2" into 5" stacks
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
We were both right.
I gave the area of one pipe, he gave the area of two pipes.
But something that gives the single 3" pipe an advantage is less surface area inside the pipe.
Surface area causes drag on the flow.
Bends cause more drag (back pressure).
Non smoth transitions to smaller or larger pipes also cause back pressure increases.
Same thing is true for the outside of the vehicle or the inside of a pipe.
If you were running with no down pipe, I could see the power being down a bit.
Once you get a flow set up in the down pipe, the exhaust moving away from the turbo helps draw more exhaust with it.
Remember, once something is in motion it continues to stay in motion until it is acted on by an equal or greater opposing force.
Exhaust gasses don't have the mass of say a chunk of steel, but the same rules still apply.
Your EGT's should drop a bit.
Your top boost numbers are going to stay the same, but you should reach your top boost number faster.
And if you are seeing 15 PSI, that is about as high as you want to go with stock head bolts.
I gave the area of one pipe, he gave the area of two pipes.
But something that gives the single 3" pipe an advantage is less surface area inside the pipe.
Surface area causes drag on the flow.
Bends cause more drag (back pressure).
Non smoth transitions to smaller or larger pipes also cause back pressure increases.
Same thing is true for the outside of the vehicle or the inside of a pipe.
If you were running with no down pipe, I could see the power being down a bit.
Once you get a flow set up in the down pipe, the exhaust moving away from the turbo helps draw more exhaust with it.
Remember, once something is in motion it continues to stay in motion until it is acted on by an equal or greater opposing force.
Exhaust gasses don't have the mass of say a chunk of steel, but the same rules still apply.
Your EGT's should drop a bit.
Your top boost numbers are going to stay the same, but you should reach your top boost number faster.
And if you are seeing 15 PSI, that is about as high as you want to go with stock head bolts.
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78fourby4f250
1973 - 1979 F-100 & Larger F-Series Trucks
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Feb 22, 2013 11:54 PM
