Hi,

I'm interested in a custom exhaust for my 2005 Dodge Dakota QC and was wondering what 'back pressure' is/means? Some kits use 2.25' pipe, some use 3' and I think it all has to do with back pressure.

Thanks in advance for any info.

-Mike

 

Backpressure is good. You need it, all you need for it is a muffler. Bigger pipes = less restriction.

 

MIke,

Back pressure and restriction are one in the same thing. Back pressure is typically measured in inches of mercury or psi. Back pressure or exhaust restriction is the pressure the exhaust gasses need to over come to exhit the exhaust manifold/cylinder head. Typically the thought of restriction is a bad thing as it takes energy to over come. You would rather that energy be transfered into flywheel power instead of absorbed in the exhaust.

Typically the bigger and shorter the exhaust the less restriction/back pressure the more efficient the engine. However with electronic engines and the advanced combustion calibrations in these engines, they are typcially designed/calibrated with an expectation for a certain amount of back pressure/restriction.

The problem with reducing back pressure is that though it helps high rpm performance get rid of exhaust gasses qiuickly, it can actualy decrease low rpm torque. This is because at low cam shaft speeds (long exh valve and intake valve overlap) the intake air/fuel charge can actually be sucked out the exhaust valve. Higher restrictions can reduce this effect and cuase a better/more efficient burn at lower engine speeds.

Just my two cents!

 

Yup

Bigger pipes = more hp, less tq

Smaller pipes = more tq, less hp