle full uncontrollable boost! So played with the boost control but soon realised that no matter what I entered into the table it has no effect on the actual boost control!!

The wastgate is plumbed in as follows. Turbo nipple to T-piece one side of t piece off to soloniod and the other off to the wastgate. And then the other side of the soloniod to the wastegate. Same as the photo attached however our middle “com” port is vented to atmosphere.

Anyone have any ideas or can point me in any kind of direction ? It is so aggressive that we can’t even get a run on the dyno as it is literally ON or OFF

Attached Files

I would pull the valve and actually check which ports were normally open and closed by running air/blowing through vac lines. It sounds like the top port on the gate is not being vented and the ref line is bleeding out.

Obviously worth plumbing the lower port on the gate direct to pressure feed to prove the diaphragm hasn't failed too.

I assume it is intended to be plumbed fail safe so it runs at spring pressure with no PWM.

First of all if I'm ever having issues with boost control I always start by removing your boost solenoid from the system and simply run pressure to the bottom of the wastegate and vent the top. Now you can check that you have control of the boost. This proves your mechanical system is working and will stop you wasting time chasing electronic problems that may not be your issue.

Just to be clear, the COM port should be plumbed to the top of the wastegate, not to atmosphere. Port 1 should be plumbed to pressure source, port 2 (COM) should be plumbed to the top of the wastegate and port 3 should be plumbed to atmosphere: https://sites.google.com/site/sloppywiki/_/rsrc/1472845745666/tuning-information/dial-a-boost/EWG_EBC.jpg