jurassicreps

further to my previous thread about this, i mow have a boost gauge fitted and whats happening is, just under 1 bar boost upto 4500 rpm then it falls back to 0.30 - 0.50 bar.
car is running a fmic, full 3" decat and induction kit, standard td04 turbo.
ecu not remapped yet but will be as soon as i get a td05 or vf35.
i have replaced all the boost valve and actuator pipework but still no different.

njberrie

iTrader: (1)

its overboosting a there 0.8 standard so if ifts trying to boost over 1 bar the ecu will stop fuel it needs to be remapped to exceed 1 bar mate i have a boost control valve and am running 1bar tht way but anything slightly above is a no no mate hope this helps
nathan

Splitpin

Is there any chance, in future, that if you're referring to a continuing problem, you could reply to the same thread rather than start a new one? Keeping it all in one place makes it easier for people to help you as all the information we need is right there.

It's still far from clear what is going on here. As explained below, boost should begin to taper off at 5400rpm. The fact that it is starting to drop so much sooner obviously indicates that something is wrong - the big imponderable is whether the wastegate actuator is being blown open for some reason, or whether the ECU is actually pulling boost.

What, exactly have you done here? When you say you've replaced the boost control pipework, do you mean you've replaced the bit from the turbo compressor output to the actuator (with the t-piece in between)? If so, have you used hard-wall boost-friendly tubing, and did you take the restrictor pill out of the old pipework and re-fit it in the same place in the new bit?

Can you replace the standard induction tract and test with that refitted? Would be helpful to get hold of someone with a diagnostic interface and some software too.


No it isn't, 0.8 bar is not "standard" on a 99-00 UK car. The OP said it was boosting to just under one bar. Boost target on the 1999/2000 UK ECUs is 0.94 bar up to 5400rpm, so his "just under one" estimation is consistent with what it should be. Beyond 5400rpm it should starts to taper back so the fact that it is going over 1000rpm early (and far more violently than it should) is where his problem lies. Fuel cut is 1.21 bar, btw.

jurassicreps

i replaced the compressor output pipe and did put the restrictor pill into the new pipe, also changed the t peice, actuator pipe, pipe to the boost valve, and pipe from the manifold to boost valve. used 3mm samco hose.

it would be a knightmare to change back to standard but a possibility, the last garage i worked has a snap on obd scanner, may be able to borrow it.



it never goes over 1 bar apart from when i drove it earlier with no actuator pipework fitted just to make sure the actuator wasnd holding the wastegate slightly open, didnt take it up to higher revs though, got 1.3 bar @ 3000 rpm.

Splitpin

Is this hose reinforced, or regular single layer silicone?

Not exactly sure what they're capable of and what they're not, but I suspect a generic OBD scanner won't help you much. You really need something like DeltaDash or similar that speaks the Subaru diagnostic protocol - and look specifically at what stuff like the ignition timing, knock correction and wastegate duty cycle are doing around the point the boost starts to disappear. If all the figures look totally normal, you're pretty much certain that the cause is a physical fault in the boost control system - whether in the pipework or possibly a knackered solenoid.

Unless you can diagnose the car like that, you're stuck with a process of elimination - changing one thing at a time until you find out what's causing the problem. If you've still got the original boost control pipework, before doing anything else I'd suggest refitting it exactly as it was and trying the car. If it fixes it, you know what was wrong. If it doesn't make any difference, move onto the next thing.

That's handy to know as that's another potential explanation ruled out.

njberrie

iTrader: (1)

sorry guys didnt read that it was a 1999

jurassicreps

its single skin silicone i think, where can i get the correct piping?


would it be worth fitting a manual boost controller temporarily as i have got one kicking around somewhere?

i cant refit the original pipework as it was pretty perished and when removing the restrictor pill the pipe split, but the problem was there before as i only replaced the pipework today.

jurassicreps

1 other thing that is fitted is a scoobyclinic bov. would it be worth removing this and trying again?

Splitpin

S'alright - it's really Jurassic's fault for not keeping it all in the same thread.

A-ha, single layer silicone expands easily under pressure so isn't really the right stuff for this job. As for the right pipe, any hardwall vacuum/fuel pipe should do you if the original is too far gone to refit.

That won't really tell you anything you don't already know and could confuse things further. Really need to find out what's causing the current issue before you branch off in any other directions.

You could remove it on the grounds that aftermarket dumpvalves usually make the car worse (and non-recircs make it sound chavtastic) but it's unlikely to be a factor in this problem, so for the time being there doesn't seem to be much point changing it.