I am contemplating on building a 3.5" exhaust with my 6466 build. But curious if I should just keep the 3" Are the gains substantial? Meaning 50+HP and up? I plan on running 40+ pounds of boost in my 2.4LR 6466 E-85 combo. I will have about an 18" section of 3" coming off the turbo then into a 3.5 straight back.

 

depends if you have a ****ty flowing 3.0 exhaust or not. if you have a really crappy system now and you go to a very free flowing 3.5 then yes maybe you can see that type of gain. but if your running a free flowing 3.0inch exhaust and go to a 3.5 i highly dought you will gain much if anything. not under 750hp at least. pushing the car hard or looking to extract every ounce of power then i would opt for the 3.5 inch exhaust. 1/2hp is better then no 1/2 haha

 

I have a straight open 3" exhaust into a magna flow muffler, I am pretty sure its free flowing. I plan on pushing the 6466 until I run out of fuel so who knows what it will make.

 

what fuel system do you have? it would not make sense for you to spend time and money building a 3.5inch exhaust if your fuel system is your limiting factor. no what i mean?

 

double pumper/fic2150's/aem fuel rail,

 

i would say its your call then. you will not see 40/50hp gains though. maybe at the absolute most would be 10hp. even that is high. but if your looking for every ounce then i vote 3.5

 

Yes.

I have 3.5", changed from an AeroTurbine to a offset in/centered out 3.5" Magnaflow and lost 50whp (794 to 739 at 39psi). Added a testpipe dump and got all the power back but the power diverged at 26psi which was 660whp in my car at the time.

 

Good info, thanks for sharing. The power difference does sound about right then.

 

If I had losses like that on an existing 3.5" exhaust imagine the difference between 3 and 3.5" The next part of the equation that really makes a difference is the downpipe. Getting that as large as possible as quick as possible (preferably immediately) helps also.

 

Very true! Well I am building my own top mount and am really running out of real estate for the wastegate and downpipe. I am confident it is all going to come together and would love to have a 3.5" coming off the turbo but still not 100% sure about the room for that. Hence my 18" of 3" into the 3.5" inch transition.

 

good info

 

No comprendo...explaino??

 

Both 3.5" mufflers flowed enough exhaust a 26psi that they made 660whp just the same on the 2.4/3586. Past that the power difference was more and more until at 38-39psi I was down 55whp from the aeroturbine to the magnaflow.

3.5" ETS exhaust with the 4" Aeroturbine vs 3.5" ETS with a Magnaflow 3.5" offset in/centered out. The Aeroturbine had a 3.5"-4" cone adapter and then the muffler (however long they are) vs the Magnaflow 12909 I think? I can look up what it is if need be. The Magnaflow dropped the drone/sharp tones at full power but also dropped power. I added a testpipe dump and got it all back though.

 

I went from a 3" to a 4" exhaust and gained 150whp!
Not sayin to expect anything like that but it helped me out... We couldn't figure out why I wasn't makin the power I was expecting and then we looked in my none eBay but jdm 3" muffler and even though the inlet was 3" and the tip was 4" inside was only 2 1/2.

 

Well going from 2 1/2" to 4" is a huge jump in reducing back pressure, so I guess I can see a big gain in power.