Boost Modulator solenoid/valve

[An old original]

This is the one that sits on the top radiator bracket, has two wires from the front loom and a pipe going down to the wastegate regulator (I think).
Now the first question is how vital is this?
The bulbous end broke off mine years ago and a bolt was inserted and it ran ok. Now with a lovely new engine & turbo, the garage people are having problems getting the mixture right. They're talk about a new carb., which I know is knackered anyway, but I also wonder if this valve might have any bearing on it.

I would probably like to replace both anyway but the second question then is where am I likely to get one from?

Any assistance/info greatly received

Ta

[arrian]

It shouldn't have any effect on it (well I can't see how it would) as its not connected to the vacuum/engine side of the carb. Yes its only connected to the wastegate and the compressor side of the turbo. The valve only affects how much (and when) boost is being produced.

Um I think you'd have to look on ebay for one or maybe someone one here has spares.

Arrian

[G96LUE]

Hi there.

Remove the bolt!!!
The end that broke off is a sort of air stone like you put in a fish tank.
What happens is the boost actuator is set to open at 4psi.
The ecu is connected to the plenum chamber via a pipe that senses the pressure being forced into the carb.
At around 4500 revs it starts to open and close the boost solenoid which fools the actuator to stay closed longer and therefore increasing your boost to about 7psi.
by blocking the end with a bolt you are preventing the pressure from venting and therefore your actuator is opening at 4psi and that is all the boost you are getting.
I havent seen a new one for sale for years.
It isnt crucial though. a lot of turbo'd minis dont use the ecu and therefore don't use the solenoid too. what they use is a bleed valve which they set giving the required boost.
The down side to just using a bleed valve is when the boost cuts in it allows the actuator go straight upto its max pressure and gives high torque. The ecu controlls the pressure and therefore controls the torque and helps save your gearbox.

It wont affect the carb mixture, however if the valve that is sat on top of your servo is faulty it will cause problems. they could try blocking this off as it vents the carb when you turn off the ignition to prevent over run. mine is faulty and Avonbar said the vent hole on new carbs is blocked already so just block off the pipe with a long shank bolt which i did.

I hope this helps a little

All the best

Darren

[An old original]

thanks chaps, good advice.

With regards to the vent valve, yes, I've had experience of this little bugger many a time. I replaced the first one after only about 18 months from new and after another 4 or 5 over the next few years, I gave up.
I've been running with a bolt stuffed up it's pipe for last 10 years or so!!

[paul]

Hi

As Darren says remove bolt, will go much better!!!

Mine is snapped too, I bought a second hand solonoid with a good air stone a while ago but can't find it amongst the parts I have stashed but I will be keeping it as a spare, think I got it on a miss described ebay auction as a vent valve or something.

Paul

[millermilla]

Paul that vent valve was sitting on your desk in the showroom, I remember seeing it when I came to look at my ERA

[G96LUE]

Hi again,
The air stone thingy in the boost valve just acts as a difuser to the air being vented so you don't get a straight jet of air. but is is only air being compressed by the turbo so it doesnt really matter.

The only time you would notice the air being vented is on a rolling road when the bonnet is up, that is unless you are reving the engine over 4500rpm with the throttle lever while your under the bonnet.

I will have a look and see if there is anyway of manufacturing some new ones and i will let you know.

[An old original]

Thanks for all the info everybody, very much appreciated

[kayball]

Hi all.
Just been browsing and found this topic. The 'air stone' on the Boost Modulator was never listed as a spare AFAIK. Just in case you ever find a complete valve assy., at an auto jumble etc., the Rover part number was AUU 1045. It can be found on fiche page K07 under Technical.
Identical to that fitted on Metro Turbo, but most of these have had engine poached and fitted to standard Mini - but you may be lucky!
Regards
Pete K