0KStuned

Post all of your Boost Creep experiences here, and what you believe to be the cause, be sure to include:
-Which Turbo you had (BB turbos are more efficient, possibly more likely to overcome a W.G.)
-Which Exhaust manifold you were using (Cast, tubular. Wastegate bleeding more than 1 runner)
-Which Wastegate (Tial, Innovative, 35mm, 40mm, etc)
-What PSI (or BAR) spring was in your wastegate
-Which boost controller you were using IF any, and the boost you were trying to achieve when boost creeped.
-What GEAR boost creeped in
-And any other possible contributing factors (some people think Air/Fuel Ratio has an effect, others suspect air temperature)

I am trying to figure out what Wastegate I will need with what PSI spring to hold STEADY boost ALL the time, EVEN at LOW boost!

I have a Garrett t3/t04e , Equal Length Maxrev exhaust manifold w/ the wastegate bleeding off ALL FOUR exhaust runners just before the turbo, I am currently using a Tial 35mm Wastegate with only a .35 Bar (5 psi) spring, I run constant .85 BAR-1.0 BAR (12-14.7 psi) using a GM Boost Solenoid controlled by the AEM EMS to control boost.
Boost has ONLY EVER creeped in 4th gear for some reason. NONE in 1,2,3rd gear, and just BARELY in 5th once or twice, but MAJORLY in 4th.

My boost would hold perfectly 99 percent of the time, however there were a few times over the summer (my car has been down for new tranny since before it got too cold) when it would creep to 1.6 BAR (23 psi)!!! It seemed to do this only on cool nights (65-70 degrees F) but it would RARELY do it, seemed to be random. I took the wastegate off and put a new gasket between the W.G. and the manifold but that didn't help. But it wasn't a big deal because it very rarely boost creeped and it was very spontaneous when it did it.


The FACTS about Wastegates are: (Straight from Tial's Website) - PLEASE READ, it is very important to understand how/why which wastegates work.

Flow capacity. Contrary to popular belief, larger higher HP applications do not necessarily require the largest wastegate available. The lower the boost pressure you are gunning for the larger your wastegate needs to be. An engine/turbo combination that is set to 25+psi has a smaller wastegate flow requirement than the same application set to 7 psi. This is because the wastegate is used to lower the boost not raise it, the lower the boost pressure is set the more flow the wastegate must allow.
3. The spring. TiAL wastegates are not adjustable. To change the boost pressure at which the valve opens requires changing the spring within the wastegate. Springs range from .3 Bar to over 1 Bar are available. The most common way to select your spring size is to pick a pressure rating that is a couple tenths or a bar or a few psi lower than the boost pressure you intend to operate the turbo/engine combo at. This way a boost controller can be used to adjust the opening point of the wastegate and help you fine tune to the exact pressure that is desired. This also allows adjustments to compensate for changes in atm pressure, altitude and temperature, which will all effect the way your wastegate does it's job.
4. Mounting the wastegate. this is one of the most overlooked areas of boost control. In a perfect world you would select a mounting location for our wastegate that allows the gate equal access to all cylinders or rotors. This promotes equal exhaust port pressures between cylinders/rotors and avoids mysterious tuning problems resulting from uneven exhaust port back pressures. Another aspect to keep in mind is the high velocity of the exhaust gas inside the exhaust manifold, sometimes exceeding 800ft sec. Gas that is traveling at such high velocities will not easily make 90 degree turns of zero radius into the wastegate inlet. Remember Newton's second law, "bodies in motion tend to stay on motion". That particle of air is not particularly inclined to make a 90 degree turn and 800ft/sec. It must be persuaded to do so by giving it a gentle radius and easy access to the exhaust flow. Simply welding the gate to the side of a tube may work in some cases where the manifold back pressure is thru the roof, but in modern high efficiency turbochargers the pressure inside the manifold can be quite low and special through should go into wastegate runner geometry. The penalty for poor gate placement and poor gate runner design is having to use a larger gate.

0KStuned

My plan to fix my boost creep problems is to get a Tial 40mm(or equivelant wastegate if another brand can prove to be better), with a .6 Bar spring. NEXT SEASON I plan to set up my Speed Dependent Boost Control that is incorporated into the AEM EMS to run off of the .6 BAR spring mainly through 1st gear (appx. 36 mph depending on tire size).
Then UP the BOOST a little bit through right around 2nd gear (appx. 62 mph, again depending on tire size), and again up the boost around 85 mph (3rd gear), then have it ramping steeply to a max of about 1.5 BAR (22 psi) before 100 mph.

The problem arises when trying to control LOW BOOST, which is when a BIG wastegate is needed. Think about it, the LESS BOOST the more exhaust gas that must GO OUT the WASTEGATE. Another possible concern is if I get a Tial 40mm w/ a low boost spring (.6 BAR, 8.82 PSI)like I want, then the W.G. will want to bleed off and keep boost low. So then to run 1.5 BAR later in the gears the GM Boost Solenoid will have to work harder to keep the W.G. closed so that I can achieve 1.5 BAR which means I will have to make sure that all my vacuum lines are short (between W.G. and Boost Solenoid)so that my boost solenoid will be quick reacting and that it gets a good vacuum signal.
Also I plan to upgrade to an Innovative Ball Bearing turbo which will be extremely more efficient and easier to spin, which makes the Wastegate work harder, so another reason why I will need at least a 40mm Wastegate.

ykracing

I had a boost creep issue with a mani that only fed the WG off one runner...
Then I added a second tube from another runner, and it fixed it perfectly...

voila!

I dont know if that helps any, but it was just my experience....

0KStuned

what W.G. were you using, what PSI?

0KStuned

Anyone using wastegates other than TIAL? Innovative seems to be at the top of their game, anyone using an innovative Wastegate like pictured below?

PureTeg420

friend has one on his 3000gt....it works as designed.

h22 civic

yea should nt have creep off a t04e and a tial 35mm try running just the spring in the waste gate and forget the ems and see what happens

alpha

My buddy's experience ...

Deltagate to TiAL - Still a problem
Drag to Inline Pro - No problem ...

GodFather of Boost

do you have the knock control on? your knock control might be too agressive use conservative fuel and timming maps and turn the knock control off.

xtal

Read Corky's book .. it has a good explaination of the causes of boost creep. The best way to combat creep is to make sure your wastegate is in a place where high velocity gas -wants- to go. If it isn't, then at high RPMs the exhaust is going to speed right 'on by that wastegate.

The best location involves a inverted-Y setup, where the exhaust flow is forced to make a decision between the gate and the turbo. This will hurt you at higher HP levels, but as Tial mentioned, it is less critical if you're boosting 25 or 30 psi than if you're relying on that wastegate to keep the motor in one piece.

ek9vboi

Motor: D16y8
Turbo: Turbonetics t3/t4 something
WG: Deltagate

i was running it off wg and it some how went all the way up to...8-9lbs? scrud the living **** outta me, but i don't care. hahaha. im getting a boost controller to fix that problem up.

Ri5e

What size exhaust piping are u running? Most of the time, a poorly located wastegate with a high flow exhaust system will cause creep.

An example would be the Drag manifold because of how they positioned the wastegate right at 1 runner. It works fine when you use a 2.5 inch exhaust system but once you upgrade to 3.0 inch, problems arises because the exhaust flow is so great that the exhaust gases zoom by the wastegate into the turbo rather than out the wastegate port.

jonnybravo

Really? So how much will it boost will it go up with the change of exhaust with the Drag manifold?

xtal

The problem with boost creep isn't the wastegate.. it's the direction of the exhaust flow TO the wastegate; you could have the wastegate completely open, but if it's not in a good location, with a nice free flowing setup - the kind you want to make power with - the exhaust will go sailing on by the hole, and spin the turbo faster.. producing more power.. making the exhaust flow faster.. making the turbo spin faster.. creeeep

The solution is to design the manifold correctly in the first case, so that the wastegate is presented with exhaust gas to bypass the turbo via the downpipe.

Hoosier Daddy

Had another boost creep experience (hence the old username )

Using a Garrett T28 with an interneal wastegate on a HKS manifold. Ended up the actuator flapper was stuck due to a plate that was installed in my downpipe. Probably really unlikely to happen to anyone else, but I figured it can't hurt to post.

Hoosier Daddy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xtal &raquo;</TD></TR><TR><TD CLASS="quote">Read Corky's book .. it has a good explaination of the causes of boost creep. The best way to combat creep is to make sure your wastegate is in a place where high velocity gas -wants- to go. If it isn't, then at high RPMs the exhaust is going to speed right 'on by that wastegate.

The best location involves a inverted-Y setup, where the exhaust flow is forced to make a decision between the gate and the turbo. This will hurt you at higher HP levels, but as Tial mentioned, it is less critical if you're boosting 25 or 30 psi than if you're relying on that wastegate to keep the motor in one piece.
</TD></TR></TABLE>

Where can I read that book?

h22 civic

mani probs

quikB18B

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hoosier Daddy &raquo;</TD></TR><TR><TD CLASS="quote">

Where can I read that book? </TD></TR></TABLE>

Go to Barnes and Noble, or other book stores should carry it.

0KStuned

Well I have read Maximum Boost, I own it, but I lent it to a friend., I will get it back, and read through it again.

As for my wastegate placement: I have a custom equal lenth manifold from maxrev, with the wastegate positioned in the collector, the only problem being that the exhaust gasses must take a 90 degree turn to get to the wastegate. But Full-Race's manifold makes a 90 degree turn too, and they don't seem to have problems.

The only manifold that I have seen that the wastegate flows in the same direction as the collector is one from Hytech.

Honestly though, I don't think the problem is from the wastegate placement on my manifold, I am convinced it is because of the wastegate.

ALSO: What does Knock control have to do w/ boost creep? Please explain how you came up with that. And as far as conservative fuel and timing, I am running extremely conservative fuel (appx. 11.5:1 AFR) and very conservative timing as well.

xtal

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Honestly though, I don't think the problem is from the wastegate placement on my manifold, I am convinced it is because of the wastegate.</TD></TR></TABLE>

It is all about placement. I highly doubt it is the wastegate.

A thought experiment: You, Mr. Speedy Turbo Honda Guy and his car, are particles of hot gas flying down a street. You come up on an intersection at 600ft/sec, give or take the flow rate of the exhaust out of the engine at speed. Is it easier to go straight through the intersection, and weave through a few slow moving vehicles (turbo turbine blades) - or would you think it easier to pull a wild 90 degree drift maneuver?

That's the dielmma faced by exhaust flowing through the manifold. It doesn't matter there's a empty 4 lane highway, it's still going to be hard as hell to make that turn at 600ft/sec. (540km/h?) At 80 km/h, it would be pretty easy. But the faster you go, the harder it gets.. and that's where boost creep comes from.

0KStuned

The fact is that my car has serious boost creep issues, but VERY RARELY, the problem is that when it happens it happens HUGE (I have had boost ramp up to 22 psi, when I had been succesfully running 13-15 psi without changing anything!) I believe it was colder outside, but not a lot, could denser air cause dramatic creep like that?

So then this Hytech design should be better because the exhaust gasses don't need to make a drastic change in direction, that makes sense. However, the manifolds that so many other people are using require a SHARP 90 degree angle from the exhaust gasses to get to the wastegate, including the Full-Race manifold which is so acclaimed as having lots of R&D go into its design. Could I possibly help my problem by shortening the pipe that the wastegate connects too?

Here is what you are talking about right? Is this Hytech manifold ideal?
How do you know, do you speak from experience? I am not trying to argue, as it makes sense, I am just trying to validate what you say.




Here is a picture of my manifold:

xtal

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">However, the manifolds that so many other people are using require a SHARP 90 degree angle from the exhaust gasses to get to the wastegate, including the Full-Race manifold which is so acclaimed as having lots of R&D go into its design.</TD></TR></TABLE>

Just because everyone is doing it, doesn't make it right. Design is all about compromises though - what is right just might not fit.

I have some background, but I don't design manifolds for a living, but the reason I suspect "most people" get away with it is because there is enough restriction in the design of the manifold and exhaust so that you con convince enough of the gas flow to vent through the wastegate. Colder air means you're going to make more power, and more power means more exhaust flow, more exhaust flow means more boost creep. You'd have to have some expensive hardware to measure exactly what is happening inside that manifold. Things don't happen nice and linearly, and any number of things could cause the creep issue to set in all of a sudden when you're dealing with exhaust flow. Including a defective wastegate.

There is NO situation where a 90 degree bend for the wastegate manifold is better than a Y. I can't really tell from the picture you posted what the wastegate is welded to - is that the collector, or a single runner?

Corkey Bell's book has a decent discussion of the various designs and compromises you can use. In a lot of situtations, a 90 degree bend is fine - but it's far from ideal.

JDogg

with the knock control it could be pulling timing and adding fuel which would send more exhaust energy out the exhaust causing creep. if the ign timing is to retarded then you will have problems like this as well. i have seen cars gain 5psi b/c there was a miss. fix the miss and the boost goes back to normal. also keep the vac lines to the wg short and fat.

GodFather of Boost

thank you JDogg i had the same problem.it kicked my *** for a month before i figuered it out .you must also calibrate the knock control to your specific motor especial if its built it will make more "noise"

JDogg

normally i dont even use knock control on built engines. they are just too noisy to use it. carfull reading of the plugs and a good dyno will show you knock. the 2l b16 im doing now is so loud that the knock sensor is only consistent below 4000 rpms. above that its all over the place.

if you have a big turbo and alot of power but want to run low boost you will need a huge wastegate. we could run anthing above 25psi and be stable w/the 38mm tial but it wounldnt go below that and not creep. got a 46mm tial on there now. nomore creep