can not hold boost

[99 gst spyder]

i cant hold boost on my 16g. usually 16g come with a waste gate springs set to 10 lbs of boost. this one's different. this is my second 16g turbo kit on two different dsm's. it should hold stock boost to around 10 lbs.

i have eliminate the bcs and connect a straight vacuum line from the j pipe to waste gate to try and hold minimum boost as possible. still this wouldn't hold any boost.

wot on 2nd and 3rd gear went to 20 psi and maybe even more if i didn't stop.

there's only two reason i can think of.

1. huge boost leak. note" pull pretty strong 1st,2nd,3rd
2. bad waste gate.

anyone have or had this problem before let me know what you have done.

thanks in advance.

 

[slowboy101]

just do a boost leak test just to make sure then go from there

 

[gofer]

i cant hold boost on my 16g. wot on 2nd and 3rd gear went to 20 psi and maybe even more if i didn't stop.

These two sentences aren't jiving, so what is it? When you mash the pedal does the gauge hold at 0psi or spool to 20+ lbs?

You can easily check to see if the wastegate actuator (wga) is blowing open by just removing the boost source off of it, leaving it blind to how many lbs of boost your building. Just be sure to cap off the boost source on your piping and WATCH that gauge carefully, you don't want to build too much boost.

If you build boost just fine with no boost source on the wga then do a BLT like mentioned above. I had a gasket blow on the rotating assembly of my 16g, it would spool and push air right out the side of it making a supercharger sound and 0 psi was all my boost gauge would go to.

 

[DSM_JAY]

+1 on boost leak test, they will often tell you everything you need to know and more . be sure to use some soapy water in a spray bottle it really takes the guess work out of pin-pointing where that darn sound is coming from

 

[slowboy101]

^^^^ yes sir they are also the main sorce of most problems boost leaks happen all the time

 

[99 gst spyder]

guess it doesn't hurt to do a BLT.

it doesn't hold boost at zero. goes up past 20 psi.

these are on ecmlink. you have to have ecmlink software to upload these logs.

some logs. the first log i did a pull 3rd gear all the way up to about 5k rpm.

second are just some other revs and second gear pull as you can see.

anyone know how to read these, please i need some info.

 

[JayRolla]

Boost creep? Normal issue on the MHI turbo housings. Research boost creep on how to fix it. Can be a PITA.

 

[gofer]

!!! You are leaning out big time and knocking like crazy!!! Don't keep mashing the gas when you see it knock man, thats retarded. Your IDC's are over 100% (120%!!!!!) and your leaning out BIG TIME, I can see that just by looking at your front o2 sensor voltage. If your still on the stock fuel system don't go into boost if its creeping past 15psi, unless of course your trying to blow up your car?

You need to port the exhaust mani, hotside of the turbo (including the wastegate opening), and the o2 sensor housing OR put a restriction in the exhaust. What that means is go back to a stock dp or put in your stock cat, that way that turbo won't creep out of control.

AGAIN!!! DO NOT for the sake of your engine, watch your boost keep creeping past 15psi because your fuel system can't keep up.

 

[hurricanecris24]

Are you running a downpipe? If so its causing you to creep my car is doing the same thing right now after I put a 3 inch downpipe and before I did it held 15 psi with no problems

 

[99 gst spyder]

great. thanks for letting me know about my logs. it's not my daily driver so i'm not going to be driving it. just only to fix my problem.
ok leaning out a lot. i have RC 1000 cc and 255 pump. will that help plus having the shop dyno/tuning? i want to get it dyno/tuning but need my car to run good first. trying to fix all my problems.

my o2 dump use to pop very loud when hitting high boost and right when it starts to knock a lot. change my champions plugs to ngk bpr6es at .028, that fix the popping noise. now only is the over boosting. i'll get the BLT done and see.

yeah i do have a 3'' down pipe and 3'' test pipe including 3'' whole cat back.

thanks a lot everyone.

 

[gofer]

Its always a good idea to do a BLT but the way you worded your OP was that your car wasn't HOLDING boost, i.e. you couldn't build boost. What you meant was that it won't hold 12lbs of boost because it spools to 20+psi. That means your wastegate isn't efficiently redirecting your exhaust gases around the turbine wheel of the turbo.

Its hard to picture in your head but exhaust will take the path of least resistance, just like water. When your at WOT and you hit 12psi your wga opens the flapper on the turbo to redirect those exhaust gases (assuming you don't have a boost controller). From there the exhaust has two routes it can take, one being over your turbine wheel spooling your turbo faster & faster OR the other going through that tiny ass excuse for a wastegate and dumping out your o2 housing. By freeing up all the restriction in your stock exhaust (3" turbo back/cat delete) the path of least resistance for the exhaust is over the turbine wheel of the turbo and not through the open dump on your o2 housing. Thats whats causing your boost to creep out of control, not allowing you to run the 12psi your fuel system can support.

Those 1000cc injectors and 255 fp are perfect for your setup, especially now that you've got dsmlink on the car. I also suggest getting a afpr (adjustable fuel pressure regulator) since you do have the 255, they've been known to over run the stock fpr and cause your car to run rich.

Get it tuned on the dyno, I do suggest it. A lot of shops though charge by the hour on the dyno and things can get pretty expensive. Before I've taken my car to get tuned by a shop on the dyno I try to street tune it as best I can so when the shop gets it they just squeeze out the extra here and there which kicks an hour or so off the dyno time.