exexx

I have a question about the details of wastegate actuator operation.

I am completing the install of a BEGI S3 with a Garrett 2554R on a 2002 NB. I am retaining the stock injectors (same volume as the MSM), so with a higher compression ratio than the MSM, safe fuel delivery will limit me to 7-8 psi of boost.

The wastegate actuator is a PN 480009-9 which BEGI and others list as a 7 psi (adjustable 5 - 11 psi) unit.

Just to check it out (engineers can be ----) I used my hand pump and low pressure gauge to verify operation.

Unattached to the wastegate the rod does not even start to move until 7-8 psi is applied to the actuator. It takes 15+ psi for full rod travel. Yes, I could adjust the rod length longer to open the waste gate, but the effect would be just a constant open position of the wastegate, since the actuator will not even move before I reach my boost limit. Spool will be horrible with an open wastegate.

Is this actuator not acting like a 7 psi actuator (mislabeled part) or are there other factors that I am not knowledgeable of that will lower the effective spring rate in the actuator?

jasonrobo02

iTrader: (13)

There is also the pressure of the exhaust acting on the wastegate flapper.

Doppelgänger

iTrader: (12)

Understand that it doesn't take much of an opening pre-turbine to bleed off enough airflow to limit boost. It doesn't need to open all the way to do it's job.

trakhoar

iTrader: (3)

As an engineer, he should understand this .

If you pressurize a vessel to 10psi...then poke a pin hole in it..what's going to happen to the pressure immediately

18psi

iTrader: (76)

Try telling that to all the people with boost creep.

Full_Tilt_Boogie

iTrader: (1)

What if said vessel already has a much larger hole in it and has a really big pump pushing air into it to maintain the pressure, then what happens when you poke a pin hole in it?

trakhoar

iTrader: (3)

Its no longer a vessel if it has a really large hole in it lulz

18psi

iTrader: (76)

So in other words you're realizing how stupid your statement was and taking it back?

trakhoar

iTrader: (3)

No, not at all. My point was, it only takes a small leak to dramatically lower pressure in a small volume system. Being that the OP is an engineer, he should understand my analogy quickly (engineers like to give other engineers ****).

Look at the size of the bleed port on an MBC...a few cranks to the left or the right can dramatically change boost pressures. Now look at the opening of the waste gate flapper...just a few mm of travel of the rod leads to relatively large leak path, which is why it doesnt need to open fully to maintain 7psi. If it did blow wide open at 7psi, good luck getting it to shut to hold higher pressures and good luck with the resulting boost curve.

Now do you have anything useful to post or are you just going to keep taking pop-shots?

18psi

iTrader: (76)

lol umad?

There's pressure and there's flow. When you have a wheel pushing a ton of gasses into the turbine you have to maintain flow out the wg to keep it bled off effectively to keep from overboosting, and not just drop pressure a little with a pinhole sized opening like you said.

Why do you think pretty much everyone always prefers EWG?

MartinezA92

iTrader: (4)

So under normal conditions, is it safe to assume that the WG arm doesn't actually move much? I've been wondering about this for a while, the arm on the flapper door only rotates about 60-75 degrees before it hits my downpipe.

/threadjack.

trakhoar

iTrader: (3)

Sounds more like you are having issues with your mangina and pissing for no good reason, but I digress. It's called an analogy for a reason, did you ever take a physics class? You know..where you learn the basic concepts of how things work, and then once you understand/master those basic concepts, you can use them to understand more complex problems/systems? Well this is kind of like that

At 7psi..the actuator barely cracks open, because like you said, its a product of both pressure at flow. At this pressure and this flow, the amount of volume that needs to be vented to maintain 7psi is small, which is why the actuator doesnt need to fully open. Thats how a waste-gate works..its designed to open and close quickly to bleed off just enough volume to maintain a given pressure. If it was designed to open fully at 7psi, you would be in world of hurt trying to tune it or operate it under real world conditions.

edit:

trakhoar

iTrader: (3)

Yes and no. It actually has to deal with a lot..it needs to remain shut during spool, deal with partial throttle conditions, and then open JUST enough at full rpm/full load to bleed off just enough exhaust gases to maintain compressor/intake pressures. Obviously at WOT/higher loads its going to be open the most and some cars do see boost creep in these areas of the map if the waste gate/DP cant vent enough air (which is why you'll see guys on here porting their WG exit). If you look at data logs of cars with factory FI or EBC controlled cars, you will see how much action the wastegate gets from the waste-gate duty cycle columns

18psi

iTrader: (76)

Umad FGT?
Can you explain something to all of us then? Why does boost creep happen (or is noticed) most often when low pressure is being ran then?
Why are EWG so much better at controlling boost?

You're not opening any eyes with your shitty explanation of how an internal wastegate operates. Just about everyone here knows the basics.

You're trying to sound smart and failing.

trakhoar

iTrader: (3)

Not at all, aint even mad doe.
Its called resolution. Given the accuracy/limits of a mechanical waste gate, the smaller the scale, the larger the error is as a percentage. Whats easier to measure out...a gallon or cup? Beyond that, if the turbo can flow more than it can vent, you will see creep. Its pretty simple to understand actually
A lot of reasons, generally they are more sophisticated in terms of construction, no actuator slop (ie direct control of venting), are larger in size, dont have to deal with cross flow from the hot side, and many are dual port. However, none of this has to do with the OPs questions of how much his actuator is opening at a given pressure

Obviously you don't if you need to resort to EWG comparisons to explain why and IWG doesnt swing wide open at 7psi. Even EWGs dont fly open at their listed spring pressure.

No, I'm actually just trying to help explain the situation. Where as you are just trying to be a forum hardass. Kudos, we are all so impressed

18psi

iTrader: (76)

EWG is better because it vents better. simple as that. Stop trying to sound smart.
And this isn't regarding trying to explain wg operation, as I've said already captain obvious: everyone knows how it works. Obviously it doesn't need to swing open completely at low boost/part throttle.

This is regarding your stupid *** pin hole vs iwg comparo.
**** off

trakhoar

iTrader: (3)

double noob post

trakhoar

iTrader: (3)

**** that bruh,its because they are shiney and tight too!
**** bruh, just answered the OPs concerns and validated my argument, **** yeah! **** man, learn some ****, ******* ay! Supposed to be a vet and **** man! damn! whoooooooo

That better for you?

18psi

iTrader: (76)

So the obvious response to "umad" is "no umad"......Are you from So-Cal by any chance?

trakhoar

iTrader: (3)

nah dog. I think I may know you from i-club doe, which is why im giving you **** lulz