Overboosting/Fuel Cut problem
 

I have done a search but can't quite find what I am after.

I have a MY00 UK Turbo with standard TD04, exhaust/filter swap and Ecutek remap.

Remapped 2 years ago, very pleased no problems at all until last week.

It was remapped to 1.25bar @ Powerstation.

Last weekend, on way to London I hit fuel cut on WOT in 5th. Boost gauge at approx. 1.45-1.5 bar.

On way home tried not to use much throttle, but it was obvious that it was keen to go over 1.25bar - previously been rock-solid on 1.25-1.3bar (probably down to inaccuracy of gauge).

Apart from overboosting it drives perfectly, no other problems at all.

So could someone give me a list in order of what to check - its due for a service so I'll ask the garage to have a look. Ideally I would go back to Powerstation but its too far.

Any help much appreciated :thumb:

My McRae develped an overboost problem, normally happened in 5th at above 4000rpm.
Turned out it was a split boost pipe.
Might be worth checking.

Boost pipe? Where exactly is that - it sounds similar to my problem as its in 5th I first noticed it, but on saying that most of my driving is around town and I don't really hammer it.

Any other suggestions for the cause of overboosting?

Thanks for that btw :)

What else could cause overboosting?

You might find this article handy.

How Subaru's Factory Boost Control System Works v1[1] 01

Personally I would take it to my local garage, but then I am mechanically inept :D

Overboosting like that is almost certainly due to too much air leaking away from the actuator, so your looking for issues with the hose from the compressor outlet to the actuator and via the boost control solenoid to the inlet hose...you haven't changed the hoses to silicon have you?

Simon

No I haven't. When it was mapped the 2 port was changed for a 3 port, but all hoses are standard.

Ok thanks, at least I have something to ask the garage to look for. I trust them to service, but I just don't know how good they will be at this type of fault finding - hence I want to know what to ask them to look for.

After looking at that diagram on Doc's link (thanks Doc :thumb: ) - I'll have a look myself first.

I know what the various bits are called now!!

Help!!

I took it to the local garage yesterday. Before I went had a look at the hoses, and the two hoses connected to the boost solenoid were definitely looking worse for wear. Where they had been cut, they were slightly split.

Excellent, I thought - couple of quid to fix. Garage sorted the hoses as it was being serviced yesterday.

On way home last night, still overboosting!!


So, is there anything else that can cause this much overboosting? Its going way over where is should - doesn't hold to 1.25bar at all :wonder:

If your wastegate actuator is dead it might not be opening. Try connecting the nipple on the turbo directly to the wastegate actuator using a bit of hose. If your wastegate actuator is working fine, you should see about 0.5 to 0.6bar maximum boost.

Finally cracked it!!

After thinking I had fixed it twice and had not, finally did today - most satisfying so thanks for everybody's help :thumb:

It was a hose problem in the end, the one on the turbo nipple which somehow I missed (and the garage).

Fixed the two suspect splits by the solenoid, fixed dodgy looking one on the actuator. Cleaned solenoid properly with carb cleaner and all hoses, sprayed the actuator with WD40 etc. etc.

Finally noticed the turbo nipple hose was fubared. Fixed that one and hey presto!!! :luxhello: