I just finished putting on my hks downpipe, exaust is leaking from the Main Cat/Downpipe flange, could this lack of back pressure cause my boost to spike like that. I am going to fix the leak but I needed to drive the car to work today, at WOT my boost is fine all the way to 4500 then it jumps to about 13-15 psi??

 

I'm thinking it is partially due to the grade of motor oil cuz that happens to me too (same brand DP). When i add a quart of 10w-30 to my usual 20w-50, i get something like 11/14/12. When i use all 20w-50, i get about 9-10/11/10. I'm sure there's some other reason tho, so i'd like to hear what others have to say too.

 

no..

I have used Redline10-30 syn the entire time I have owned my car. I believe its from a lack of back pressure, but I dont know. It seems like only a small leak, of course I have never put my hand under the car to feel at WOT so who knows??

 

I don't see a SMALL leak being that much less restrictive than your cat. Are you SURE you didn't knock something out of place when installing your downpipe? And be more careful with your description, are you spiking to 13-15 psi or is it going there and staying there? Sounds like your wastegate line or something similar.

Whatever you do, don't drive the car hard until you get it figured out.

 

thats kind of what I was thinking, maybe the wastegate actuator hose? The exaust leak is deff releaving some restriction though.. the car is loud, real loud, and not from the tail pipe, from underneath the car..

 

It sounds as if you pre-control actuator isn't working properly. I would think if you added more restriction to your pre-control hose or bumped you precontrol actuator and messed it up during the DP install.

Meaning that your Primary Turbo works fine... But the pre-control actuator isn't working to limit the amount to pre-spool to your Secondary Turbo. So that when 4500 comes around and your secondary kicks in, there is way too much exhaust gas spinning the Turbos. Giving you 14-15 psi at transition.

My .02