PSA: Internal Wastegates and ATP turbos

[Lex]

**This applies to all MS3/MS6 years and models. Really this applies to all turbo cars.**

Alright boys and girls. I have seen this happen so many times now that I feel it should be common knowledge:

The ATP turbos with internal wastegate (WG) will creep. Badly. Boost will be hard to control and keep below 23-24 psi in most setups and this pegs the stock MAP sensor and is not a desirable situation in terms of safety and control.

A principle that everyone should be aware of is that a boost controller (MBC or EBC) can only INCREASE boost from what the turbo does on spring pressure alone. If boost creeps up to 24psi just on spring pressure, not matter what controller you have on there, it will NOT lower your boost.

What is boost creep?

It is the phenomenon where the wastegate can't flow enough of the exhaust gases to keep the turbo from spinning faster and increasing boost. If the WG can't flow enough of these gases, they will start going through the turbine. This in turn spools the turbo faster causing more boost. More boost = more exhaust = faster turbine = even more boost. You see, if the WG is inefficient, poorly flowing, and too small (and the internal ATP ones are big time) it will not allow you to properly control boost even though the actuator has a spring in it that is set for low boost (such as 8 or 14 psi).


Here are the things that will make creep worse with an inefficient WG:

- A big intake
- A nice open exhaust (no cat, aftermarket downpipe)
- A well flowing intercooler
- Cold weather
- Higher gears will generate more creep
- High WG arm preload

Here's how to fix it. The best fixes are done before the install

- Run an EWG. These are large and generally have no issues with creep.

- Port the stock WG hole and the path that gases travel to get out through it. Port this hole so that the flapper door seals it, but it is just a few mm smaller than the flapper door. Remember to remove the turbine housing when doing this - you don't want metal shavings in the turbo

If you have already installed the turbo, here are things that may help:

- Run a smaller intake (COBB SRI versus 3.5 inch)
- Run a cat, or restrict the exhaust (I know this is counter-intuitive to power but it helps)
- Reduce preload on the WG arm
- Feel comfortable with running 24 psi and buy a 3 bar MAP sensor and get a good tune
- Buy a boost gauge and keep an eye on boost!

While we're talking boost control and big turbos - the most consistent and easiest method to raise boost is through an MBC. This is after you have taken control of creep. The GS EBCS is ok in some cases, and in some it will cause boost oscillations that are sometimes hard to tune/smooth out. This can increase the difficulty and time of the tune.

An important note on choosing wastegate spring pressure. Choose the spring that is closest (but under) the boost you plan to normally run. This will result in the best response and control. A boost controller becomes less effective at controlling boost levels that are much higher than spring pressure. Aim to not exceed 2-2.2x (this is a maximum) wastegate spring pressure via a boost controller.

Below is a datalog showing a classic example of ATP boost creep. Notice that the WGDC is at 0 - meaning the ECU is doing all it can to reduce boost, and the MAP sensor is pegged.

[TRSpeed]

Great write up Lex

Sent from my DROID4 using Tapatalk 2

[09Speed3Z]

Sticky.

Go.

Now.

[TWOptSL0W]

just a note on internal wastegates and their wastegating power

Always gotta 1-up me huh


Edit: you CAN'T run 24 psi without creep with free flowing exhaust and big intake. It will still creep. I creep to 29-30 psi at redline at some points

[86AmishMs3]

Good write up. Like I've told everyone port the wastegate it's so easy to do when the turbo is off the car. Buy a dremel and get to work. If you have better shop tools then use those like I did. Even with a moderate porting job and catted downpipe I creep to 18 psi @ RL with 15psi spring pressure. I can deal with 3 psi.

Before I went catted downpipe I was seeing around 25psi @ 6100 which was crazy. I'm pretty sure even if I agressively ported, with a big intake, high flow intercooler, and no cat I would still creep fairly well.

IWGs are just finicky. In my case down right frustrating and was debating on going EWG. But with the right parts and know how I was able to manage it...and now my car runs perfect.



Also as an add on Lex I would put something in about spring pressure and boost response.

Spring pressure determines boost response. The closer the spring pressure boost to the desired set boost pressure the better response you'll have.

When I first got this turbo and installed it was soo loose at like 6psi and it would actually bind in the open position. I preloaded it all the way and still was at like 7-8 psi and boost response was horrible. It wasn't until 5000+rpms that I would reach 20psi. This is typical in a very overdamped process. The MBC can only multiply the effects of a wastegate spring pressure by so much.

So like me and others have done...we've had to cut the wastegate arm down. You may have to do this in your case. I ended up cutting 3/4" off mine. It would have been better to contact ATP and get the correct spring.

When you cut the wastegate actuator arm and you have to use force to get the arm back on the flapper you are extending the spring and effictively increasing the spring pressure. This does come at a cost though. By cutting the actuator arm to increase spring pressure instead of swapping wastegate cans you run the risk of an underdamped process and getting mechanical spike. This spike will show up with a MBC or EBC. In the MBC you will see one spike and then it settle. The EBC will try to correct the spike, overcorrect and create boost ocillations.

I've had every problem in the book with my ATP turbo. Through fail I've gained a better understanding and have been able to cure and manage the flaws of an IWG.

[p057]

Not to be a naysayer or anything, just another point of view:

I "recently" purchased and installed an ATP GT3071r. No sign of boost creep, but im feeling its more my BPV leaking just a small amount and almost stabilizing the pressure.


But could it be that either some of these are ported properly now or just new ones are? There are people buying new turbos with the same excessive creeping they did before?

[uncorked11]

Originally Posted by p057 Not to be a naysayer or anything, just another point of view: I "recently" purchased and installed an ATP GT3071r. No sign of boost creep, but im feeling its more my BPV leaking just a small amount and almost stabilizing the pressure. But could it be that either some of these are ported properly now or just new ones are? There are people buying new turbos with the same excessive creeping they did before?

This turbo was received around the 4th of April, installed last weekend it will be ported very soon or swiched to EWG. I heard ATP "fixed" the issue and rolled the dice only to lose, for future buyers after all the ass pain to install, just take the extra time to port first, I wish i did.

[TWOptSL0W]

Smaller turbo less creep. 3076 will give more creep

[p057]

Ahhhh, i just read your post @TWOptSL0W

Originally Posted by TWOptSL0W tl;dr atp iwg is good for 20-22 psi but not more or less

I am sticking at 21PSI tapering to 19.8... i see your point.

However, i am not putting the boost higher because i promised g/f and myself no more racecar and halt modding for now................, at least until i move away from florida (a year from now)

it will be interesting to see how it reacts when i decide to upgrade MAP sensor and up the boost to ~25.

[driver311]

Running a high flow magnaflow 3 inch cat and atp 3 inch intake and I had no creep on my gtx3071 with no porting. I had control all the way to 13psi. ONce the cat came off the car creeped bad. So in other words a nice hf cat will help the issue ALOT if not entirely eliminate it. With minimal loss in power maybe 3-5whp at most. Oh and the car will sound much better in my opinion. The car will have more of a deep groal vs any rasp.

good write up and just my .02. LOL

[dooderek]

moving to teh stickying

[CWP_MS3]

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