so i've been reading about this myth that says you will OVERBOOST LIKE CRAZZYYZYZYYY with full exhaust as your only mod, but what if you're running full non-sequential with no boost controller (see: 6psi)

will it raise the boost past 10? or will it just run lean under 10psi???

 

You have problems if your only gettin 6 psi bud. Good luck.

 

I run dp and catback on non-seq. If my MBC isn't set right, it has overboosted before. Be CAREFUL of that sh*t I tell you.

Once you go non-seq this means you're not getting the proper restriction from the pills which, if you have done the non-seq. conversion, means you have bypassed some of those lines..

Thus, you will get 7psi.

You will need to install SOME type of boost controller after going non-seq. if you are wanting anything more than 7psi. 7psi aparently is the stock setting on the wastegate.

The whole point of the pills is restriction, thus, creating more boost, same concept of any "boost controller". When you go non-seq you bypass those pills in certain areas, thus, 7psi.

Perrin or Hallman would be fine for an MBC...Profec B Spec II for electronic, till you go Power FC, and even then.

My 2 cents, and personal experience.

 

You'll almost always get a bit of creep, especially if you have intakes and it is a cold night/day. It'll start out holding at 7, and creep up to around 12-14 then you need to lift a bit to hold 10-12. Every car is different, though.

 

so an exhaust is going to yank my boost from 6-7psi (wastegate spring) to above 10 and make it creep even higher than that? yikes.

as for the intakes, i am running the stock airbox, and plan do cut out the bottom to do that poor mans intake thingy...

maybe i'll just get a catback and keep my crappy stock cat :/

 

go for the turbo back, just set the MBC correctly and you should be ok.

 

It's not a myth. On a car with a properly functioning set of turbos (boosting 10psi), a full exhaust puts you right at the edge of boost creep. Depending on what mods are installed on the intake side, it may or may not creep. With a completely stock airbox, intercooler, y-pipe, etc, it's quite possible you will have enough restriction to not see boost creep. But most people will not run a full exhaust with a fully stock intake side.

If you're only getting 6psi right now, there is another problem. Boost leak probably. But when you do fix it, be aware that you should look out for boost creep.

Dave

 

hello dave,

i'm curious as to why i have "another problem."
my only mod is a downpipe (see also: stock cat and catback), i did the full non-sequential mod with no pill in the wastegate signal (that means the turbos are running off of the wastegate spring which is 6-7psi) and i have no boost controller to raise the boost back up to 10.

Jacob

 

A boost controller wont help in this situation. Either pull your turbos and port the WG, or dont do a full exhaust. A silencer or restrictor or smaller section of pipe will usually help with top end creep. For reference you should be safe at 12-13psi on an otherwise stock engine.

 

BTW stock FD WG spring is 7psi. But most boost gauges can easily be off by a pound.

 

If the 6-7psi limit is due to removing the stock boost controller (pill + wastegate solenoid), then nothing is wrong. I assumed that your baseline was supposed to be 10psi. Going to a full exhaust without adding a boost controller is not a big deal - you'll need to watch for boost creep, is all.

Dave

 

Yep, that's right. Your "boost controller" won't be able to do a damn thing unless your wastegate is bleeding off boost to your desired level.

I recently bought a car which was done non sequential, and it was also equipped with an open exhaust and aftermarket intake. After 4k RPM @ WOT, I get 14 psi--EASY. NOT GOOD (stock ECU)! I'm going to install a hi-flow catalytic converter and if that doesn't help keep boost levels down, I'll also install my OEM air box. If that doesn't work, I'll have to yank the turbos and port them (more than the previous owner did), as Mr. Ressurrection has mentioned.

Be careful man, because if you run lean for whatever reason (overboost, crapped out injector, lack of fuel... etc.) your engine is gone.

 

ok thats interesting input. i have the stock intake and such, but i suppose i'll keep the stock cat or the stock catback and just set the MBC to 10psi...

and believe me, i'm no noob at blowing or rebuilding motors :x ask kevin

 

Jake, if you want to keep 10psi, then retain the stock WG solenoid...it'll do that for you. Think of it as a free EBC permanently set at 10psi. It will react quick and is worlds better than your MBC. IT still cannot save you from creep, though, it can only raise boost above the 7psi spring.

So put your pill back in the WG feed line from the compressor; uncap the other side of the actuator, and run that hose to the WG solenoid. You can leave the other nipple on the WG solenoid open for simplicity...the boost just needs to vent to atmosphere for it to work, though it was originally routed back into the primary turbo intake inlet.

 

i thought one nipple on the solenoid had to be the signal IN (from the compressor) and one had to be the signal OUT (to the wastegate...)

 

nope. the WG gets its signal in from the compressor...just like a FC turbo. The actuator has a 2nd nipple used to bleed off some of this pressure via the boost solenoid...like an s5 t2 would have stock. By venting some of the boost out of the actuator chamber, you keep the WG from opening. The ecu controls the solenoid duty cycle based upon map sensor readings of boost, so it is effectively an EBC.

 

Just run a good H-F cat in place of a midpipe. I can hold a solid 7psi up to redline in any gear with my mods.