3.5 downpipe?

[04TurboStroker]

hey yall. right now im running a straight 5inch mbrp exhaust with a 4inch dp cat and muff delete, not much done to the truck just mbrp exhaust and a AFE stage 2 w/ pro gaurd. I see that everyone runs on a 3.5dp. So I was wondering if I should switch to a 3.5dp and run a 4inch exhaust. I heard 5inch exhausts are made for trucks that make 450 to 550hp to the wheel. Would a 3.5dp make a difference on my truck?

 

[patrickc]

I run a 4 inch downpipe and 4 inch the rest of the way back. (duals) 3.5 inch downpipe is not going to make any difference on your truck but 4 inch is you have is better. The 5 inch downpipe back is a little overkill but I bet ya it sounds good. The only thing I might do is kill the kitty but other than that I would leave the 5 inch on.

 

[powerstrokeguy]

do not go to a 3.5dp. keep the 4. that will cut down your flow. just do a strait 4 and ull be good.

 

[Mark Craig]

04TurboStroker,

Is that the down pipe you got with the MBRP 5 inch system?? If so it's a 3.5 inch down pipe. MBRP made their initial 6.0 systems on my truck, we did 4.0 and 3.5 inch down pipes and could not get any dyno HP increase or EGT drop by going to the 4.0 and the install can be a PITA on a 4.0 too, so they ONLY see 3.5 down pipes on the 6.0's. Figured you'd want to know.

Mark @ DPPI

 

[bushpilot]

the stock pipe IS 3.5" even the MBRP doesnt got to 4" til after the CAT.
the only real diff between the factory & mbrp 3.5" is the bend quality...
mandrel vs. CRIMP (factory)

 

[04TurboStroker]

Mark my downpipe right now is 4inch, and the rest is 5". So putting a 3.5dp and 4" straight through is the way to go?

 

[Mark Craig]

bushpilot,

The stock pipe is 3.0, the rest of the system is 3.5 on a stock truck.

Mark @ DPPI

 

[Mark Craig]

04TurboStroker,

If you have already got a 4.0 I would leave it alone.

Mark @ DPPI

 

[Maxtor]

3 1/2 vs 4 inch downpipe.

My system is completely stock. 3" downpipe and 3 1/2" after that.
I have heard pros and cons about changing the downpipe to 4" some say do not go over 3 1/2" on the downpipe, while some say go to the 4". It would be nice to get some real dyno information the the two.

 

[f100cleveland]

I G-teched my 01 before I installed the 4 inch turbo back. Same day same road just a few hours later the 0-60 mph times were just a little slower but picked up mph in the 1/4 mile. I think you lose some tq. on the bottom end, but it more than equals out.