225 Coupe Requested boost falling around 4k RPM or WOT
 

Hello lovely people! First post here, be kind.

I have an 02 225 coupe. Stock other than a Stage 1 Unitronic Remap. New MAF, N75, DV (stock newer revision), new plugs (BKR7E), new coil packs (stock, newer revision). I tested multiple times for boost leak with my homemade soup can tester (8-9 psi), and I can't find/hear any leaks.

My problem is that my boost falls off when accelerating at wide open throttle. Naturally, I monitored the boost using my OBDEleven (both requested and actual boost) expecting to see the actual boost falling with the requested boost staying normal, but no! I hit solid boost at around 3000RPM, but by 4000RPM the boost drops from 17-18 psi to 8-10. It is especially noticeable at higher gears, when I try to accelerate in 5th or 6th gear. If I apply partial throttle, it will accelerate faster. At WOT it falls flat on its face. Basically the car has good power from 3k to 4k, then feels much slower. I can actually hear the waste gate dump boost when I hit 4K rpm. Here's a couple screenshots to show you.

This is about 5 seconds of full throttle in 3rd gear (the bit between the 2 readings I show). Starting off it looks good to me. Requested boost peaks at about 18psi, with the actual boost catching up relatively quickly. But then, requested boost falls off and settles back down at around 8-10 psi. This is shown on the 2nd screen shot. The hard falloff afterwards is me lifting off the throttle.

Honestly I'm not sure what to think. At this point I am wondering about metering the MAF to see if the airflow becomes restricted when WOT (collapsing air intake perhaps? Was that ever a real issue?) I haven't logged misfires yet, but since the plugs and coils are new, and I can't hear any engine weirdness, I don't think that's it.

Help me Interwebs!

Boost leak under full load. Need to do a pressure test. Use higher pressure similar to what the turbo puts out. Or, inspect the big fat rubber hoses for tears/loose clamps.

Also a chance the actuator on the turbor is not working correctly for some reason. Or, wor$t case, the turbocharger is reaching the end of its' life. https://www.turbobygarrett.com/turbobygarrett/

A reply! Thank you sir.

I went back and pressure tested once again. This time, I found there is air leaking out of the TIP, right at the connection with the PCV hose. Since this is after the MAF, maybe this is the cause - it might lean out as boost builds up. I guess I'll monitor the AFR to confirm this or not. In any case, looks like I need a new TIP.

Stock? ECS Tuning? Forge? Any opinion on what I should get?

ECS does not sell junk. Up to you if you want stock or be able to take advantage of your tune with a different exhaust one day with different engine components.....

Cool. Thanks again for the response! I'll try to get it done tomorrow depending on whats available locally (Vancouver BC). I'll update this thread so this can at least be useful to someone else. Hopefully this is it, but my TT experience tells me there's probably another leak somewhere down the system as well. We shall see.

Well got the new TIP installed today and.....Nope. Feels exactly the same. The hose coming from the PCV valve to the intake is pretty collapsed, but I don't imagine it could cause any kind of boost/vacuum leak, right? I'm at a loss now... I guess the next step is to send it to a proper garage and get it pressure tested professionally. What a PITA. Still open for suggestions.

I know it is an old post, but have you ever found what was the issue?? I have the exact same problem and I don't know what to do anymore???