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View Full Version : Boost dropping at WOT!


dds78910
03-07-2009, 01:22 AM
So when I floor it my boost hits 19-20 psi then slowly drops down to 12. Is my wastegate failing and being pushed open? I by passed the WG solenoid and have the nipple on the compressor housing going to the manual boost contoler then going to WG.
turbovanmanČ
03-07-2009, 01:42 AM
What type of MBC, some are crap and won't hold boost.
dds78910
03-07-2009, 01:46 AM
TurbosXS
turbovanmanČ
03-07-2009, 03:38 PM
Try running manifold vacuum to the WG and see what happens. If its rock solid, then its your controller, if not, then your can is bad or too tight/loose.
Turbo3Iroc
03-07-2009, 05:18 PM
You're not running a stock BOV right? Cant really tell in your engine pics.

The stock turbo on a TIII will not hold 19 psi up top anyway but 12 is too low. At redline you should still see ~16.
bradp
03-07-2009, 05:28 PM
Do you have a BOV? Damn beat me to it.
dds78910
03-07-2009, 11:08 PM
Yes I have a blow off valve, I have the TurboXS FRL on it now. I messed with it today the WG feels really strong takes some effort to pull out. I put a spring on the WG and it still does it. It seems the higher gear you are in the more boost it will hold. 2-3 gear it spiked to 21psi then slowly dropped to 12psi, then from 3-4 it would hold 14psi then 4-5 about 16 psi. I ddindt want to test too much, I havent put on my A/F guage yet and the water temp was getting high so backed of and drove it nice.
GLHNSLHT2
03-07-2009, 11:33 PM
sounds like a weak wastegate can to me. My daytona used to do that, it's spike to 18psi then fall to 15. When I put a 2.5 under it'd fall all the way to 11psi. Going to a big can solved that.
dds78910
03-08-2009, 04:42 PM
sounds like a weak wastegate can to me. My daytona used to do that, it's spike to 18psi then fall to 15. When I put a 2.5 under it'd fall all the way to 11psi. Going to a big can solved that.

The WG feels really hard to pull out by hand plus I put on a stiff extention spring and it still drops. I would think if the WG wasnt holding the spring would keep the WG closed.

Could it be I'm exceeding what the turbo is capible of? I dont have a whole lot done. 3" mandrel bent exhaust w/magnaflow hiflow cat and muffler from turbo all the way back. FWD stage 2 computer with 20% injectors, manual boost controller and a 8.5 wires. I have the stock IC setup now, but that is my next project is to put a bigger FMIC.
GLHNSLHT2
03-08-2009, 05:05 PM
wire the wastegate shut and go for a drive then :)
bradp
03-08-2009, 05:13 PM
I still think it might be the BOV
dds78910
03-08-2009, 05:22 PM
I have tried 2 BOV's a Biltz and Turboxs RFL. Both the same. I think the FRL is suppose to ho 30 PSI.
Turbo3Iroc
03-08-2009, 08:59 PM
Has any port work been done to the head intake or exhaust manifold?
dds78910
03-10-2009, 07:02 PM
Has any port work been done to the head intake or exhaust manifold?

None that I know of, the person I bought the car from had the head rebuilt and crack fixed and a 3 angle valve job but I dont see anything about porting. And I didnt see any signs of it when I pulled the intake manifold off.
RJ138
03-11-2009, 11:24 AM
It could really be a number of things... But my guess is the turbo and the stock intercooler are maxed out. I would spike to 21-22 psi and steady out to 16 to 18 psi with the Spearco and stock turbo.

Check for vacuum leaks.
JamesL
03-11-2009, 11:41 AM
It could really be a number of things... But my guess is the turbo and the stock intercooler are maxed out. I would spike to 21-22 psi and steady out to 16 to 18 psi with the Spearco and stock turbo.

Check for vacuum leaks.

It could be a number of things but I always check for boost leaks using a compressor, a regulator and a simple device that uses a tire valve, a PVC cap and a silicon boot.
Turbo3Iroc
03-11-2009, 12:54 PM
Your turbo could even be on it's way out. Have you looked inside the hoses for oil or coolant?
dds78910
03-11-2009, 10:38 PM
I did see some oil residue inside the intrcooler tubes the last time I had it apart, and the car puffs out a blue cloud of smoke when I start it but goes away after a few seconds.
dds78910
03-11-2009, 10:44 PM
It could be a number of things but I always check for boost leaks using a compressor, a regulator and a simple device that uses a tire valve, a PVC cap and a silicon boot.

So you pump compressed air in the system and wait to see if it will loose pressure over time? Is that right?
glhs727
03-11-2009, 11:52 PM
yes, and with the motor off, it is easier to "hear" the leaking air and find where it is coming from. We have a couple of boost leak checkers at work and we use them alot. It will cost about $5 to make one, and it will come in handy a lot over time. If you pressure the system, don't use a lot of pressure 15-20 psi ( so turn down the pressure on your comressor) is good, and then listen.
later,
Cindy
JamesL
03-12-2009, 10:30 AM
What she said but it takes a bit of volume before the pressure will rise. Bring it up slow and just listen and feel around. You could also put some soapy water in a spray bottle to check for small leaks at connections and such. You can also watch the WGA to see at what pressure it wants to open.