Hi all,

For some reason in the last 24 hours, the car has started to cut out momentarily under full boost at high revs. This only seems to happen so far in third (but I haven't had the chance to try 4th & 5th yet), and doesnt happen everytime.

I immediately think that a fuel cut out is kicking in because of overboosting.

Thing is, the boost gauge is showing my boost at almost 30psi!!! Granted its a crappy type R effort that is defo not accurate (would have been about £15 off ebay), but it used to only go up to about 20ish beforehand. There is every chance the gauge is misreading, but I can't help but think this is more than coincidence.

Would a turbo suddenly start boosting more for no reason? The car has no mods other than induction and exhaust. Im understandably worried so any advice/ things to check would be much appreciated

 

boost control pipe has come off actuator at a guess

 

Good call mate but the actuator pipe is still on. Infact, all the pipework seems to be fine. Would this sudden increase in boost generally come from a leak/ disconnected pipes?

 

yup, if air pressure to the actuator is being lost it wont open. Check for split pipes as well as pipes that are clearly off.

 

Could be a number of things, I would first check all boost pipes are not leaking from joints or pin holes. Then clean out the boost control solinoid if that fails I would run a boost pipe straight from the turbo to the actuator so that it runs on actuator pressure about 7psi this will check that the actuator is still working.

 

As Paul says, the pipework you need to concentrate on first is the vac plumbing between the turbo compressor nozzle... to the BCS... and onto the the wastgate actuator. Also check the vac line from the inlet manifold to BCS's MAP sensor.

If all okay, then check all the other vac lines.


Plus do the w/g test as burbling mentions... Indeed, I'd do that before anything else just to make sure (you could be wasting effort/time otherwise).

 

Cheers guys, I really appreciate the help on this one

I went out again to check and one of the pipes that runs from the t-splitter at the actuator end just snapped when I moved it.....about 6 inches of pipe was completely brittle ! I've changed it while at work but not yet had chance to run the car, will see what happens when I go home. As a matter of course I will check out the remainder of the pipework over the weekend, taking into account the above advice.

Another quickie, what vac pressure does a classic normally run at tickover? Mine seems to be hovering about the -20 mark.

 

Yeah, vac and coolant hoses can get really brittle and fragile between the 10-15year mark.


What units is your vac/boost gauge calibrated?

If I can recollect, I think - although not totally sure! - a totally closed throttle at a steady, warmed-up idle produces something like -0.5 to -0.55kg/cm^2.

I think this "kg/cm^2" unit is numerically all but the same as "bar", therefore it equals circa -0.5 to -0.55bar too... so easy to remember.

 

there is a brass restrictor in the pipe from the turbo compressor housing to the T piece that broke, make sure you don't lose that if you replace the pipe or you will have 7psi of boost.

 

Good point!!! ^^^

 

teemsta.

Just checked my boost gauges today and at steady idle on a thoroughly warmed engine, my aftermarket gauge reads -0.7 bar and the OEM Lamco one reads -50 cm Hg (which is indeed the equivalent to -0.7 bar).

I forgot to check the Commander's reading - I'll do it when I get in tonight...

However, if your gauge is calibrated in in Hg (inches x mercury), then it will indeed give a reading of -20 in Hg, which you say yours is showing.

HTH

 

Cheers Joz for that update on the boost gauge....

Just thought I would share where I am up to with this. I have now changed all hoses leading to/ from the actuator, turbo, and boost solenoid. The pipe was supplied 'FOC' from work but unfortunately no joy

Plan today is connect the actuator to the turbo with a single pipe as mentioned above, plus put the car in test mode and clean out the boost solenoid with some brake cleaner to see if that helps.

Until this is sorted I have decided not to boost the car if poss to stop anything going pop...

 

Yeah, defo make sure the OEM boost system/target is spot on before even considering upping boost, etc.

Hope you get it sorted...

 

Ok guys, I just put a single pipe connection between the actuator and turbo outlet and went for a run.

The car boosted up to 12 PSI and would not go any higher in all 5 gears. Considering it was hitting almost 30psi in 5th beforehand this is a pretty significant change! Now, I know I mentioned above that the gauge is probably misreading but this seems high nonetheless. Do you reckon the actuator is actually ok based on this?

 

just a quick one, when you replaced pipe work i take it you put the resrtictor pill in new pipe work?

 

teemsta, as mike says, is the restrictor pill still in.

FTR, the raw boost level the wastegate allows is in the region of 0.5bar (7psi)... so 12psi is getting on for double that!

 

teemsta, do you have another boost gauge that you know works properly (say, from a mate's car) that you can temporarily use, just to rule it out?...

 

I did put it into the new pipework I installed, but not into the single pipe I used to test the actuator. Should I have?

 

Yeah, Commander corroborates all of the above - it reads -500 mm Hg which is obviously the same as -50 cm Hg.

So, depending on what your gauge is calibrated for vacuum, then a warmed-up steady idle should yield an inlet manifold partial vacuum of:-

bar = -0.7
kg/cm^2 = -0.7
mm Hg = -500
cm Hg = -50
in Hg = -20

 

Ok, so it looks like I've cracked it! Another problem has raised its head but Ill go into that later......

To help anyone else, I did the following:

- Cleaned out boost solenoid with brake cleaner by putting car into test mode and spraying it into inlet (connected 2 green connectors under steering column, turned ignition on and relays go on/off continually)
- Changed ALL pipework to/ from actuator, solenoid, airbox, maf with silicone hose (making sure I retained brass restrictor pill)
- Checked actuator operation by connecting pipe between turbo outlet and actuator to check it works (should run about 7psi but mine ran more like 10-12 )
- Checked wastegate wasn't seized by connecting bike air pump to actuator outlet and lightly pumping to see it open/ close

Any of the above could have helped, but I have a sneaky feeling it was cleaning solenoid.

So onto the new thing. Went out for a celebratory run, was driving the car pretty hard on the dual carriageway and it was boosting great in every gear. When I stopped at the lights and set off, the car now wouldnt boost past 10psi! Felt kind of like a 'limp mode', but no faults came up on the ecu when I checked and car ran great apart from this low boost. It was like this when I went out again this morning, but on way back it started boosting like normal again! Hope it was isolated case, but I'd still like to know what happened. Any ideas

 

I suppose it couldv'e gone into limp home mode temporarily. Normally 7psi (but your "7psi" seems to be 10 lol).

If it does it again, post up et, and we'll all try to bang our heads together, etc.

BTW, after replacing all the vacs/cleaning BCS, did you reset the ECU before going on that test drive?

 

I think everybody should get the same gauge as me, its even optimistic in bloody limp mode!! Didn't reset ECU before test drive no, but have done since and done it again once car reverted back to normal.

Will post up if it happens again, but for now cheers for all the help its MUCH appreciated

 

My car haz now started doing this too it was nealy 30 psi have checked pipe work all seems ok. Can here a clicking noise when turning my ignition on and off is this boost solonoid.

 

Clicking is probably the boost solenoid valve.
Note. 30psi, even briefly on a standard Subaru engine is enough to total the engine.
Start by thoroughly checking the pipework and wiring on the boost control lines as described above.

 

Its holdin boost though not leaking ordered another boost solenoid is there a way of testin the old one or would it show up on a obd check

 

I got fault codes 44 and 45which are pressure control and sensor also 23 which is maf sensor is 44 and 45 boost solenoid

 

Run the ECU reset. The process automatically checks all the sensors, inc. the BCS. If working okay, you should hear it rapidly clicking away.

Also, some of those codes may well be historic, so some may go away after the reset. Do the reset first and see what's thrown up...

 

How do you do reset. A few weeks ago my so called mate cleaned my engine with some cleaner it got into maf and boost solenoid and its played up since then

 

Next time you clean the engine remember to protect the electrical parts with plastic bags and dont cover over the top with the jet wash