Hello guys. I just purchased a used evo 8 with 180k on it in surprisingly good shape. I have been working on this thing non stop to fix all the small things that bug me and this is the one thing i just haven't figured out yet.

I just came from a evo x i had since new for 6 years and i dont know a ton about the 8s and 9s.

So he is my issue. I have searched and searched and have tried to narrow down as many things as possible. Im only getting 16 psi peak boost and holding the solid 15psi. I know factory is roughly 19 and will taper down to holding 15. So im holding the correct amount just cant get it to do the factory peak boost.

Car is stock other then a injen intake.
-I have swapped out 2 different boost gauges
-I have boost leaked tested everything and corrected all found leaks including leaking throttle body seals
-It has the factory boost controller hooked up correctly with the boost pills still installed.
-I have swapped out 3 bovs, and am currently using the stock 9 bov.

Any ideas?? This is really bugging me. Only thing i can possibly think it may be now is maybe the catalytic converter is plugged?? But i would think the boost would be alot more affected then just a few psi. Can the wastegate arm be out of adjustment?? Is it adjustable? Maybe someone has screwed with the tune before but its pretty much stock so i really doubt it. These are just the last ideas i have of what could be wrong.

Thank you so much for your input.

 

The WG actuator is adjustable

 

have you checked the turbo for shaft play?

 

I'd check the wga, since you don't have a boost leak. Could be opening too soon.

 

yes, turbo has very minimal normal shaft play.

 

sounds good to me. Let me see if i can dig up the spec for it! Thank you!

 

I am gonna check the preload this weekend and see what i get. Cant find too much info other then setting it to about a half a hole to short. So i will check it and adjust as necessary and see what happens and report back!

 

How often does a wastegate actuator get loose though? Just curious.

 

I wouldnt think very often if ever. But this cars mileage might suggest its been messed with at some point in its life. When i bought it it was only on 7 psi hahaha. Thats how many things ive already had to figure out and fix lol.

 

That's impossible unless it's taken off. It could go bad, I guess. I've never seen that happen though.

 

Possible boost leak. If it really bothers you and you still can't find the problem, check in with a reputable tuner or shop and have them check it out for you.

 

Have you checked the spark plugs? If not, I would look into that and check the gapping. NGK bpr7es at .025 is what i have mine to and it runs fine and no more sputtering as it did with the old plugs.

 

my stock wga went bad, ruptured diaphram, but that resulted in overboosting. I kind of think it would be a good idea to throw a MBC on there just to see if its a problem with boost control or something further up the chain. For example, if you have no problems hitting your boost target with the MBC then you can start concentrating on the stock bcs. If however you cannot, then you can concentrate on the turbo / engine.

 

i did a boost leak test, found a few leaks, fixed them. Still same thing.

 

Im hoping maybe just maybe the spring in the waste gate diaphragm has possibly weekend over time and adding a turn might help a little. Wish full thinking maybe lol!