Mods: Fujita CAI, Stage 2, 2.8" pulley, GMPP Exhaust Manifold, XTC 2.5" Downpipe w/ cat, GMPP Performance Exhaust... that's it for Engine Performance mods.

Alrighty... just a quick question on my boostage. I've been running this set-up for a while, close to 10 months to be exact. Right around February, my cat "broke in" (or so JBP claims) and started throwing the P0420 code... inefficient cat. No biggie, I could care less... exhaust got louder, no big deal - in fact I love it. But here recently I've noticed that my boost is topping out MUCH lower than it used to. In fact 2nd gear doesn't go over 15psi at all, and it's not until 3rd gear that it starts to creep up to around 15.5 psi. Now, i know that once the exhaust side of the engine is opened up, supercharged cars "lose boost" because it doesn't have to force that air as hard. My car just sat for 3 weeks while I was with the Marine Corps, and I didn't notice the boost hitting THAT low before I left. Maybe I'm just losing it. The car doesn't FEEL any slower... but I have been driving a 160hp HUMVEE for the last 3 weeks.

My question is simple: Should my Boost drop THAT much? Or should I start looking at other things (i.e. S/C rotors/Boost Leak)? I'm open to options here folks.

I'm cracking the beast open here pretty soon to install my Forged pistons & cams... so I want to see if there was something else that I should consider replacing.

I'm too paranoid.

 

Still the factory boost gauge?? They are known for not being too accurate at times. It's possible that your boost could have dropped a pretty decent amount cause of the exhaust opening up more.

 

Hmmm... I did have thoughts of the boost gauge being inaccurate. I was just curious... I had never seen or heard of anyone on here having that much of a boost drop do to opening up of the exhaust.

 

i have that same code. and i've got the magnaflow high flow, i'm seeing 16 psi max on a 2.9.
2.5" downpipe.. 2.5" catback. this is really all i can say. i dont know why you're seeing less boost. maybe the hot weather? has it been 100+? i think its about 85*F here.

 

i had a problem like that. but all the honeycombs inside my cat were blocking my exhaust all up. when i took my cat off all the honeycombs fell out on the floor. this all happened when i had 5000 miles on it.

 

sweet. now you're catless

 

High heat and humidity will drop your boost level since it makes it harder for the super to move air into the engine.

 

5th gear boost all the was up to 16.5 to 17 today... I dunno. It's probably all in my head, but a LOT of cars have been pulling away from me right off the bat from 35-40 rolls. TURBO Cars that didn't used to do that.

Yesterday, I tore my downpipe off to see what the cat looked like... my lovely XTC 2.5" Downpipe. Took me 2 hours to take it off because one of the bolts on the Mani to DP connection was being stubborn. So I finally get it off and shine a light down the piping into the cat. EMPTY! My cat is empty. Which is funny, becuase when it first started throwing P0420 codes, I messaged Cobalt-Addiction about it... they told me that it was throwing the code because, finally after 10,000 miles and 5 months on my car... it had "Broke in".

FUN STUFF!