Why no 5 inch down pipe?

[08-450dually]

So, why does nobody make a 5 inch downpipe? Is the Turbo outflow only 4inch? This must be the case, right??

[Preems14]

I'm guessing there is a clearance issue between cab and engine.

[08stroker250]

5" won't fit!

[WallyD]

The stock one even requires a significant indentation to fit.

[08-450dually]

So, if I were to cut into the cab to make room, and re-plate a tunnel such that I will have enough room to fit a 5" DP, will this affect the current tuners available? In other words, if I were to place a 5inch downpipe will this have an untoward effect on individual tunes??

What is the diameter of the stock turbo outlet?

[Stroke4Fun]

Based on what i read 4" is plenty and anything bigger will yield no gains with a straight system so you may be looking at alot of work for nothing!
Chris

[Ipkyss]

I can't see the reason for a 5" down pipe. Getting rid of the stock one is a great Idea. Its amazing these motors make any power with the stock one. The turbo is a 4" outlet I believe. Or really close to that. My truck is 5" from the down pipe back. I really don't see a need for more size than that.

[sleepertruck]

Try it out. Post your results. I doubt it will make a difference but you never know. I haven't heard of anyone doing this either, fastest 6.4 runs a 4" DP thou.

[08stroker250]

5" won't work....it doesn't fit.

[sleepertruck]

If you cut the firewall out you could make it fit but it wouldn't be worth it to me. I'm with Jeff. It doesn't fit