Do straight pipes loose power?

[MR_SRL]

Hi guys, i have rt hf cats on my gen3, and thinking of going straight pipes. I remember some time ago hearing that with out any mufflers to provide back pressure, there will be power loss. Anyone with this setup and have sound clips?

 

[Jerome Sparich]

Needing backpressure is a myth.

Choking something will in no way help power, it will reduce it.

You want as little BP as possible. When you reduce it, you may find a loss of some low end power. This is nothing that having the car tuned won't bring back.

People confuse scavenging with BP. And scavenging does not happen at the muffler.

 

[351carlo]

Needing backpressure is a myth.

Choking something will in no way help power, it will reduce it.

You want as little BP as possible. When you reduce it, you may find a loss of some low end power. This is nothing that having the car tuned won't bring back.

People confuse scavenging with BP. And scavenging does not happen at the muffler.

Great post! I saw this on my phone earlier and was afraid people would agree with the myth.

I've never seen a properly tuned car lose power with less restrictive exhaust.

 

[lilgookiemonsta]

Here's some good info

Exhaust Theory

 

[Twister]

Youll pick up 10 to 15 rwhp going with straight but lose 5 rwt..vipers have too much darn torque anyways

 

[bluesrt]

i found on a stock tune reducting back pressure robbed my lower end, but gave me more horsepower on top end winded up tight on rpms, so if you want to drive like a complete crazyman or bonniville salt flats, it will work for you.

 

[Dom426h]

ok Carlo, lets get alittle more technical here Mr. Mech.E.

Backpressure from restrictive stuff like some stock cats, and mufflers rob power yes. But i think the reason that this "Myth" came about is people hearing about loosing bottom end power when going to an oversized diameter pipe and/or oversized diameter header. People took that statement(which is true) and applied it to everything else in the exhaust.

There is a diff between the headloss(restriction) from changing the pipe diameter -VS- changing components in the pipe that present restriction by rapidly increasing velocity by constriction and then immediately decreasing velocity with expansion for example Cats & Mufflers

Internal Combustion Cycles is the one chapter in thermodynamics that i read over and over and over....
The Pressure/Volume chart for the Otto Cycle illustrates how power is made. Any time intake or exhaust conversations come up this Pic comes up in my head:

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The total power your motor makes it the area of the upper section Minus the area of the lower section(pumping losses). This lower area is comprised of the intake & exhaust stroke. By putting a less restrictive intake & exhaust on your motor this area of the chart Shrinks making the Net Power of the motor greater.

For those looking at this chart shaking your head like ***, here is an illustrated picture that goes through the 4 strokes of the otto cycle while plotting the position on the above chart:
VIPRATECH::: Animation: FOUR-STROKE CYCLE / OTTO CYCLE by ITC Leipzig

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