hello, i have an 05 evo. i have been fighting a boost problem for some time. my car will not hold boost. i did the boost leak test to 25psi, held fine. at this point i have unplugged the w/g actuator and wired the wastegate shut! i get a spike to 20psi then it drops al the way down to 5psi above 6k rpm. now if i keep it at part throttle it will hold boost alot better, but as soon as i hit WOT it drops fast.

the car has cams, dv, intake, exhaust, new plugs, apex neo, header, 680cc inj,



i logged a 3rd gear pull and front 02 showed .95 volts timing stayed good also.
the car is new to me and a wild thought is that maybe it has a stroker motor and is just overspinning the turbo. not likely but i think it is either that or a junk turbo.

any help would be nice, thanks

 

that sounds very odd

 

Really odd... I can only guess that it's the DV. Try putting back on a stock valve and see what happens.

 

sorry forgot to add that the dv is a forge and i have adjusted it every way i can. i dont have the old one.

 

So what's the boost control method on this car?

 

wastegate wired shut

 

Could be the WG actuator. My actuator went bad and I couldn't boost right, not even when the WG lines were off. My car would spool to 15lbs and then drop like a rock. Those days sucked...

 

He already eliminated the possibility of it being the WG actuator because he removed it and wired the wastegate shut; which is why I'm guessing the DV. Maybe someone around you has one that you can borrow?

 

If you artificially create boost at the turbo and it holds 25psi then the DV and such should be good to go. The problem then points to the source of the boost... the turbo... Check to see if the exhaust manifold to turbo bolts are tight and the gasket is solid. You may even want to spin the turbo by hand to see if it freely spins.

 

sounds like a faulty dv to me. it doesnt sound like an exhaust leak

 

thanks for the input, i will block off the dv next.

 

Put the stock one back on to see if it holds. I wouldn't block the forge off as bad things might happen.

 

sounds like the dv to me

 

Pull the intake hose of the turbo and grab the bolt that is in the center of the hole in the front of the turbo. Try to move the bolt in and out of the hole. You should have almost no movement. If it moves in and out then you need to look at your turbo. Bad thrust bearing can cause the compressor to machine itself down to almost nothing and produce the symptom you describe. Ask me how I know about this one

 

yes thats true i didnt even think about it til mentioned but my friend has a 240 with a s13 swap and that happened to his turbo