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Should I Dump My Exhaust System Early, Right After the Muffler Exit?

A reader emailed us the following question:

I have an after-market performance muffler on my truck, but it’s not loud enough. I have a friend who has “dumped” his exhaust system under his truck – he’s removed all the exhaust tubing behind the muffler, so that the muffler exit is now immediately under the truck. His exhaust system sounds amazing – should I do this to my truck too?

Here’s the short answer – this isn’t recommended and it’s potentially unsafe.

Is it Louder?

Yes. While it’s true that removing the section of pipe between the muffler exit and the exhaust tips will make a small difference in sound levels, most of the additional sounds you hear when you make this modification are reflected off the ground and reverberating off your vehicle underbody. These reflected and reverberated sounds can make your existing after-market exhaust system seem quite a bit louder.

However, it’s important to remember that exhaust gases are toxic. You want to carry them away from your vehicle interior as best you can, because if they leak into your interior they can:

  • give you a nasty headache
  • cause you to fall asleep while driving
  • potentially, exhaust gases that seep into your vehicle interior could kill you or your passengers (it’s been known to happen)

Depending on where your muffler ends, it may be that exhaust gases will sit directly below your vehicle’s passenger compartment. Most people don’t realize that all vehicle interiors have drain holes which allow air to move through the floor relatively easily. Therefore, if you’ve got exhaust gases accumulating underneath your car, some of those gases are going to end up in the air you’re breathing inside.

It’s also important to consider that relatively hot exhaust gases will be exiting directly onto your vehicle’s underbody. The heat and moisture from your exhaust gases could cause corrosion problems given enough time, especially in winter weather.

How Can I Make My Exhaust System Louder?

Instead of removing the exhaust pipe behind your muffler, you may want to consider:

1. Replace the muffler. You can get a new Magnaflow glasspack muffler for only $35 online, and it will probably be louder than whatever after-market muffler you have. You can also wander over to the local muffler shop and tell them you want a loud muffler – they’ll sell you a generic brand Turbo muffler (or something like that) that will be as loud as hell for only $75-$100 installed.

Remember, you usually don’t have to pay too much for loud performance mufflers. It’s the quiet performance mufflers that cost money.

2. Go with short side exit pipes that end just in front of the rear wheels. This is an old-school look, but it sounds great and is usually easy enough to do on a truck. You won’t get the echo/reverberation effect from ending the exhaust underneath your vehicle, but you won’t risk carbon nonoxide poisoning either.

4 Comments Post a comment
  1. Bryce
    Mar 19 2015

    You also have to check state regulations I know in some states they will only let you dump the exhaust after the gas tank. Even if you do side pipes….

    Reply
  2. John
    Mar 17 2016

    Do you have a formula for the flow rates of mandrel bends in specific sizes ? I have a late model 5.7L truck and have designed the tailpipe to exit just in front of the rear tire. I stayed with the factory size piping of 2-3/4″. I built the whole tailpipe from the oem muffler back, using a 180 degree bend, a 45 degree bend, a 90 degree bend and some short straight pieces. As an example, I know that in water systems with 1″ fittings, a 90 is equal to 5-6 feet of piping. I am thinking that I want to stay as close as possible to the overall length of the oem tailpipe. ( 1-90degree bend, 1- 60 degree bend, 1-45 degree bend, 1-30 degree bend and 38″ straight pipe. I know the exhaust flow on the newer vehicles are all built in to the pipe sizing and lengths. Just with my tailpipe removed with a straight muffler it wasn’t much loader, but even the transmission shifted a little different. Just want to make sure I don’t have to much back pressure with the 180 degree, 45 degree and 90 degree just 18 ” off the muffler. Again, my new system is all built with 2-3/4″ mandrel bends. Thanks in advance for any thoughts…….John

    Reply
    • Jason
      Mar 18 2016

      John – Good question. The short answer is no, I don’t have a formula.

      The longer answer: The flow rate of the tubing is mostly determined by the temperature of the gas. At cooler temps, your tubing will flow considerably more exhaust gas than it will at higher temps. Unfortunately, temperature isn’t a constant…exhaust gas temps depend very much on engine temp, throttle position, and ambient temps the further back you go. This makes calculating the flow rate of a bend a difficult math problem based on a host of assumptions.

      So, basically, you want to choose a tubing size that will generally work for your engine, and then minimize tube bends as much as possible. Most of the after-market companies aren’t doing these calculations, btw. It’s cheaper to test different sizes on a dyno than to invest in precise measurement and finite element analysis for bends, tube diameter, etc.

      Reply
      • John
        Mar 18 2016

        Thanks for getting back with me. It’s funny how some of these aftermarket companies build these systems with larger than stock piping and make claims of 400% airflow increase and 15 ft lbs torque and horse power etc. This may be true at high RPM, but who drives their daily driver at 5000 RPM plus. In all my vehicles over the years with numerous exhaust systems, I found that most factory designed systems can’t be beat. The reason for my tailpipe relocation and design was due to frame and suspension mods. Just wish I could find a generic formula for airflow of mandrel bends in comparison to straight tubing

        Reply

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