I've got a 3 inch TID w/ cone filter, FCD, Walbro, MBC, Downpipe, and TB mod.



At 5k rpm i hit 10 psi, but then as i hit 5800 it drops to 7 psi and at redline i'm hitting 5 psi. I know that the boost dropoff is normal, but its worse than it was when i still had my cats in. And you notice the car doesnt seem to have much pull past 5k rpm. In fact, i feel a noticeable loss of power. Any ideas? It does this in every gear btw.

Sounds like a vac leak.



My car did the same thing when I went to track and it pissed me off because I shouldve been running alot faster than I was. Next day, took a look at it in the day and one of the couplers slipped off. IT SUCKED.

A vacuum leak could mess with my boost levels that much?



And yeah i know i have a vac leak somewhere cuz my idle is raelly screwy.

look at/ tighten the hose clamps on the ic piping. under vacuum they wont leak that much, but under boost they will leak a bunch more

My buddies car is doing the same thing. What kind of boost do you make in the higher gears?

Bad turbo? https://www.nopistons.com/forums/pub...IR#>/dunno.gif

Do stock turbos/ports hold boost to redline?

no! this is why i keep telling you not to port the black one!

Its being ported right now! WOooOOoT



In all seriously then this is normal???

Boost dropoffi s the same for all gears. And, as to what mike says, i thought you have tow orry about boost creep with mods? And my boost is dropping off a lot. It's really frustrating and feels like i've lost half my powerband. Anyways i'm rippin everything apart and am gonna put it back together again this weekend so we'll see then.

yep, mine was down to 6-7psi by redline from about 11@5000ish

is this characteristic because of the SWEET ass design of the exhaust mani?

small turbine/turbine a/r of the stock turbo https://www.nopistons.com/forums/pub...DIR#>/wink.png

Dude call that Rob guy, I'm tellin ya, he knows his shyte





My 7 is coming together soon, see ya on memorial

The stock turbo wont hold boost to redline. Its a very common problem that almost everybody has. They dont even hold boost to redline when theyre stock from the factory. Only way to fix it is to upgrade turbos.

It could be both. the small stock turbo will not hold boost to redline and a vac leak could easily drop boost that much but the combo of the two seems very likely too.

Are you using the stock Mazda black vacuum lines? If you're using silicon lines that is a BIG no-no. Silicon lines will swell with heat and pop off, and could easily be the problem.



Basically, it's either a vacuum line that's leaking or an exhaust leak.



My brother's T-25 in his SR20DET would spike to like 16 and settle down to like 14 until he is is in either 3rd, 4th, or 5th gear, then it's perfect. It hits 14 and stays right there. He tells me it's his manual boost controller that is causing the leak, but he used to think it was just the size of the turbo. I don't know.



I've got a T3/T4 on my S5 motor, and I'm going to have to use a manual boost controller because I'm not sure what the stock boost on that turbo will be, and I don't wanna blow my motor...:/

Interesting. I'm using some silicone vacuum lines, i've never heard of the swelling thing before. Thanks for all the points on the stock turbo, the reason i'm sure about the vacuum leak. I just always thought that if anything i would get boost creep, because you always hear people talking about boost creep with the stock wastegate.