cant hold boost

[98eclipsekidd08]

I have a 96 GST only mods are intake and a 1G BOV. I did a boost leak test and i was leaking at my flange for my BOV so i fixed that. No other leaks found. I am stumped because my car will hit 14 psi for a second and then drops to 10 psi. I read fourms on this but didnt get any real answers. I just changed my plugs and gapped them to the appropriate space, changed oil, no shaft play in the turbo, and like i said i did a boost leak test and fixed my 1 leak. Can the T25 only hold 10-12psi?

 

[jessicas gst]

Check that the turbo is bolted tightly.
I had this happen in my MR2, it would hit 16~ by 4200 rpm then fall to 10~ by 7200.
I had lost 2 of 4 nuts holding my turbo on.

 

[joe]

First question is if your only mods are intake and bov. How do you know that you are only getting 10-12 psi.? Do you have a boost gauge? Im not sure what the stock electronic boost controller sets the boost @. But a t-25 should be able to hold 15-16 psi to redline. You should consider buying a manual boost controller if you would like to turn up the boost. Thats only if you already have a boost gauge.

Here's the MBC im using seems to work fine.
http://cgi.ebay.com/ebaymotors/High...009QQitemZ190153072135QQrdZ1QQsspagenameZWDVW

 

[silver eclipse]

The stock boost controller usually is between 8-12 (ive heard people say differently from the boost guages). So if your not running an MBC, you may be spiking then settling to 10 psi.
What rpm and how fast does it hit 14 psi?

 

[VETTE_50_TH]

If you do have a MBC and boost gauge, it could be a bad wastegate, or cracked turbo. Hell, it could be a lot of different things, such as your engine is on the way out. Need some more info, first, such as a full list of mods on the car.

James

 

[98eclipsekidd08]

Sorry, i forgot the MBC its a turbonetics good to 25psi. and yes i have a boost guage. Ill check the bolt mounting the turbo tonight and let you guys know if that works for me. thanks, keep giving me ideas ill try any.

 

[hevenz]

What plugs are you using? Mine did that untill i went to ngk's 7's

 

[98eclipsekidd08]

there brand new like less than a week old NGK Platinum G-Power plugs. and yes around 4-4500rpm the boost drasticly drops to 10 from 14. Could this be as simple as both 02 sensors went cause they did haha.

 

[Jordanbutter]

Mine is doing the samething the only answer I've found points the the Wastegate Actuator. Just a list of somethings I did was, take the manifold off and check for cracks, check the gaskets for cracks, take the wastegate arm off and make sure its strong (i.e. you can't pull it out easily), make sure the flapper closes all the way, and shim the wastegate (which did nothing and was not worth the trouble). Hope some of this helps.

 

[hevenz]

its your plugs.. i had Bosch Platnums and i found out this weekend that our cars cant do platnum and iridium plugs. you have to go and ask for NGK BPR6ES. I had the same problem you did for 6 months. got som BPR7ES and it works SO much better

here http://www.dsmtuners.com/forums/showthread.php?t=233421
Read #4

 

[98eclipsekidd08]

that would help but... im new to turbos and dont know how a wastegate exactly works or what a flapper is so I dont know what i would be looking for

 

[98eclipsekidd08]

what plugs worked for you what would you recommend?

 

[cbrue122]

The little T-25 spools so fast that an initial boost spike is common if the wastegate/mbc cannot respond fast enough. Another consequence of the tiny turbo is a drop in boost at higher rpms because it just can't flow enough. I have noticed both these results with my T-25. It usually spikes to about 12psi before settling at 10psi and then it starts to fall below 10psi around 5000rpm. By 6500-7000rpm it falls to almost 6-7psi.

 

[Jordanbutter]

Ha ha ok well I have to remember my T-25 but it should look like this. There should be something that looks like a gold mushroom with a silver metal rod coming out of it. Thats the Wastegate Actuator, the Arm is the metal rod and the flapper is where the rod connects to the turbo (on the exhaust side) what it pushes open and closed is the flapper door (inside the turbo).

 

[rich3389]

the T25 craps out at higher RPM(5500-7000rpm) and you could have 15 psi at 4k rpm but it will drop to 10-11 at the higher rpms. The turbo is to small and will not be able to feed enough air at higher rpm.

 

[hevenz]

its your plugs.. i had Bosch Platnums and i found out this weekend that our cars cant do platnum and iridium plugs. you have to go and ask for NGK BPR6ES. I had the same problem you did for 6 months. got som BPR7ES and it works SO much better

here http://www.dsmtuners.com/forums/showthread.php?t=233421
Read #4

 

[Jordanbutter]

I'm sorry I just can't jump on the spark plug bandwagon. Like I said my 16g is doing the samething and I am running almost brand new NGK BPR7ES' so I just can't say thats it.

 

[98eclipsekidd08]

i just dont get how my friend holds 14 psi on a stock t25 then? the only mod he has that i dont is a full 3in ss exhaust but tomorrow i will check the actuator and all that and let you guys know. Its probably just the fact its a small turbo like you guys are saying, thanks everyone who has helped

 

[98eclipsekidd08]

there brand new like less than a week old NGK Platinum G-Power plugs. and yes around 4-4500rpm the boost drasticly drops to 10 from 14. Could this be as simple as both 02 sensors went cause they did haha.

SO all you experianced turbo experts can the o2 sensors have anything to do with this problem or most likely not? both mine are bad I just need money.

 

[joe]

T-25 will hold 14-16 psi till redline unless you have either a boost leak or an exhaust leak or something wrong with your boost controller. END of story.....tired of hearing that T-25 cant hold at least that till redline. I used to hit a 20+ boost spike with mine( which had no performance benefit)@ 4k.

 

[98eclipsekidd08]

T-25 will hold 14-16 psi till redline unless you have either a boost leak or an exhaust leak or something wrong with your boost controller. END of story.....tired of hearing that T-25 cant hold at least that till redline. I used to hit a 20+ boost spike with mine( which had no performance benefit)@ 4k.

ok so i checked it all no boost leak, turbo is secured to manifold tightly no leaks, no cracks in manifold, no exhaust leaks, no shaft play in the turbo. So i guess its my turbo or something cause my definatly doesnt hold 16 not even 14 psi to redline, 10 to 12 it varies on when my car feels like it i guess only thing i can think is maybe my stock exhaust is just to restrictive.

 

[voodoogsx]

The little T-25 spools so fast that an initial boost spike is common if the wastegate/mbc cannot respond fast enough. Another consequence of the tiny turbo is a drop in boost at higher rpms because it just can't flow enough. I have noticed both these results with my T-25. It usually spikes to about 12psi before settling at 10psi and then it starts to fall below 10psi around 5000rpm. By 6500-7000rpm it falls to almost 6-7psi.

I noted this with my stock t25 though not really falling to 6-7, it would peak at 14, then drop down to 12 then slow descend to 9, I ended up getting a big t28. It holds boost where the other didn't.

 

[98eclipsekidd08]

thats exactly what mine does eventualy gets to 9psi damn now i have to by a new turbo haha. Its not cool my friend hold 14 but whatever. what would be a good turbo for me any advice, i want to boost around 14-16 psi. I will be getting a full 3" s.s. exhaust soon. I was thinking a evo 3 big 16G but then again i hear good things about other turbos to. I want it to mount up to my stock manifold and not have to do much other mods for the time being. preferably under $600 is there a good turbo around this price for me??

 

[Jordanbutter]

The t-28 will bolt right up for everything, an e3 16g will require a j-pipe new oil and water fittings and lines. For under $600 go with the T-28 its a total sleeper, spools a bit faster, and will hold that ammount of boost.

 

[98eclipsekidd08]

The t-28 will bolt right up for everything, an e3 16g will require a j-pipe new oil and water fittings and lines. For under $600 go with the T-28 its a total sleeper, spools a bit faster, and will hold that ammount of boost.

thanks for all the advice i have heard many good things about the t-28. so its quick spool and holds up to 16, will it hold that to redline? and are you or anyone you know running this turbo¿ thanks