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Turbosmart Iwg75 & Over Boosting


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  • Member For: 7y 2m 26d

Have talked to a bloke up here with the same actuator and he has it working well with 1.8mm preload. going to leave mine like it is at the moment and leave it on the spring till next year. Shes making 366rwkw on 15ish psi on a 35c+ day so that will do over xmas, a little less preload and 20psi next year :)

Edited by 048oss
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  • 5 years later...
  • Dad Chicken
  • Gold Donating Members
  • Member For: 7y 7m 26d
  • Location: South Australia

There isn't a one size fits all approach to this but if you wanna set it and forget it make it very light.


If you wanna run your boost level at the max the spring will make, you want more preload. If you're running your boost level closer to the spring pressure you want less preload.


If you have a free flowing exhaust you want less preload. With a factory exhaust you can have more preload.


With a larger wastegate you can have more preload, with a smaller hole you'll want less.


With a manual car you will usually want more preload, with an auto usually less.


With a larger turbine wheel you can run more preload, with a larger compressor side you might want less.


Ported housing can have more, non ported might still be sh*t even with the lightest possible preload.


None of this is mutually exclusive, there are exceptions to all of these, some of them mixed will be the opposite, there will be many more scenarios to consider and there is more than one way to skin a cat.


Tl;Dr Set it so the flap is only just closed and then wind the rod about 1/4 to 1/2 a turn more.

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  • Member For: 11y 8m 5d

Maybe a better way to put that question,


If targeting x boost with y spring, assuming everything else being equal and correct, what are the symptoms of too little preload and too much preload.


x =1 * y (I.e. boost 12 psi, spring 12psi)

x = 2 * y (I.e. boost 24 psi, spring 12psi)

x = 1.5 * y (I.e. boost 18 psi, spring 12psi)

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