Out of interest, and possibly to help identify the cause of the boost problem I think that I may now have cured, please can someone identify the components in this photo and what they do!!??

http://www.evolutionmms.co.uk/subaru...components.jpg

A = Boost solenoid(?) - opens and closes wastegate(?)
B =
C =

Also, there is a pipe that goes between the air entry to the turbo and the wastegate which has a T-piece off to component A, which has some sort of restrictor or valve in it. Should it be a one-way valve or is it just a restrictor? Mine allows air to pass through it in both directions.

My other question is that should component A (boost solenoid?) allow air to pass through it at a certain pressure with the power to it switched off (e.g. 40psi) as a safety feature or something? Mine does this anyway (using a compressor to test it and probably had it up a bit high!)

Thanks

 

A = Boost solenoid - alters air pressure the wastegate solenoid sees, which opens and shuts the wastegate
B = MAP sensor - reads the air pressure in the manifold and converts it to a voltage for the ecu to read
C = press exchange solenoid.. dampens the air pressure the map sensor sees so that it doesn't see extreme quick changes or fluctuations (I believe).

Simon

 

The pressure exchange soleniod (C) actually switches the input to the MAP sensor so that the ECU can read atmostpheric air pressure. it does this at several points/times. idle and before startup iirc. it can then compensate for pressure changes, including altitude.

most aftermarket ecu's dont use it.

Steve

 

Thanks guys for the replys, most interesting! I didn't reply yesterday as NTL was down all day.

Someone at work mentioned about the MAP sensor, I didn't know one existed and just thought that he was getting it mixed up with the MAF.

So how about my other two questions:

Also, there is a pipe that goes between the air entry to the turbo and the wastegate which has a T-piece off to component A, which has some sort of restrictor or valve in it. Should it be a one-way valve or is it just a restrictor? Mine allows air to pass through it in both directions.

My other question is that should component A (boost solenoid?) allow air to pass through it at a certain pressure with the power to it switched off (e.g. 40psi) as a safety feature or something? Mine does this anyway (using a compressor to test it and probably had it up a bit high!)

The car is still playing up, cleaning the pipes only fixed it for a short time. I'll price up a new boost solenoid probably and get one anyway if they are not too dear.

Thanks again!

 

Dave,

its actually fromt the compressor outlet, not inlet. and it is part of the boost control system. the air is fed between the output of the compressor and the wastegate and then 'bleed' off through the t-piece to the boost soleniod (A)
the speed this soleniod opens and shuts determins how much air gets to the wastegate , therefore determining how much it opens. the more it gets, the more it opens.

the boost soleniod is just an electronicly operated valve. open or closed. so yes, but 40psi is way outside of its operating pressure!. blow through it, and it should, and if you put 12v's across it, it wont etc...

no, its just a restrictor. with something like a 1.2mm hole in it to dampen the response. take it out and you will get boost spikes etc

if the car plays up boost wise and cleaning the boost pipework and soleniod fixes it for a while, then i would check your oil level isnt too high (3/4max!) and that the breather pipes arent clogged. could also be your turbo giving out a bit of oil. you can take the intercooler off and check the pipework for oil. there should be some, but not masses!

also, whilst cleaning (with brake cleaner or similar) use the 'test' connectors to make the solenoid 'tick' so that you can properly clean it. 2 green single connectors underneath the dash. turn ignition on. fans will come on and soleniod will tick.

Steve

 

Ah, it's logical when you think about it, the intercooler takes the heat out of the air that the turbo has added which is then fed into the inlet manifold.

I was going to set the compressor to 20PSI and see if it works ok with that, if it does the fault cannot be with the boost solenoid.

So it's not that then, I was just told wrong.

I'll check the oil level, breather pipes, and use the 'test' connectors when cleaning the boost solenoid and let you know how I get on.

I replaced the turbo with one that had done less than 40k miles as mine had done 92k and was leaking oil into the exhaust. I took the intercooler pipes off a few weeks ago and there was not a lot of oil in there. I have some Samco's on order and will clean out the I/C when I fit them.

Cheers Steve

 

It seems to be working ok at 20PSI, with the green 'test' connectors connected together you can see the actuator oscillating, if there was a fault at 20 PSI the actuator/wastegate would just stay open.

The oil level is just over half full, not sure what you mean by breather pipes though.
I think I'll wait until my Samco's arrive and see what it runs like with them on, if it has no affect I'll have to take it somewhere.

 

good
breather pipes are the ones that come out of the heads (on the top - plastic moldings)and then from the block. sometimes they can get clogged 'cause of excess oil.
if its 1/2 full , then it shouldnt be that. but might have been coz of your old turbo....
but you've cleaned it already...
what are the actual symptons your getting?

 

In first and second you don't notice anything, from 3rd upwards when you accellerate, the turbo kicks in at 2500RPM, puts you back in the seat, then drops off (i.e. looses all boost) at 3000RPM then accelerates to 3500RPM when the turbo kicks back in again - on/off all the way through the rev range.

I have replaced the MAF (with a second hand one I have to admit) which solved the problem of it stalling, but still the above problem remains.

Wish I had left it alone now!!

 

humm, sounds a bit like what mine does going up a steep hill @ WOT, the boost oscillates. I think thats because i have no restrictor in my 3port setup and possibly the solenoid duty is a bit too high. so i need to experiment this week.

it does sound like its backing the boost off because it is either too high, or not able to control it properly. so it does sound like the cleaning route is a good start...