changing actuator spring rating on standard actuator
Turbo Mini Forums

ok, sorry for all of the straight forward questions - i have just restarted with my turbo build.

i was under the impression that the standard actuator spring could simply be replaced by an uprated one, in my case 10psi

however, on closer inspection today it seems that the standard actuator is a sealed unit? i didnt want to force anything as i feared that this is the case, and i dont want to ruin the standard one for the sake of it.

so do i need an aftermarket actuator or is there a way to dismantle and change the standard actuator spring for the 10psi one?

many thanks

I dont think you can, they were pressed steel iirc

It's sealed as you said, so no you can't really open it to replace the spring. The standard Cossie one gives 10psi I think, this is what a few chaps use.

WWW.TURBO-MINI.COM

i have seen people file around the edge that is folded over, replace the spring and then have a plate either side with bolts to re clamp it, i have a picture of one but cannot find it,
i got 2 for 99p on ebay so not really worth the hasle

Yes i moved to the darkside

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With all the nice stuff nowadays to control boost why not keep std preload and use an electronic valve/controller?

or a very cheap and simple bleed valve.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

cheers for the input chaps. i realise that fitting a bleed valve is quite straight forward, thanks to this site there is a foolproof diagram! however, i have fully rebuilt the car over about 3 years. i have chenged a lot on it, originally going from spi, to run a carb'd turbo engine with megajolt. my reasoning is that i want to keep as much of the engine setup simple/standard, with a view to changing parts when i get the thing running. the less fancy parts the less problems is how i see it. it is my first FI build so there is a lot that can go wrong! however i think i will have to go with the bleed valve. thanks for the input.

can anyone reccomend a cheap tried and tested bleed valve?or should i just look on ebay? am i right in thinking by running the standard actuator will give me 3-4 psi off boost, which i would be able to bleed to 10psi plus with the bleed valve? thanks

you can take one from std mety turbo, and just use a switch to power it, then you have 2 stage boost, just preload a little bit more you actuator to have 6/7 psi of boost

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

We got one from turbo phil, didn't cost much at all. Had a few on his site last time I looked

I used the standard actuator with a bleed valve and some more preload to give 12psi. I couldnt get it to hold more than that.

cheers, thanks for the replys. i have searched on here and also had a look on the web.so it seems i have a few options really

-standard metro actuator with more preload and a bleed valve?

-aftermarket actuator with 10spi rated spring and correct preload

- cosworth actuator, with more preload to give around 10psi?

in increasing the preload am i right in thinking that i have to make the arm shorter?

is there a way to measure preload /estimate boost with a certain rated actuator before the car is run? ie i am tempted to try a cosworth one for simplicity at the moment. i have read they are set at around 8psi, so how do i guage altering the preload to an estimated 10 psi?

when the car is going i am going to use a boost gauge, but would like to get things as near as possible when putting the thing together.

many thanks, dan

and what model of cosworth am i looking for? would this be any good with a 10psi spring fitted (i already have the spring). thanks

http://cgi.ebay.co.uk/RS-TURBO-COSWORTH-AL...=item43a50ce384

I have spent a good few hours looking into this and still haven’t come to a definite conclusion.

I am now thinking along the lines of a cosworth –31 actuator, set with 1mm preload from the wastgate being closed. I have read on here that this should give around 8psi? and that each complete turn of the thread will give aprox 0.5 of psi boost extra?

Does this sound about right to people? I want to get this as near as I can now at this stage of the build. Once I can clarify whether this sounds about right or is miles off (!) i can get on with putting it all together.

Many thanks, Dan

I have found by experiment that no matter how much you try to work out what boost you will get from any particular actuator/spring/bleed valve it ends up as a suck it and see job.

Just try the -31 actuator with the usual half a hole preload and see what you get, Bleed valve is easy to fit and adjust afterwards.

cheers, i think i will go with this idea. hopefully it will give me a base boost of around 8-9psi. many thanks

Schrödinger's cat - so which one am I ???

cheers rod, i did see this when i searched, but wanted to be absolutely clear on things. if the stardard -16 one boosts at standard 7-10 psi, is this in conjunction with a bleed valve as per the -31 ones?

if so the -16 would be looking at maybe 5-7 psi?

i have seen a couple of the -31 actuators for sale second hand, but havent been able to find the -16 rated ones.

if all i can get is the -31, if i ran this with a slightly longer arm, giving less preload, would i get the same desired effect of 7-10 psi?

i will also be looking at tac welding a nut onto the arm for ease of in car adjustment as stated on this site elsewhere

as stated this is my first forced induction engine, i am coming to terms with what does what. i just want things to be as good as they can be.

the feedback is much apreciated,

dan

Edited by welshdan on 13th Feb, 2011.