Does an aftermarket exhaust really help increase power, or just sound good? If so, how much increase?

 

I'm actually looking to know this too?

 

Most people claiming to have power increases based on their exhaust are talking seat of the pants impression not a true test where rwhp is measured using a stock oem exhaust set up as their baseline with aftermarket measurements to compare.

Even the claims by some mfg aren't always scientifically based but I do think IMHO that increases can result with some exhausts if they are combined with the right combination of intake as well as something like a superchip or hypertech. You need to know if the mfg or person claiming improvements has multiple upgrades or just the exhaust alone.

In our years of building up different rides the one thing I noticed is that no one component made that much difference on it's own.

 

Marginal gains if any for me.

 

I noticed a little difference, not much. If you're considering an exhaust upgrade, you might want to go talk to your local muffler shop first and see what they can do for you. I went to a muffler shop where I live and they installed an axle back system with a Flowmaster 40 series muffler, and a double wall stainless steel tip, and I payed $250.

 

Be very careful here. You reduce the back pressure and you WILL loose low end torque and you MPG will fall.

Been there done that!

 

Me too!

Put a 3" pipe on my '67 Chevelle, picked up speed at the line but lost ET.

As for the JK, the stock can is awful. It acts as a large heat sync, slowing exhaust gases and velocity. The better avenue is using a straight through can that isn't chambered and the same diameter as the stock exhaust. Do not exceed the 2.5" diameter of your stock exhaust and stay away from dual exit systems. These will rob you of exhaust velocity and proper cylinder evacuation and scavenging.

Last item, if you can place a heat barrier coating on your exhaust, holding heat in the pipe this will improve your exhaust velocity and low end performance. Even stuff like black grill paint will help hold some heat in and give you a moderate gain in performance.

Also as others suggested it's a system of components and taking care of your intake side will help what your exhaust brings to the table.

 

You would gain some power or think you will because of the sound, in a Jeep you want the low end torque to crawl, you will lose the back end pressure as someone above me said.

 

So more heat in the exhaust causes more velocity coming out it kinda of sounds like an aircraft engine haha I will have to look into this sounds interesting because I was thinking of painting my muffler.

 

The problem is with the long tube headers, you will drop in back pressure... and that will result in drop in power. I had a crack in my exhaust manifold and it dropped my mpg by 2! The problem with new technology is its so finely tuned that changing any aspects such as exhaust can actually impact performance versus improving performance.

To see any gains, you would need to re-program your Jeeps chip.