Actuators,preloads and turbo spool.


Ok just wondering about different actuators, preloads, and the way the turbo spools.

After reading the below thread for the forge actuators and them mentioning spool up pressures as well as operating pressures I am wondering if all actuators work the same?

After fiddling with a forge actuator on my gtir and a adjustable td actuator on my uno I would say that forge are proberly correct,in that increasing the preload does not really affect the springs running pressure to much but affects the spool up pressure?

But then you read about people on other forums ,like the ford fellas, that adjusting the preload gives you more boost over than what the spring is set for?
Is that just because the wastegate is now restricted in how far it can open?
Or is it because some actuators are designed differently in spring designs,either way if you go to far with the preload what ever the spring its possibly going to decrease the wastegates travel, and possibly give you boost creep at the top end if your not carefull?

The reason I ask is because I have just got a td turbo with a surposibly 1 bar, possibly garrett actuator,just to pull by hand off the turbo it feels very stiff when compaired to my 1 bar forge.
The thing that worried me though is the garrett seemed to have proberly 10mm odd of preload on it,it was completely clear of the wastegate pin once it came off!
Forge and the regular way to setup is 2-3mm off the pin,around half hole offset from the pin,although I generally add half a turn extra or ¾ hole offset max.
I have not checked it yet but with that amount of preload I am guessing that it would have been affecting wastegate travel also.
Or is this how you set a garrett actuator with extra preload like the ford guys do to gain higher boost,I am not so sure about all that tbh.

So back to the 1 bar forge actuators,I can understand why it is easyer to pull than the garrett if it is designed differently,as forge springs are conical and for a 15psi running pressure spring they are quoting 9psi for the spool up, so it will be easyer to pull.
Do all actuators have this spool up pressure before the main pressure or just forge,I can see that having a progressive spring/ spool pressure should help eliminate spiking, but is it needed and on all actuators?

Also with this spool up pressure,does that not mean that its possible to be losing some spool up time, if say for instance you are wanting to run 1.5+bar on a 1bar actuator (with a spool pressure of 9psi )and a boost controller.
I am not 100% sure how most boost controllers work valve wise during spool,full shut,full bleed or straight through actuator pressure.
Going from what I have read about the avc-r I would guess just actuator pressure until it reaches the desired boost level then it starts bleeding?

I say this as I have read about ramping up the boost with the avc-r to basicly keep the wastegate fully shut and improve spool,I would guess most boost controllers are the same?

Setting the AVCR to ramp the boost up as fast as possible;

Another great aspect of the AVCR that can be acheived from the RPM specific adjustment is the fact that we can keep the wastegate closed 100% at early RPMs to help bring on the boost a lot sooner. This is a little bit complicated to get 100% accurate so we will just set this at an average (safe ) setting. Go and check your boost level again, and this time monitor when the AVCR comes onto full boost ( most cars with smaller turbos should acheivethis around 3000rpm ) basicaly when we have learnt where full boost occurs on the RPM scale, simply take 500rpm off this number and we get an RPM number that i like to call a SAFE rpm zone. A area of the RPM where the turbo isnt ramping up very hard and an area that can withstand the wastegate being 100% closed and not getting any spikes from it.

Now we can go along in the RPM/duty adjustment graph and take the lower RPM points including this SAFE RPM zone and below up to 90% dutycycle.

So surely running high boost with a low spool pressure actuator spring is going to hurt your spool up time?

I also beleave I have notice this on my uno,running a 14-15psi ish actuator it seems to start to open at 6-7psi spool up,and with the period lol bleed valve open (same sort of thing as avc-r 90% duty above?)it seems to spool a touch quicker and noticeably harder.

I also wondered if in some cases with a weak spool up pressure if it could cause the wastegate to get blown open in the high revs?
The reason I mention this is because my old nd 1bar forge actuator on stock turbo and elbow, with 3/4hole preload used to hold a perfect 1bar but majorly dropped in the high revs,no matter what I set the boost controller to?

Anyone else had issues with forge actuators?

Is it me over setting the preload?

I thought it might possibly be a problem inside the actuator,but I have recentally stripped it to replace the spring and replace the diaphragm and its as new in there, so i am still unsure why I had the problems with the boost dropping.

Anyway I have now gone with the forge blue 14/18psi spring and half a turn extra preload,I cant over do it as I am using a .64 hot side and don’t want any creep,but if the above is correct I may have a play with the avc-r when the time comes.

What do you guys think?
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