denracho

Wazup.. i just need help. Im running a 3 inch downpipe 2.5 test pipe and 3" inch exhaust.. is the 2.5 test pipe will give me problem with backpressure? i need help

sirtef9

iTrader: (4)

why not 3" it all the way?

Schister66

Yes, if you're running 3" everywhere else, the section of 2.5" is going to be a restriction.

yungkhmer

take the test pipe out.

DirtyDA9

That technically means your flowing like a 2.5" exhast. Your exhaust is only as large as the smallest part.

Schister66

A dramatic example of this would be an hourglass. The top and bottom sections are very large, but are still limited by the bottleneck in the center. This isn't an entirely accurate example as gas (compressible fluid) flows a bit differently than sand (or incompressible fluids), but for simplicity's sake, we'll use that as an analog.

JohnnyLawless1

Agreed , you only need back pressure if naturally aspirated!!!, the more air/fuel in, the more evacuation capabilities you need.

Schister66

Yes, to a degree. Flowing gasses create areas of low pressure; therefore, keeping some minimal level of backpressure in a system increases exhaust scavenging. For this discussion, its an irrelevant fact