NefMoto

Noob question here:

When upgrading a turbo but keeping an electronic boost controller with an internal wastegate, does the actuator have to match the ebc being used? (Ex: n75 paired with a k03/k04) or does the actuator have to be matched to the turbo?

Im upgrading my k03S to a gt2860rs and have been digging into boost control and pid tuning and im slightly concerned how sensitive controlling the turbo will be to spring pressures, wastegate actuator rod positioning and such.

In order for me to fit the turbo in and get the intake piping where i want it, i will have to clock the turbo  a few degrees which will force me to bend the actuator bracket because it bumps into something, if i bend it into place it may change the angle that the actuator contacts the flapper and may need to be tightened, ive heard if this is tightened too much its called "wastegate cranking" which im trying to avoid. Should i just buy a k03 actuator to match the n75?

I called ATP turbo and they said the actuator i have is rated for 1 bar. Not sure how that relates with an ebc...

Sorry for the noob question, wastegates and turbos still perplex me a bit.

N75 is just a EBC, it bleeds air to control boost it doesn't care what actuator is on the turbo.

The Ecu however is set for the pressure of the actuator and as such is expecting the original pressure spring to be in the actuator. If you have a 1 bar actuator it will not work correctly unless you modify the relevant maps, or tune using fixed duty cycle. Relying on the PIDS to control your boost takes some work and remember also they will only do so upto 22.5psi as thats the limit of the Map sensor so unless you plan on the 5120 hack as well you are going to be limited to what you can achieve unless you spend the time in doing the maps correctly, which is not something that can happen in 1 foul swoop

I dont mind taking the time to do it right both regarding hardware and software. Would it be best you think to use the wastegate that came on the car? Will this limit the turbo's boost range or something?

k03 actuator wont hold the boost tbh, I think you would struggle. Maybe try it and see how it goes and if you end up running 95+% duty and still got power to make then you know its too weak.

I have used a chinese 8psi actuator on my friends gt2860 and that one is perfectly matched to the turbo. I have full control over the wastegate so far (at 1.4 bar) without going over 70% dc. 1 bar actuator seems a bit overkill to me, you wont have any control over the turbo for 2/3 of its range :-\

There are maps to adjust for different wastegate preload.

which gave absolutely great result with a fast-spooling turbos like a 2860

Ok cool, thanks for all the help, 8 psi wastegate actuator and tune maps to suit. Ill study. Thats what i was looking for, what kind of hardware i would need.

You will have to tune for throttle plate angle in any case with an uprated actuator to compensate for the lack of boostcontrol below your actuator spring rate  :)

Anyone have any experience or opinion on the Turbosmart iwg or kinugawa actuators?

You really should learn on a stage 1 tune first :/

Can you share which maps are you taken about?

Also I have read something about differential pressure between exhaust and boost pressure, that generate some empirical functional max boost value up to about two (2) times wastegate spring pressure. In other words a 12psi wastegate can manage up to around 24psi boost. Maybe I am not right but I have read something in the past to avoid exhaust pressure starts to force and open the wastegate. What to think friends?

wiki covers it pretty well
maybe thats true about some turbos but completely not at all. because different A/R etc.
stock k03 with 0.3 bar spring can gave up to 1.4 peak and 1.0 @5000
which isnt *2 at all range :)

Agreed, but currently the K03S in the car is dangerous over 5 psi as I cannot guarantee it is properly balanced and I've already bought a gt2860rs kit so we are too far in to stop now.

I will be putting together a tuning strategy I'm going to post about in a month or so when I have a more concise handle on these things. Turbo isn't going in until I really understand this and have done a bit of limited testing on the setup I have now.

-or-

I may get it professionally tuned using my spare ecu and learn how to tune later.

I agree with fukenbroken, the compressor/exhaust/housing are big factors for the amount of spring pressure you need. My 0.3bar actuator can spike over the MAP limit without problems, only at high revs it cannot hold boost. This is not because the gate is opening, but because the compressor cant deliver enough air anymore. I think it is very important to understand the PR your compressor wants to be in, there is no point in taking a 20psi actuator in a gt2860rs turbo because there is no power to be made above 2.5PR (so even on a perfect intake/cooler system you will not be efficient at 1.5 bar boost).
How much pressure is there in the exhaust pre turbine for a given boost pressure? I don't know... Depends on flow of the exhaust vs flow of the inlet...

I went with the turbosmart iwg75. That way i can trade out springs for future changes, starting with a 7psi spring (i couldnt find an actuator with 8psi) I will be dropping in rods and getting a LSD, coating pistons and higher torque clutch in the near or far future, depending. Air to water intercooler is already in so the boost levels will be changing dramatically over time which may call for heavier springs.

Does anyone know the pressure limits on a gt2860rs turbo?

(http://www.atpturbo.com/root/maps/images/gt28rscompress.gif)

Dont expect too much boost on this thing.. you will need a gtx compressor to be efficient at high boost.

(http://www.atpturbo.com/mm5/graphics/00000001/Catalog%20Images/Turbochargers/GTX2860R-vs-GT2860RS.JPG)

And you're not worried about the 2550 mbar limit? Yea, this isn't going to end in tears.

11 psi will be the limit until i get rods and clutch and lsd. 20 psi after that. Im not mr. Moneybags gentlemen. And yes, ultimately, 5-10 years down the road, there will be some form of gtx or efr in this car. And i will be keeping the car for life.

 Its ambitions will ultimately be involved in rally but not for a while so no big frame turbos. It wont see anything near 2550 mbar

seems like you`ve never take any logs

On the anticipated setup, no. Still working out hardware and learning.

You do understand that when we say 2550, roughly 1000 of that is atmosphere?
So 1550mbar of boost? You said it will never see near that and also said 20psi high boost.
20psi is roughly read as 2300-2400 depending where you are in the world.

no real need for crossing the 2260mbar limit on a gt2860.. if you request 22psi, you will be well on your way to a pressure ratio of 2.8 on most intake/charge setups.