Boost drop in higher gears?
 

Ok, I need some advice.

My mods:

Large air filter, piping in 2"5, intercooled, blow-off, cold spark, polished head, new valve guides+headgasket changed 8 months ago, healthy T2, full exhaust line 2"5, standard ECU management in 8 spark head model...

I fitted a MBC, i set up at 12 psi in 2nd gear at same rev in 3rd it dropped at 10, in 4th went to 8, sometimes 6 (not on cheap boost gauge, it's a TIM).

I rechecked all lines (air/oil/water) for leaks, only in steering rack...

What can be checked more?

Who went from MBC to EBC? Does a EVC can hold the same boost in all gears?

Thanks.

The only thing can think of that changes on the car between gears is windspeed out side (because with each gear you are traveling that much faster). Are you measuring boost before or after the intercooler?

Maybe it's cooling the air quicker than the little T2 can fill the intercooler :wack

Either way loose the T2 and get either a T25 or T28 on there ;) :D

Thanks! I'll check the boost before intercooler.

In case of a MBC, must i set in 3rd gear the desired 12psi, despite of spike in 2nd gear?

;)

the best way to check your boost is in 4th gear. If its dropping off i would say your actuator is probally week.

or you have a boost leak, before i got my intercooler setup, i had a small leak in the orange gasket thingy, that did the same, 1st and 2nd wasnt really noticable as you go through them to quick, but 3rd and 4th was very noticable as thats when you stay in it for a longer time.

i would check yer pipes and anything else between the turbo and the inlet.

The orange thing was replace by this: http://img528.imageshack.us/img528/5...e478bm2.th.jpg when i fitted my intercooler set up, i knew it was prone to break.

Tomorrow i'll set the desire boost in 4th gear, will know if in 2nd the boost is stable.

P.S: i checked the timing it's at 15°, warm condition.

Are you agree that in same rpm, i'll get the same amount of boost +/- 1psi?

;)

i knew you had taken off the orange thingy, i was using that as example coz mine did leak, with same effects, when you say boost drops, how far does it drop, also what type of boost controller do you have, if its bleed, it will spike then drop. if you make it run std boost, i.e put the std pipe from the turbo housing to the actuator, do you still get drop???

boost on a t2 is always going to drop off at higher RPM, the exhaust housing is tiny, the T25 does the same thing exactly on the DET

:wack Some news.

Seems I was afraid for my car because if just turn the screw for just an amount to only feel more torque and let it as it is.

I explain, I've turn 3 times (in 1/4 turn step each) the screw now in all gears i've constant 0.6 bars, no drop and a few spike at 1.0 bars. :D I'm very happy! What a car!

When i turn 1/4 turn more, I have the same boost except that the spike goes up to 1b (like 1.1, i mean the needle goes pass the 1b mark on gauge), seems the limit of this MBC (it was sold to maintain 1 bar... but for 15$...).

Thanks for all support seems the next tape will be an electronic devices but really expensive even old ones...

;)

P.S: I love more my S12, what about you?

It shouldnt spike from 0.6 bar to 1.1bar,You still have a problem. Also 1.1 bar will destroy that little t2 and is completely pointless. There is no point in going more than 12psi on the standard turbo.

Have you removed your 'pov' safety valve on your inlet manifold?
:)------------------------edit---------------------

Just found a picture of your engine bay, Get rid of that diaphram dump valve and see if it still does it and im assuming those boost hoses have jubilee clips on them now :)
http://membres.lycos.fr/srteam/IMAGE_2.jpg

So I still have trouble.
Yes 12psi will be my goal, it sufficent for me :p .

I'll check my car to find something later.

Some hints for reflexion: I'm at 3rd gear around 2000rpm, stabilize my cruises. When i went full throttle, it goes 1B and drop to 0.6 (spike appeared) but when i reached 0.6, when i upshifted, no problem it went to 0.6 and maintained the boost until 5800/6000 rpm.

I tested in 4th gear same thing, 2000 rpm, full throttle, spike appeared too :confused:

According to me: perhaps I have a leak hided, the spring of MBC is not enough hard,...

Thaks for all ;)

i think your actuator is week. The actuator cant hold the waste gate back against exhaust gas pressure causing it to open and reducing boost.

i would buy a adjustable actuator from turbo technics (around £80) fit it and remove your bleed valve

http://www.turbotechnics.com/docs/co...t2actuator.htm

Problem solved!

:D

It was the screw that was enough screwed.

No drop at all! Incredible!

Thanks fo all supply ;)