too much boost

[davidgt97]

I just put a new motor, turbo, stainless manifold, and o2 housing in the car. Aside from some annoying oil leaks everything seems to be good. When I drove the car down the road I tried to be easy as I am still breaking in the motor, but as I gave it a little more pedal and let it rev to about 4k the car bucked very hard which I suspected was the infamous fuel cut I"ve heard so much about. But this should not be as I am running stock boost w/ the mbc out. So sure enough I hooked up my boost guage and the boost was running on up to 20 psi so obviously for some reason my wastegate is not working. Any ideas?

 

[ScottH]

Is this an internal or external wastegate?

 

[B-Man]

Is there a delay, or does it spool pretty quickly? Make sure your wastegate arm is connected to the flapper. Mine has popped off before.

 

[Gstclipse69]

Yea make sure the arm and flapper are correctly engaged. Also make sure the flapper is opening all the way and nothing is obstructing it. Some porting of the turbine hot side may be required. Are you still on the stock bcs?

 

[97gstjosh]

but as I gave it a little more pedal and let it rev to about 4k the car bucked very hard which I suspected was the infamous fuel cut I"ve heard so much about. But this should not be as I am running stock boost w/ the mbc out. So sure enough I hooked up my boost guage and the boost was running on up to 20 psi so obviously for some reason my wastegate is not working. Any ideas?

Ok remember you might be running stock boost but theres a big difference between
stock boost on a 14b or stock boost on a 16g. The 16g is going to require more fuel and is pushing more air then the 14b or whatever turbo you had before this one. Take that into consideration. Did you have the MBC in before this turbo? What was the boost set to? If its internal gate the flapper arm isnt working right. If its ext. let us know then we can help?

 

[97gstjosh]

Yea make sure the arm and flapper are correctly engaged. Also make sure the flapper is opening all the way and nothing is obstructing it. Some porting of the turbine hot side may be required. Are you still on the stock bcs?

If its going up to 20 pounds the flapper is def. opening all the way.
He shouldnt need to port it. Thats not the problem. It sounds like
fuel cut to me not the BCS flicker. Did it feel like you hit a wall
and you looked behind you for your engine?

 

[Mr Peepers]

Having the flapper disconnected will cause you to run no boost at all, since it will blow open and allow all the exhaust to bypass the turbine.

Make sure the flapper moves freely and that there are no kinks or leaks in the line running from the pressure source to the wastegate. If you are still using the BCS, bypass it to get rid of a variable. Just run a line straight from your j-pipe or similar to the wastegate.

EDIT: Also make sure the WGA itself isn't leaking, a large enough hole in the diaphragm will cause the symptoms you are describing as well. Pressurize the WGA with about 10-15 psi and make sure it moves the flapper. If it's an eBay turbo, make sure the WGA arm is adjusted properly and the flapper moves freely. My friend's eBay 16g flapper had to be opened and closed by hand multiple times before it would work smoothly, and there have been other reports of this as well.

 

[davidgt97]

I currently don't have a mbc hooked up, It's just a straight line between the intake pipe and the wga. It is an ebay big16 so I'll try pressurizing the wga w/ 15psi and manually opening and closing it several times.

 

[theebluecrx]

I would blame the actuator all the way.Do you have a stock exhaust?

 

[davidgt97]

No: aftermarket tubular stainless manifold, stainless o2 housing, 2.75 stainless downpipe, 2.5 catback. Haven't got a chance to check the actuator.

 

[Mr Peepers]

I've had the same experience with my friend's ebay 16g. I can almost guarantee you will need to port the turbo keep it from creeping, but after working the flapper back and forth it would at least hold 10 psi for a little while until 4-5k in the higher gears. Make sure the wastegate arm is adjusted properly as well.

 

[davidgt97]

I pulled the actuator arm from the flapper and used my compressor to push 30 psi to the actuator in several short bursts. I also adjusted the actuator out a little and now it boosts to 13 -14 psi. Thanks a lot for all the suggestions.