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hi
i have hks 2871-10 turbos, fcon-pro, and a greddy profec b boostcontroller on my gtr34. normally i drive 1.9 bar in high boost.
the boost always goes up to 1,9 bar but then lowers to 1,4-1,6 bar.
sometimes it stays on 1,9, soemtimes not. it happens more in higher gears.

my actuators are from HKS. i know my 70mm intercooler is rubbish and the air temp goes over 50 degrees in higer gears but this cant be the reason. it also happesn in 2nd gear sometimes.

i think it could be that the hks actuators are not good anymore or it might be because i dont have a hard pipe kit. the rubber between the turbos and the air filters are really weak, i can push them together really easy with two fingers. if they suck together the boost breaks down i guess?

any idea what it could be? i dont want to buy an expensive hard pipe kit or new actuators without solving the problem.



weak rubber pipe is marked yellow
 

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A few things to try.... to keep anglo german relations up. But there are many causes to your problem so it could be quite tricky to diagnose..

The black rubber hose you have identified on the inlet should have a metal spring inside it to help it keep its shape.. it shouldnt be that easy to squish together.. if it is it could be collapsing as you say..

Or maybe you have boost leak somewhere when up at higher boost.. what happens if you set your boost controller to 1.4 bar or 1.6 can the turbos hold that easily or have you had to increase duty cycle on your boost controller to get the same boost level.. If you have your turbos could be dying or you have either a boost leak (the standard piping may not be liking 1.9 bar of boost check it all for splits ntercooler and check intercooler for holes). A good way to test this is to make some custom blanks to blank off the pipes going down to the intercooler and up into the inlet plenum. Insert and glue/seal a tyre valve into one of the blanks and use comprssor to put compressed air into the intercooler and its pipework and see if you can hear air escaping anywhere.

Could be leak to your boost pressure transucer so really you are getting 1.9 bar but your boost transducer is seeing less. I had this happen to me.. A good thing to check is your afm readings if you still have AFM's if they shoot up when at 1.9bar and then reduce as the boost reduces you know that its NOT a boost leak in the piping to your boost controller and that its either turbos dying or boost leak

Then again.. could be cracked exhaust manifolds or leaky exhaust manifold gaskets..


Maybe your dump valve is tired.. try removing it and blanking off the pipework to remove any problems with the dumpvalve..

As i said few things you could try but really your best off taking it to a tuner.
 
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