My 4wd is set to peak at 20psi (stage 1) and has
never gone above this but today it's suddenly boosting to 30psi (max reading on gauge) and car started missing. Obviously backed off straight away and doesn't seem to have done any damage.

Could this be an actuator problem or split boost hose somewhere? Need some ideas please. Cheers.

 

Mate i had the same problem mine was the actuator.

 

Cheers, guess that's the first place to check then.

 

Check that first, don't think it will, normally though I would of thought it would be the opposite, I.E less boost as the spring is weaker therefore not keeping the gate shut, but clearly it can happen as above. Don't think it will be a boost leak as you are reaching that figure therefore so clearly it's reaching the plenum, the missing is probably actually overboost protection.

If not the above maybe something funky going on with the Amal.

Martin

 

Cheers martin. The tuner that set my car up four years ago changed the Amal valve for a bleed valve but I haven't messed with it at all. It's as if the wastegate isn't opening rather than the spring in the actuator getting weak and not shutting it properly.

 

have any vacuum pipes come off?

 

mine did this, wasa pipe to the amel volve had come off

 

I'll check all the pipes tonight. Mine doesn't have an Amal valve as I've got a bleed valve instead. I'll check for splits.

 

Is the bleed valve passing? Try winding it in and se what happens, count the winds thow so u can put it back 2 where it was.

 

cowboy way of tuning as the ecu has now no way of stopping the car over-boost

i would first see if there is split in the boost pipes
buy and refit the amel valve (thats if the chip you have still utilises it)
fit a -31 actuator and have the car properly setup

The amel valve its there for a reason, without it can't moderate the boost you can however fit a Dawes device after the amel valve between the actuator pipe this will stop any boost creep occuring.

The best test you can do is pipe the actuator straight to the compressor housing, given that you have a fully work actuator on i'm sure on a -31 it will open at around 13psi
whatever you do don't just wind the actuator rod in as this will just lead to further damage

 

It was engine advantages that fitted the bleed valve. It has run sweet as a nut up until now so if it's a split I'll just replace the relevant hose. I'm planning on a decent set up with msd in the near future as it's 12k miles since the last set up.

 

Overboost protection will still happen although as you say it won't be able to cut boost, the problem is when people adjust them so you run to much boost, left alone they are fine although they are still inferior to electronic boost control (Amal) as ECU can control boost if ACT'S are to high for example.

I actually forgot about the pipes, check the one that goes from the compressor to the valve and the other one which will go from the valve to the actuator, firstly that they are connected and secondly they are not split.

I was saying if the actuator had gone it's normally the spring that weakens, hence you run less boost due to the actuator not being able to keep the waste gate shut, so the complete opposite to what you have.

Martin

 

it could be the actuator if its seized
a mate had an evo do that

 

Cheers for all the advice chaps. Gonna have a look at it tomorrow. Got some idea what to look for now.

 

Now sorted: I found a half inch section of pipe between actuator and turbo that appears to have melted through - I guess it must have touched the turbo somehow. Anyway I have cut out the melted section and all repaired and cable tied well away from the turbo. Many thanks for all the help.

 

No problem, glad it's sorted.

Martin