VNT Turbo gurus, help and ideas please.

[Dum-Dum]

Today I took apart my Holset HX55V to clock the turbo and see how it worked.

As Darren had predicted it is a sleeve movement type thing that I can only assume acts as an exhaust brake too.

Video of the movement here. Essentially those blades go up into cutouts in the exhaust housing.



My question is twofold.
Firstly when you close up the sleeve will the turbo be spinning faster and then when you open it all the way it be like a normal HX55?

Secondly when you apply boost to the actuator it closes the housing/vanes up and I can't mount the actuator the other way around because of the water outlet. Where could I get hold of an actuator where it's rod is out to start with and as you apply boost it's rod gets shorter.






EDIT:

If you look at the below video and picture it looks like Stav (ex Redline Editor) is running his with just a spring holding it closed then opening under EMP?

[Piggy]

Work out what effectively restricts flow from manifold to the turbine...
Because that thus has the effect of increasing EMP and then velocity.
Whatever you use to contril just ensure fail safe is vanes fully "open". Also if space is an issue...try a reverse linkage?

[bashbarnard]

No idea but looks fricken cool


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[Dum-Dum]

Work out what effectively restricts flow from manifold to the turbine...
Because that thus has the effect of increasing EMP and then velocity.
Whatever you use to contril just ensure fail safe is vanes fully "open". Also if space is an issue...try a reverse linkage?

Why does it need to be failsafe? If it jams shut it will instantly kill all the power and I'll have to stop or crawl in effectively limp mode but as I always carry tools I can unbolt the actuator and cable tie the arm in the open position and it's problem solved surely?

And yeah your right, you just put it right in my head, restricting the flow increases the EMP and the velocity and so spins it faster. Cheers buddy.

No idea but looks fricken cool

Thanks buddy. It's all the little bits that get you on this. I could have stayed with the standard turbo but wheres the fun in that lol

[Piggy]

Because if you go for a full power pull... Launch hard etc...

And something goes wrong....you don't want vanes shut at full load/high rpm!!

[Ruan]

It's identical in effect to any variable geometry turbo... It just happens not to use adjustable angle vanes, rather a sliding vane ring.

As you can probably see, as the vanes go further in, the orifice the gas can fit through is smaller, therefore the gas has a higher velocity when hitting the turbine wheel.

Part 1: Don't think of it "like a HX55" without and with you get "fast spool". Since with the vane ring slid back all the way, it'll have an larger effective A/R than the largest turbine HX55. But yes, when the vane ring is slid all the way in and the orifice closes up, you'll have greater EMP and a smaller effective A/R.

Part 2: Best way is to take the current actuator, strip it down and put the spring on the other side of the diaphragm. If not - I've not seen many that are actuated by pressure that pull the rod in, so probably a mechanism to reverse the action - sure there's enough room to fab something up. Seen the same done on a GT2256V down the back of an XUD before now.

The way Stav did it is hold it with a spring on the vane ring lever so it's purely the exhaust pressure causing high pressure on the vane ring and forcing it backwards under higher EMP, then regulate the overall pressure with an external wastegate. Not how it should be done, but yeah, it'll work.



But yeah, tbh, in the case of that car, it's not requiring much boost but has mega exhaust gas energy... Diesels need nearly the opposite of that - they have relatively poor exhaust gas energy but need lots of boost.

[Dum-Dum]

Ruan that's absolutely champion, thank you sir.

Essentially if I flip the actuator (either by rebuilding it or making a linkage) I can run boost control to open the vanes when the actuator sees boost. Obviously it's not as good as proper ECU control but it'll work.