9 Dying Diesel Fads

• May 25, 2018
• Story By
  Mike McGlothlin

As with any automotive niche, a lot of trends come and go. Some you can live with; others you can definitely live without. The diesel world is not immune to such fads. Throughout its short history, the diesel movement has seen its fair share of cringe-worthy performance, cosmetic and childish blunders that—for whatever reason—caught on for a period of time. Over the past decade and a half, diesel-heads have seen massive exhaust tips, train horns and bull hauler stacks all used as fashion statements, engines come apart at the hands of propane or stacked performance modules, and morons that’ve deliberately made their trucks “roll coal.” Below, we’ll spell out nine of the most egregious fads to grace the diesel industry. Are you guilty of any of them?

1. Train Horns

This one has been on the decline for a number of years and our ears are especially thankful for it. Back before LED light bars, 14-inch wide wheels and stretched tires were “in,” you could find a train horn setup aboard just about one out of every three trucks. Multiple trumpets, onboard air compressors and oxygen storage tanks could all be found hidden in beds or along undersides when these auditory offenders ruled the day. At truck shows, it wasn’t uncommon for one quick blast from a train horn to kick start a 10-minute melee of others. Yours truly even discovered a pair of plastic, hand held trumpets under the hood of his ’97 F-350 after purchasing it in the spring of 2006. They were quickly unbolted and laid to rest in a garbage can.

2. Bull Hauler Stacks (and Stacks in General…)

Like train horns, this fad stemmed from the type of thing you’d find on heavy equipment: namely Class 8 trucks (i.e. semi trucks). Bull hauler exhaust stack systems were designed for cattle haulers and with the purpose of pushing exhaust fumes and smoke out into the air instead of routing it directly onto the trailer behind them. While the bull hauler stacks had their day and may have even served a purpose for some trailer-toting diesel pickup owners, for most, the cosmetic appeal was hideous—especially in cases where the stacks protruded a foot above the top of the truck’s cab.

3. Stacking Boxes

Back before EFI Live and other custom engine tuning software was available, diesel owners were known to stack electronic power-adding devices (i.e. boxes) on top of each other to make as much power as possible. While certain “stacks” worked very well (namely the Smarty/TST PowerMax on the common-rail 5.9L Cummins), injection rattle, excessive smoke and poor drivability were par for the course. For some, stacking came with catastrophic consequences. For instance, combining two devices that both added injection timing could cause cylinder pressure to go through the roof and lead to internal engine damage. Thankfully, soon after the release of aftermarket tuning software (EFI Live, Maxx Calibration Control, SCT, Smarty UDC, HP Tuners, etc.), calibrators were able to create safer tunes that made just as much (if not more) horsepower.

4. Mega-Sized Exhaust Tips

It’s a cosmetic detail that’s either executed subtly or way over the top in the diesel segment. Thankfully, the four-inch inlet, 10-inch outlet exhaust tip days are all but behind us, although you still find an isolated case of a tin trash can doubling as a traditional exhaust tip or bed stack here or there. For whatever reason—be it the current big wheel craze or enthusiasts turning their efforts toward making more power—this diesel truck fad has rapidly diminished over the past decade. Just an FYI, for diesel trucks making less than 800rwhp, running an exhaust system with a diameter larger than four inches is a waste of time, money and resources. While they’ve grown immensely in popularity (primarily for looks) and won’t have any negative effects, five-inch exhaust systems are overkill for more than 90 percent of the trucks they’re installed on.

5. Propane Injection—It’s NOT Like Nitrous for Diesels!

In the early days of diesel performance, propane was cheap, increased fuel economy and could add as much as 100hp to a bone-stock truck. However, once enthusiasts began to experiment with larger injectors and other, more serious modifications in addition to injecting propane, premature ignition was often the result—and in a diesel, pre-ignition (i.e. detonation) often means broken hard parts. Because there is no way to precisely control propane’s ignition point, it can lead to the aforementioned pre-ignition scenarios, excess in-cylinder heat (melted pistons) and even corrode injector nozzles. The use of propane as a means of improving fuel economy died out years ago as well, mainly due to the price per gallon. A decade ago it was roughly $1/gallon, but now it's approximately $2.50.

6. Running on Vegetable Oil

Back when diesel was $4 a gallon or higher at the onset of the Great Recession, thousands of diesel-heads were on the prowl for older oil burners (namely ‘80s Mercedes diesels) that could be converted to run on “veggie” oil. Older, lower tolerance mechanical engines didn’t seem to mind burning it (“it” being primarily the waste grease from restaurants that were all too willing to give it away rather than pay a disposal fee) and you could drive around for darn near free—if you set your system up correctly. However, setup was key to burning vegetable oil successfully. This entailed a specific lift pump, fuel lines, appropriate filtering and the ability to pre-heat the vegetable oil before injecting it. The fad died out almost as quickly as it began, and we haven’t heard a peep about veggie oil in nearly 10 years. We suspect the drop in diesel prices had a lot to do with its abrupt demise.

7. The Bigger the Turbo, the Better the Performance

In a culture where it’s believed that bigger is always better, sizing the correct turbo for a given application used to be a much larger challenge. Oftentimes, you had to let a customer order a 71mm charger when you knew he needed nothing more than a 66mm, just to let him discover for himself how poorly the truck performed. If the definition of performance meant you were willing to accept slow-spool up and poor drivability in exchange for a hard hit up top, the latter scenario was for you. Today, things are different. Enthusiasts expect good response down low, solid mid-range feel and strong top-end power—and thanks to immense improvements in both turbo technology and engine tuning over the last decade all of this is possible from a single turbocharger. Thanks to new-age compressor wheel technology, some smaller turbochargers can even outperform their larger counterparts—while offering better drivability to boot. On the other side of the equation, precision engine and transmission tuning allows you to run virtually any size turbocharger you want and still keep your truck street-friendly.

8. The Expectation of Great MPG While Towing

Back before diesels became mainstream, many would-be owners believed a diesel pickup could achieve 20 mpg while hooked to a trailer. Thankfully, for the most part diesel owners (and prospective diesel owners) have more realistic expectations in 2018. While it’s possible to see 15 or 16 mpg with a trailer in tow, the possibility of seeing 20 mpg is highly unlikely—especially with a diesel pickup barely capable of reaching that level of efficiency when empty. Rolling resistance, poor aerodynamics, excessive weight, altitude and how hard the engine is working all play into the kind of mileage you’ll see while towing—and none of those ever work together in perfect harmony. If you come across a diesel owner that levels with you, depending on what he or she is hooked to, anywhere from 9 to 15 mpg is likely all that’s being realized.

9. Smoke Switches

This one has gradually worked itself out over the years (bring up a smoke switch for discussion on any diesel enthusiast forum, we dare you!), but a few years back this was big business for DIY’ers on YouTube. On newer diesels, it boils down to keeping the exhaust vanes from moving via disabling the VGT solenoid. With the turbocharger unable to clean up the added fueling, excessive black smoke (i.e. unburnt fuel) is the result. Thankfully, a lot of self-policing has taken place within the diesel performance community on the subject of smoke switches to help eradicate this special kind of stupidity. Still, it happens from time to time—and we cringe every time we see it.