i have a quick question,
i have a 06 evo 9 mr, its pretty muh stock except a catback and k&n drop in.
i just installed my 3" down pipe a few days ago and discovered a little issue.
(i left the stock catalytic converter in place since i live in CA, plus don't have a HFC yet..)
before the new down pipe my car hit max boost and held it - about 1.25 bars.
after the down pipe i noticed during 1-4 gear WOT pulls the boost spikes at 1.25 bars then drops to 1 bar.
my question is, the downpipe shouldnt have an effect on boost levels due to it not being a resirculationbg part of the turbo system, so why does my car fluctuate boost all of a sudden, just a little prob im having.
thanks for the help guys!

 

Sure it will have an effect on it. You've moving the restriction further downstream, the further back you move it, the more of an effect it will have, once you've removed it you will boost alot more. When I go from the stock cat to a test pipe I gain 4-7 PSI without touching anything else. As you add parts you need to get retuned to make those parts effective, even something as simple as that.

 

so your saying if i put the test pipe on i should see my boost stabilize at 1.3 bars and not fluctuate?
i still need to get a o2 bung welded on my test pipe, would be a cheaper alternative than getting a HFC..

 

Update!

So, I installed my test pipe and am currently running a full 3" TB and K&N drop in.
The carar is noticeably louder, also boost now seems to spike at around 1.4 bars tapering down to 1.2 bars.
But in the higher RPM's, about the 4-6RPM range, the car seems to have a drone to it, it wasn't there with the stock cat. Can this be fixed so that the car sounds smoother and doesn't drone??
Appreciation for any input.