Do I need a 3" DP?
 

Hey guys,

I am wanting to buy a DP before starting the install.

What are todays best options?

I am thinking of a 3" DP and 3" back with a magnaflow.


Is it worth it using 3" or are there other bottle necks with the Greddy that cancel the benefits? (such as manifold etc)
Should I just go with 2.5"?


Thanks

A three inch downpipe is a great idea if it fits. The turbo placement might make this size a little difficult on a greddy kit.

Word is that the tubing "donuts" make the tight bends needed to get the downpipe going down help immensely.

Go for it. It may not make more power for the lil' greddy, but you know it's there and ready if you ever want to go crazy.

Agreed ^^^

Yes, it's always worth it.

I think the turbine outlet is only 2"
I'd match and swage. A 3" would be tough.

I betcha Corky would recommend against it.

match and swage is just as benefitial for flow/velocity.

I think you are right the outlet is probably ~2"
what do you mean by match and swage?
2" seems kind of small though.

start at something like 2.25" or 2.5" and step it up to 3"

like for example, my t3 has a 2.25" turbine exit, my DP is 2.5" and then steps up to 2.75". My cat and exhaust is 3".

Yah step it up. Big right at the turbo flange isn't ideal if the turbine outlet is comparitively tiny.

But all things considered i'd go as big as you can fit. Wo hoo

3" exhaust is the same as vagina
whether you need is arguable
whether you want it is obvious

I betcha next time I dyno will make you think twice about a 3"

with your new breathing mods, let's shoot for 10 psi at idle :x:
:bigtu:

10psi at idle would mean a .5" exhaust and tons of backpressure.

lets shoot for 10psi at 2000RPM :rofl:

10 psi @ 2K.....that would be very boner inducing

Seeing 12psi @ 3800RPM with my turbo vs 4200RPM is pretty close.

indeed...what size is your DP/exhaust?

right now it's a 2.5" to 2.75"

however my cat and catback is 2.25"

the muffler is also a dual exit with dual 2" outlets.


so I have absolutely the worst setup for flow, as it progressively gets smaller.

I did minor headwork and have shaved about 500RPM off my spoolup time.

I have a 3" on the way, so I'm excepting to see even better results. Hopefully something like 20rwhp at the same boost level.

that would be great success...
are you gonna do a write up on your head-work?
did you do it yourself or at a machine shop, i hear a lot of people saying they did it at home, but have no info to back it up, etc...
i have a spare motor, so i may want to experiment myself with some headwork
let me know if you did it yourself

I did minor headwork and have shaved about 500RPM off my spoolup time
thats impressive