7 replies to this topic

[Detta]

Next stumbling block in daily trials. As part of my quest to diagnose why I'm only holding 15PSI boost (when it used to be 18), I have had a look at all the hosing and it seems ok, am holding a vaccume without any issues. I've also read a handy document that Nev was kind enough to send me regarding the workings of a VX/VXR turbo and assosiated gubbins.

 

As such, and having yet to find the problem I'd like to fiddle with my (actuator) nuts to see if it helps as I can't help but wonder if said boost is creeping out of the wastegate.

 

So, If possible, I would like a little clarification as to how best to go about this. I've done a search here and read numerous threads of differing opinion, but none seem to have pictures, and what isn't 100% clear to me is what side people are talking about when they say moving the nuts up or down, or indeed having more or less thread showing.

 

So, to tighten the preload and increase the PSI required to open the wastegate which way do I twiddle?

 

 

 

From what I've read here I assume that I should consider moving the nuts closer to the end or bottom rod (fewer threads)?

I've also googled other forums (Astra etc.) and one chap said it should be adjusted like this to hold 18-20psi of boost (presuming the map is trying for it):



But that looks a little extreme to me?

Any pointers?

[Detta]

p.s. It should go without saying but a HUGE thank you for the ongoing help that this forum and you kind folk provide.

[P11 COV]

More threads where you have marked it will provide more boost.  Strange - your bar doesn't have thread very far up it. Mine is completely threaded all the way.

 

I adjusted mine very steadily by turning the nut a few times, test drive, adjust, test drive etc until is at 18psi. Not having the heat shield in place makes it easier and of course you have to let the engine cool down each time as it gets hot down there.

Edited by P11 COV, 21 April 2014 - 03:51 PM.

[Detta]

The current setting is how it came to me stock as fitted by BoT, which is why I wonder if it's the cause as I know that S4 will be asking for more boost than a VXR astra.

 

More threads provide more boost? To confirm: so there would need to be MORE rod showing under the wastegate to increase held boost?

I was under the impression that less threads where I have marked would increase passive held boost. You're sure about this before I go have a fiddle?

 

Anybody able to tell me how wrong/write my (100% presumed) understanding of the actuator workings are. You'll have to forgive the crappy drawing skills:

 

I thought that the adjustment rod tensions itself against the close wastegate penny and pushes up into the sprung diaphram. Therefore by decreasing the thread at the bottom and effectivly pushing the rod 'up' into the actuator, you are decreasing the distance that the spring can travel, and increasing the tension so that more positive boost is required before the diaphram has the strength to push the spring and atached adjustment rod down to open the wastegate.

 

But judjing by what you've just told me P11 COV, I'm well off the mark!

Anybody else able to clarify?

[Detta]

P11 COV, does your look like this:



Or is it on the opposite?

[P11 COV]

This is mine - the best picture I can get in situ. The way I understand it is that by moving the nut upwards (creating more visible threads at the bottom of the rod) you are preloading the wastegate.

 

This is a thread I started a while ago.

 

http://www.vx220.org...cate-me-please/

 

Edited by P11 COV, 21 April 2014 - 05:49 PM.

[Detta]

Thanks man, you're a legend. I can see from that picture that you have an uprated CMS actuator, I'm running a stock VXR one complete with yellow sticker (that, as I understand it, should still be fine to hold 18PSI). This would explain the difference in threaded rod.

 

I'll try adjusting it with a little more preload and see if it makes any difference.

[Detta]

So I ended up tightening it up 2 full turns of the nut, which equated to about 2 more visible threads down the bottom. Having done some very minor testing, it seems to have elevated the creep issue in 4th and 5th, but not in 3rd. 3rd has improved; it's not creeping down to 15PSI quite so fast, but it's still getting there at higher RPMs. I wonder if it's worth giving it a couple more turns when time allows to see if the situation in 3rd improves?

Edited by Detta, 21 April 2014 - 09:11 PM.