[94-5.0]

What type and series of mufflers gives you the best back pressure and the most HP??

I have Shorty headers to 3inch pipes to Flowmaster 50s. no cat or anything (true duals)

What should i do to get the most HP gain out of my 5.0

[69fastback]

Back pressure is a myth. You want the best scavenging possible.

[F8L GT]

Originally Posted by 69fastback Back pressure is a myth. You want the best scavenging possible.

Sent from my HTC Wildfire using AutoGuide App

[flowmann]

Originally Posted by 94-5.0 What type and series of mufflers gives you the best back pressure and the most HP?? I have Shorty headers to 3inch pipes to Flowmaster 50s. no cat or anything (true duals) What should i do to get the most HP gain out of my 5.0

94-5.0 – Actually back pressure isn’t a myth…back pressure does exist. Needing back pressure to run well is a common urban legend or misconception. Many muffler shops will install a new 3-inch diameter system on a car with 350 HP. It ran great with the old 2.5-inch system and now with the 3-inch system it lost power and torque. The assumption is that it needs the smaller system to create back pressure. That’s not the case. The new 3-inch system was too big and reduced velocity. Velocity is what helps the exhaust flow out of the exhaust pipe faster and that’s what makes power. If the engine is blowing into a huge pipe, the velocity drops considerable. If you installed a 2-inch diameter exhaust on the same engine, the exhaust couldn’t get out of the system fast enough…causing back pressure.

The key is to get the right size tubing (and muffler size and construction) to promote velocity…not back pressure. This is why so many street and race cars run Flowmaster chambered and non-chambered mufflers. Their internal designs manipulate exhaust pulses to increase velocity. The science, technology, dynos, and track time prove that our mufflers work. This is also why our mufflers need to be installed in one direction. Mufflers that install either direction are only slowing the exhaust down without using science to promote velocity.

What other modifications have you done to your Mustang? You may have the best exhaust system for your car already.

[johnGT]

I'm with flowman^

Unless you are pushing some heavy mods, 2.5inch is pretty ideal. Hell, the stock 2.25inch is great up until about 280hp or so.

[67Sleeper]

nice info there

[69fastback]

I'm pretty sure it was obvious what backprssure is a myth meant.

[fogged306]

lol

[ReverendDexter]

Not contradicting what anyone's said so far, but I thought that I had read somewhere that the backpressure that's important for torque production is established by the size of the exhaust manifold collector and/or primary exhaust tubes. I'm extrapolating that that's why Tri-Ys have a different torque curve than 4->1s.

[69fastback]

Originally Posted by ReverendDexter Not contradicting what anyone's said so far, but I thought that I had read somewhere that the backpressure that's important for torque production is established by the size of the exhaust manifold collector and/or primary exhaust tubes. I'm extrapolating that that's why Tri-Ys have a different torque curve than 4->1s.

See post #2.

[fogged306]

Originally Posted by ReverendDexter Not contradicting what anyone's said so far, but I thought that I had read somewhere that the backpressure that's important for torque production is established by the size of the exhaust manifold collector and/or primary exhaust tubes. I'm extrapolating that that's why Tri-Ys have a different torque curve than 4->1s.

For further explanation read this.

[94-5.0]

I dont have many mods. so i think after i get the smoking fixed ill change to 2 1/2 inch pipes

[flowmann]

Originally Posted by 69fastback I'm pretty sure it was obvious what backprssure is a myth meant.

69Fastback - We knew what you meant. We just wanted to clarify for other members. You never know how new some members are to the hobby.

By the way, how big are the tires on the back of your sweet ’69 Fastback?

[69fastback]

The street tires are 275/60/15. The ones you can see on the prostars in the sig pic were 275/55/15 because it was a gutless turd when I bought those, but now it has a 28X10.5 ET Drag on those.