Weird boost problem, boost dropping off.

[futeki_supra]

so recently my car has been running great at 10psi,
well last night I noticed in second gear, I would build boost hit 10psi around 2700 rpm, and then by like 4.5k it would drop down to almost 6 or 7 psi.

but in 3rd and 4th gear it holds 10 psi pretty steady.
I have a basic ball and spring mbc, kn fipk 3" dp, 3" exhaust.

I am wondering if it is a problem with the boost controller, or my dsm friend said his car was doing the same thing when his turbo was going out, like the turbo was working past its efficiency, but in 3rd and 4th gear it was fine, only in 2cnd it does this...

my turbo has like 178k mi. on it, and has a decent amount of shaft play
but I dunno


what could it be?

 

[mkiiSupraMan18]

Boost leak?

 

[CampbellsChunkySoupra]

hah, i just fixed my first boost leak last night. it was the pipe right off the turbo on the lower intercooler piping. its not hard to get at to check but might be a cause. take ur accordian assembly off, then u can get to the clamps on that pipe and then get under the car and check or just feel. otherwise ur turbo might be taking a poop on u.

 

[futeki_supra]

no I have already checked and fixed all my boost leaks,
I boost great in 3rd and 4th holding a verry steady 10psi, but for some reason in 2cnd gear, I get full boost (10psi) right around 2700, and it holds fine untill around 4600rpm, then it starts to drop off and by the time I get to
6k it is down to 7 psi.

 

[OneJoeZee]

and it holds fine untill around 4600rpm, then it starts to drop off and by the time I get to
6k it is down to 7 psi.

That's normal for a stock CT26.

 

[futeki_supra]

seriously?

it has never done this to me before. it would normally raise to 10psi and hold there through out the whole rpm band. I have been running 10psi for about a week now and it has been fine, just last night it started.