Cat Back Exhaust

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by 85 mustang lx, Nov 24, 2013.

  1. I need to replace the exhaust from the cats back. I want an exhaust that has a nice mellow sound but not real loud at highway speeds. Also would like it to be 3" with big tips. Not sure if this is possible but am hoping there is one out there that will fit the bill.

  2. That's what she said
    85 mustang lx likes this.

  3. For
  4. The car currently has MAC shorty headers on it..
  5. I may have my info criss-crossed but I think a magnaflow type muffler will be quieter on the hwy than a chambered type like a flowmaster
  6. 3" is huge for a stockish engine. If you are lacking cats, you may lose a little torque. It's also a pain routing 3" piping over the axle. If your car is lowered a tad, you may hit the pipes over bumps. It gets annoying fast.

    MAC sells a kit that is 2.5" tubing, but uses 3" SS tips. Maybe this is more what you are looking for

    It does have some tone on the highway however.
  7. 3" here, but im running a turbo. Flowmaster sells nice 3" cat backs that will mate up to any other cat pipe. Now for a stock or even mildly modified vehicle, its overkill and may even cause you to lose a bit of hp
    85rkyboby likes this.
  8. 2.5" is more than enough for a stockish setup. As mentioned, too large a diameter pipe and it will hurt your performance.

    Use the guide below when calculating pipe size for custom exhaust work. Keep in mind that the goal is to improve exhaust flow. In most cases, just changing the restrictive OEM muffler and replacing it with the same size straight-through, Wide Open Performance MagnaFlow muffler will do the job.

    To reduce additional backpressure, the OEM exhaust tubing can be replaced with mandrel-bent tubing of the same size or one size up from the OEM. As a general rule, you can enlarge the pipe diameter of your OEM exhaust system by 1/4 to 1/2-inch to increase your horsepower. However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque.

    Single Exhaust Dual Exhaust
    150-200 CID 100 to 150 2" to 2-1/4" 2"
    200-250 CID 100 to 200 2-1/4" to 2-1/2" 2" to 2-1/4"
    250-300 CID 150 to 250 2-1/2" to 3" 2" to 2-1/2"
    300-350 CID 200 to 350 2-1/2" to 3" 2-1/4" to 2-1/2"
    350-400 CID 250 to 550 3" to 4" 2-1/2" to 3"
    Use as a general guide for engine size and performance
    #8 mikestang63, Nov 27, 2013
    Last edited: Nov 27, 2013
  9. I've got Pypes Race Pro mufflers in a 2 1/2" diameter on my car. Nice and mellow (darn near stock sounding) at cruise, but outright violent when you get on it. I like em. There's no reason to go with a bigger exhaust diameter than that. You'll split the stock block before you reach the flow limits of a 2 1/2" exhaust.