Exhaust size and gain in relation to the pain......

[Lone Ranger]

From study of the Forum, I have a 3 1/2 Turbo back down pipe on the way. Now, also from research, and with fuel economy in mind, I am going Sct Xcal 3 and for big towing a EGT probe...

Question: For just Fuel Economy, Since I am going 3 1/2 downpipe, is there any gain to be had in going to 4" with the rest of the exhaust??? Or should I just carry on with kitty gone, straight as possible, free flow straight glass pack type muffler and stay in 3 1/2 "

What do you think, any sense in going 4"? Or go 4" anyway as I may want to upgrade the engine studs and HP in the future? Or a waste over 3 1/2"?

Or just carry an extra pair of socks in my pants... and go straight 3 1/2"

And God Bless America! Even if it is an "Obamanation" now

[town kid]

go 4 so the egt's will stay down.

[Lone Ranger]

Ooooooooooooo GOOOD POINT !!!!

Didn't think of dat one !!! Well 4" is it !! That way if I want to get stupid over stacks and 500 HP the 4" will still do..

Thank you for the point well taken... EGTs and 4" it is... !!! Regards from Oz

[town kid]

no problem just trying to help some one out
what kind of stack would u do.

[town kid]

no problem just trying to help a member out
what kind of stacks would u do.

[Lone Ranger]

Stacks would be good looking, but probably will not fit the KR Dually inside the bed... Big Kenworth style Chromies outside the bed in front of the Dually fenders would be Coooool, but not parked in front of my office..

[HeavyAssault]

EGTs are best measured pre-turbo. Since the CFM between 3.5" and 4" is like 400CFM difference you need a larger turbo to move the air to see the difference in EGTs.

[Lone Ranger]

Thank you for that HeavyAssault.....

So now I am back to Zip, zero, nada, nuttin......

Alright, if the move from a 3.5" downpipe to go to 4" does not help EGTs, is there any sense in it? Or stick with a straight 3.5 all the way?

The other concept to consider: If there is not enough flow, there will be carbon build up in the system, without enough CFM to blow it out if you go too big... It will naturally build up soot until the CFM is big enough again to blow it out, lining the exhaust system.....

I am not enough of an Engineer to manually calculate just where that point is..

OK.... What now? 3.5 straight? or step up to 4".... What has been the experience doing it in the field?

[town kid]

no u dont want a stock pipe cuz u will have high egt's

[town kid]

it does'nt matter wat size the turbo is it just maters wat size exhaust u are running.