Here is a list of my mods:
-Built short block with low compression pistons
-APS single turbo kit
-Forge Actuator with 15psi spring
-APS intake tube known for collapsing replaced
-Scavenger pump replaced
-650 CC DW Injectors
-Walbro 255 pump
-APS exhaust designed for APS S.T. kit
-Osiris
-Competition Clutch Stage 4 Clutch
-JWT Lightened flywheel
-AEM boost controller

Car was making about 7-8psi until about 4k rpm then dropped to about 2psi all the way to redline. After multiple trips to the dyno (Runs looked like an upside down V) with no real answers it turned out that carbon build up on the wastegate caused a leak. Now it is boosting consistent at 8psi but I would like to push more.

There is a tiny amount of shaft play in the turbo which I can replace the CHRA pretty easily. The question I have is this, is the stock APS housing too small to get more boost or am I missing something? I can upgrade to true GT35R housing with external wastegate but do not really want to drop another several grand unless absolutely necessary.

Let me know as this is driving me crazy.

Jeremy

 

Did you do the install yourself or a local Shop?

 

A shop did install as the motor had to be pulled for build.

 

i ran that setup on a built block to about 15psi. if you want to max it out, i recommend getting some headers and converting it to an external wastegate setup that dumps to atmosphere. keep in mind i did neither of those things (i did have an external wg but i had it recirc back into the dp), but i think i would have gotten a bit more power out of the kit had i did.

 

Forgot, the car has megan headers on it from the previous owner. Would an external wastegate really allow the boost to double?

 

i don't know what kind of actuator you have on the turbo, but i had an aftermarket FORGE actuator and it would push open past 10-11psi...no matter what i tried to do to keep it shut. that's your primary reason for converting to an EWG setup. what kind of power did your car make at 8psi?

 

I have the forge actuator installed on the car with the green spring. It was done at a shop.

 

what is the green spring rated for?

 

wait, if you have a 15psi spring then the spring should keep it closed to nearing 15psi.

So if the turbo doesn't produce enough to build boost to 15psi then there is a boost or exhaust leak. It could also be the spring is incorrect and it's actually a lower pressure spring.

also, i'm not familiar with internal wastegates but don't they require a boost reference in order to keep the wastegate closed? I know on external they need the boost reference in order to open properly but i thought that the internals were opposite.

If that's the case then maybe something is wrong with the boost reference that is supposed to hold the wastegate closed.

 

The green spring is the weakest spring for the aps turbo. I believe it is rated at 5-10psi. You won't get any more than approximately 8psi like you are getting. The aps kits are hard to get the full ratings out of the spring due to the design. I have the blue springs in my setup they hit 15psi then taper down to around 13psi on wastegate setting. This is the nature of the beast unfortunately.

 

good info. problem solved

 

I don't know what spring I had in mine, but I ran 17psi all the way to redline without issue. I bought my car with the kit on it already, and way told that the hotside of the turbo had been upgraded. I don't know how true that is, but it maybe something to look into.

 

Thanks guys. I am ordering the red spring on Monday and will keep you posted. The shop that intalled it told me the green spring would give me the most boost which I found to be incorrect. Hopefully the red spring will make the difference. Thanks for all the input and will update the thread as soon as the red spring is installed.

 

seems like u dont know too much about ur car and how it works...heads up if ur going for more boost u will need a re-tune...hope u know that much...

 

Of course the car will be retuned when the spring is installed. Thanks for the comment captain obvious.

 

are u serious right now..u made a thread so u could figure out how to get more boost..really...think u might want to end it now..

 

Good luck with the new spring. Don't be surprised if you can't use it to the fullest extent of its rating. It is very hard to get high boost with the aps single setup with the internal wastegate.