Search on porting your wastegate and upgrading flapper.

yeah that's what one DSMer said around town. Do you think a Greddy Profec will fix it. It's supposed to help you controll you boost alot better with Boost Creep functions and boost Spike Functions?

1997turbodsm said:

I have a 97 gst with an evo III 16G. I have my manual Boost controller turned completly off! It will Hit 12PSI then Creep Until about 19PSI. Will a Electornic Boost Controller Fix this or will i need to go with an External Wastegate Setup.

P.S. It didn't creep until i put my Greddy Full Exhaust System on.

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That's very typical. You put an evo3 on and it's fine until you upgrade your exhaust. The creep isn't at all related to the boost controller. All it does is tell the WGA when to open, but the WGA doesn't flow well enough to maintain low boost (the evo3 is much happier at 20psi+).

Check out post #5 here.

EDIT: You have 3 options: 1) Get supporting mods so you can run 20psi, 2) port, and 3) go with an external wastegate. Those links focus on the porting option.

Good luck!

1997turbodsm said:

yeah that's what one DSMer said around town. Do you think a Greddy Profec will fix it. It's supposed to help you controll you boost alot better with Boost Creep functions and boost Spike Functions?

Click to expand...

Here's a good test. Disconnect the WGA arm from the lever on the turbine housing (remove the small clip without damaging it and slide the arm off). Let the arm hang there and do a full throttle pull while monitoring your boost gauge. If you get more than a few psi boost, it's creep, and you should be able to convinse yourself that no boost controller is going to fix it.

yeah i will do that. never thought of that. Thanks.

I am getting ready to have my EVO2 and Helix DP installed. Next will be a EVOIII 16g. If I am planning on adding a EVOIII exhaust mani and O2 housing will that prevent boost creep, or will I still need to port those? Also related to boost over 15 up to around 20-22 is it just fuel mods needed, or am I looking at internals (pistons, rods, heads, etc)? I have on the way a EPROM ECu and DSMLink, and a walbro 190.

Locutus78 said:

I am getting ready to have my EVO2 and Helix DP installed. Next will be a EVOIII 16g. If I am planning on adding a EVOIII exhaust mani and O2 housing will that prevent boost creep, or will I still need to port those? Also related to boost over 15 up to around 20-22 is it just fuel mods needed, or am I looking at internals (pistons, rods, heads, etc)? I have on the way a EPROM ECu and DSMLink, and a walbro 190.

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The biggest problem with the evo3 is that the WGA only has about 1/2" of throw, so it doesn't open the flapper all of the way. You can port, and it will help, but a few of us have been talking about finding a WGA with a longer throw. If you're going to run 20+psi boost, you may not have a creep problem. By this point, enough of a fraction of the exhaust is getting out the wastegate to stop creeping (that's why you see people saying they get creep up to 20psi or 22psi or something - once it gets there, the WG is flowing enough to stop the boost from going higher).

Since you're buying all of the parts involved, you might just want to get an external wastegate setup or an internal O2 housing gate (uses the stock WG hole in the divided turbine housing, but then vents it through a different mechanism than the lame flapper of the stock internal gate mechanism). Since you haven't purchased anything, you have that option.

Mack, I swear I see you answer this question every other day. You should really save it to a file so you can just copy and paste it whenever you need to.

Port, people. That's the easiest and cheapest answer.

hey guys thanks for all the information. I've got one more question. My Buddy's got a 240sx with a SR swap and he's got an HKS Adjustable Wastgate Actuator. I was wondering if that would salve the problem also? and do they make one for the Evo 3?

http://www.dsmtuners.com/classifieds/showproduct.php?product=48141&cat=7

For example this....

http://www.slowboyracing.com/more.php?id=2446&


Also this one?

It's a never ending cycle

1997turbodsm said:

hey guys thanks for all the information. I've got one more question. My Buddy's got a 240sx with a SR swap and he's got an HKS Adjustable Wastgate Actuator. I was wondering if that would salve the problem also? and do they make one for the Evo 3?

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Well, one of you evo3 owners is going to have to try it out! (I don't have an evo3 or creep). I'm wondering if the adjustment is just for getting the arm at the right position to preload the flapper closed and may have nothing to do with how far the arm moves. Hell, someone could make one out of a linear actuator or something, but that'd probably start costing a bit more.

donmagicjuan said:

Mack, I swear I see you answer this question every other day. You should really save it to a file so you can just copy and paste it whenever you need to.

Click to expand...

I'm getting there. Eventually, I'll have one post that addresses everything about the evo3, porting, and WGA throw in it, and then I'll start referring to it. I've already done that with porting. I'm still learning more details on the subject, so I occasionally add something .

So it's possible that it could work? it's gotta have a stiffer spring then the stock WGA. I'm gonna try it out because it seems the easiest way to solve the problem because i dont wanna take the turbo back off.

1997turbodsm said:

So it's possible that it could work? it's gotta have a stiffer spring then the stock WGA. I'm gonna try it out because it seems the easiest way to solve the problem because i dont wanna take the turbo back off.

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Dude, when working on these cars you take 1 step forward and 2 steps backwards. If like me you'll be pulling that turbo more than just a few times just to play around with things to try and make it spool faster. The easiest way for this boost creep issue is just to port your turbo, manifold, and while your at it o2 housing.
Luke

yeah i might try that. Should i do it myself or give it to a machine shop? How much would they charge to port manifold, turbo, and o2?

So if i port everything that would defintely fix my problem and i could still run stock boost with no problem?

1997turbodsm said:

So if i port everything that would defintely fix my problem and i could still run stock boost with no problem?

Click to expand...

Maybe. Depends if you do a good enough port job. Read, read, read until you understand the issues fully.

In my opinion, the porting is a bandaid for a WGA problem. As for the WGA replacement, a stiffer spring won't increase throw. The mechanism bottoms out, and spring rates won't do diddly for bottoming out. You need a deeper unit with the right spring rate for the flapper mechanism. It has to open at the right boost level (opening at 20psi won't help you if you wanna run 15psi, because your MBC will open at 15psi, but the WGA won't open until 20psi), must hold the flapper closed at 30psi+ (assuming backpressure is 2x boost), and must have enough throw to open the flapper 90* or so. You could evaluate a WGA with a spring scale with a hook on it. Find out what force it starts to move (tells you the preload which is what will hold the flapper closed when you want it closed), find out how far you can extend it (tells you the throw), and find out the load when it is, say, half extended and 95% extended to get an estimate of the spring rate. Then you could use a pressure tester connected to the WGA nipple to find out what pressure it takes to start moving it (tells you what the minimum boost the WGA will let you run). And you'll need to keep cranking up the pressure and measuring the throw to find out how high the boost has to go to open the flapper up a certain amount.

You'd have to measure the distance from where the arm connects to the lever to the center of rotation of the shaft at the base of the lever, and you'd have to measure the distance on the inside of the housing from the center of the shaft to the center of the flapper disk. And you'd have to measure or calculate the throw versus shaft rotation angle.

With that said, you could find out on a benchtop whether or not the WGA would work. If it did, you'd probably have to fabricate a bracket to mount the WGA to the evo3 compressor housing, and may have to extend/shorten the actuator arm.

But if someone could get one working properly and ship it off to SBR or somewhere like that, maybe they could start making and selling the modded part to all of you evo3 creepers (and give you a royalty?).

Bolting a proper WGA for the low-boost evo3 situation is way easier and cheaper than porting. But no such WGA design has been demonstrated.