so it goes as follows... my evo has recently been acting a little funny with boost. a few weeks ago, i dont know how this happened, but the black elbow pipe coming off the turbo was loose as f*** so i tightened it to the max and checked all my t-bolt clamps to make sure they were tight. i noticed that on my stock MR gauge still wont hit over 1.0-1.2 kg/cm2 which is 14-17psi. i checked all vac lines including the dreaded one on the egr valve. i dont know if this is because of the weather or if its a leak or *knock on wood* bad turbo. car has 43k miles build date 08/2005. mods are Greddy catback, ebay interfoooler, injen piping/intake otherwise bone stock. my friends tell me it still glues them to the seat but idk.

BTW on my stock gaugs when the car is turned off the boost needle sits a line below 0 so i dont know if maybe the gauge is off? and yes my boost pills are present. please help me diagnose this guys!

 

Step one should be to perform a boost leak test it hard to visually find a boost leak if it's something like a split coupler or cracked pipe.

Here's what could be wrong with the turbo that would cause what you're experiencing.

- Turbo is beginning to seize up due to improper lubrication. This is easy to check pull the intake hose and see if the turbo will spin freely, if it does move on. If it doesn't then you already know the answer.

- Compressor wheel has FOD damage. Something small might have come off and got sucked through your turbo and resulted in damage to the inducer tips of the compressor wheel. Easy enough to check with the intake pipe off take a peak at the wheel and inspect for damage.

- Turbo is rubbing/scraping on the housings due to axial/radial play. Again easy to check with the intake tube off rotate the wheel and push it up/down and side to side as well as in and out and see if you're able to get the compressor wheel able to touch. If it does well again you know the answer.

- WGA actuator is broken and allowing for the wastegate to be blown open at lower than target boost pressures. You can test this by hooking the WGA up to a regulated air source and slowly turning the pressure up. If it's a stock WGA it should open at around 15psi or so. A good tug on the WGA arm might tell you something as well. This is unlikely though usually when WGA feel the diaphragm gets damaged and they don't open at all, but you never know.

- Waste gate flapper door is broken, there have been instances, very very rare instances, where an MHI housing has a flapper door failure. Where the door actually separates from the arm and doesn't cover the hole completely. This is a little more difficult to check and requires you remove the o2 housing and inspect.

- Turbine wheel is missing part of it's inducer tips due to FOD. Your motor has spit something out taking half of the turbine wheels inducer tips with it and this reduces shaft speed. If this has happened you'll know soon enough because the turbo will develop shaft play pretty soon and then fail in a most spectacular way. The only way you can properly check this is remove the turbo and the turbine housing. You might get away with inspecting it by pulling the O2 housing but if the damage is only on the inducer tips you won't be able to see anything.

Good luck.

-Michael

 

Thank you Michael for the quick response. I just went out pulled the intake pipe off an everything on the compressor side looks healthy. No radial play and shaft play is minimal (1-2 mm at most) but I figure that's due to the engine not running. I gave the wga arm a tug and it gives force and I can hear/ feel the flapper door opening and closing. My next step will be testing for leaks. I also took the heat shield off the mani and looked for signs of exhaust leaks anywhere but came up with nothing and all nuts and bolts are tight. I do know for a fact however that I have a slight leak between the cat converter and cat back. Can that be related?

 

Are you able to easily pull the WGA arm open and closed with your hand? If so that's probably your issue.

- Michael

 

Well i made a leak tester this morning hooked it up and voila! 3 couplers leaking, 3 injectors leaking, and throttle body seal leaking!!! i set my compressor to 20-21psi and my gauge was showing the same 1.0 kg/cm2 as it does when im driving.

 

no its hard to pull it gives alot of force

 

If you are running a stock tune and boost control system then you are in the right range since stock gauge isn't exactly 100% accurate. You have changed parts so I would not expect it to run 18-19psi like it does 100% stock. I suggest you get the car tuned so you know that it is running correctly. Don't be surprised if a bone stock evo is faster than your car.

 

everything was good until about a week ago my gauge was hitting 1.3-1.4 and pulled hard but at this point a geo metro is faster lol. mil spec shaft seals and new injector insulators are on their way along with two new couplers for both sides of intercooler to replace the stock couplers i was using there. if all goes well a good tune will soon follow.