Possibly the waste gate it being pushed a bit further when in one setting and getting jammed.

Higher boost possibly?

_________________
[color=#000080]ST205 WRC 1994
Hybrid turbo
Apexi AVC-R
Apexi Power FC (Not being used ATM)
Apexi Power commander (Not being used ATM)

You say you get 8 odd psi. Is this reasonably easy to get or do you have to rev the engine out in top to achieve this

If it will hit 8psi pretty easy this is stock actuator pressure give or take. That indicates that the turbo wastegate is acting normally

I think it's a control issue with your ebc

Right I've just spent 4 hours faffing

I've just lagged the charge cooler

Now we undone most of the bolts on the down pipe and used a screw driver as a lever on the down pipe.
No noise was evident of the waste gate snapping shut.
I could not see the waste gate so have no idea if it was open.

what I did find was a pipe from the actuator that has been capped off. The plastic cap had been badly heat damaged and was crumbling away in my hand.
I didn't have anything to had so had to Bodge it for now with RTV sealant.

Now generally I can hit 8 psi really easy. However when I last drove the car it was really hard to get boost. I virtually had to redline the car.

Ill be taking the car out later to see what happens then.

Air leak from the actuator would give more boost. The pressure pushes the wastegate open, bypassing the exhaust gas round the turbine.
Another way to tell if the wastegate is stuck open is to feel round the back of the turbo for the wastegate arm and see what angle it's at. Pic. below shows in it's closed position, fully open is about 70 degrees away from the actuator. (do this cold )



Very poor boost at lower revs would indicate wastegate stuck open, or damage to the turbo wheels.

_________________
If at first you don't suck seed, try drier grain.

Another option

Remove the lambda sensor from the downpipe
Get youself something slim and shiney ( I use the polished handle of a metal teaspoon )
Poke said shiney thing through said hole in downpipe
With some waggling and a torch you will eventually catch sight of the wastegate. Greddymop, who I haven't seen about in ages, even managed to take some pretty decent pictures with this method

If you have convinced yourself the wastegate is closed...
Get a cable tie
Attach it to the actuator rod butted up against the body of the actuator
Now you have a marker that shows if the wastegate is open or shut
Next time it's playing silly buggers just pop the bonnet and check the wastegate position

Right just took her for a spin. Again I had to nearly red line 4th and then hey presto boost is back to normal. I was out for an hour or so and it was fine. I didnt touch the boost controller though.


Popping a cable tie on the actuator arm sounds a good idea. I think I'll try that.

Can you move the actuator arm by hand??

not easily but you can yes.

You should be able to pull the pressure pipe off it and pump it up with a bike/footpump to make it move

One thing I would say is that until you have verified the wastegate is closed just assuming that because the actuator is in the closed position the wastegate is closed is not necessarily true
viewtopic.php?f=2&t=4384&hilit=wastegate