Exhaust backpressure fail...

[Meow]

http://www.exhaustvideos.com/faq/how...pipe-diameter/

"A good section of straight pipe will flow about 115 CFM per square inch of area. Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size:"

[FlyboyS4]

http://www.exhaustvideos.com/faq/how...pipe-diameter/

"A good section of straight pipe will flow about 115 CFM per square inch of area. Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size:"

There's no mention of the pressure drop for those flows, I'm guessing that it is assuming a NA engine which is not a good reference for a forced induction engine.

[GrapeBandit]

maybe im interpreting this wrong, but a 3" single exhaust can only flow enough to make 339hp
doesnt make sense to me, like every BT b5 a4 uses 3" and puts down well over 339

[julex]

maybe im interpreting this wrong, but a 3" single exhaust can only flow enough to make 339hp
doesnt make sense to me, like every BT b5 a4 uses 3" and puts down well over 339

It is not like 3" will suddenly stop flowing at 340hp you know.

My example mirrors yours almost to the dot. I still make ~550WHP on dual 2.125" (estimated ID with 2.25 OD) which is exact equivalent of single 3" pipe (7.09 vs 7.06 in^2). But, I can probably make 600WHP by just upping the exhaust to dual 3" as per table above which will cause the backpressure to go from 10psi+ to 2-3psi, if even that.

What the table tells us that with piping properly sized, you will have negligible amount of backpressure and thus very minor power loss due to hampered VE.

[FlyboyS4]

maybe im interpreting this wrong, but a 3" single exhaust can only flow enough to make 339hp
doesnt make sense to me, like every BT b5 a4 uses 3" and puts down well over 339

The table is unlikely to have been intended for a forced induction engine. Leaving the amount of pressure drop out is a critical omission for a turbocharged setup.

Sent from my PC36100 using Tapatalk 2

[Meow]

The table is unlikely to have been intended for a forced induction engine. Leaving the amount of pressure drop out is a critical omission for a turbocharged setup.

Sent from my PC36100 using Tapatalk 2

airflow is airflow, leaving out backpressure means the table was likely intended for turbocharged vehicles as having enough backpressure is tossed out the window when talking about turbocharged car performance and only a discussion of the required airflow is necessary. Only NA cars worry about needing back pressure for maintaining midrange torque. Stop posting in this thread, you have nothing to add and your comments are irrelevant and ignorant.

[FlyboyS4]

airflow is airflow, leaving out backpressure means the table was likely intended for turbocharged vehicles as having enough backpressure is tossed out the window when talking about turbocharged car performance and only a discussion of the required airflow is necessary. Only NA cars worry about needing back pressure for maintaining midrange torque. Stop posting in this thread, you have nothing to add and your comments are irrelevant and ignorant.

I said pressure drop, and when determining air flow rate it's necessary to specify at what pressure drop the flow rate is being measured.

What you are thinking of is a completely different subject and not what I am referring to.

[Meow]

I said pressure drop, and when determining air flow rate it's necessary to specify at what pressure drop the flow rate is being measured.

What you are thinking of is a completely different subject and not what I am referring to.

Flow is what matters, moving volume... pressure is a byproduct of flow restriction, pressure drop is irrelevant, much like your comments.

[FlyboyS4]

Flow is what matters, moving volume... pressure is a byproduct of flow restriction, pressure drop is irrelevant, much like your comments.

What creates flow?