iam the proud owner of a 2005 gti 1.8t. so far i have lowered it with a set of adjustible coilovers and struts by kw. i have an apr 93 octane chipped ecu also with an ram air intake. i recenly purchased a greddy profec b spec 2 automatic boost controller. i have heard with minamal upgrades a stock 1.8t can push a safe 19-20 psi. i would be adding an exhaust system. 3 inch is what i plan on. should i get a turbo back, downpipe, or just a cat back for now. i plan on full exhaust in the future. so after the exhaust would i be eligable to push that much boost without worrying too too much? any hepl or comment containg feedback about products or companys and expecialy advice are welcome thanks!

 

I personally don't recommend pushing 19-20psi, you can do it but then you have to make a choice, is this a daily driver? How long do you want it to last? Especially running on a stock transmission. 15psi is a good number to play with. You'll have traction issues even at 15psi. If you're going to do exhaust, save your money, cat-back systems in my opinion are a complete waste of money unless you're buying it for noise. If you're doing this for turbo purpose, go downpipe back, 3" (or whatever the max diamater of your downpipe is. Honestly though, if you want a sleeper, just get an exhaust cut-out welded in. Keep your stock exhaust. You can run those things a 1/4 open all the time and when you want the power, just push a button and you have open downpipe. Which is the best to squeeze any ounce of power out. It all depends on what you wanna spend and if you're going for noise as well. But nothing sounds better than an open downpipe. Least amount of bends and least friction and resistence is what you're shooting for. Should look at headers as well, makes a big difference, or have the stock ones ported, depending on the way it's casted. Also, in the case of an open downpipe, you'll actually get an additional 2-3psi without increasing the boost controller. It's forced induction, really fun stuff.

Good luck!

 

thanks for your hepl. that open downpipe thing sounds pretty interesting. could u describe it in further detail so i know exactly what it is capable of doing. i am already pushing 15 psi even 16 at some times thanks to my apr chipped ecu and it dosents seem to be all shes got. it fells better thank stock but i bought a gti to feel a lil more power. maybe i was lookin for a 10 sec car but my hopes were up. please hepl me figure what are the best steps to take remember that i stil;l have the boost controller to hook up.thanks for all your help!

 

You can have a 10 second car if you want, but you'll have to start dipping into the motor. A spec turbo cam would increase the power but you're looking at $1k roughly. Just remember they don't build 10second cars from factory lol unless you wanna spend $500,000 and up hahaha. Crazy. Forced induction (turbo, supercharger) don't require the back pressure like in a naturally aspirated motor, it's a whole different ball game. Open downpipe will give you an extra 40hp, or around there, depends on the setup and your exhaust manifolds as well as the downpipe size. The problem with exhaust systems is that all that forced air has to make turns and the air is pretty much crashing into itself. With an open downpipe you go from exhaust manifolds through 2-3 feet of wide open minimal bend pipe. The faster you get the air in the engine, the faster you want it to get out. That's why I also mentioned porting or buying aftermarket headers, depending on the way each port is bent and directed can reduce performance, you want it as straight as possble into the exhaust collectors and to the downpipe. If you install an exhaust cutout, which is only $200 or so, depending on the make, (don't be cheap, quality is important, you want it to last) you'll have an open free-flowing exhaust when you need it. 3" exhaust sounds great, looks cool but it's asking for trouble from the cops. They will just hassle you, even though you're not doing anything illegal, depending on the by-laws and noise ordinances in your area, you can be fined for excessive noise. With a cutout you can have the luxury of horsepower on demand, and a quiet car for all other times (though in some places they are illegal, but hidden under the car so it's hard to notice unless you have it open while you're driving).

You really don't want to drive around at high psi all the time, it's hard on the engine, transmission etc. You don't want to have to constantly get out either when you want more power to adjust it, unless the boost controller is installed in the car, (some aren't) depends on you and easeof installation. This brings up another point, you might want to look into 2-stage boost controllers. Gunning right off the light is a waste (unless you have slicks) and is definitely very hard on the car, 2-stages, can start you off at lower psi, then switches the psi higher when your car is gaining speed, not as hard on the transmission. I dont know if you've looked into them or not, just thought I'd throw that out.

If you have any more questions, feel free to ask, or if I failed to explain something clearly let me know lol....
Hopefully other members might have some suggestions to offer you as well...

-Jeff

 

thanks man for your knowledge u sure do know your stuff. ur sayin go 3in dpipe with 3 in all the way back, yes i said 3 in. f the po pos. and have a cut out. i was thinkin tectonics dpipe. whats do i need? dpipe, high flow cat, and muffler right? i wanna get it all at once than start putting it on. at 15 psi my car is just a hair faster than my brother from another mothers crx with a b-16a on the bottle. but not with someone of my calibur, ya know? so i def wanna run more than 15psi. stock it runs 12 in stage 2 it runs 15-16psi. if u can give me any more info it all helps every bit i study and learn from thank u so much. if there are any other helpful hints to building a gti (in the stage im in now) please help me out/ i do know a lot about cars im not a wannabe mechanic i just havent ever delt with edm's b4 thanks for your help peace.