Toady1
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| posted on 18/12/07 at 04:49 PM |
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how a turbo actuator works?
just wondering how exactly an actuator on a petrol turbo works. Does it rely on vacuum pressure from the inlet manifold pulling on the diaphragm in
the actuator to open the wastegate? Therefore a stronger spring in the actu will provide more turbo pressure before the wg opens and vice versa? also
by lengthening the act rod the boost is increased...
Or am i totally wrong? trying to get the boost on my skyline down!!!
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imp paul
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| posted on 18/12/07 at 04:58 PM |
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re turning your boost down
to up the boost shorten rod to turn down lengthen rod  hope that helps
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MikeRJ
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| posted on 18/12/07 at 04:59 PM |
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quote:
Originally posted by Toady1
just wondering how exactly an actuator on a petrol turbo works. Does it rely on vacuum pressure from the inlet manifold pulling on the diaphragm in
the actuator to open the wastegate?
Nearly, but it relies on positive pressure in the manifold pressing on the diaphragm to open the wastegate.
By fitting a stronger spring, or shortening the actuator rod (i.e. applying more pre-load to the spring) you can raise the boost level at which the
actuator opens the wastegate.
Easier to use a pressure relief valve to adjust boost pressure though. This is a little device that sits in the pipe between turbo outlet and
wastegate, and won't open until a pre-set amount of pressure has been reached, which keeps the wastegate closed until the boost pressure you
require has been reached.
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Toady1
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| posted on 18/12/07 at 05:04 PM |
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yes ive used dodgey things like bleed valves on the old 5gtt's i had years ago, but my skyline is running at 1.2 bar boost with HKS actuators
on. This is too much for the R34 turbos as they have ceramic exhaust wheels that like to break above that and quite often killing the engine in the
process. I spent the best part of 3 hours today getting to the barstewards to shorten the rods on the turbos, as I was told to shorten them by a well
know tuner! I though shortening them made it boost more but hey! Well ive shortened then by about 8mm, but it is still over boosting?
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imp paul
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| posted on 18/12/07 at 05:07 PM |
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no don't shorten
you have just up ed the boost you need to lengthen the rod 
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MikeRJ
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| posted on 18/12/07 at 05:08 PM |
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Every setup I have seen has the actuator pushing rather than pulling, so the rod needs to be lengthened to reduce boost. Perhaps the Skyline is
different in this respect.
Changing the length of the rod only varies the preload on the actuator spring, if it's long enough that the preload is reduced to a minimum and
your still have too much boost then the only thing you can do is change the actuators to lower pressure items.
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Toady1
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| posted on 18/12/07 at 05:50 PM |
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cheers guys, thats what I thought. I do have the std act to put back on, but when i got all the plumbing out the way i realised what a bugger it was
to get them off with them in situ! so shortend the rods.
Its really annoying not being able to use full throttle!!!! aarrrgghhhh!!!!
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zzr1100rick2
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| posted on 18/12/07 at 05:50 PM |
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they dont have a pre drilled brass plug in the accuator pipe do they like on subarus if so it needs the orrifice altering
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Toady1
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| posted on 18/12/07 at 06:15 PM |
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no i dont think so.
The system is running a closed loop at the mo, ie the std boost control solenoid is dissconnected so that there is no boost bypass on the actuator
system. This was dissconnected prior to adjusting the actuators as it was boosting even more! 1.5bar!!! Ive not reconnected that yet, but its confused
me as to why the system is running at 1.2bar+ when there is technically no air being allowed to run through the circuit due to the std boost solenoid
being closed constantly?
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MikeRJ
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| posted on 18/12/07 at 11:00 PM |
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quote:
Originally posted by Toady1
Ive not reconnected that yet, but its confused me as to why the system is running at 1.2bar+ when there is technically no air being allowed to run
through the circuit due to the std boost solenoid being closed constantly?
The boost control solenoid does exactly the same thing as the bleed valve you used on your R5, but under control of the ECU, i.e. it bleeds off boost
to make the actuator "see" less boost pressure than is actualy being generated.
If you are running at 1.2Bar with the solenoid disconnected, this is purely down to the operating pressure of the wastegate and the pre-load on it
(rod length).
One point worth mentioning, if the rod is shortened too much the actuator may not be able to open the wastgate far enough to control boost pressure,
this would present itself as boost "creep" at higher RPM.
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craig1410
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| posted on 19/12/07 at 12:45 AM |
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Hi Guys,
I can't remember where I read it but I remember reading that messing with the actuator rod length was not a good way to adjust boost level. I
think it was in a David Vizard book on engine tuning that I read this but wherever it was I remember it as authoritative not just rumour. As I recall,
the actuator length is fixed with respect to the wastegate range of movement and the range of movement expected at the actuator for a given pressure
level. I think you are risking premature actuator diaphragm failure if you go outside this range if I remember correctly.
Anyway, the better way to adjust boost level is either using a bleed valve or an electronic boost modulator. The bleed valve will simply bleed away
some of the pressure from the actuator such that it "feels" less pressure than the engine and therefore opens later. Very cheap - all you
need is a fish tank aerator valve or similar and a t-piece.
The electronic modulator allows you to map your levels of boost in whatever way you see fit. The big advantage of this approach is that you can reduce
boost in the mid range where the turbo-torque might be likely to damage your clutch or gearbox while maximising torque and power higher up the rev
range. This gives you the feel of a large capacity V8 with a big f(l)at torque curve but without compromising gearbox reliability. Also lets you drop
back to normal boost for poor conditions or to save fuel.
Cheers,
Craig.
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MikeRJ
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| posted on 19/12/07 at 08:44 AM |
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quote:
Originally posted by craig1410
Anyway, the better way to adjust boost level is either using a bleed valve or an electronic boost modulator. The bleed valve will simply bleed away
some of the pressure from the actuator such that it "feels" less pressure than the engine and therefore opens later. Very cheap - all you
need is a fish tank aerator valve or similar and a t-piece.
Unfortunately neither of these devices can reduce boost below the operating point of the actuator, only increase it.
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Aico
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| posted on 19/12/07 at 09:51 AM |
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Isn't the HKS one adjustable? You should be able to download some instruction manual about it. If that doesn't work properly then just get
stock actuators back on there.
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Toady1
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| posted on 19/12/07 at 11:10 AM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by Toady1
Ive not reconnected that yet, but its confused me as to why the system is running at 1.2bar+ when there is technically no air being allowed to run
through the circuit due to the std boost solenoid being closed constantly?
The boost control solenoid does exactly the same thing as the bleed valve you used on your R5, but under control of the ECU, i.e. it bleeds off boost
to make the actuator "see" less boost pressure than is actualy being generated.
If you are running at 1.2Bar with the solenoid disconnected, this is purely down to the operating pressure of the wastegate and the pre-load on it
(rod length).
One point worth mentioning, if the rod is shortened too much the actuator may not be able to open the wastgate far enough to control boost pressure,
this would present itself as boost "creep" at higher RPM.
yeah i understand what you're saying cheers, i think the problem lies in the HKS actuators. They are meant to have more than std boost pressure,
about 1bar iirc. Im guessing they have been played with to get more boost by the guy who fitted them! Ill check what theyre opening at with a pressure
gauge and air line on them and try re-adjusting them that way.
Thanks for all your help guys!
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