Following a rather protracted and at times frustrating experience of trying to get my car remaped to get it closer to figures it should be producing - we have discovered today that the reason for low boost is looking more likely to be a fault with the turbo.

Having replaced and swapped - wastegate actuator, boost solenoid, checked the dump valve, split hoses, leaking intercooler, seems like the only item which could be causing lack of boost above 1.0bar is the turbo (standard VF48). other mods listed below:

Supertech Pistons
Cosworth H Beam Rods
Nitrided Crank
ACL Race Bearings
Cosworth Head Gaskets
ARP Head Studs
Cosworth High Rev Valve Springs
New Valve Stem Seals
Ported and polished Heads
Top Mount Perrin Intercooler
Full Miltek 3” Turbo Back Exhaust with Sports Cat Downpipe.

Samco Red Hose Kit
HKS induction Intake kit
Stage 1 Exedy Clutch

Turbo was sent away for investigation - returned with NO FAULT FOUND !!
I, my Scooby mechanic and one of the best mappers in the UK are all stumped !!

I know it's going to be something simple - but what???? we are all out of ideas.

Car had a new uppipe month or so back, didnt seem different after that, there was only one small noticable fault which seemed to be getting more frequent - and that was after coming of a motorway (freeway) - 10 miles or so (not hard driving), on coming off and hitting a junction where I was required to stop, the car would often stall? would start again ok, idle was never very smooth and seemed to rise and fall, the mapper guy put this down to a bad previous map, hence the reason why I was having it remapped.

No the turbo will not boost more than 1.1bar, and even with all controls and some pipework removed (which would normally see it run up to 2 bar) even then it wont boost past 1.4bar.

Really stuck for what this could be now - any suggestions are really very welcome.

 

As you have mentioned it sounds like the turbo, if I was you I'd want to put that turbo on another car to prove its performance or put another turbo on your car to see it boost properly.

I only say this because professional or not they could have missed a fault with the turbo and this way you see for yourself.

 

restrictor pill in hoses?

 

Checked the pill, all clear, and on the correct side of the T piece,

Just pulling my hair out !!!!

Even with controls removed (so the turbo could effectively run away) it doesnt see more than 1.4 bar, but there is no audible leak, (which I assume there would be), exhaust is not blocked,

Surely it has to be something simple???

 

say youve checked the dump valve? mine was running rough for a little while because the DV was sticking open and venting pressure. wouldnt of thought it would stick open under load but possible?

 

Tested the DV - with a pressure test (as I thought the springs might be a bit tired), but all was OK -

Keep it coming guys ! one of you may just have that nugget of info that I need.

Scooby specialist now thinks we should start looking at engine ! timing etc..

 

Is this a problem that got gradually worse over time or just all of a sudden ?? Did the problem start after you had installed certain mods??

 

Uppipe to manifold gasket blowing so not getting full on pressure of exhaust gases? Or manifold gaskets?

 

May seem a bit of an odd story, but I'd only had the car since May, and not driven it very much between then and july as I was using another car, one of the few trips I took was to get it MOT'd and litteraly just as I came off the motorway the uppipe fractured, so MOT cost me loads, this was replaced by a new standard Subaru unit, and work completed by the specialist who is currently working on the problem.
After that the car didnt drive any different, maybe a bit down on power, and it did start to stall more often when coming of a mway and stopping at a junction, it would start again no problem.

So maybe there is a possibility of a gasket leak ?? all new gaskets were installed. Turbo is back from being tested so will be going back on again and then another dyno. I assume a leaking gasket would be obvious on the gasket itself once visible ? and probably audible when engine running on boost ??

 

I couldn't hear mine leaking.but it was sorted with a new gasket.
I could feel the leak with my hand.
Could be any gasket before the turbo especially if you keep taking turbo off etc.
I'm not an expert but my power was definitely down with a leaky gasket.

 

cheers guys I'll get them to check and double check the gaskets once its all bolted up together again.