Loss of boost

[Hojo]

I used ECS in CT for my dyno tune. I was happy with their work and my result. I asked for a fairly mild tune. My max boost was 15 psi on the printout from the dyno and on my Cobb to confirm it. 2 years later my max boost is 8. I’m not knowledgeable enough about tuning to know what to do without another dyno tune. I can look at my table with my computer but it’s Greek to me. Any suggestions?

[mikeb75]

That's slightly above stock boost level - assume stock EJ-205 & TD-04 turbo or EJ-257 & TD-05. Without more information to go on, try checking the wastegate lever on your turbo - is there play? If the solenoid goes it won't hold the wastegate closed properly and you won't build boost level. Just spit-balling here, but the tune shouldn't change, so assume something about the engine/turbo/intercooler or exhaust has changed.

[lpmagruder]

Yeah depending on the turbo, that looks like wastegate spring pressure. My '07 EJ255 does ~8-9psi with the boost control system turned off (target boost, and all WGDC set to 0). Wastegate solenoid is probably where I'd start diagnosing.

Another common problem people run into; the short rubber line coming directly from the turbo outlet has a restrictor in it. Sometimes people don't realize, and redo all their engine bay hoses and replace it with a line without a restrictor. I believe doing this will cause low boost, because the boost controller is no longer able to keep up.

This page has a pretty good description of how your boost control system works, understanding it well should help guide your diagnosing: https://cobbtuning.atlassian.net/wik...l+System+Works

[mikeb75]

This!!

Yeah depending on the turbo, that looks like wastegate spring pressure. My '07 EJ255 does ~8-9psi with the boost control system turned off (target boost, and all WGDC set to 0). Wastegate solenoid is probably where I'd start diagnosing.

Another common problem people run into; the short rubber line coming directly from the turbo outlet has a restrictor in it. Sometimes people don't realize, and redo all their engine bay hoses and replace it with a line without a restrictor. I believe doing this will cause low boost, because the boost controller is no longer able to keep up.

The infamous "pill" restrictor. Also, while at it, check for leaks from the solenoid to the boost controller; old, heat-cycled rubber tubes do crack.

[idf]

I used ECS in CT for my dyno tune. I was happy with their work and my result. I asked for a fairly mild tune. My max boost was 15 psi on the printout from the dyno and on my Cobb to confirm it. 2 years later my max boost is 8. I’m not knowledgeable enough about tuning to know what to do without another dyno tune. I can look at my table with my computer but it’s Greek to me. Any suggestions?

I'm responding jointly to this and your other post on MA registration thread as it seems to fit better here. I'm also no expert but agree with those below that the problem is more likely mechanical than tune. Matt tuned my car in 2015 and I found him to be a great guy to work with and am happy with the tune. I'm sure he can diagnosis your issue. I also asked for a mild tune and he came up with 325 hp (more than I need), and said he could have found 25 to 50 more. His recommendations for aftermarket parts included: Cobb air intake, Perrin turbo inlet, Blouch Dominator 1.5 turbo, Cobb EBCS, Walbro fuel pump, Injector Dynamics 1000 injectors. I deleted the TGVs and air pump. Added a Greddy BPV when I changed to an AWIC. I also added a Grimmspeed AOS which Matt doesn't like and feels is not as good as the OEM system, but I didn't have his opinion until I had done it.

[Sgt.Gator]

Could be a boost leak. I've had plenty of them. You need to test the system. The quick & cheap way is soapy water in a spray bottle. Run the engine at 3.5K rpm and spray all the boost tube joints. If you see bubbles that's a leak.
A better test is with a smoke machine. I ended buying my own DIY style smoke tester. I think it was about $80. Or make your own for about $20.
Google: boost leak smoke tester.

[idf]

Happy to loan you my smoke machine.