Boost issue- actuator recommendation?

[bigdur]

Took my 5 out tonight for a shakedown after changing the turbo for a t25 and sorting out a weak fuel pump etc, fuelling seems nice now but the boost isn't holding properly.
I've got it set to around 19psi atm, the boost winds up nicely straight up to 19 then immediately drops back to 15/16. Is the actuator not up to the job? If so what would be a good unit for reliably holding 20psi?

Btw, over the winter I'd forgotten how much fun these things are! :D

[bigdur]

Is this a suitable one?
http://www.ebay.co.uk/itm/Collins-Performance-31-2wd-RS-Cosworth-RED-Actuator-/150419236793?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2305af67b9#ht_500wt_1054

[Markey Mark (BD)]

Does sound like a weak actuator mate, yeah that one in the pic should do the job bonus with that one is you can change the spring rating if needs be

[bigdur]

Thanks Mark, is the spring in that one good for 20-22psi?

[Markey Mark (BD)]

Thanks Mark, is the spring in that one good for 20-22psi?

Doesn't actually state what spring is in that one but they are all normally stronger than a standard actuator so you should be able to run abit of boost through that one. If not enough try bleeding abit off and see if it holds nicely when doing that

[bigdur]

Ok, I want to try and avoid bleeds if possible, if that one is good for the job I'll try it out unless the forge or another brand are better?

[SCHWARTZ]

Garrett -31 holds 1.7 bar on mine no bleed valve and still has a lot of adjustment left:D

[bigdur]

Having had a good search round the interwebs and here Garratt ones seem a good bet.
http://www.ebay.co.uk/itm/Garrett-31-Wastegate-Actuator-Rs-Cosworth-Turbo-/280815248345?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item4161e4a3d9#ht_2404wt_1037

[Ian S]

"The -31 actuator has an initial lift pressure of 8psi when used without boost control"

Way back when, in the old days of old, we used the Rally design 'T3' actuator with a Forge -12 spring.

The advantage of that is the diameter of it. The spring is very hard, if I recall correctly about 60 lb. So it completely keeps the turbine wastegate shut, no creep. It takes about 15psi of boost to start it moving with no tension from winding in the the rod. The diameter means it's about 4 square inches, hence 4 x 15 = 60lbs.

Looks like this: http://www.forgemotorsport.co.uk/content.asp?inc=product&cat=0001&product=FMACCOS4

I seem to recall they were nearer to 1/3 of that price though.

Fitting it was a bit of an issue. I had a bracket and rods and longer 'winder' end made. And then the the end can't be pulled over the wastegate spigot due to the 60lb spring. A pump is needed such as a MityVac pushing into the 'boost' side or I think some one was making some fancy adjuster at the 'winder' end so the could be tightened after hitching over. In my case it was possible to hitch it then tighten the bracket back onto the compressor housing, but only with the turbo off the engine.

Once done though, no creep even at 24 psi. Even using some bleed, I seem to remember it just shot up to 24 and stayed there. The memories are a bit hazy at the though, I guess it's been at least 6 years.

http://www.rtoc.org/boards/picture.php?albumid=259&pictureid=2114