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Equipment Hub: Pros and cons of straight piping

Andy Overbay for Progressive Dairy Published on 19 April 2022

We’ve all heard those diesel pickups pulling away from a parking lot – black smoke rolling with the distinctive roar and whistle of a turbocharged diesel engine. Honestly, it is music to my ears, but I guarantee there are just as many (if not more) who frown upon the excess racket.

The age-old argument for deleting the muffler from a truck or tractor was the claim of horsepower boosts. Whether more horsepower is achieved can be a subject of discussion, but it is certain the “tone” of your engine will change.

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I have owned several fine old tractors over the years – and over the tenure of my ownership, several of them have found themselves with straight pipes. Just yards from where I write this, I have two tractors sitting in the shed that are fitted with straight pipes instead of mufflers. I also have a few more “shed mates” (tractors are like potato chips … one just won’t satisfy) I wouldn’t operate without a muffler.

So does a straight pipe make a difference? As an old lawyer would say, “it depends.” Removing the muffler from a tractor reduces back pressure, which can result in substantial horsepower gains. The amount of your tractor’s individual power boost will depend on several factors, but the most important one is the amount of fuel and air already going through it to begin with.

Think about the heavily modified trucks and tractors you see at pulling events. The amount of pressure they “exhaust” is extraordinary – way more than a normal farm tractor or pickup would create. A muffler on those beasts would end up heading for the sky (or scarier – the spectators).

My colleagues and I once (once is the key word here) tried to use a large self-propelled forage harvester to cut our corn silage test plots. Each plot’s forage test requires a sample to analyze for nutrient density and moisture content. We normally collect these samples with a bucket placed into the crop stream near the spout of the harvester.

On that occasion, we collected our bucket off the ground more than we care to admit. Gains from a muffler follow the same principle. The more you flow, the higher you go.

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For me personally, my straight piping adventures were primarily on older tractors with turbocharged motors. In those cases, the turbo tends to serve as a bit of a muffler; at least I think it tones down the blare as compared to a naturally aspirated motor.

Oh, I have had one of those too. The old tractor I used to run the mixer wagon had a straight-piped, naturally aspirated engine. Needless to say, it woke the neighbors if I drove it out on the road. Operating it under any circumstances required earmuffs … and good earmuffs at that.

So why straight pipe that one? Well, it was the tractor we used to harvest corn grain via a mounted picker. It was oversized for that job by most standards, but it did such a great job. Running a straight pipe got rid of excess heat, which helped with the fear of catching anything on fire in the dry fodder and chaff blowing about.

That old window-rattling tractor does bring us back to an important point about straight piping: You will increase the decibel output of that engine. That is absolutely going to happen, and exposure to excessive amounts of noise can and will damage your hearing. Hearing protection is a requirement when working around these beasts – turbo or not. Even if you are seated in a nice tight tractor cab or truck cabin, you will tell a difference.

Speaking of the pickups we started with at the beginning of this column, I had an exhaust leak in one of my diesel pickups years ago. I pulled it into the shop and began the repairs but, wouldn’t you know, I needed a part from town and the truck was the only available vehicle that day.

“Well, heck, everyone else operates theirs like this,” was my thought, so the dogs and I loaded up and headed for town. Before I got through the first mile, I knew one of two things needed to happen: I needed to restore the original exhaust completely or move the exhaust point as far away from the cab of that truck as possible. It sounded great idling in the driveway – not so much driving it down the road. The dogs both looked at me like, “We can’t even hear the radio.”

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The point about the cab is fitting for today’s tractors as well. One of my newer tractors turns 20 in April. Its exhaust stack, like many modern tractors, runs right up the right-side front pillar of the cab. I replaced its old muffler last year with a straight pipe (chrome, of course, to drive my wife crazy), and for the most part, I like it fine.

I like the throatier tone of the motor, and it did seem to give it a bit of a boost in power, but there are points in the power curve where, at certain RPMs, the dull roar finds its way into that cab in a less-than-pleasant way. Throttle up and it goes away. So for the sake of horsepower and turning the wife’s head (she acts like she doesn’t care – but I know better), the chrome stack stays.

Like anything else, the best course of action regarding your equipment is up to you. Modifications of any kind to the newest of tractors or trucks will almost certainly void your warranty, which is one of the reasons to purchase new machinery in the first place.

Let me leave you with one parting thought, regardless of your preference to exhaust systems. Get in the habit of keeping hearing protection handy and wearing it. A hundred dollars of earmuffs placed where they are handy are cheap in comparison to thousands of dollars of hearing aids on the kitchen table.  end mark

Andy Overbay holds a Ph.D. in ag education and has more than 40 years of hands-on dairy and farming experience.

Andy Overbay
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