I just installed a Prosport Boost Gauge, which is t'd off the fpr vac line to the intake manifold. All of the i/c piping hose clamps are tight. I have read here about these particular gauges being off by quite a bit, but i'm only seeing a constant 10-11psi max from the gauge, with no tapering at redline. I haven't done a boost leakdown test yet, but I'm thinking the culprit is the wastegate actuator. There are some relatively new looking zipties around the vac lines that go to the turbo and the wastegate act. I guess I'll have to investigate a little closer. I just wanted to see if anyone else has had this problem on their stock Evo.

 

The easiest way to diagnose this is to do a boost leak test. You have a couple options.

For all options you need to make a boost leak tester pipe. I took some stock IC piping from my Talon (because it fits over the turbo inlet), took a PVC cap and drilled in a valve stem and sealed it with RTV.

1) My ghetto way: Go to a gas station with an air pump. Take off the intake and put the boost leak tester on the turbo inlet. Turn on the pump, but make sure you set it low at first (like 10psi). Turn it on and listen for leaks. Get a bottle of soapy water and spray in areas that you think might be leaking. If all is well set pump to higher pressure. Continue this until you find a leak or until you have high enough pressure.

2) Same as above basically, but get an air tank and just fill it up at the gas station and bring it home to do this in the garage.

3) Buy an air compressor and do the same as above.


It's a pain in the butt sometimes but helps diagnose a number of problems. Boost leaks = poop.

 

Do you have a manual boost controller installed, an electronic boost controller, or the factory boost control system? If the factory system and you bought the car used, then you may need to purchase a new factory boost/vacuum line assembly rom your Mitsu dealer, as the previous owner may not have reinstalled the specified factory boost lines which have a couple of internal restrictor orifices.

 

I think thats exactly it. There are several places where I can tell someone has done something to some vacuum lines because mitsu doesn't use zip ties on them. The vacuum line routing to and from the boost solenoid is still in oem configuration, but the lines themselves aren't factory, plus the ends have all been ziptied and the pills that should be in the lines are gone. I like how the previous owner did this without ever installing a boost gauge to confirm what they did actually helped or not. They also took off the hood insulator, never changed the tranny, tc, nor the rear diff. fluids, and there were neon bulbs previously installed. Oh well, the car will be taken care of from here on out.

 

He(the prev. owner) probably removed his MBC before he sold you the car and just jerry rigged some hoses. But there is another detail. 11 PSI is what base boost pressure is without any tension on the WG arm. So, the actuator rod is adjusted to its loosest setting which gives slowest turbo spoolup.

At any rate you can pickup the factory lines preassembled with the appropriate "T" and the restrictors installed, for about $17.00. There are several threads on this forum with installation instructions and schematics.

 

got the stock lines in, about to take a test drive

 

let us know how it goes. the difference in power is night and day

 

i think that's a good i dea to find out....what is leaking

 

Oh yes, the boost is BACK! What goes up (boost needle) must come down (gas needle). I am indeed a happy man.