i have a 05 sti with a aps 3 1/2 turboback exhaust. what uppipe would you guys suggest? aps makes one and it looks nice but what is the difference between flex and not flex and which would be better for me. thanks

 

I have a PDE up and down pipe with the flex section on the up pipe. I think its one of the best around.

Flex (if high quality) is great because it help you seal up against the turbo and the headers. The install is a pain in the a**. You have to unbolt the passenger side engine mount, jack up the engine from the oil pan, slip the old up pipe out and the new one in. There is not enough room between the block and the frame of the car to get the flange piece out. Of all of your exhaust mods... this one will be the hardest.

Last piece of advice... follow the following procedure. When bolting it all together, loosen up the middle header flange, loosen the passenger side header flange, tighten the header/up pipe flange, tighten the up pipe/turbo flange, re tighten the header/passenger side block flange, finally tighten up the middle header flange. It will help you eliminate exhaust leaks.

 

the flex just makes a better seal to the turbo. Actually the STi's dont have cats in there up pipes. So its kinda a waste of money. But if you are going to get one i would recomend a Helix flex up pipe.

 

05 sti does not have a cat in the up pipe as mentioned above. keep your money and save up for engine management if you dont already have one. or i would go with steel braided brake lines, pads, and fluid

 

Agreed. Save your money and spend it elsewhere. Now if you had a WRX on the other hand...

 

Have there been ANY comparisons made between the stock catless uppipe and aftermarket ones? Is it REALLY insignificant to change it to a Helix for example? Are the results miniscule?

 

yea, i think you should just leave the stock up pipe since there no cat anyways . . . but if you decide to get one just go with helix flex

 

Ok,
To up-pipe or not to up-pipe...

If a person has an aftermarket up pipe, he (or she) will most likely recommend that you get one as well.

If a person doesn't have an aftermarket up pipe, he or she will most likely recommend that you don't get one and that they are a waste of money.

Some things to consider:

1) An STI has no CAT in the up pipe so you are switching from a pipe to a pipe.
2) Back pressure is created by cats but is also created by fluid/gasses flowing in a turbulent form. Turbulence can have a greater effect than you think and is influenced by the velocity of the pipe, the diameter of the pipe, the temperature of the pipe, the surface of the interior of the pipe.
3) Aftermarket, high quality up pipes take turbulence into consideration and smooth the walls of the pipe and use materials which have good heat distribution.
4) There is a decrease in turbulence with and aftermarket pipe.
5) An aftermarket pipe should not cost more than $200.00 (cheep compared to the rest of the parts we install on our car, much less the hours on the dyno for tuning.)
6) You will get faster spool up with a PDE or HKS up pipe.
7) You will get 2 to 4 whp with an aftermarket up pipe.

My thoughts: If you are building your car and have goals above 320 whp - get one (sooner or later). If you are building your car to have a little edge over the other STIs or Evos out there you will spend your money better elsewhere.

 

thanks everyone

 

Get some headers with a built in up pipe like Invidia or GT spec. I have the Invidia Headers on my STi with an Invidia catless turbo-back. You will actually gain a lot more power on the STi with headers. Its a waste of money for the WRX unless its highly modified.

 

I have DC Sport Headers and PDE up pipe. How was the install of the header/up pipe combo? My up pipe install was a huge pain in the a** even without thinking too much about the headers.

 

The headers werent too bad. I know that the up pipe alone is a pain. I had my friend help me who knows what hes doin (mechanic) so it went pretty well. I've heard a lot of other ppl say that the headers are easy. I hope that helps