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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 04-08-2014, 01:41 PM   #1
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Default Overboosting/boost creep

I know the Greddy wastegate can is ****. That and the turbo are all that is left of the Greddy on my car. I've got a new manifold, I've got a 3" exhaust on the car now and with the MS3 I've got no intake box anymore and now the thing won't hold down the boost at all from what I can see.

I've got the EBC solenoid that I haven't hooked up yet. Does the EBC end up clearing up the boost control issue entirely or do I need a helper spring on the wastegate or new wastegate as well?
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Old 04-08-2014, 01:48 PM   #2
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it can you if you find out how much you creep to, then use the EBC to raise you boost from the get-go so it's the same in the low-end.
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Old 04-08-2014, 01:53 PM   #3
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Try installing an all tread rood in place of your canister to hold the wastegate open all the way and all the time, if you go over your boost target that way you will need a larger wastegate opening or a secondary wastegate on the manifold.
If your boost is below your target with the gate open all the way is probably your canister spring rate that is too high or bound up
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Old 04-08-2014, 02:16 PM   #4
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the problem is your exhaust being so good it's too easy for gasses to flow over the turbine, and spin the turbine and not bypass the turbine directly into the exhaust.
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Old 04-08-2014, 02:52 PM   #5
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Yeah, the wastegate seems to be useless at this point. It hits the fuel cutoff if I get into it for a bit. The default seems to be cutting it around 10-12 psi, which is probably for the best since this thing needs some work tuning.
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Old 04-08-2014, 04:10 PM   #6
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Turns out the vacuum hose between the wastegate and the turbo was shot. The thing looked like it was the original hose from the Greddy kit. I replaced that and now it holds steady at 5psi.

Now for EBC install and tuning!
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Old 04-10-2014, 02:18 PM   #7
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Okay, so it still creeps a bit after getting up over 5000rpm, the gate holds it around 6psi to there, but then starts going up to 10 by the time you hit redline, but that seems like it is expected with this wastegate and the big exhaust. It's not nearly as stupid as it was when the hose was bleeding air out and it doesn't hit fuel cutoff, but still not as predictable as I would like. I guess I need to ditch this can at some point or work with the tips that others have given for putting a helper spring on it until I can find another can to fit.
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Old 04-10-2014, 02:28 PM   #8
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I don't see any sort of spring being helpful at all. Usually a helper spring is used to help hold a wastegate closed to build/hold more pressure, which you don't want if you are already creeping. And if you for some reason tried to use one to hold the gate open that would not help as you would spool up more slowly, and are already overrunning the wastegate as is on the top end. You either need to port the 'gate so it flows more, or tune for the extra airflow.
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Old 04-10-2014, 02:53 PM   #9
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I guess I have the wrong idea. I suppose this overboost thing is more due to the larger exhaust.

I guess I should throw on the EBC and see what I can do there?
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Old 04-10-2014, 04:20 PM   #10
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The EBC will, as Brain noted, allow for better control on the lower end. But you are pretty much stuck with a creeper unless you restrict the exhaust flow or enlarge the wastegate port.

If you have injector and clutch capacity for the extra air, you might as well tune for it.
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Old 04-10-2014, 04:46 PM   #11
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Well, I've got 440s, so I should be good with the extra boost. Clutch needs an upgrade, but I have that in the garage as well, just need to put it in.
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Old 04-10-2014, 08:55 PM   #12
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The solution for boost creep from 6psi to 10psi is "run 10psi".
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Old 04-10-2014, 09:38 PM   #13
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Quote:
Originally Posted by Savington View Post
The solution for boost creep from 6psi to 10psi is "run 10psi".
I like this logic a lot
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Old 04-10-2014, 09:45 PM   #14
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If someone answers my question about the solenoid in the MS forum I might be able to make that happen.

I just don't quite know how to verify the thing is working.
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Old 04-11-2014, 02:23 AM   #15
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Flyin Miata sells an exhaust restrictor specifically to combat boost creep. Cost$12.95. It is made to fit a 3 bolt flange though.

Keith
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Old 04-11-2014, 02:42 AM   #16
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that's moronic

that's like having a supermodel girlfriend and using a fleshlight while looking at her
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Old 04-11-2014, 09:39 AM   #17
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Quote:
Originally Posted by Savington View Post
The solution for boost creep from 6psi to 10psi is "run 10psi".
QFT

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Old 04-11-2014, 09:43 AM   #18
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Sav is on to something.

You're going to want more than 6psi very very soon ... might as well make the leap.

-Zach
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Old 04-11-2014, 10:24 AM   #19
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I just need to know if Brain's build with the center connector that shows IAC2B as one of the connections will work for the boost control. I hooked it up to a 12v source on one line and to that IAC2B line in the center connector and then put IAC2 as the pin in the software.

Not sure if that will work.
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Old 04-11-2014, 10:46 AM   #20
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boost should be going to a green/red wire on the center connector and set to BOOST as the output.
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