aint it great turning heads?!

 

I have bit my lip long enough. I think the 3" is to small for FI. I think power is being left on the table with 3"... just my 2 cent that is not worth a red cent.

 

unless your on a t6 flange and making 800rwhp at 8,000rpm, a 3 inch is all thats needed. these are trucks that dont rev high.

remember its a turbo, there is no scavenging. a 3inch will flow big power, ive make 650rwhp through a stock 3inch exhaust and dual 2.5inch out of a muffler. a 3.5 is overkill, a 4inch is a waste.

a 4inch exhaust might make 20rwhp over a 3inch at 7k rpm. personally just add 1psi of boost.

note: on my personal truck i would run an open wastegate with the stock 2010 performance exhaust. that way you have the quiet daily driver sound and when the wastegate opens at max boost it dumps the exhaust. i would run a 60mm jgs gate. that would be 2.25inches of additional flow when needed.

 

as big as you want. my turbo has a 5inch outlet that i neck down to a 4inch. thats a 418cu motor that revs to 7500rpm. a 5.3 or 6.0 reving to 6k rpm on a t4 flange would work great with 3inch

 

I have a Trick kit with a 76mm, 3"dp, magnaflow 3" in/dual 2 1/2" out, with a cutout on the end of the dp. It made 623/652 through the exhaust.

Like blue0453 said, about every 3rd or 4th time I get gas, someone asks me how I got it to sound like this, so I get to pop the hood, and show it off.

 

So 3" sounds better than 4"?

 

You definitely want to be a bit bigger than the exhaust outlet on the turbo since you are bound to have bends in your exhaust somewhere after the turbo. ex 3.0" outlet on the turbo I would do a minimum of a 3.5" exhaust setup. Air doesn't like to turn so going bigger on the exhaust than the turbo outlet helps prevent any choke points that cause backpressure. In general with turbos you want the highest flowing exhaust possible. Had a 3" on my truck, went to a 4" and shot myself in the foot as the gate isn't flowing enough now with the reduced backpressure so it's creeping pretty bad in the higher RPMs. There was quite a bit of backpressure there that was eliminated.

 

I'd think that 4" would be a deeper sound than 3", but I haven't heard a truck with 4" exhaust in person, and a 30 second video can't do justice. I would think 4", and bigger would sound pretty good, but I think it would look funny on a gas rcsb, and I think dual rear exit is what should be on a truck.

 

3'' is plenty for 600 hp.. Nuff said..

 

And worst case....throw a $30.00 cutout on it and be done.