Drop in boost as the car warms up?!

OK, so this one I don't get at all.

Since fitting the hybrids the car was running fine. Went into a garage for MOT and when I got it back took it for a blast. When the car started to warm up (as in after 5 or 10 mins) the peak boost slowly dropped from 1.1 to about .88 bar and stayed around there. Along with that was a very faint whistle noise, not a turbo whistle but like air sucking through a pipe very fast and whistling (like when you breath in and whistle with your mouth).

The loss of boost and that nosie goes hand in hand, but only after 5 mins of driving. Taken the BOV off and blanked the pipes to see if that was leaking - nope.

Only thing that is worrying me is that the temp gauge is fine, as normal, BUT I'm sure the engine bay is far hotter than normal. The metal pipe leading into the intercooler pipe that goes over the induction kit/air box is almost too hot to touch - is that right? Surely that should be just cold air, compressed and on its way to through the intercooler not running at what feels like 80 - 100c?

Let it cool down over night, and it is back to working fine until it warms up and then back to the same low boost?

Any ideas would be very welcome as I am slowly tearing my hair out over this car for the past 3 or 4 months.

why would it be cold? its just gone through your turbos from a already hot engine bay

and warm temperatures outside mean less dense air and lower boost levels

why would it be cold? its just gone through your turbos from a already hot engine bay

 

and warm temperatures outside mean less dense air and lower boost levels

Well I have never noticed that particual section of the system being that hot before. If someone else has noticed this then it would put my mind at rest (or has just literally been out and could pop the bonnet to see what they are like?!). Something is not quite running right since fitting the hybrids, and I am struggling to get to the bottom of it.

It all gets bloody hot, as for the boost drop and noise it sounds to me like you have a vacuum or boost pipe leak that is opening up when hot, have you checked all the vac and boost pipes? especially the silicone ones, i also wouldn't put it past a garage monkey to knock one/damage it.

It sounds too mechanical to be a small hose?! Could something be happening to the turbo getting too hot or something??? I have checked all the pipes (but will probably do it again just to double check.)

Are you still running the mushroom ?

Are you still running the mushroom ?

Nope, Apexi fitted a long time ago (I take it you mean the HKS mushroom I had on it for about a week!). If you are thinking internal engine temps I have a heat shield in there, the filter is boxed off from the main bay.

I have had all the pipes for the VSV's off and on again, and pretty much all the turbo pipework too. Thought I had found the problem (silicone hoses kinked going down to the far rear actuator (EGBV I think) but after fixing that I went out and once engine warmed up straight back down to the same 0.88 bar figure.

If I change the boost controller settings that does raise the boost too, but that noise is still there, the high pitch sucking/whistling noise that comes in with the loss of boost. If I turn the boost down, it still makes the same noise when I reach the peak boost of whatever pre-set I set it to.

This must be something to do with the turbos and boost pressure isn't it? I am fitting UK injectors and EMU in a few weeks time, I'm hoping that once they are fitted this will be sorted but am not convinced.

I am thinking is it a fuelling problem and something is getting too hot? What is this detonation and knocking I keep reading about, is this anything to do with that? I am grasping at straws here I know!!!!

There is one possibility that has just come to me, have you checked the pressure tank is holding pressure, as that is what is used to operate the VSVs and actuators for the second turbo, so if its not working right the second turbo is prespooling but may not be allowed to come in properly, IE the IACV not opening, its a long time since i used sequential so i can't remember to much:)

The hybrids do wine a bit on full boost, you will probably notice it much more than the j specs.

Have you tried pressure testing the full turbo pipework including the IC?

Sounds like you have a leak, and if you can hear it inside the car under boost it'll be a big hose leaking. Check all the turbo to I/C to throttle body pipes properly.

Dump valve leaking? If it's a stock one then even that can make a fair bit of noise when the airbox has been swapped out for something else....

"Taken the BOV off and blanked the pipes to see if that was leaking - nope."

Ok cool, thanks for the thoughts. Why as it heats up though? as the pipe material becomes more maliable? the leak is pushed open due to air flow??

There is one possibility that has just come to me, have you checked the pressure tank is holding pressure, as that is what is used to operate the VSVs and actuators for the second turbo, so if its not working right the second turbo is prespooling but may not be allowed to come in properly, IE the IACV not opening, its a long time since i used sequential so i can't remember to much:)

This wouldn't change with temp/run time would it?!

"Taken the BOV off and blanked the pipes to see if that was leaking - nope."

Doh! Serves me right for skim reading a post after being rudely awaken by my car alarm...struggling to get back to sleep...and then deciding to browse the forum for something monotonous to help me drift off again! Sorry guys - obviously missed that key point!

Could be leaking at a clip or at a split, temperature can make the pipe softer, as you say. that's where I'd initially concentrate a search anyway.

To add, took it for a decent long run on Sunday, and it fixed itself ie: full boost after long run. Took it ouit last night, 1.04 bar until 10 mins in then .82 again with funny noise. Must be something sticking now if it fixed itself afgter running for a bit longer??!

Do you have a boost gauge in the car? you may have a split hose in the cabin, which may be the noise you can hear??

Yes but why would that suddenly fix? i didn't touch anything??