Originally Posted by dgeesaman

Rynberg has said it clearly, but for your understanding here it is, boiled down differently:

First, 'full exhaust' doesn't mean midpipe, but many folks run a straight-thru downpipe and a performance muffler already. These are good, simple mods with few complications. It's the midpipe replacing the main cat that makes it a full exhaust and is the point where you need to be much more educated and observant about the car and it's boost levels.

Midpipes cause two things to happen:
1) Your boost will spike and/or increase in level
2) Your boost will not reach a constant max level - it will 'creep' higher and higher the longer you stay in full boost.

1) is something the stock computer's boost control system simply cannot keep up with. You need to install some sort of boost controller that is more robust - either a manual boost controller or an electronic boost controller. The stock duty-cycling solenoid + restrictor pill setup is simply out of it's useful range.

2) Boost creep pops motors, especially with an aftermarket ECU. (The stock ECU will *usually* cut fuel before going too lean, but ... one day it won't...). The solution is to port the stock wastegate so that it can vent enough exhaust. That's it, but it's not a 5 minute job since the turbos must be pulled and disassembled.

The whole tuning issue depends on the ECU and level of boost you want. Once you get a sufficient boost controller and your wastegate is ported to meet the demands, you have control. But you still need to set your boost to a level that doesn't exceed or push your fuel supply. Stock ECUs = 10psi. Remapped ECUs w/ stock fuel system = 12psi, and so on.

You have 3 options if you're about to install a midpipe.

1) Install the midpipe, and install an adequate boost controller, port the ECU, and upgrade the ECU and/or fuel system as required. Also figure out what you're going to do about emissions (smog tests?), noise levels, and odor.

2) Install the midpipe and install some extra restriction. This reduces the boost control issue and enough restriction will stop boost creep. It may even be enough to remain with the stock boost control system, though I don't recommend it. Restrictor plates or more restrictive components elsewhere (stock intake or stock muffler) are how to add restriction.

3) Don't install a midpipe. Stay with a stock cat or high-flow cat. The high flow cat may require better boost control, but usually it won't creep. High flow cat with a downpipe and muffler can produce nearly as much power as a full exhaust.

So think about it: 1) is a lot of work, which if you're simply after power is better obtained by other mods. Some people think because a midpipe is a little cheaper that it's a good idea - wrong. 2) is adding performance only to restrict it again since you don't have the required supporting mods. Tell me if that isn't silly. 3) is simple, easy, practical, and cheap, and won't pop your motor.

Dave

Originally Posted by chrisdrx

will the standard boost controller on the pfc not do the trick ? i was lookin to slapp on a turbo back and mid pipe to my cat back just dont want to pop my motor is all as u said it would be a silly and very expensive mistake

Originally Posted by Mahjik

......Now, simply adding a midpipe does not automatically mean you'll get boost creep. I've known several owners who had midpipes and never experienced boost creep. However it is more likely to occur after a midpipe install.

Originally Posted by Sgtblue

Is creep affected at all by cooler ambient temps like spike? If so, it might explain why some can get away with it and others can't.

Originally Posted by chrisdrx

its a tublar manifold stainless for stock twins is what is telling me its made by autobahn88 oh and a fuel set up of a 255 lph fuel pump and 1300cc sec and pri 850's

http://www.carparts.com.hk/promotion...r_cp_mar07.htm