Is External WG the easiest way to fix my creep problem?

RipperXX · Nov 15, 2006

Well I had a 34mm flapper installed in my Evo 3 16g, and the sob still creeps to the sky, it will boost to 15psi set there for a sec, and soon as I go anywhere past 5k is starts climbing at a incressing rate. I have to short shift to keep it under 20psi.

(Mods in profile) but this is on a evo 3 manifold, turbo, and e3 o2 houseing w/2.5" exhaust, with no CAT and stright threw muffler. I really didn't expect this thing to creep, honestly I kinda expected the oppiset.

The only other idea I had was since it's not tuned yet, maybe it's running so rich fuel is burning in the manifold and overspooling it? Is that possible? I dont really think thats it though cause after the DSMLink and 750cc injectors EGT's droped alot. The sensor is in the o2 houseing, and it used to read mid 1300's now It doesn't read much more than 1100 I dont think. (if memory serves)

Just a FYI I have seen as high as 26psi OMG

DSMunknown · Nov 15, 2006

Have you ported the O2 housing? If you haven't, then now would be a good time to consider doing so.

My boost is too strong! Is there a fix?
My boost won't stay where I set it - it keeps going up! Is there a fix?

This is called boost creep, and occurs when the turbo is pushing so much air that the wastegate, even when fully open, cannot dump all of the intake pressure. This results in a continual increase in intake pressure, and is common with upgraded turbos, especially with upgraded downpipes - the exhaust would rather flow through the turbo/exhaust than the more restrictive wastegate, which spins the turbo ever faster. Cars with this problem can develop mind-blowing (and engine-blowing) intake pressures in a hurry.

The general solution to this problem is to port the oxygen sensor housing, turbine housing and/or wastegate to allow them to dump more air. Otherwise minor malfunctions of the wastegate may also exhibit themselves as boost creep, such as poor travel on the wategate actuator arm. Some people use an external wastegate for better pressure control.

For more information, search the archives on this topic, or read these posts by Jack Zhe, Ken Okazakik, Samuel Merritt, Dan Kim and Frank Mowry for the highlights.

People interested in more theory behind this problem will enjoy Dennis Grant's Turbo Fundamentals Series.

EDIT: I see that you have a 2.5 inch exhaust. You also should consider going 3" all the way to try and alleviate the problem. Additionally, did you have the WG flapper section of the turbo ported? This should also be considered.

EDIT x2: You may also consider purchasing one of these:

http://www.extremepsi.com/store/customer/product.php?productid=19758&cat=1080&page=1
http://www.extremepsi.com/store/customer/product.php?productid=19461&cat=1080&page=1

EDIT x3: Here is another link you may wish to read:

http://www.allpar.com/mopar/boost-creep.html

EDIT x4: Another interesting link where a GS-T Spyder was being used:

http://www.sportcompactcarweb.com/tech/0207scc_boost_control/

The quote below is from the link above:

Boost Control Basics
Every modern turbocharger uses a wastegate to regulate boost. The wastegate is simply a valve that allows exhaust to bypass the turbine, limiting the energy available to drive it . When designed into the turbine housing, they're called internal wastegates, the kind found on nearly all production cars. External wastegates are located separately from the turbocharger, somewhere between the exhaust ports and turbine housing. The remote location allows the valve to be bigger and flow path smoother, resulting in better boost control and the ability to safely manage a more powerful engine.

The wastegate is held shut by a spring, and as boost builds, the wastegate actuator diaphragm pushes the wastegate open against this spring. The size of the diaphragm and strength of the spring determine how much boost it takes to open the wastegate.

All the boost controllers in this test act on the pressure signal that opens the wastegate. Reducing this pressure will keep the wastegate closed, allowing more boost to build. When the desired boost setting is reached, the controller lets pressure into the diaphragm, opening the wastegate.

Electronic controllers use either stepper motors or solenoids to do this. Stepper motor assemblies vary the opening of a precision valve, similar to a water faucet. This action is accurate, though somewhat slow. Solenoids, however, operate in either a fully open or closed position, but can change this state very quickly, feeding and releasing full pressure so quickly that the pressure in the diaphragm can be accurately controlled. Dual solenoids will give an even greater degree of precision. The HKS EVC EZ, EVC IV, and GReddy PRofec A all use an identical stepper motor assembly. The GReddy PRofec B and Blitz SBC i-D share a common dual solenoid design, though they drive them differently. A'pexi stands alone with its single solenoid design.

If a wastegate is set to 10 psi, it may start to open around 6 psi, slowing the turbo's acceleration and finally reaching equilibrium at 10 psi. Boost controllers can improve turbo response by keeping pressure off the wastegate as long as possible, making more energy available to drive the turbine. Just as boost reaches the set point, pressure is dumped on the diaphragm to rapidly open the wastegate, and hopefully keep from spiking the boost.

EDIT x5: Here are a couple more links found right here on DSMTuners

:

http://www.dsmtuners.com/forums/showthread.php?t=186525
http://www.dsmtuners.com/forums/showthread.php?t=96678

andymoraitis · Nov 15, 2006

DSMunknown said:
EDIT: I see that you have a 2.5 inch exhaust. You also should consider going 3" all the way to try and alleviate the problem. Additionally, did you have the WG flapper section of the turbo ported? This should also be considered.

A 3" downpipe will actually make the problem worse. More restriction on the hot side helps alleviate creep which is why some tuners add high flow cats. Either is a bandaid and I would certainly agree that installing a larger flapper door by itself won't do it. The wastegate passage needs to be ported as well as Anthony already mentioned since the gases will need a larger passage, not just a larger opening at the end.

Aside of that, a manifold mounted external will certainly do the trick.

With your injectors, you should easily be able to tune the motor and set the boost to the point at which it creeps. This also generally solves the problem but a combination of porting and a proper tune to allow for more boost is the best solution.

Make sense?

Andy

DSMunknown · Nov 15, 2006

andymoraitis said:
A 3" downpipe will actually make the problem worse. More restriction on the hot side helps alleviate creep which is why some tuners add high flow cats. Either is a bandaid and I would certainly agree that installing a larger flapper door by itself won't do it. The wastegate passage needs to be ported as well as Anthony already mentioned since the gases will need a larger passage, not just a larger opening at the end.

Aside of that, a manifold mounted external will certainly do the trick.

With your injectors, you should easily be able to tune the motor and set the boost to the point at which it creeps. This also generally solves the problem but a combination of porting and a proper tune to allow for more boost is the best solution.

Make sense?

Andy

Thank you Andy for the clarification. Just to support what you are saying about porting the mouth of the internal WG or switching to an external WG, here is a link and two quotes to go with it:

http://www.turbobygarrett.com/turbobygarrett/tech_center/faqs.html#t8

What is boost creep?
Boost creep is a condition of rising boost levels past what the predetermined level has been set at. Boost creep is caused by a fully opened Wastegates not being able to flow enough exhaust to bypass the housing via the Wastegates itself. For example, if your boost is set to 12psi, and you go into full boost, you will see a quick rise to 12 or 13psi, but as the rpm's increase, the boost levels also increase beyond what the boost controller or stock settings were. Boost creep is typically more pronounced at higher rpm's since there is more exhaust flow present for the Wastegates to bypass.
Effective methods of avoiding or eliminating boost creep include porting the internal Wastegates opening to allow more airflow out of the turbine, or to use an external Wastegates.

How does a Wastegate work?
A Wastegate is simply a turbine bypass valve. It works by diverting some portion of the exhaust gas around, instead of through, the turbine. This limits the amount of power that the turbine can deliver to the compressor, thereby limiting the turbo speed and boost level that the compressor provides.

The Wastegate valve can be "internal" or "external". For internal Wastegates, the valve itself is integrated into the turbine housing and is opened by a turbo-mounted boost-referenced actuator.

An external Wastegate is a self-contained valve and actuator unit that is completely separate from the turbocharger.

In either case, the actuator is calibrated (or set electronically with an electronic boost controller) by internal spring pressure to begin opening the Wastegate valve at a predetermined boost level.

When this boost level is reached, the valve will open and begin to bypass exhaust gas, preventing boost from increasing.

As you also rightly noted, an aftermarket catalytic converter would help with the boost creep problem. As most of us notice when we first replace the exhaust system (and replace the OEM cat with a test pipe), the boost reponse is much more responsive and higher. This shows how restrictive the exhaust system and catalytic converter were. But it also shows how the cat acted like a "boundary" so that the boost didn't rise too high (unless you set it too high).

So my question to you Andy is this - Is it because the external WG physically comes before the turbine housing that the exhaust gases tend to "want to" escape the piping as soon as possible and make the external WG more effective? I know that because external WGs are physically larger than internal WGs, this is why they can handle more boost, but what makes them more effective than internal WGs?

andymoraitis · Nov 15, 2006

DSMunknown said:
So my question to you Andy is this - Is it because the external WG physically comes before the turbine housing that the exhaust gases tend to "want to" escape the piping as soon as possible and make the external WG more effective? I know that because external WGs are physically larger than internal WGs, this is why they can handle more boost, but what makes them more effective than internal WGs?

I'd say it's a bit of both Anthony (good job figuring that out). If you consider the diameter of a manifold mounted wastegate opening, the fact that it's regulated with accurate spring pressure and it's placement before the turbo, it makes sense as to why the externals work so well. As you know I have a Tial 38 mounted on number one and recirced into the exhaust. Irrespective of weather conditions, ambient air temps, intake charge temps or any other factor, I see a hair over 25 psi in 2nd-5th gears (my setup uses 21 psi of spring pressure and 2 flat washers as shims to increase it). Also compare the size of my recirc pipe to the size of a flapper opening and you'll see why it diverts the exhaust charge easily and regulates boost so accurately.

In theory you're right on both counts.

Cheers,

Andy

wishihadatalon · Nov 15, 2006

andymoraitis said:
A 3" downpipe will actually make the problem worse. More restriction on the hot side helps alleviate creep which is why some tuners add high flow cats. Either is a bandaid and I would certainly agree that installing a larger flapper door by itself won't do it. The wastegate passage needs to be ported as well as Anthony already mentioned since the gases will need a larger passage, not just a larger opening at the end.

Aside of that, a manifold mounted external will certainly do the trick.

With your injectors, you should easily be able to tune the motor and set the boost to the point at which it creeps. This also generally solves the problem but a combination of porting and a proper tune to allow for more boost is the best solution.

Make sense?

Andy

Yeah man boost creep is like vtec haha. The higher you rev the louder and faster your car gets. Well I guess it has one thing in common with vtec

andymoraitis · Nov 15, 2006

wishihadatalon said:
But seriously just tune for it and you will be fine. Or just set the boost to that amount and have fun

That's what I did on the 16G and it seemed to work. With the amount of fuel available for the original poster, I'd be running that thing at 24-25 psi and not worrying as long as it wasn't knocking all over the place. It'll be tough with those 750's but a little high octane in the tank would certainly help offset the knock propensity from the high timing/airflow subtraction issue.

VTEC boost creep...Good one TJ!

wishihadatalon · Nov 15, 2006

andymoraitis said:
That's what I did on the 16G and it seemed to work. With the amount of fuel available for the original poster, I'd be running that thing at 24-25 psi and not worrying as long as it wasn't knocking all over the place. It'll be tough with those 750's but a little high octane in the tank would certainly help offset the knock propensity from the high timing/airflow subtraction issue.

VTEC boost creep...Good one TJ!

You know creep just gives the other guy a chance.

Then when it finally settles and the car is running balls out, you can pass him and get the WTF

JayRolla · Nov 15, 2006

It also makes tuning hard when you dont get a steady boost. thats always fun!!!

selmerguy · Nov 15, 2006

In about a month I am going to remove the flapper on my 14b and buy an o2 housing with a external wastegate. I am going to port the crap out of thre wastegate hole and the hot side of the turbo. I saw a nice bolt on o2 housing on one of the DSM vendor sites. I have heard nothing but good things from people the own such systems. I have heard alot of people the dont own one say it dosent work but the system looks good to me.
Right here:
http://www.punishment-racing.com/biography.html

RipperXX · Nov 15, 2006

http://www.extremepsi.com/store/customer/product.php?productid=19460&cat=1080&page=1

Is what im looking at, Punishment has the same part for alot less. My only concern is has there quality got alot better or what? If the punishment part is a good quality piece i'll go with it, otherwise SLS.

oldman · Nov 15, 2006

If the turbine housing is not properly ported, an O2 mounted external will not guarentee to work, same reason why your 34mm flapper didn't work. If you don't want to port your turbine housing, get a manifold mounted external. An o2 mounted external used as a cure for boost creep is a waste of money since the required porting of the turbine housing alone will solve boost creep in most cases. O2 mounted external becomes worthy when running higher boost levels where boost creep isn't an issue but keeping the internal flapper shut is.

Black95TSIawd · Nov 15, 2006

oldman said:
If the turbine housing is not properly ported, an O2 mounted external will not guarentee to work, same reason why your 34mm flapper didn't work. If you don't want to port your turbine housing, get a manifold mounted external. An o2 mounted external used as a cure for boost creep is a waste of money since the required porting of the turbine housing alone will solve boost creep in most cases. O2 mounted external becomes worthy when running higher boost levels where boost creep isn't an issue but keeping the internal flapper shut is.

AGREED.

I have a ported b16g with a tial 40 off the o2 on a 2.5in tubular o2. Although I do not get any creep, this turbo spools so fast that it will spike upwards of 3 to 4 psi and then settle to whatever i have it set to. A manifold mount will remedy all of that as it ices the cake before the air enters the turbine housing.

selmerguy · Nov 15, 2006

oldman said:
If the turbine housing is not properly ported, an O2 mounted external will not guarentee to work, same reason why your 34mm flapper didn't work. If you don't want to port your turbine housing, get a manifold mounted external. An o2 mounted external used as a cure for boost creep is a waste of money since the required porting of the turbine housing alone will solve boost creep in most cases. O2 mounted external becomes worthy when running higher boost levels where boost creep isn't an issue but keeping the internal flapper shut is.

I agree with this. However the way I look at it is I can buy this 180 part and a 100 wastegate. Thats 280. Porting is free if you do it yourself. All this should bolt up to my existing downpipe. Now if I was to get the mani with the external. I would have to buy the mani-200 then the wastegat-100 then I want the wastegate to dump into the exhaust so that is more money. So I would not call it a waste, this is a cost expediant way to have a setup bigger then 34mm to allow better flow of exhaust. And you can do all of it yourself. You dont have to take the car to a exhaust shop to get flanges welded or anything dumped back into the exhaust. I have a 2g 420at that has a atmospheric dump and it is messy.

selmerguy · Nov 15, 2006

Sorry to double post but I would argue that there is little to no difference if you have a flange at the collector or if you use the o2 housing. The hole for the wastegate on the o2 is before the inlet for the turbo. Think of it thiswauy if there was no flange for the turbo and the manifold. And they were just welded togeather or better yet cast togeather there would be no difference. You would have a hole before the turbo inlet just alittle closer to it.

oldman · Nov 16, 2006

selmerguy said:
Sorry to double post but I would argue that there is little to no difference if you have a flange at the collector or if you use the o2 housing. The hole for the wastegate on the o2 is before the inlet for the turbo. Think of it thiswauy if there was no flange for the turbo and the manifold. And they were just welded togeather or better yet cast togeather there would be no difference. You would have a hole before the turbo inlet just alittle closer to it.

It is not the flow capacity of the wastegate path, rather it's the flow characteristics of the poorly designed wastegate path that contributes to boost creep associated with running low boost levels on a Mistu turbine housing. There are two main areas of concern,

1. The sharp angle on the entrance of the wastegate path leading to the flapper, the key here is to remove material on top of the entrance to help guide exhaust flow towards the flapper when it opens by reducing the angle of entry.

2. The inability of the flapper to open fully, this can be adressed by 1)uppgrading to a larger flapper, 2)reduce the throw of the pivot arm or 3)porting of the inner side walls (towards the divider) to reduce the angle of exit after bouncing off the flapper itself. #3 is the best IMO as 1 & 2 will result in the flapper being blown open earlier.

This is why although the wategate path is before the turbine itself, a manifold and an O2 mounted external on a unported (properly ported for boost creep) turbine housing will not produce equal results. If you do a detail search you'll find some examples of creeping even with an O2 mounted external, even more so on plain old internal O2 dump for the same reasoning.

Steve93Talon · Nov 16, 2006

To illustrate the point above, we're running a 60-1 in a Bullseye housing with a Tial 44mm (1.2bar spring) on the o2 housing, and it will creep to 30psi with no MBC, just vacuum line straight to gate. Porting the hell out of the wastegate passage helped but didn't cure it. The solution for now is to just run 30psi.

selmerguy · Nov 16, 2006

Steve93Talon said:
To illustrate the point above, we're running a 60-1 in a Bullseye housing with a Tial 44mm (1.2bar spring) on the o2 housing, and it will creep to 30psi with no MBC, just vacuum line straight to gate. Porting the hell out of the wastegate passage helped but didn't cure it. The solution for now is to just run 30psi.

That is a great solution. :thumb:

I will be porting my 14b out soon and installing the o2 mounted gate. Does anyon have pics ot the o2 gate installed. I am curious about fitment issues.

Steve93Talon · Nov 16, 2006

selmerguy said:
Does anyon have pics ot the o2 gate installed. I am curious about fitment issues.

http://homepage.mac.com/stevestrzempek/PhotoAlbum19.html

Last pic

DSM90AWD · Nov 16, 2006

selmerguy said:
That is a great solution. I will be porting my 14b out soon and installing the o2 mounted gate

I'd try the porting first and see if that correct your creeping issue as a 14b really does not flow that much to warrant an external. So unless you are running super low boost levels, the stock flapper should have no problem dealing with the "unused/wasted" exhaust

selmerguy · Nov 16, 2006

DSM90AWD said:
I'd try the porting first and see if that correct your creeping issue as a 14b really does not flow that much to warrant an external. So unless you are running super low boost levels, the stock flapper should have no problem dealing with the "unused/wasted" exhaust

I plan on upgrading to a bigger mitsu. turbo later. so in the grand scheme of things it looks like the way I want to go. I was told the the 16/18/20g turbos all use the same hot side or the turbo. If this is wrong tell me so I dont go waste any more of your hard earned tax money(in the army :tease:

)

oldman · Nov 16, 2006

Another thing to be careful with when using an aftermarket tubular O2 housing is to check clearance on the o2 flange before porting the wastegate exit on the 14b. Unlike stock O2 housing which can be port matched to work done on the turbine housing, you'll not have the same option with a tubular o2, don't over port the 14b which can create dead spots at the turbine/o2 flange.

DSM90AWD · Nov 16, 2006

Some 18/20Gs come with different turbine wheels/AR Turbine housings than the 16G, but all will fit a Mitsu-flanged O2 housing. The Mitsu-flnaged O2 housign will also fit any of the PTE SCM turbos and BEP Mitsu flanged turbos too

The Central Hub for DSM Community and Information

Is External WG the easiest way to fix my creep problem?

RipperXX

DSMunknown

andymoraitis

DSMunknown

andymoraitis

wishihadatalon

andymoraitis

wishihadatalon

JayRolla

selmerguy

RipperXX

oldman

Black95TSIawd

selmerguy

selmerguy

oldman

Steve93Talon

selmerguy

Steve93Talon

DSM90AWD

selmerguy

oldman

DSM90AWD

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