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Discussion Starter #1
I threw a 15g kit on my 98 Civic EX. I am having problems with it holding boost. With the rod at stock length, it will boost up about 4 psi and then drop down to 3psi. Ive tightened it up several rounds, and it will boost up to about 5-6psi and then drop to 4. Is this a common problem with the stock greddy actuator? I am running a FMIC and 2.5" piping, and the wastegate is connected directly to the compressor housing nipple.
 

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That's a common problem with the greddy TURBO.

Small hotside, tiny cast elbow with a 2" outlet. They all die off in the top end. Killer low and mid range though.
 

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I threw a 15g kit on my 98 Civic EX. I am having problems with it holding boost. With the rod at stock length, it will boost up about 4 psi and then drop down to 3psi. Ive tightened it up several rounds, and it will boost up to about 5-6psi and then drop to 4. Is this a common problem with the stock greddy actuator? I am running a FMIC and 2.5" piping, and the wastegate is connected directly to the compressor housing nipple.
That is probably your issue.

I have it hooked up the same way on my 15G kit and the pressure drop is similar.

I've been too lazy to relocate the boost signal source to after the intercooler, should make for a more stable PSI.

So drill a hole in a coupler or intercooler pipe (after the intercooler) and install a barbed fitting of some kind that you can attach the vacuum line to for the wastegate.
 

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Discussion Starter #4
I understand that the turbo will not flow a ton of CFM top end, but i don't believe its an airflow issue thats causing it to drop boost level.
 

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I thought that they came pre set for either 5psi or 8psi.
Also running it off the compressor will give you psi drop because of the intercooler and the wastegate opening when the turbo hits the set rate vs the wg opeing when the intake is at that set rate.

But yea small piping they die off. and try to find out what the wastegate is rated for and how much you trying to push?
 

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Discussion Starter #6
That is probably your issue.

I have it hooked up the same way on my 15G kit and the pressure drop is similar.

I've been too lazy to relocate the boost signal source to after the intercooler, should make for a more stable PSI.

So drill a hole in a coupler or intercooler pipe (after the intercooler) and install a barbed fitting of some kind that you can attach the vacuum line to for the wastegate.
I guess running the WG off the intake manifold will be my next step, i will post the results in the next day or so. Just need to buy a rubber cap to block off the compressor reference.
 

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Discussion Starter #7
I thought that they came pre set for either 5psi or 8psi.
Also running it off the compressor will give you psi drop because of the intercooler and the wastegate opening when the turbo hits the set rate vs the wg opeing when the intake is at that set rate.

But yea small piping they die off. and try to find out what the wastegate is rated for and how much you trying to push?
I've read the 15g comes set for 5psi so my boost levels make sense after the pressure drop from FMIC.
 

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I guess running the WG off the intake manifold will be my next step, i will post the results in the next day or so. Just need to buy a rubber cap to block off the compressor reference.
if its just a nipple and your using a silicon cap zip tie the crap out of it. but if its a npt thread then your all good.
 

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IIRC this is a very common problem with the greddy kit, the actuators are shit. MBC and a spring to hold the wastegate shut.
 

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Owning a Greddy kit for a few years, i've gone through this before.

Tiny turbo, don't expect it to hold boost all the way to redline. I've had mine at 6psi drop to about 4.5 or 4 psi by redline. I've also had it at 20psi, and it would drop to like 17psi by redline--- keep in mind that this was basically the wastegate unhooked lol.

Routing the wastegate line to the IM or the cold pipe would be best; however, running the wastegate to a vacuum source i've been told isn't a good idea. You can fix that by running a MBC in line to the wastegate though. Worked great for me for several years.
 

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Owning a Greddy kit for a few years, i've gone through this before.

Tiny turbo, don't expect it to hold boost all the way to redline. I've had mine at 6psi drop to about 4.5 or 4 psi by redline. I've also had it at 20psi, and it would drop to like 17psi by redline--- keep in mind that this was basically the wastegate unhooked lol.
IIRC the 15g is out of its efficiency range after 15 or 16 PSI. No wonder you were dropping to 17.
 

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Discussion Starter #17
I ran the wastegate line directly to the IM and it holds boost much better now. Actually boosts all the way up in 1st gear now also. It only drops about 1psi now.
 

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Glad to hear that helped. Keep in mind that the internal wastegate isn't made to see vacuum. I've heard that it can decrease the life of the actuator, someone correct me if i'm wrong... just heard that locally from a tuner.
 

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Glad to hear that helped. Keep in mind that the internal wastegate isn't made to see vacuum. I've heard that it can decrease the life of the actuator, someone correct me if i'm wrong... just heard that locally from a tuner.
I believe your right. I heard something about that too. I think the vacuum sucks the diaphragm up around the spring causing it to rip over time. But not 100% sure just relying what i've heard.

@green91
glad you got it fixed. Just keep an eye out for overboosting
 
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